Part of the disjuncture in almost everything has to do with a paradox described formally in a paper that examined test subjects taking an examination on technical material and then estimating their performance. Amazingly, those with the LOWEST scores on the material always rated their performance on the test HIGHEST of the group. The “experts” on the material that virtually aced the examination rated their probably scores MUCH lower.
I call this “”don’t know and don’t know they don’t know.” Generally, we over estimate our knowledge on any particular topic, and grossly so on topics we know little about. I fancy myself a medical expert, which is very odd in that I see a doctor about once every five years.
Actually, I know a lot about a lot of different things. WHich is little comfort, as it makes me generally uncertain about my knowledge of anything. THis is a world where everyone is SURE they have the answer. Confidence tends to trump uncertainty.
Worse than uncertain, in any problem I can usually find a pretty handsome solution. Alas, I am further plagued with a ready realization of all the other problems solutions tend to generate. So if you want to solve the national debt, I can probably work that out for you. But there are 75 corollaries that result, and I’m not sure you’re going to be real happy about some of them.
My refuge is to test. The nice thing about electrical work is you can usually put a meter on it. You can set up some sort of test with usually a pretty definitive result one way or another. Apparently this is not universally admired.
Viewers of EVTV will no doubt be familiar with our achilles heel. No, it isnt’ batteries, though occasionally. It is audio. The irony of video is that it is mostly about audio, and audio is where we fall down most often. Mics whose battery goes out during one of our longish boring recordings. Audio connections that are a little tenuous. Wind noise. Rattles. Lapses and gaps. About the only audio we actually get right is our opening song, and many of our viewers really want us to do something a little more hip and catchy there.
But we do a lot of audio checks and “testing, testing… 123.”
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The past three weeks, I’ve been suffering a huge confidence deficit. I have just NOT been able to get the Autoblock AMP device to drive our tachometer and gas gage, and similarly the HPEVS Curtis controller to present RPM to the tachometer. And so with a car essentially done, we’ve been struggling with pretty basic instrumentation issues.
The nature of these issues is actually not precisely rocket science. A tachometer basically integrates a series of pulses into an average current deflecting a needle. A gas gage basically heats a bimetallic to position a needle according to a variable resistance from the tank sender. So I feel kind of up to the task of dealing with these things. But I was failing miserably.
Ever in the background of course, is the death of my father, two uncles and an aunt all from a particularly clear cut and unequivocal gruesome death from ALzheimers disease. They still debate whether or not this stuff is genetic. Everyone but in the Rickard family. Half of us believe it IS genetic and the other half can’t actually remember but would be pleased to describe what happened 42 years ago on a Tuesday if you want to talk about that.
So it might be that I’m just slipping a little bit. A little bit at a time. Something I would not have precisely invented.
How else can we explain my inability to perform very rudimentary electrical connections and instrumentation tasks.
Well actually there IS another possibility. How about product developers who don’t precisely TEST anything before shipping.
In fairness, there were some assumptions going on here – largely driven by pretty web pages and of course I’m accustomed to unobtainium beautifully described. But in the case of REchargeCar, I think I may have overreached. I wanted them to be done with the development of both Autoblock AMP and Macchina. And they wanted to be done as well. And I wanted it. ANd they of course wanted me to have it. And we were all in violent agreement…..
In truth, I WAS the test pidgeon. And probably not a very good one.
So it worked about well enough to make me WANT it to work REALLY BADLY. ANd so it did work, REALLY BADLY. I’ve apparently blown up three of them. I’m not sure how. And the fourth, on Speedster Nippon, would calibrate badly when hooked up to a laptop or on a bench, but in the car, the gas gage would never go down. As it turns out, the pullup resistor in the reset line was a might too high, and so any noise on the line would reset it. So it WAS going down, it just got reset to full every few minutes – with the car sitting still.
