This week and last has been fun. We received Otmar Ehbenhoech’s 1990 Vanagon DoppelKabine and were pleasantly surprised at the straightness and condition of this very rare (in the U.S.) VW variant. We think it will make a great build and I kind of picture a yellow VW Thing and a yellow VW DOKA side by side here in the shop. We kind of plan to do an “off the shelf” build using the Siemens motor and DMOC645/GEVCU we have on hand, along with some very inexpensive Nissan Leaf cells we have coming. The “treasure chest” low amidships makes the perfect battery location and the rear engine compartment should be relatively spacious. A modern liquid heating system in the vehicle will make heat easy. Indeed the main investment and difficulty should center or rust control, paint and glass and that we will outsource.
We feature Matt Hauber/Michael Bream in this issue with a quasi serious note on fusing high voltages I thought was good and timely. That they did not make a watermelon explode no doubt puts Gallagher’s mind to rest that he’s still the king. But behind the scenes there’s more going on with the EV West team. Young Hauber is not a fan of C++ and heavy electronic theory, but he’s quite a hand with fabrication and transmissions. I can recommend his video on marrying two Netgain Warp 11’s together with a hydromatic transmission sans bell housing and torque converter. Quite good really.
But more of our interest, Hauber has a secret personal project involving a Camarro he’s been wanting to convert for himself for years that I know of. And most recently, he had a local machine shop help him put two Siemens 1PV5135 motors he got from the AZD auction together siamese fashion. What this will allow is basically a dual motor AC after the fashion of the Warp11 twins. As demonstrated by the Escalade and subsequently HPEVS, what this REALLY does is allow you to use two inverters/converters on what appears to be a single motor. And THAT allows you to double the power.
So instead of a single DMOC645 at 118kw and about 220ft lbs of torque, he’ll be able to have TWO of them going for 235kw and 440 ft-lbs of torque. Actually, the DMOC645’s are quite large for a Camarro, so he’s picked up a couple of Rinehart Motion Systems inverters for his project. So he wanted to trade them for two motors, which is asking a bit much. What we worked out was I would send him FOUR motors, for the two DMOC645’s, and he would send two of them BACK married together after the fashion of his. You see, unlike Missouri, same-motor marriages are LEGAL in Southern California.
So at some point, we should have a DUAL Siemens package to use in something or another.
We’re making some other progress (????) on the Siemens Motor front. Some are daunted by the splined shaft (which I kind of like actually) and unusual face. So after Sebastien Bourgois kind of threw us under the bus on this concept (I tried to get him to do it as he makes great adapters) we have designed basically a B face adapter for the Siemens motor. It has a little coupler that fits over the splined end and is held in place by a center bolt. But it changes it into a longer 1 1/8 inch keyed shaft just like a Netgain or HPEVS motor. And we are also making a bolt on plate that turns the motor into a B face.
Now I admit, this makes no sense at all. BUT. There are hundreds of different B face adapters out there. Randy at Canadian EV has the largest line of these but EV West does quite a few and Rebirth Auto and Brian Hall at Thunderstruck all have a line of adapters basically designed to interface the original ADC8 B face motor to various transmissions – Miatas and Toyotas and Chevy S10’s and so forth. It is kind of crazy to suggest that you buy a B face adapter for a Siemens, and then buy ANOTHER adapter for your transmission. But I thought I would have a few made up anyway.
Along the way, it has generated some CAD drawings that I know little about. But they do provide the data for the Siemens face and the coupler. And so if you knew what you were doing (I don’t) and took THOSE drawings and modified them for your flywheel and transmission, in theory it would make it easier to do adapters for the Siemens directly.
We also started shipping GEVCUs yesterday. I have 30 to start with. It will again take about a month to come up with another 30. I’ve actually had them about two weeks hardware wise, but I’ve been trying to do some last minute software changes to clean up the interface a bit, and most importantly some stuff for the VW Thing. The assclowns team had broken the serial terminal method of updating accelerator and brake stuff. They had also broken the pre-charge thing which cost me several contactors on the THING and a couple on the test bench. But we got it worked out and you can now simply enter a delay time in milliseconds and which output to use for your recharge relay, and which output to use for your contractor relay. You simply connect those outputs to the coil ground side of each relay and GEVCU will control them.
I also have a couple of howling-assed fans on the Derali heat exchangers on the THING. In town, and certainly in February, I really don’t need these fans on at all. But on the freeway, in summer, our little solar pump and AN-6 cooling system can’t keep the inverter out of current limit without the heat exchanger fans. So I wanted to be able to control those as well. So we now have a COOLFAN output you can designate and a COOLON and COOLOFF temperature that is easy to set. You would then have the fans come on when the inverter reached the COOLON temperature and stay on until it reached the COOLOFF temperature. You would set these to different temperatures to prevent cycling on and off so much. Like 120F for COOLON and 100F for COOLOFF for example. When it reaches 120F, the fans come on, and they stay on until it falls to 100F. We actually get motor stator temperature, motor rotor temperature, and inverter temperature from the DMOC645 by CAN. Inverter is the most sensitive of these and so that’s what I cool to.
So we have hardware, some basic working software, and GEVCU lives. I received an e-mail from one of the assclowns in rebellion, Michael Neumiller.. He’s actually been the most derisive and predicted of course that it could not be done, and most specifically could not be done without HIM. I guess that isn’t working out exactly as he thought so he sent an e-mail warning me of DIRE consequences to my fortune as I would be hung with hundreds of Siemens Motors. Apparently the vast body of EVTV viewers did not abandon us in favor of his GEVCU.ORG site and follow them into the void a glorious GEVCU future led by him. I tried to tell these guys this months ago. The software never was the problem.
This goes to the enormous gulf between ideas, and actual products. I’m perhaps too familiar with it. I like publishing. Not manufacturing or retail sales. At conception, I could see how GEVCU was precisely the right thing at precisely the right time. We needed a CAN opener (pun intended – I should probably change the name from GEVCU to CANopener) to access the future rain of spares from wrecked electric cars. All of them use CAN driven inverters, chargers, DC-DC converters, etc. With the GEVCU CANopener, reverse engineering these things becomes plausible, and control of them relatively easy. But you have to have a device to hook up to it in the first place and that can be coded. But I have been drowning not in software problems, but in the detritus of back and forth and BACK and forth over the wire harness order, and the size of the enclosure, and whether it was black anodized or powder coated, and the plate showing the AMPSEAL 35 pinout, and the RP-SMA pigtails connecting the wireless module to the antenna, and the antenna. And the cardboard BOX we pack all that in. And the documentation. See open source guys don’t believe in documentation. You should already know how it works if you had been contributing to the code and if you don’t like the documentation, you’re invited to write it. This has been the ongoing attitude in the open source community for decades. I have 72 e-mail messages with the Canadian assembly house that turns out to really be located in China.