No idea what the HPEVS problem was, but the Recharge guys brought a nifty little oscilloscope and we checked the output of the controller – 1v square wave at 9.6kHz. It doesn’t vary with RPM at all. So it’s not the opto-isolator, the wiring, or anything to do with the tachometer. Whatever they did at HPEVS doesn’t precisely make a tach output on pin 2 as advertised. Software, hardware, who knows? They kind of lost interest in my problem so I have too. We use an Automation Direct inductive pickup on the flywheel – tested and proven and available in our online store. We have rpm now.
And so it goes. We had a very enjoyable visit with ALL the REchargeCar guys along with Nathan KNappenburg of Team Illuminati, the Progressive Insurance X-Prize entry SEVEN. Seven, as it turns out, is having its handmade foam board/fiberglass outline replaced with cabon fiber for a spring tour they plan in conjunction with the release of a book on the X-Prize competition largely featuring them. They would like to fast charge in Cape Girardeau if we can get the PulsaR in operation by then.
So it broke into a little mini-EVCCON in the shop this week with pizza, beer, and lots of tinkering and measuring and testing and theorizing. I actually haven’t had that much fun in months. We’ve been dealing mostly with misplaced or mispacked orders for EV components and badly in calendar arrears projects for Speedster Nippon and Aptima Motors eCobras instead. My Escalade is unfinished. My wife’s Ford Edge sits forlorn. It’s actually operational but has a half of a battery pack not even connected and a couple of other minor “features” that need a little attention. The Mini Cooper has eaten a DC-DC converter (recurring theme here at EVTV). And the entire concept that electric vehicles do not require maintenance appears to be a fantasy of Chelsea Sexton and Plug-In America gone sickly comical. Point me toward ONE that works.
In reality we just have a few too many projects on the table. All of them are kind of known and easily doable, but we are living day to day on what fire burns hottest. I have a LOT of people now with very shiny new Siemens motors and billet aluminum DMOC645 inverters and even deluxe eGearDrives from Borg Warner. Of course, none of them actually WORK yet. And so some focus on CAN bus.
The good news is that CAN is just not that hard. Like most onions you peel, what you find under all the layers is just mostly more onion. CAN is a message based protocol. You make messages and throw them up in the air. You receive messages, and usually find out about three things expressed in eight bytes. Compared even to RS-232 serial communications of the 1980’s, it’s really quite simple. The “ID” has little to do with addressing. It just identifies what the message purports to be. And the data is it being it. All the rest is handled by the transceiver chip. And you don’t really do anything about that.
Macchina is RechargeCar’s attempt at making an Arduino do CAN for a car. They’ve rather ambitiously included ALL five of the OBDII protocols on the device in hardware, but we only have a C++ library for CAN. They have protected the inputs to the chip, which is a big deal for Arduinos actually. The Arduino boards are very inexpensive, which is good because you will blow one up by breathing on it. The inputs to the ATMEL are entirely bare and any spike kills the microprocessor, which is most of what is on the board. The REchargeCar guys have put a zener diode on each of them anyway. And while they were here I talked with Aaron Shephard, their EE designer about BAT schottkey diodes and some other techniques I think are a bit better yet. He not only agrees, but has some special tristate device he thinks would improve on THAT and so Macchina 2.0 is at least conceptual.
They also added a very nicely beefed up power supply system that can take a much wider range of DC input – essentially the automotive 12v range, and convert it to up to 3 AMPS of 5v power. Arduino is more like 500 mA. I actually struggled with a LEM HASS hall effect current sensor only to find I was loading the Arduino Mega power supply down to about 4.85v which was throwing off my ADC readings considerably. So 3 amps of 5V is non-trivial actually.
Enter Nathan and Jack. We’re kind of collaborating on a C++ program using Macchina to control a TCCH charger. This week, we got it off the ground and in flight.
The TCCH charger is kind of an enigma. Bang for buck, this has emerged as THE charger selection for the EV community – almost entirely on price. For $1300 or thereabouts you can get a 4 kW charger that will do the typical 156volt charge at about 29 amperes. I know the math doesn’t work out correctly. This is the typical Chinese modesty. The 4 kW charger routinely puts out 4.5 kW. But they CALL it a 4kW charger. This will charge a 180Ah battery pack in about six hours if you run it down to nothing. That’s pretty cool. Other solutions in this power range are both hard to find and then tend to be north of $3000.
The other thing we like about the charger is it is VERY good at hitting a voltage, and then holding it in CV mode, and then terminating. These chargers, unless assisted by a high quality BMS< just pretty much refuse to burn a car or a house to the ground.
It does have a couple of downsides. First, it is semi-enormous. It weighs about 30 lbs and is roughly the size of a flattish toaster oven. But the big draw back is you have to pick a charge curve when you buy it, and then you have to live with it. It is NOT configurable by the end user. In the lead acid version, it advertises 10 “profiles” you can select. But they have gotten to be very reluctant to do that for Lithium cells. You usually get one. Some are able to wheedles a few to select from at fixed voltages. But basically you cannot configure it and to have it changed you either have to return it to China, or to a guy out in Sacramento that rather rudely insists you need to buy a BMS from him and that whatever curve you DO want is the wrong one anyway. Then he generally holds your charger for about two months until he gets around to it.
The TCCH charger does have an option. You can get them with CAN bus control for another $75. This is their attempt at BMS compatibility. Here is the CAN bus specification for the TCCH CHARGER.
Basically, the TCCH charger puts out a single CAN bus message. Bytes 1 and 2 show the current battery pack voltage. 156.5 volts would have 15 in the first byte and 65 in the second. How’s that for encoding? Bytes 3 and 4 have the charge current in two bytes the same
way. 21.5 amps would then be 0 in the first byte and 215 in the second. The 5th byte is a status byte with each bit representing a different fault, battery dead, battery polarity wrong, AC input out of range, communications failure, etc.
It starts sending this message automatically on startup. If it does not RECEIVE a control message within five seconds, it shuts down, terminates any charge activity, and refuses to do anything further until the input power is cycled. This is my favorite feature. In fact AT ANY TIME during charge, if it does not receive a valid control message from the controller for five seconds – it terminates. So if your Macchina or BMS or whatever gets lost in space from a lightning strike, the charer doesn’t. It terminates charge.
It expects several messages from the controller. BUt only one of them is actually of any importance. It contains the voltage and charge current. The voltage is your target voltage you want to charge to. The charger will charge to that voltage, and then hold it by decreasing the current, to whatever level it has to, to maintain that voltage. During the constant current phase when the voltage is lower, it will use the current level in the message. If it can. If you enter a current HIGHER than it can produce, it just produces all it can until the target voltage is reached.
So the same four bytes with voltage and current in the same format. Byte 5 is a control byte and if you set this to 1, it terminates the charge. We do the comparison to the terminate current actually in the Macchina code.
But quite usefully, you CAN set a current less than maximum and it will charge at that. So for example, if you are on a 15 amp AC circuit that keeps blowing the circuit breaker, you could set the current to a lesser DC output level and reduce the AC draw in this way.
The charger operates from 85 to 248 VAC. So it does not seem to care whether you have 120v or 240v AC input. Lower output on 120vac obviously.
And this week we got our program and Macchina working with the charger.
The trick on the Maccina is a C++ class called MCP2515. In Arduino speak, this class is a “library”. ANd it provides access to all the functions of the onboard MicroChip MCP2515 controller/MCP2550 transceiver that actually does the hard work of CAN communications. This link provides access to a lot of data on this chipset and even general CAN information you might find useful.
One of the neat features of the MCP2515 is that it has several buffers for received messages. You can configure this to set a hardware interrupt from the MCP2515 chip to the ATMEL chip on the Macchina board. This is kind of interesting in that it appears the REchargecar guys used a pin for this that shows up as INTERRUPT 6 on the Atmel and in the Arduiono IDE. Interrupt 6 is kind of interesting in that it doesn’t precisely EXIST. Actually it DOES exist and IS supported in the Arduino IDE code, but it isn’t documented as one of the Arduino MEGA interrupts. So you can be pretty certain this interrupt is not going to be used by other shields and so forth.