In the end, you can’t hack together an afternoons code and tell them to build the hardware themselves and actually get anything done. A working prototype is one thing, and even a small run of finished boxes is another. I have to say, Paulo Almeida has been a stallion through it all. What he does easily, I do in great pain and frustration. But he’s been very patient in working through the issues with me and I think the end result is pretty good as a start.
The heart of GEVCU is all about CAN – ergo CAN opener. CAN was originally proposed by Bosche in 1987 specifically for automotive applications.
More specifically, GEVCU is designed to control three-phase AC inverters – power switching electronics designed to drive AC induction and brushless DC motors – essentially all modern motors used in OEM electric car design. These “inverters”, including those from Toyota, Nissan, General Motors, UQM, Rinehart Motion Systems, Tritium, Tesla, and many others all use sensor management devices to gather driver inputs, and communicate that information to the “inverters” via CAN bus in the form of torque or speed commands to drive the motor.
The Atmel SAM3X8E ARM Cortex-M3 CPU used in the GEVCU actually has TWO independent CAN bus controllers built IN to the chip itself. But these controllers represent HALF of the necessary hardware to perform CAN communications. They also need CAN TRANSCEIVERS – devices that actually create the transmitted pulses on the bus.
GEVCU uses two Texas Instruments ISO1050 galvanically isolated CAN transceivers that meet the specifications of the ISO11898-2 standard. The device has the logic input and output buffers separated by a silicon oxide (SiO2 ) insulation barrier that provides galvanic isolation of up to 5000 VRMS for ISO1050DW and 2500 VRMS for ISO1050DUB.
Used in conjunction with isolated power supplies, the device prevents noise currents on a data bus or other circuits from entering the local ground and interfering with or damaging sensitive circuitry.
As a CAN transceiver, the device provides differential transmit capability to the bus and differential receive capability to the Atmel CAN controller at signaling rates up to 1 megabit per second (Mbps). Designed for operation in especially harsh environments, the device features cross-wire, overvoltage and loss of ground protection from –27 V to 40 V and over-temperature shut-down, as well as –12 V to 12 V common-mode range.
We refer to the two CAN buses as CAN0 and CAN1. CAN0 has a differential transceiver output available on pins 9 (CAN 0 high) and 10 (CAN0 lo) of the AMPSEAL 35 connector. CAN1 similarly appears as CAN1 high on pin 11 and CAN1 lo on pin 12 of the AMPSEAL 35 connector.
For GEVCU end users, there is nothing you need to know about CAN. The wiring harness provided with the GEVCU already connects the GEVCU to the DMOC645 CAN bus, handles all terminating resistor issues, and has been tested repeatedly to drive the DMOC645 and Siemens motor combination. There is really nothing to configure here.
But a bit of detail is provided here to illustrate the future growth and possibilities inherent in the GEVCU device.
The details of the CAN transmission are basically handled first at the transceiver level, and then at the CAN controller. But to effectively use all the mask and filter capabilities provided by these chips, and make CAN communications easier to program, a special software library is required to do CAN. This is the DUE_CAN library available at https://github.com/collin80/due_can. This allows fairly simple C++ commands to manage CAN communications quite effectively.
The ability to manage two CAN channels separately provides enormous flexibility. Of course, it could conceivably operate two separate inverters this way, each driving a different motor for example.
More commonly, it would be used as a CAN bridge, porting data from one CANbus to another. It is not uncommon to have CAN buses operating in the same vehicle at different speeds, one at 250 kbps and one at 500 kbps for example. Using GEVCU, it is relatively trivial to port data from one to the other.
The basic and immediate design of GEVCU is to command the Azure Dynamics DMOC645 controller directly via CAN. This is a 250kbps CAN bus that is simply two wires between GEVCU and the DMOC645.
The second bus would more likely be connected to the vehicles’ Onboard Diagnostics Version II or OBDII bus. This has been required in virtually all vehicles worldwide since the late 1990s. Originally using a variety of manufacturer specific protocols, it has evolved in recent years ever more towards simply a J1939 standard CAN bus.
At the very basic level, the CAN protocol most often uses a 29 bit address and up to eight bytes of data. ANY device on the bus can transmit these packets and ALL devices on the bus can receive them. In broadest terms, the 29 bit address identifies WHICH device is sending the data, and often the specific nature or type of data it is sending. The eight data bytes then contain the data.
Using filters and masks, any specific device on the bus might set up to basically “look for” packets from another specific device, with specific data in it. It would ignore all other signals on the bus. And the software in the device would intelligently recognize not only the packet, and the eight databytes, but specifically the format and significance of every bit of the eight byte data payload.
Collision detection and priority are rather cunningly handled in the address itself.
And so we wind up with a bus, that might have two, but also might have two hundred devices, all more or less blindly sending packets and receiving packets. But by selectively filtering packets at the chip level, the receiving devices only get data they are interested in and know how to act on. The air conditioning controls on the dash have no use for inverter information generally speaking. The gear selector doesn’t need any information at all, it simply transmits lever position periodically. The variable steering device only looks for RPM from the inverter. And so it goes.
Sending devices are more less simply “announcing” data that might be of interest to others by forming the data in agreed format, and sending it with the right identifying address – more or less one assigned to that device. Note the address is NOT who it is sending it to. It’s just a message identifier showing the source device and nature of the message.
So GEVCU is completely capable of announcing drive commands from the address and in the format that is expected by the DMOC645. And it can also receive packets from the DMOC645 that contain data on inverter temperature, motor temperature, motor current, motor voltage, pack voltage, pack current, and much more.
Normally, GEVCU would get accelerator position from a hall effect pedal as an analog input. But it is not only completely possible, but has already been done, to connect the second bus to an OBDII bus and “capture” pedal position from the CAN bus signals transmitted by a CAN capable accelerator/throttle assembly. That data is then used to form drive commands going out the first CAN bus to the DMOC645.
It would be entirely feasible to program the GEVCU, using the PWM output of one of its digital outputs, to drive a vintage gas gage in a 1957 Porsche. But it is JUST as feasible with GEVCU, to put the proper address and data format together on the OBDII bus to drive the gas gage in the instrument cluster of a 2014 Porsche.