The interrupt will go low whenever a message has been received and placed in the buffer.
And os in this way, you use a statement like “attachInterrupt(6, interrupt service(), FALLING);” to connect this external hardware interrupt to a routine in your program to process incoming messages. How cool is that? Well, pretty cool actually. So your program doesn’t have to waste time checking for incoming messages, it can do whatever you want it to full time until the interrupt is received. The microprocessor will THEN stop your program, and go run the routine you provided a pointer to in the statement to process any incoming messages. When it is finished, your program continues right where it left off. So a bit of real time programming without much effort.
BETTER. The MCP2515 has a series of masks and filters you can apply to messages before they ever show up in the buffer. And so if you are on a CANbus with tons of traffic, you never get an interrupt at all until a specific message ID shows up that gets past your masksa and filters.
This reduces the overhead on our little ATMEL by about three orders of magnitude. And so it doesn’t need to do ANYTHING with respect to CAN other than send a message once every five seconds. And it can be the same message every time.
There are actually a couple of shields out there with MCP2515 chips on them for Arduino. Also several REALLY BAD classes for MCP2515 and all of them named, conveniently enough, MCP2515. The RechargeCar guys did a pretty good one. And then Collin Kidder, who happens to be working on a DMOC645 as it so happens and did the only Mercedes Benze 190SL conversion we’re aware of (gorgeous car) improved it a bit in January to include the filters and masks function. RechargeCar has a pointer to the GITHUB on their website.
So I’m a little giddy about all that. We’re ordering in a bunch of these CAN bus version chargers and going to offer the charger and controller for about $1700 which I think will be a fantastic value proposition for a charger, in a world with a great gaping hole under the title of CHARGER for electric vehicles. We await PulsaR (still) and we have filled in with a few bargain priced Brusa’s which are going very quickly. So we need a good charger in our line of EV parts.
So we’re ready to mail em out! Great! Excellent!
Well not quite. You see, getting it to work once in a row on camera is not precisely making a development project road ready. I’m sorry. Only really GIFTED engineers and scientists can do that. For dumbies like me, we have to slog it out by hooking it up and watching it work about 60 dozen times and trying to figure out little glitches and gotchas that, and I’m just guessing here it is true, but MIGHT spring up along the way.
So another cool project. We’re building the MOTHER LODE. The battery bank in steel box on wheels I’ve always wanted. We have 73 Thundersky 100’s in it now, all strapped up. We’re adding cabling to it. And probably fusing, contactors, JLD404 meters, etc.
This will serve as part of our new test bench – the electric car conversion with no car – and should position us to test PulsaR when it is ready – charging cars from the MOTHER LODE and the MOTHER LODE from cars quite indiscriminately. WITH a PulsaR it will eventually be a fast charge station. ANd meanwhile it can power our test bench to get the DMOC645 and Siemens motors turning.
As such, it should also qualify as officially the longest range electric vehicle ever built. It is basically a battery box on wheels, and it will go as far as you care to push it on a single charge. This is the one that WOULD HAVE won the X=Prize no doubt.
In any event, lots of testing of the Macchina. And lots of testing of the TCCH charger. And that’s the only way I know how to build something and get it to run more than one time in a row.
42 thoughts on “TESTING…TESTING…1…2…3….”
Finally, a charger that meets my needs on the Ranger Project. I had about settled on the TCCH (Elcon version) – sans the CAN bus – when you mentioned the possibility of a complete package last week. Needless to say I was surprised to see the quick progress on getting it connected and running with the Macchina. As you indicated, one test on video does not make a completed product, but it a huge step.
So sign me up. When will they be in the Store?
How about “pretty soon now”. I don’t expect a lot of problems. We have to come up with a little relay. The TCCH charger has a 12v output but good for 50 ma. I neeed to find a little relay to switch 12v to the Macchina using this. In this way, power to the charger causes 12v output which closes relay and starts Macchina.
That way they both come up together each time. Understand 999% of the time, you just want it to run. Once per blue moon you hook ANY device with serial terminal to it, and enter a couple of key strokes.
We were going to have a display, but decided it was just overkill for the little you might ever look at it.
We’ll probably package the TCCH CAN adapter, the relay, and the Macchina all in one enclosure. Connector to the charger and a 12v input from the car.
Could you use a MOSFET or DC Solid State Relay? I had good success using a beefy MOSFET in a bottom balancer
Doesn’t that hold true for all EV’s Jack. They all go as far as you can push them on a single charge.
Maybe. But in this case you have to push it by hand.
Yes I just had a problem with my charger. I planned to use 38 cells with my AC50 and dropped to 36 on advice from my fellow-travellers in this community. My charger was set up for 38 cells. TCCH have made me up and sent some kind of one-time auto-recalibration device which when plugged in will carry out an automated lobotomy and load a new charge curve. This saves the horrendous round trip shipping costs but cost a bit and sadly doesn’t seem to be configurable.
I should say that I have had good experience so far dealing with TCCH. They have been fast, efficient and courteous. My first “Houston I have a problem” email to them about the change in number of cells was sent on the 9th Jan and if DHL had got their act together, the device would have been in my hands on the 16th. That would have been a swift turnaround from the next town, never mind from the PRC
That’s the first time I ever heard of them doing this. I have been on them for two years to just do a configurable charger. They just won’t. So now here they are mailing a one time configurator. Why don’t you sniff the link and figure out what it’s doing to reflash that flash memory?
That was indeed in my mind although I don’t want to risk knackering either the charger or the configurator. I have a feeling that your Macchina/CAN approach is probably more open and supportable
John, why the decision to drop down to 38 cells? I switched to a higher voltage contactor, reset one parameter on the AC50, and no apparent problem with 38 cells in my Saab Sonett conversion. See AC50 EVTV forum for more details. Eric Kriss
Let me guess – John wants to stay within “Extra-low voltage” (50 VAC or 120 VDC) for the same reasons I do, which is that going over those limits at least in these parts means permits and the like. 36 cells fully charged with a wee bit of load should be nicely under 120 VDC. See http://en.wikipedia.org/wiki/Extra-low_voltage
Here are some links about the battery problems in the 787, I think that they might be interesting, for meny different reasons, there are meny interesting bits of information in these articles I think:
There might be a business opportunity hidden here, for some of the bright people here on this blog, that could put together a very safe and reliable battery pack with the CA cells, the battery straps and Nordlocks, and keep the betteries within safe operating conditions, bottom balancing them, undercharging them, and not over discharging them.
It is not the easiest of business adventures, but that also mens that it is hard for other people as well, and that will keep the competition very low, and with the knowledge that Jack and others have provided about the CA cells, it seems like a very good fit for the application that Boing is using them for.
Full disclosure, I have no clue about delivering products to the aviation industry, and all my battery knowledge comes from watching EVTV and reading the blogposts, so with that disclaimer, their might still be an opportunity there.
Just out of interest for the sake of speculating, what would it require, and cost to develop and put together a demonstration version, or proof of concept version, that could be submitted to Boing for testing and approval? 🙂
Thank you for a very good show.
One more “expert”, advising more cooling instead of not overcharging batteries:
I have had a question for a while and this show has re-ignited my interest.
You mentioned that you do not like Anderson type connectors (used in the Recharge Car power disconnect), and you have not met many connectors that you did like. Could you be specific about your reasons for dislike?
That is scary. Was your charger can bus controlled or did it use the enable line?
Hi Jack, My elcon 4k (120v) went coo coo on me back in october. It now just turns on and charges at 30amps untill???. I didn`t want to stop driving the car right away ,and I did not want to overcharge the batteries, so I programmed the jld404 to shut it off at 126volts. Would you forsee any problems doing this? s
It’s the same as doing the CC phase of the charge and just not doing the tapering CV phase at all. As long as your meter ends the charge in time, you shouldn’t have a problem, other than not getting every last bit of juice into the pack. You may in fact lengthen the life of your pack, in exchange for some range. If you get enough range as it is you could keep charging like that forever.