This opens up enormous flexibility. For example, there are a number of devices on the market for trivial amounts of money ($20-40) that plug into the OBDII connector under the steering wheel of a modern car that transmit data from the CAN bus over either 802.11b/g Wifi or Bluetooth wireless. And there are already multiple versions of programs for the Apple iPhone, iPad, and Android tablets as well to capture CAN data from the vehicle and display that data on attractive and highly customizable gage displays. In this way, an Apple iPad could rather easily serve as a graphic display for your electric car, displaying kWh, amperes, battery state of charge, motor rpm and current, inverter temperature, and much much more.
The implications for CAN are actually hard to get your head around. For example, conventional thinking would indicate that GEVCU is quite limited with only 4 analog inputs and 4 digital inputs, and 8 outputs. Those accustomed to Arduino having over 50 inputs and outputs would find this very limiting.
In automotive applications, an evolution has occurred that is quite fascinating and perfectly logical. Look at the wiring harness that comes with the GEVCU. It is already sufficiently complex and enormous that we have individually colored each wire AND inscribed the logical label of the wire along the wire length – encased it in nylon braid, and it is STILL quite a thing to deal with in a car. It causes a lot of wiring.
The CAN philosophy is to reduce all that to two wires. If you need more than 4 analog inputs an 4 digital inputs and 8 digital outputs, you basically need ANOTHER CAN device closer to its logical purpose.
And so you would not incorporate measurement of battery voltage and temperature and current and state of charge in GEVCU. You would more likely devote an ENTIRELY SEPARATE device, located right AT the battery, and connect it to GEVCU with precisely TWO wires, the CAN bus wires. And so basically you have two wires running through the car, connecting dozens of highly specialized devices whose only wiring is very very short and very very local to just what it is doing.
Actually you COULD use two GEVCUs. One with the GEVCU software in it, and the other with battery monitoring software in it. The CAN bus is how they would communicate.
How far can this be taken? To the extreme. On modern cars, if you look at the 4 window controls on the drivers door, you will find it is a CAN device all by itself, and it communicates with three others – the window controls in the other three doors. The Chevy Volt actually has a total of 104 microcontrollers in the vehicle, each with its own built in software and function. But they can all communicate with each other. The future of automotive technology looks like, sounds like you could check to see if any of your car windows were down, from your pocket phone, while in a building 112 miles away. Better yet, you could roll them up.
And so the real power of GEVCU, beyond giving us access to existing inverters and motors, is the two CAN bus channels. And added functionality is not so much a function of hanging more wires on GEVCU, but on intelligently designing and placing devices in the car to talk over the CAN bus. Fortunately, beyond perhaps a battery monitoring system, modern cars already have CAN for throttles, windows, door locks, radios, gas gauges, air conditioning, auxiliary fans, window washers, temperature sensors, and all of this is increasing at a logarithmic pace. If we can determine the address and commands, the open source nature of the GEVCU software will allow us to command it. Bosche actually invented CAN to REDUCE the weight and cost of copper in the wiring in an automobile. That was the original purpose of CAN. And it works.
Back to earth a bit, the GEVCU was born to drive the Azure Dynamics DMOC645 inverter and paired Siemens motor. But from the first instant of conception, we envisioned a very modular object oriented design leveraging the power of the C++ object-oriented language.
As such, a class motorController, is available. An object, inheriting from that class, is the dmocMotorController. It is actually a very small bit of program that intelligently takes concepts such as forward torque and regenerative torque, voltage, current, and temperature, and keys that to the SPECIFIC CAN messages and addresses EXPECTED by the DMOC645 already. And it intelligently knows how to recognize messages from the DMOC645, by address, and how to decode them to get actual torque, actual rpm, inverter temperature, battery pack voltage, etc.
To customize GEVCU to work with an inverter from UQM or Rinehart or Nissan Leaf, if you have the documentation defining the addresses and data formats used for those devices, it is a very doable if non-trivial programming task to add an object, much like dmocMotorController, to the motorController class. Ideally it’s a single file. Call it uqmMotorController. The SPECIFICS for any controller are confined to really a tiny part of the GEVCU software. You don’t need to know very much about how the rest of the program works, or why, to do this.
In the case of a UQM or Rinehart, these CAN data digests are actually published documents. In the case of the Nissan Leaf, it might be a little more difficult requiring some reverse engineering – basically driving a LEAF and sniffing out CAN codes on the CAN bus to the inverter. That’s how we did it for the Azure Dynamics DMOC645.
But in this way, we hope to open the door to cogently reusing the cornucopia of excellent components deriving from the salvage of many many cars developed by the OEM manufacturers. Electric motors and controllers can conceivably operate for DECADES of use. But one tree planted in just the right place 30 years ago can take out a Nissan Leaf in a split second. The Tesla Model S is such a delight to drive, and will indeed do 0-60 in a little over 4 seconds. In fact it will do 0-45 and 45 BACK to zero in less than 4 seconds if it hits the right tree. And the Model S owners are out there desperately trying to prove us right on this theory.
And so we see a future land strewn ocean to ocean with glittering motors and inverters and battery packs that are virtually brand new, lacking only a car – and a device to talk to them nicely in a language they understand – GEVCU CAN. So I’m pretty jazzed up.
I received another e-mail from viewer Jonathan Hanson pointing to an absolutely fascinating video presentation of Dr. Jeff Dahn, Dalhousie University, in Halifax Canada. Dr. Dahn is trying to work out how to make lithium batteries last longer. He’s traced almost all of the deterioration in battery capacity to parasitic reactions between the reactive elements of the cells, anode and cathode, and the electrolytes. These side reactions form the solids over the anode – the so called “passivation layer” or solid-electrolyte interphase (SEI) layer. He traces the decreased capacity to the thickening of the SEI caused by these parasitic reactions and very interestingly notes that these reactions are exacerbated by heat. The heat he refers to is 50C or even 60C but he also connects this to the TIME spent charging or discharging in the presence of such heat. He diagrams LiCoO2 cells, LiFePo4 cells, and LiMN04 cells, the latter used in the Leaf and the Volt. The Volt features temperature management and the Leaf does not.
The worst of the offenders was of course the LiMnO4 cells used in the Leaf. This sensitivity to heat did NOT show up in Nissan’s testing at 1.5C or 2.5C. They were concerned with heat during fast charging for example and it does not appear to be much of a factor. But at lower discharge levels, it rather markedly DOES. In other words, it is the TIME spent charging and discharging under heat that does the damage.
He and two graduate students came up with a novel way of measuring cycle life. They actually measure charge efficiency. If you discharge a battery, removing a certain amount of energy, how much energy do you have to put back to charge it? The ratio is the charge efficiency. For example, if you use precisely 1000 watts out of a cell, and it takes you 1020 watts to replace it, you have a charge efficiency of something less than 1.000. He found a VERY strong correlation between this charge efficiency and cycle life or loss of capacity over cycle life.