Most alarming. This is the first failure of an Elcon in this mode that I have heard of and it is most alarming. Overcharging cells is the way to a horrifying fire. It is a miracle that you caught this before it caused one.
We routinely undercharge the cells ANYWAY so omitting the tapering charge is not only no problme, but the tapering charge is really almost irrelevant. We are intentionally NOT seeking to fully charge the pack anyway. BTW, this is emerging as a strategey for essentially ALL the OEM electric vehicles as well.
I personally would not rely on the JLD404 to terminate an unintended charge. It is nice to have as a backup on the enable line to this charger. BUt I wouldn’t generally rely on it. You need a properly operating charger in your car and it is very important to have one. I wouldn’t play any games with this at all. I would want BOTH. A properly operating charger AND the JLD404 monitoring it as a backup.
I’ve been thinking of having a meter controlling the main contactor so that it would only engage it if pack voltage is within defined parameters. This way it would take care of both an overcharge and over discharge scenarios with a single setup. Yes, the battery pack should bounce above the set limit once load is disconnected to allow charging again. The set limit would however be below controller minimum voltage so it should never be reached, unless there is a problem which would need a proper check of the systems anyway.
This is why I am putting a PLC with a 0-150V to (0-10V) Transducer in my system. The PLC will power the relay that allows the charger to work. If the PLC sees that the pack is getting above about 128-130 volts, it will shut the charger down.
I just dont feel comfortable relying on a single point of failure on the charging circuit….
The chances of the PLC and the charger and the relay failing at the same time would be quite low….
Do you envision a touch screen shield as an option on the macchina system?
There are several LCD’s with and without touch available for the Arduino Mega, which the Macchina is based on. Here is one:
2.8″ TFT color LCD shield with touch screen interface. Its large (320×240) screen resolution, 65K color space and touchscreen interface are ideal for developing nice user interface device.
Thanks for the info .The charger was being shut off by the enable line to the jld404.Anyways, I took it out of car this morning a returned it for repairs. thank God for the jld, Now I won`t be needing a boeing sticker for the side of my car
Amen to that…
Re: your audio situation. You undoubtedly have more experience than I do in this area, but when I was doing some video recording, I grew to mistrust battery powered microphones. They lose power at the worst possible time. I switched to wired microphones.
Especially when you are not moving about, just sitting at the table, you should do just fine with wired table top microphones. You could even get ones with a retro look! http://www.amazon.com/Samson-Meteor-Studio-Microphone-Cardioid/dp/B004MF39YS
Even when I was moving back and forth to a white board, I did not really have that much difficulty managing with a wired lapel microphone, and I did not have to reshoot video due to a lost audio track.
Just a thought.
I am also using a PLC to controll all interior and exterior lighting on my conversion vehicle. I have chosen the Millenium 3 model from Crouzet. I am curious about what PLC you have chosen. The Millenium 3 line has a 12 volt modle. That was a big factor in my decision. The base unit has 16 inputs, both digital and analog. It has 10 output relays.
I work for an Allen Bradely Distributor. I am using the MicroLogix 1100. The model I am using has 10 10-24VDC inputs (3 can be high speed inputs for pulse counting up to 40Khz) and 4 high speed 24vdc outputs and two relay outputs. I am also using a 4 channel Thermocouple input card. In addition to thermocouples, the inputs on this can can be independently set to read +-50ma or +-100ma so it is great for keeping track of AMP/Hr and Kw/Hr going into and out of of the pack with a simple shunt. I have a 800A 0-50mv shunt. The analog card is signed integer accurate to 15 bits of data so that works out to an accuracy of about +- 200ma. (800/32768) The Micrologix 1100 does have an ethernet port to make programmign easy and HMI updates faster than is possible with serial data.
The Base of the 1100 also has two 0-10V analog inputs. They are only accurate to 10 bits (0-4096) I might use one of these for the 0-10V output on the pack voltage transducer. That will give me 150Volts/4096 or 0.03V pack accuracy.
I also have a Spectrum Universal Analog 4 channel Input/4 Channel Output card. I think I will use one of the 0-20ma analog outputs to drive the gas gauge in the Thing. I plan to replace the needle assembly with a 0-20ma meter needle. Finally, I have a 8 channel Relay output card for what ever… I can add one more I/O card if needed.
I am am also using a little 4″ Color HMI touch screen called the Panelview Component. It is fully programmable.
The Micro 1100 is available in a 12vdc version, but I chose the 24vdc version because it has two PWM outputs and I have to have a 24vdc buss for the HMI anyway. Also the transducer for the pack voltage also operates on 24vdc.
I also like the fact that the Little Micrologix 1100 can do 32 bit floating point math. This makes calculating Amp/hr a little easier that trying to do it in integer math only with less round off error.
I hope to read some of the Curtis controller data through the serial port. However, I might add an Modbus to CAN bus gateway so that I can read the data out of the controller using CAN bus…(Not sure this is possible as Curtis does not publish their CAN Data Mappings )
Your Crouzet PLC should work fine. I am using the AB stuff because that is what I know best and I get them at cost….
I suggest for various Adrduino items like screens, have a look here:-
A few experiences…. a little bit off-topic here, but maybe useful for somebody
Fuel-gauges of many newer cars (VW from 98 and later) have “switched current” that means the measuring current flows only
in short impulses. This makes it impossible to drive them by simple pwm.
in this case it is much easier to drive them simply by applying a voltage (normally about 0-5V)
Atmegas (as used on Arduino shields) have some problems when being disturbed during booting
This may end in a loss of EEprom-data sometimes……….
Placing a 18V suppressor-diode and some extra capacitors at the Power-Input is the easiest thing to be done.
The round table discussion.
EMI, RFI, EMF, You name it. The whole bundle. Due to low power digital equipment we really need to get to grips with the black art of clean up the electrical feed, signal via balancing feeder like canbus and ethernet and best means to avoid radiating and picking up these sproggies.
Jacks Mini for instance has done odd things with magnetic and current feedback. Clocks reading bad. BMS’s picking up bad signals killing packs and burning houses down.
Lets not forget the issue has come up as a test requirement in many EU countries to ensure electric vehicles do not give off high RF fields nor become affected by them too!
How about a discussion/video on it whenever Jack? 🙂
Jack does not like 12V lead acid. Most electric cars do have a medieval 12V system including its own 12V lead acid battery. Why?
As a hamradio operator I do need 12V and I have seen 120 Watts from the lighter socket is not enough and 27 amphere hours (Mitsubishi i-MiEV) is not very much either. I never could use 12V from the socket in our old ICE car at least. I always had to use a filter for my radio and I have seen they do sell filters for HiFi.
So a filter between the 12V bus and the arduino is a good idea and easy to do. A filter that isolates the DC-DC from the 12V bus with a big capacitor towards the 12V bus, a coil and an 18V zehner towards the DC-DC. There are those hybrids between capacitors and batteries. One of those parallel to the 12V bus might help too.
The killer must be a spike. Where do they come from? A coil and a contact opening. Any electric motor could be. The traction motor most likely.
Who says the killer is on the 12V side?
A filter on the HV side of the DC-DC is easy to do again because there is not much current. You could use the coil from one of those HiFi filters but drop the board and get decent capacitors because we have got high voltage after all.
The motor controler feeds the 3 motor windings with 8 kHz PWM. Those pulses must be seen on the battery side as well. That looks like the prime candidate.
You have stated the problem rather succinctly Andy. It is a black art. Everyone poses as an EMI/ESD expert, largely because most of them think it is easy and assume expert status because of their ability to restate the problem. Having lived with this stuff in my military contractor days, I can say only a handful of engineers in the entire country are any good at it. I’m not one of them.