This is kind of a profound leap. Instead of hundreds or thousands of bulk cycles, you can accurately predict cycle life by measuring charge efficiency over a tiny fraction of the cycles – 10 or 20 perhaps. But to be useful, you have to measure this charge efficiency very very accurately.
A couple of graduate students, Aaron Smith and Chris Burns actually built a charger system capable of very accurately measuring the current and voltage and power into and out of the cell and so charge efficiency. Mr. Burns continues with the project while it is kind of interesting that Mr. Smith has left to work for Tesla motors. The other thing I found surprising, was that lithium cobalt chemistries, like that used in Tesla, and the newer NMC chemistries, appear to be the MOST resistant to heat as a factor of cycle life.
By being able to very accurately measure charge efficiency, and so by proxy cycle life, they can test their theory of this capacity loss being based on the parasitic reactions causing the SEI layer. Indeed, it would appear a given as they are now quite past that comparing charge efficiencies based on various electrolyte ADDITIVES that improve charge efficiency and by extension, prolong cycle life. And they have the hard data to prove it. So in effect, they have developed an advanced cycle life meter they can use to test improvements in battery chemistry on for cycle life. And the differences they are implying are immense. Like 20 fold increases in cycle life from simple electrolyte additive combinations.
The other thing that jumped out during this video I would like you to watch for. He is talking about Nissan cells which normally charge to 4.2 volts. But in the process, they graph cycle life charging to 4.1, 4.15, 4.2, 4.25 and I think 4.3v. As you get higher in voltage, cycle life decreases DRAMATICALLY. I mean turning a 2000 cycle cell into a 200 cycle cell. Recall our strategy for extending cycle life, BOTTOM BALANCE AND UNDERCHARGE. It appears the undercharge component cannot be stressed enough. I was stunned by the differences in cycle life among these really pretty close charge voltages on those particular cells.
I found it all sufficiently energizing, I can’t wait to get back to my Sendyne chip project. Recall this is a chip specifically designed to VERY VERY accurately measure currents using very small resistive value shunts. If I can get that module wired up to an Arduino Due and more accurately measure voltage and current, and drive a couple of contactors, I think we can duplicate hundreds of thousands of dollars in “accurate charge” equipment he’s amassed there for $1000 or thereabouts. Of course, he does 100 cells at a time. But we should be able to compare Nissan Leaf cells to the new NMC cells to CALB CA series to CALB SE series to the old Thundersky cells as a function of charge efficiency. And I’m sufficiently persuaded by this data that that IS a true proxy for cycle life. And so we could compare cycle life on different cells with just a few charge/discharge cycles establishing charge efficiency.
Don’t be confused by all the “new chemistry” and “glucose battery” BS literally spumming onto the network today in a huge gush. THIS guy is the real deal and this is a profound breakthrough in battery testing. It kind of only holds for current cell chemistries that exhibit this passivation layer. I don’t know that it translates to coming lithium sulphur and silicon anodes and solid polymer electrolytes. But for the current chemistries actually available, this is a huge step in battery testing and opens the door to some truly amazing advances in cycle life.
In the future, it might well be that we’ll move on in our cars to more advanced chemistries. But then that leaves the current LiFePo4 cells as the low cost “yesterday’s news”. If its cycle life were to improve 20x, it kind of automatically becomes the grid storage technology default And if we are to truly move toward renewables such as wind and solar, we will badly need such a low cost long life grid storage solution. Bravo Dr. Dahn.
95 thoughts on “CANopeners and Battery Life. Heat does appear to matter…”
Jack, I’ve a question that is totally unrelated to this weeks show. On the motor controllers you are using a heat sink to draw the heat away and using a heat exchanger to dump the heat be it a radiator or something of that nature. Since I have not yet built an ev I don’t know how much heat is generated by one of the controllers and don’t know if this would be any help but I wondered if you could tie a heater core to the circuit and use that in the winter time to dissipate heat into the interior of the car. You may have already tried this, or it may just not put off enough heat to be worth the trouble, I don’t know but I wanted to make the suggestion anyway. I saw you and Brian talking about the Carmen Ghia AC/Heat system and the though crossed my mind.
It’s not that it can’t produce that much heat, it’s that you don’t want it to. Imagine trying to heat a room with a computer in the middle of winter. Sure, you could slow down the fans and get more heat to build up, but you’d fry the CPU in the process… That is, if the protection circuitry didn’t shut it down first. The same goes for a motor controller / inverter. You’d never want your cooling system carrying enough heat to heat your vehicle cabin.
Chuck, the whole idea was to use the available heat off the controller, not use the controller as a heat source. As I stated in my question I had no experience with controllers and I don’t know how much heat would need to be dissipated and if that heat would be usefully in the colder parts of the year.
How much controller heat? Assume the controller is 95% efficient. At 60mph I see about 22kw pass through the controller and 5% of that would be 1100 watts. So for highway cruising on a 50 degree day it would be enough to warm the car up. At the max power levels I see (150kw) and 95% this is 7500 watts. Good thing I dont operate at those power levels for too long. Those numbers are just estimates. It is probably better at some power levels and worse at others. Motor heat would be two to three times this amount at 60mph and perhaps six or more times that at max power. So yes there is plenty of energy there. The problem is the temperature gradient is wrong. For heating air you want the temp of the fluid to be up near the boiling point of water but for cooling the controller you want the temp to be nowhere near that. The motor heat would be the most useful as you could let it get up to those levels without risking damage to the motor.
Oddly enough, I just answered a tangentially similar post by you on DIY… A Soliton1 running at 300V input and delivering 150V/1000A output (ie – 150kW) will have total losses of 2220W; that equates to an efficiency of 98.5%. 2.2kW sounds like a decent amount of heat, but it is “low grade” heat – ideally the volume of coolant pumped through the controller is high enough to keep the heatsink temp below 55C (130F) and low of a temp rise is barely worth bothering with vis-a-vis cabin heating.
Furthermore, the ideal delta-T across a heat exchanger for HVAC applications is around 25F/15C, so using the controller to “pre-heat” the coolant going to the heater that really gets the temp up so that the cabin heat actually works means the controller then receives 65-75C coolant in return; hardly ideal for the controller!