Perhaps I can track one down and bring him on the show to do a walk around of a car and point out the major items.
Excellent point Jack. Dealing with electrical noise and interference is about 1/2 of my job….. Some of the things I have seen I would has swore we’re not possible until it had to wall with them….
This is my main adversion to these little processors. It is difficult to harden them to work n a car…
I am certainly not qualified, but would be happy to help if needed…..
This test is our major problem here in europe……
On the one side our politicians demand for much more electric vehicles
but on the other side the conditions for getting them street-legal are becoming worse
from week to week…….at least we dont have to bring six prototypes for crash-tests…… 😉
for vehicles after 2002 it is almost impossible to get any certification without having
the complete vehicle tested and for older vehicles it is “enough” to have documents
for EVERY!! part you mounted into the car. So we can choose only very few components
that have already been tested succesfully or if someone is the fist to use a special part,
he has to do the “EMV-Test” with his vehicle.
In newer cars, we are not even allowed to install a radio without that “E”-Sign……
That is the reason for that low number of conversions here in europe! Here in Germany
it is at least possible, but expensive, in Italy for example it IS almost impossible for private people.
At the point when a conversion does its first successful test-drives, the fight against
all those buerocratic windmills is just beginning……..
On the other side, it is clear, that there must be some regulations. Place Your handy
beside the PC-speakers and You will hear if somebody calls you before the phone rings.
What will happen when it is near the cables between throttle-pot and controller?
Boeing could save billions of dollars by hiring all of us as battery conultants.
On a whim (no chance of being noticed), I did fax them offering input for free and saying in effect that they were an embarrassment to the EV community
Haha. Nice one John!
I wouldn’t jibe Boeing.
Yuesa attempting to do what they have no mileage in? That’s something else..
Self build radio hams are good guys to listen to; like Peter. Lead acid batts can be good…. mainly for the spare parts market and keeping the auto workers happy. But if no cell ever exceeds 3.35V each.. What can it matter?
Jack, I’ve built nuclear bomb hardened equipment. Looked into systems and wondered “WTF have they done that for? It’s only an external lead to set off a detonator”.. Without knowing the issues. Some things I’ve done seemed so silly to me at the time yet were so important. Like sticky aluminium tape across gaps in the joints of corners etc. Co-axial cables with twin leads inside. Joints between items tested to many amps and dropping millivolts. I’ve personally made boxes for projects that needed a thicker box! Not forgetting tantalum beads, feed through chokes and then the chunky low pass stuff for power which can create more issues.
Hint. If we can only send data via optical cable. Most of our woes would be helped greatly.
I though the thermal runaway scenario sounded familiar. I can’t believe they’re using lithium cobalt based batteries. Aren’t these the batteries that have restrictions on the number of spares you can take on board when flying? Why? Because they will catch fire and or explode. No BMS in the world is going to stop that. Another case of an engineer only caring about the numbers on the paper, not caring about the history of failures. I can see him sitting there looking at the energy density and saying “this 50 pound battery will do the work of 200 pounds of that other battery” and ignore the fact that they can go into thermal runaway.
What gets me is the idiots in the press. The reporter sounded like she knew nothing about the fact that there are 2 dozen different chemistries of lithium ion batteries. She implied that ALL lithium batteries are fire hazards (aka dangerous) not just the ones that can go into thermal runaway. They never stop to learn anything about the subject matter surrounding the the story. What they don’t know they make up to the detriment if us all.
This morning it is running on the news that the NTSB has basically cleared the batteries and is looking at the “battery monitoring system” as the culprit.
yay. My faith in them just went back up. It will be interesting to see where this leads the BMS developers.
BBC reporting much the same but substituting “JAL” for “NTSB”. Fix being costed at $350 Million – disregarding the fact that no one in authority knows what the problem is, how DO they spend that much money on this kind of thing?
Because the obvious answer is MORE monitoring, not LESS…
Anyone interested in electric cars go have a look at this:
I guy has posted pictures of the inside of the Tesla model S pack.