I think you all miss my point. At no time had I thought that a “heater” would be used to cool the motor or controller. What my idea was passing the coolant though the heater core and then pass the coolant through the radiator then back to the controller. The heater core would just be used in colder temps and the radiator would always be used. When it is warmer the heater core would be bypassed and the radiator still used. I asked the question mostly out of curiosity because I had not seen that anyone had tried it but I also noticed that a lot of people don’t even have a heater and it seems that everyone has made sure that I understand that the heater core would not cool the controller and or motor. I understand that. According to what you just said apart from the water not being near boiling point it would in fact heat the interior and that was my question. One other thing, I own 2 Chevy Caprices and both cars have reverse flow cooling with 160 degree thermostats. Both of these cars heat very well and the water is no where near boiling point. Thanks for you answer as you did tell me what it was I wanted to know.
You could use the heat from components such as the controller/motor as a pre-heat to the heating system. But there is no real advantage other than the energy savings during winter operation. During moderate cool weather when using a small amount of heat for the cabin, you would need to cool the hot water you just warmed up before it re-entered the motor/controller. It’s an ideal that creates more complication than is necessary with little gain (if any).
The greater challenge is that you would ideally want to harvest the most heat possible for the passenger heater core AND provide the coolest liquid to the heat abhorrent devices. What makes it tricky is that these electronics are quite efficient and will not produce nearly enough heat to suffice for personal comfort.
You could, of course, make things complicated with various semi-parallel loops that branch and join. Or implement a liquid to liquid heat exchanger. This would of course require two water pumps, since you would have two separate circuits. But you still have the likely possibility that the lowest temperature seen in the heater loop is well in excess of the otherwise hottest in your cooling loop. In that case, you’d want to use a peltier in between. And you’d still need a distinct heat source for passenger comfort and a radiator for electronics’ comfort.
It’s a pregnant idea, and we did try it. On the Mini Cooper. It just doesn’t quite matchup. You are trying to do two missions at the same time, and at any given time you’re doing the wrong thing. We could get some heat in winter. But then had in adequate cooling in summer. We could do enough cooling in summer, but then no heat in winter. And on and on. You very quickly realize it would all be simpler with two separate systems. I know that’s counterintuitive, but try it. It comes out the same way every time.
Reading through a blog by the white zombie guy it appears that the Chevrolet Volt had a heat pump system. Efficient on long drives but to slow for quick comfort. Recently some of our respondents commenting on the Leaf in other countries have mentioned heat pumps. Given that we like liquid heating in the cabin and liquid cooling on the electronics it makes me ponder about two liquid systems with the heat pump between them. The pump could also be connected to shore power for what appears to be coming….battery chargers with active thermal management during charge cycles.
In the i-MiEV we do have two separate “cooling” systems, one for heat and one for cooling. The guy who looked for a place to add a diesel powered heater perfectly elected the wrong system. I am glad I decided to stay with electricity in the first place.
An other thing I learned you can save a lot of energy insulating doors, trunk lid and front lid. The reservoir for hot cooling fluid is behind the front lid. Insulating also made the car a lot quieter, inside at least. And the stereo sounds better.
60 Celsius is too hot for cooling the electronics but it is barely enough for heating.
Thanks, that is what I was curious about, if it had been tried and the out come. I would not think that a heater core would be sufficient in the Summer as they are just not very big and not in good air flow and if much heat was generated it would not keep up. I was thinking more on the lines of a system with a heater core inside and a heat exchanger in the grill(or air flow in the case of VW). In the Winter route the coolant through the heater core and then through the heat exchanger and in the summer just use the heat exchanger. That is what lead to the question in the first place as to whether or not it would even be worth the trouble. Me not knowing hot much heat needed to be removed left me with wondering if there is enough heat to be used. I guess caolivieri said it best, it would add more complication with little if any gain.
The little PLC and display system I sent you a while ago would make a great battery tester. With a slight modification it could accurately read a cells voltage down to 0.001 volts and measure current across a 100 amp shut to 0.001 amps. This would probably be enought resolution to do the tests that you propose. If fact it could be set up to measure this across 4 or eight cells at the same time.
Since it also has two PWM outputs, it could be used to vary the amp draw into or out of the cell using a MOSFET or IGBT…
It could also log all of the necessary data down to 100ms intervals….
Let me know if this is on any interest to you….
It is. Let me see if I can find that box of stuff…..
That’s extremely timing to me that the subject of accuracy in voltage and current measuring is coming up, as I have been working away in my “lab” to do just that (part of my own BM[monitoring]S project utilizing Atmel’s Mega2560 AVR and some current sense ICs, to start).
When you say you can measure current across a 100A shunt down to 1mA, what type of shunt are you using? Any part numbers, online sources, etc.? I quickly realized that the 75mv shunts, like the type that come with the JLD404, are “only” accurate to +/- 0.5%, which means that at full sweep that type of shunt would be out by +/-500mA. The 50mV shunts (Deltec, Blue Sea, …) are a bit better with +/- 0.25%, meaning +/- 250mV at full sweep. Is there such a mythical creature as a +/- 0.1% shunt (or better)?
Also, I did find a source of 100mV shunts that are also +/- 0.25% (canada.newark.com, search on “100mv shunt”. Also do the same search on DigiKey and there’s a few). I ordered some to compare the accuracy to a similar rated (current and accuracy) 50mV shunt. My theory, and anyone please jump in to stomp on it, is that there is more mV to actually measure for the same current and accuracy, so… perhaps more accurate at smaller currents? I dunno, but I’m gonna try it unless someone dares stop me.
At any rate, the main thing I’m currently (pun intended) finding in measuring these high current systems such as the ones you find in our EV environments, is that an accurate shunt is just as important as the accuracy in the instrumentation/circuitry used to measure it. This also goes for trying to monitor at the same time the small 100-200mA constant drains of our DC/DC converters and instrumentation that keep drawing away in the dark long after the garage door closes…
Any pointers by the resident EE’s out there would be greatly appreciated! I’m enjoying this thread.
I picked up one of these on Ebay a few months ago for $100
I actually have some time this weekend, maybe I’ll mess around with it
Hey, cool toy, thanks for sharing. That sounds like a great testing rig, and it looks like there’s a 0-to-150mV jumper setting, so that may mate up nicely to a 50, 75 or 100mV shunt (or 150mV, if such an animal exists). I assume that’s bi-directional, but if not, perhaps you just use another differential input and reverse the polarity.
Those differential inputs are a nice feature, too — and I am assuming they are isolated, so you have the added bonus of pack voltage half/trident/quadrant monitoring ( a la Lee Hart bat-bridge on ‘roids — see Jack’s BMS spec for reference), without causing shorts when/if using a single-ended or non-isolated system. I could be full o’ crap there, though…
Mos shunts migh not be dead accurate, but they are usually repeatable. I calibrate the shunt with a very accurate fluke meter…
Jeff, except according to the video you need accuracy to the fourth digit which is 10x better than you are suggesting. Pretty amazing video. It sure does explain why those folks in Arizona who were charging at home and at work on level 1 chargers were seeing so much degradation. They were constantly in the heat and either charging or discharging nearly all day long.
Amps and Volts to third decimal give you Kwhr to close to the 4th..
It would be on the edge but I think it would still work…
Also I think repeat ability is more important than ultimate precision you would just need more samples to get to the same trend line…
Thanks for sharing the lithium battery video Jack. Truly fascinating. I might have to watch it ore than once to fully understand it. So far the best Lithium battery video I’ve seen. He didnt touch on the cycle life comparison between the LiFePO4 & LiCo. What we know is LiFePo4 has more cycle life than the other chemistries but he showed on the graphs that LiCo is better in maintaining charge efficiency. and how about the Yttrium that was supposed to increase cycle life in LiFePo4?
ok, but in the video they had current measurements to the 5th digit, and said that they needed it to the 4th at a minimum to get useful data in this type of testing. I’ve not checked the math to be sure, but he had CE differences from .985 to .995 on one of his graphs. He never showed capacity in kWh, but rather Ah in all the slides. I’m not saying it wont work, but look at the specs on all the equipment you are using and then run through the math quickly to be sure you’ll get useful data before spending all the time on this test.
Actually I was stunned at how loose the resolution was that he considered the very accurate charger. He was talkign digits and you’re talking decimal places. When he said four “digits” he was showing like 21.25 as an example. Two left and two right, not four right of the decimal point. He clearnly indicated 4 digits total. That’ s not that hard to measure actually.
So he had CE differnences of .985 and .995??? Those were CALCULATED values not measured. You calculate the charge efficiency by dividing the discharge energy by the charge energy required to replace it. You can carry that out as many decimal points as you like.
All that can be done at least to that resolution pretty easily. Hell the JLD404 will do it to four digits. I think we could quite accurately measure current to the thousands of an amp with the right amplifier and shunt combination.
Ultimately it has no absolute value. Because nobody else is doing it. BUt COMPARATIVELY it might be very instructive. So calibration is moot. It just has to be quite precise. We would charge at a very accurate rate of current until it reached an EXACT voltage to three decimal places and shut off immediately RIGHT there. And then discharge at the same rate of current until it reached PRECISELY 2.500 volts and cut it off there. And then charge at teh same precise current rate to 3.500 v or whatever. The specific top and bottom voltages used DON’T MATTER. We’re not really checking capacity. We’re checking charge efficiency. Then divide the discharge power in AH by the recharge current in AH to get CE.
Comparing CA cells to SE cells to NMC cells to OLD Thunderskies should all be very instructive.
The only thing I didn’t like that he said, was to “keep the batteries as cold as possible” without the caveat of NOT charging them at really cold temperatures.
It is also worth pointing out that it is difficult to even find an A/D with more than 15 bits of resolution these days. Most are 8, 12, or 14 bit with sign…. It is nt that they do not exist, but that they are typically not in a very user friendly format…
It is no problem to get more the 14 bit, the are frequently used in combination with load cells. you can get a 24 bit A/D converter for under 2£
John Hardy’s data would be pretty interesting to parse from this perspective. Doesn’t he have cycle data from two or three different chemistrys or at least different manufacturers?
@ palmer_md: Good thought. I only have Headways and CALB CAs so far, and plan to take a look, but have just emerged from hospital and am struggling to do much of anything at the moment. If I can extract anything useful I’ll send Jack a segment but it may be a while…
John, nothing serious I hope. Best wishes for a swift recovery.
Many thanks Nick: more tedious than serious I think fortunately.
Definitely hope you are feeling better soon…..
Hi Jeff, I’ve seen a home brew circuit with stacked ADC’s. It was stunningly simple.
I also like this one-bit babe. So cute! I don’t know it’s linearity/repeatability and the need for a CPU – pulse length counter to determine and store/use the value..
Thought you would enjoy China’s Kandi Machine electric car share program. http://www.smartplanet.com/blog/bulletin/chinas-electric-carshare-vending-machine/?ftag=TRE4eb29b5&s_cid=e660&tag=nl.e660&ttag=e660
hey, I’ve been looking at the webcam probably 4 times a week for the past 6 months, and lots of Fridays, but today is the first time I’ve actually seen some filming going on. Filming the show in the shop in front of the Thing this week instead of the “studio”. Awesome.
Yes, we were filming a spot on the new UQM drive train we received this week. I suppose we need to set up streaming cameras and actually go live on Fridays.
Get some good streaming cameras. I think live would be great. Here is an ELR ad if you have not seen it yet.
Just looked at the new UQM Powerphase motor controller in your store. But found something odd. The list price struck out shows $4530, but your price shows $9995. Is that a mistake, or is that the correct amount under your policy of beating any lower price .
For those who don’t like math all that much I did a spreadsheet a couple of years ago that does the math presented in Brian’s presentation from the Feb 7 show. Just make a copy and put in your own numbers.
Thanks Doug, that really makes it easy.
This is great, Brian and Doug did a great job on this – Now I know that my Miata will have max torque from 0-77 mph, and will redline at 7000rpm 141 mph!
Does anyone knows what is the CALB news is?
I am making progress on my Miata The AC 75 is in and secured with a custom motor mount… if anybody wants it I will share the drawing.
The battery box drawing are also available.
I am not an electrician: I would love for someone who has done an HPEVS-Curtis car to look at my electrical high voltage drawing and answer some questions from a guy with no experience. – email me or I could post the document.
Jack, in case you drop another bolt.
I can still reach the ground but sometimes things are in the wrong place then those tools become very handy. It may be a good idea to insulate the shaft. The grip is insulated.
Interesting video again. Curious how Jehu’s batteries perform. 88 of those cells should be able to connect parallel to our i-MiEV’s 330V bus. 4.4 kilogramms, might fit into a fuel cannister. We could carry it to the next power socket.
Peter and Karin
Enjoyed this week’s (7th Feb) show. I guess you’ll be aware that there was a blip at one point where you introduced Anne but we got Brain.
Not heard of Sanford and Son. For the UK audience, it was apparently a US sitcom based on “Steptoe and Son”.
Will this weeks show be on youtube?
Its been on youtube since sunday, but no hd.
Just showed up on my youtube now. Guess we’re a bit slow in Ireland 🙂
I may have been thinking of last week, at times the video wont play on jacks site, then I go to youtube. Seems to be an on off thing on a windows machine, have no ide why it is so.
I am downloading Jacks’ hd files. Takes some 14 hours but the audio is much better for my ears and video looks much better as well, even without glasses.
You mentioned a company a long time ago that was a supplier for the polymer powder that is in the lithium batteries. I can’t remember the name of the company, but I was thinking about investments, and if Tesla/Panasonic is about to build a new factory that will more than double the current production of lithium batteries, this company might benefit and would be a good place to invest. This is assuming that they are a supplier to the Panasonic batteries that are used in the ModelS, and that they will also continue to supply this new venture.
I just wish I could remember the name of the company so I could do a little research. Perhaps they were the supplier to CALB, TS and the other LeFePO4 manufacturers and I’ll have to keep looking for the Panasonic supplier, unless they are more integrated and have their own plant.
Alees Systems of Taiwan was discussed at one point. They make a LiFePo4 powder that is somewhat interesting.
The size of battery factory contemplated would probably involve the development of their own cathode and anode materials processes.
A yellow VW chicken wagon, you say? This may be a pregnant opportunity to convert a certain Canadian chicken shack’s delivery fleet back to a simpler time. http://www.st-hubert.com/entreprise/historique/annees-1960.en.html
Great show, again!
If heat matters, the question rises, how do these (Leaf) batteries respond to cold. I know capacity suffers quite badly, but what do temperatures below freezing do to the cycle life? Is charging below zero (Celcius) as bad as it is for the CALBs?
Keep up the good work!
ok, here is a link to a paper that shows the accuracy of the instruments he is using….
Interestingly Aleees went public in December. Not sure I want to invest, but I did put them on a watch-list, and after a few quarterly reports are out, see how they are doing. Right now there’s not much to go on.
Jack Nice show Feb 7, you talked about the UQM motor on the Borg Warner eGeardrive. I got to thinking is the connector the same as used for the Siemens, thus you could use your Siemens VW adapter to connect the UQM to the VW. So is that connector the same?
Steven, I’m assuming by “connector” you mean motor mounting face. The answer is no. The Siemens uses a 250mm bolt hole diameter and the UQM utilizes a 215mm diameter. It might be possible to take the VW adapter and have more machining done to it to change the bolt pattern, but it certainly won’t be a bolt on fit out of the box. It looks like the motor shafts are compatible though. When comparing the eGearDrive that was designed for the Siemens, compared to the one on the UQM, they’re not the same either. The gearbox itself is mostly the same, however the “E-machine Interface” is different. It’s basically an adapter plate on the gearbox that makes it adapt to a Siemens or a UQM, or a Remy, etc. AZD used a mechanical park pawn and the UQM unit uses a CAN controlled park unit Borg Warner calls e-park. I need Jack to verify it but I thought the gearbox on the UQM has a different gear ratio than the one on the Siemens…
Precisely so. It is a different gear ratio but slightly. I can’t recall it off the top of my head but I can find it somewhere.
No the motors have entirely different face as does the eGearDrives. I would expect the shafts to be similar.
What’s the possibility of you having an adapter made that would interface a “B” face motor to the eGearDrive and selling these in the store? This would allow an HPEVS motor to interface to the eGearDrive. This could increase sales of the eGearDrive. Any thought to having the CANopener work with the eGearDrive, to control the parking pawl?
to Jack and Brian_C sorry I was not clear. I should of asked about the shaft connector. On the Seimens I think Jack said that it is a 19 spline shaft. Is the shaft on the UQM a 19 spline shaft?
Steven, the shafts on the Siemens and the UQM that Jack is selling are the same. Don’t make the assumption that if you buy those components elsewhere that they will be the same. You can verify they are the same by looking at the dimension sheets. For the UQM system, check the online store and scroll through the pictures, you will find the spline dimensions there. For the Siemens, go to the Forum and on the very first page Jack has the dimension pdf for the siemens motor.
Larry you took the words right out of my mouth! Have a B-face adapter available would broaden the available options. A HPEVS motor would be perfect for this. I am only thinking that because I am starting to think a Warp9 would eat this transmission up if your not careful.
All the best,
@Aaron and Larry, you guys do watch the show right? Jan 17th, starting around 1:16:00 – I even made notes for you 😛 http://evtvindex.blogspot.ca/2014/01/january-17-2014.html
Jason, Aaron, and Steven,
If you guys are trying to mate a eGearDrive up to a HPEVS motor, it might not be worth your while unless you have a very light vehicle conversion, or you are OK with vehicle acceleration specs of 0-60=yes… The only HPEVS offering that comes close to the performance of a Siemens or the UQM motor (for use in a single speed gearbox) is the AC35X2. I also didn’t go through the entire engineering and torque curves, to compare the two you also need to know your tire diameter, and max vehicle speed based on HP and max motor RPM based on gear ratio.
Also, as for the required adapter, Jack was making a B face adapter to mate a siemens motor to an adapter designed for a B face. He was not making an adapter to adapt the eGearDrive to a B face (different gender B face).Thus you’d have to make your own adapter and coupling to mate the HPEVS AC35X2 to the eGearDrive. By the time you paid for the AC35X2, adapter and coupler, you’d have more money spent than if you bought the UQM system in the first place.
Whoops! Thanks for setting that straight… I definitely read it backwards, must be Friday haha. Sorry all.
Your all over it again Brian. We are just barely under $10K on the HPEVS AC 35×2 and we are doing the UQM and inverter for that. For another $3000, you get the eGear drive, both front axles, and the tree that hangs the motor. An adapter would be $1500 or so.
We have actually sold about 36 eGear Drives but they rarely tell us what they want with them and most have gone to projects that didn’t even use any of our motors.
You can do maybe 160kW with the HPEVS 35×2 and of course this is a 100kw system. The other HPEVS motors and inverters tend to max out about 80kw.
So it’s not crazy talk power wise. But encomomically, we are liquidating bankruptcy here with the UQM stuff. HPEVS has product support and warranty etc. We still sell more HPEVS than anything else actually, including our Siemens motors. I kind of expect GEVCU to shake that up a little bit. But many of our viewers like the HPEVS package and I have to say, every build we’ve done with one has just come out a honey.
The THING is looking pretty good these days with the Siemens though.
What is the plan on having the CANopener control the UQM inverter? Any thought as to if and when it might be available?
Yes, I watch the show religiously!
Jack is talking about a “B” face adapter for Siemens. I would like to have an adapter that would allow any “B” face motor to connect to the eGearDrive.
What I understood from Dr. Dahn was that the charger they built used high precision current supply’s that were accurate to 5 digits which is most likely microamp range. A standard current supply would do miliamps so for 3 decimal places one would not need a precision current supply.They also measured this current with precision resisters to double check the current. He used two terms precision and accuracy which are not the same thing. Precision is the measure of how close the measured values are to one another. Accuracy is a measure of how close the value is to the actual value (i.e. offset). Precision current supplies can go from microamperes to femtoamperes.
To Brian_C Thanks for the information on where to look for the spline dimensions. Just got done looking at the diagrams. Jack says the Siemens has a 22 tooth spline and the diagram for the UQM in the store says that that motor has a 24 tooth spline. So close but Jack smoked the cigar.
It is a 24 tooth spline I believe.
I marked a tooth #1 in the coupler on my desk and counted the teeth. I get 24.
Jack, Looks like the youtube live stream has Live Comments as well and would be pretty easy to have people post questions/statements. It may work better for a “show” if you had a third person sort of pick out questions or consolidate repeat questions while you and Brian are discussing the current topic. I’m in for next Sunday
here is an example of an 8 hour live stream where they answer viewers questions http://www.youtube.com/watch?v=Nr9-BQgnsRM&feature=share&t=3h15m52s
Sunday would also be nice, because the questions can be direct from the Friday show posted the night before, watched by insomniac Californians…
…and then there is the 50% of us outside the US. I usually watch Sunday late afternoon/evening which is middle of the day on Sunday in Cape: but Jack and Brian need a day off occasionally too
Sunday is about all there is. We work Monday-Friday. I edit on Saturday and often Sunday morning after church. And Sunday afternoon is about all there is. We might be able to work it in Friday – like in the morning. But that would be sort of a low viewer participation time I would think. A lot of people watch the show Sunday.
So it would kind of fit.
I could see the live event possibly being a useful tool for future EVCCONS, if it could be set up as a paid subscription cast for the presentations. This would allow those in other countries or with schedule conflicts to be part of the convention and would give you some extra audience numbers that would be helpful in getting top quality speakers, not to mention some extra revenue from the event.
It may also be a good tool for new product introductions where you could show the product, answer questions, then take orders after the presentation. For instance, could you sell out your new Better Place battery packs in just one webcast?
Enjoyed the show again this week.
With all the duct tape, it’s nice to see Mr. Red Green has not lived in vain.
Mr. Red Green is one of my favorite showes
Soon you will be visited by number 1.000000 🙂
Well done …..
The Ivanpah Solar Power Facility, 392 Megawatts… enough to power all the iPhones in China
Speculation time – what caused the latest Toronto Model S fire. Reportedly not plugged in but just come in from a drive (like one of the Fisker fires) Maybe a faulty bus bar connection or faulty cell whose temperature was kept under control by active thermal management when driving but ran away after shut down? (just a wild guess)
Front of car. Non-battery. I would guess air conditioner or heating system.
We have a raging war about
the fluid in the air conditioning system. Daimler say it tends to release fluoric acid and burns holes into everthing. It burns like hell and releases deadly gasses.
The reporter did no background research whatsoever. Refrigerants have had traditional qualification tests of non-flammability and relative non-toxicity. Compressor oil is usually flammable, especially if it is compatible with refrigerant. R-12 run through a propane flame makes a very toxic by-product used in the trenches of WW-1. When a electric motor driven compressor using R-22 burns out, the fried insulation in R-22 produced hydrogen fluoride among other things. There are compressors for compressing breathing air that use a water-soap based lubricant. Trouble is, refrigerants as we know them, are incompatible with water. I suspect most synthetic ester based oils used in compressors on R134-A will burn quite vigorously when atomized and sprayed across a red-hot turbocharger. One refrigerant tested has caused a hubub. Big whoop. It’s a chicken little story.
great show this week..!!!
I really enjoyed it… I like the idea of a web casdpt talking head session… That was the best part of EVCCON. You learn so much talking to people about what ever…
Jack – I’m about half way through the book you mentioned on last Friday’s show “Internal Combustion”. It is interesting to speculate whether with a clear run Edison and Ford might have made successful EVs with Nickel Iron cells. Back of the envelope, my Ampera does 28 – 48 miles (winter/summer) on ~10 kW-hr. A 10 kW-hr pack of NiFe cells would be nominally 250 kg and $2000 – $5000 in today’s money. Cycle life and calendar life appears to be unlimited. Power would be poor though – 25kW max. Availability of nickel might have become an issue – I don’t know enough to assess that.
What is even more astounding is that (if Wikipedia is correct), the NiCd cell was invented in 1898: so Ford and Edison could in theory have built most of the EV1 – apart from the power electronics.
I think that they could have done an honest 50 mile range car with good performance with Nickle Iron. I still think that it is the best chemistry for Solar applications due to the extremely long life cycles… I saw several companies trying to revive the chemistry for that specific purpose…
P.S. I Hope that you are feeling better…
could you have the “Internal Combustion” book in store? Amazon does not have the guts and my local bookstore cannot get it.
I accidently ran into the Bilderberg gang and another – or the same? conspiracy.
Interesting – I bought it from amazon UK on Kindle and I can see it on amazon.com in several formats
Padraic – that’s fascinating: thank you for posting it. I hope they are all buying copies of the Chinese version of my book! I think in the next edition it might be worth adding a footnote to suggest using a faceshield when arc welding (How DOES he do it?)
Jack mentioned he was following the works of Yi Cui an associate professor at Stanford. Here are some findings from a recent publication.
About 6 months ago I used the PowerLab 8 to charge 360 in parallel A123 20ah cells to all have the exact voltage of 3.518 vdc. As you can imagine charging at about 15 amps took several weeks. The last charge was several months ago and now the 360 cells in parallel have settled to exactly 3.353 vdc. I truly have a perspective of how little stored energy is stored over 3.35 volts. I like Jack’s analogy analogy of the bar patron trying to make it to the bar when the bar is almost near capacity.
Now the question :If one was to build a pack with with the least potential voltage sag and the most amp hour capacity what would be the detractors? e.g. If the maximum voltage of an inverter is 420vdc, 420 divided by 3.335 equals a 125 in series.
Here we have one major reason I’ll always pick conversion over OEM :
My cars have a lifetime warranty and I know the maintenance tech personally!
Precisely. Buying an OEM car, you are victim of the dealership. They don’t even like electrics. They can’t get parts. All the Leaf owners in this forum accept the fact that their Leaf is a “very very complicated car” and that’s why they should wait weeks and months for a fix with no loaner car. What if someone should tell them that they are actually MUCH much simpler than the gasoline Versa and that it takes about 10 minutes to read the voltage of every cell in the car.
If something goes wrong with my Model S, I call an 800 number. I am helpless in the face of it.
Looking forward to battery talk this weekend. Lots of commotion in the back room today… 😯