Ed Clausen provides a seasonally appropriate description of a somewhat advanced application of postive temperature coefficient heating to his BMW 320iS electric car. The 320iS is actually a somewhat rare and very interesting BMW and may be the perfect electric vehicle car to start with as a donor. It was the precursor to the e30 series that has been extremely popular for many years now. We’re starting to get a little excited as this is a four door all weather car in a cold weather region of the country. It features a nice manual transmission that is mated to one of our Siemens 1PV5135 motors, an Azure Dynamoics DMOC645 inverter, and our Generalized Electric Vehicle Control Unit.
Ed drives a Leaf and found it sufficiently engaging that he very nearly gave up the idea of doing a conversion. I’m kind of confident that when he completes this BMW, he will see things rather differently, having a longer range from his 400v 180Ah pack of CA series cells. As the 180’s almost always come in at 200Ah, we’re looking at an 80kWh pack – larger than the Escalades. He is a bit critical of the Leaf’s short range. If he remains on the good side of 4000 lbs, we think he’s going to be very surprised when he drives this thing 200 miles on a single charge the first time. The battery weight will actually IMPROVE the BMW ride, and the Siemens will drive it very pleasantly. His dreams of competitive drag racing may take a bit of a blow with this power plant in a car that size, but with the manual transmission, I think he’ll find it pleasant. And with his 1500 watt PTC heater, apparently quite warm. His location in Methuen Massachusetts probably doesn’t get a great call for air conditioning actually.
My own project this week stems from an infuriating change in the CALB specification sheets. In fact, as I review much of the information online I’m finding that the available info on LiFePo4 cells is actually losing ground, with myth and conjecture creeping into all but the Scientific journals and papers, which are increasingly becoming pay per view.
The heart of the issue is that they have reduced the maximum charge rate to 1C for not only the CAM series cells, but oh so quietly for the CA series as well, which HAD been rated at 3C.
Something must be afoot and so I spent some timing talking with our counterparts at CALB on how we got there. They noted two problems, temperature and cycle life. I asked for the data on both several times and it gradually came to light that they don’t have any. But they really like this American custom of just typing yourself smart. It eliminates a lot of testing expense.
And so they noted that my test of 3C in 40Ah cells was not persuasive because it is the same materials as the 72Ah or even 180Ah cells, but the actual current rate goes up and these higher current rates cause an increase in temperature. When I inquired as to what level of temperature, they became a bit vague. And as it turns out, they haven’t actually tested anything to make that determination.
The cycle life position is much more assured though. I pestered them repeatedly for the “test” data that shows decreased cycle life in high current charge cycles. They finally admitted they had no “test data” in the cycle sense, but had firm REPORTS from one of their customers in China who used the CAM72Fi cells in a BUS. After about 800 cycles in a bus, regular all day daily service, they were losing cells. The fast charge rate was a little vague. They were doing a couple of hundred amps of REGEN charging – not at a charge facility at all.
I have six or seven hundred problems with all of this. If they are doing a couple hundred amps of regen on a bus on CAM72FI cells, that implies to me that they are DISCHARGING them routinely at the 700 or 750 amps level during accelerations.
We have demonstrated that these cells can produce 10-12C of discharge current for periods up to 30 seconds. This is of interest if we want to take advantage of the maximum power capabilities of any particular vehicle. That is not to say we advocate USING the maximum power capability of your vehicle in any sort of continuous sense. It means if you needed, for some reason, maximum acceleration for 15 seconds, these batteries would provide the power. You would not be power “limited” by the batteries.
Now I’m picturing a single string of CAM72 cells trying to drive a BUS. Where ALL accelerations are more like 20 and 30 seconds and at max current.
I use 400Ah cells in the Cadillac Escalade. Indeed, I have the motors and controllers to do 2000 amps at 170 volts in this beast. And the 400Ah cells will easily do it. But generally in driving it it is an EVENT to do more than 750 amps on any particular acceleration. I CAN do 2000 amps. I HAVE done 2000 amps. But that’s just not how we roll almost all of the time.
If you are constantly tapping your cells for the max power they can put out, it will certainly decrease battery life. And it is almost certainly not because of excessive regenerative braking.
So do size your battery pack to your application. If you are doing 600-700 amps dozens of times per drive, I would want to see you in a 180Ah size battery cell. It will simply last longer.
So I was feeling a little bit like I’d been thrown under the bus on the maximum charge rate. So this week we ran a basic test to see what the temperatures would be on a 3C charge of a 72Ah cell – a 216 ampere rate. In absolute terms, this is of course much higher than the 120A we tested the CA40FI cell at.
Take a look at the resulting charge curve. In our normal charge process, we might have a fully discharged pack to 2.75 volts per cell. When we apply current to it, it immediately rises climbing quickly to 3.00v and perhaps a bit beyond. But by 3.05 or 3.10 volts, it has passed the “knee of the curve” and enters a much flatter area of charge where large amounts of charge current result in very tiny increases in voltage. This continues to about 3.45 volts where it again turns up and starts to increase in voltage at an accelerating rate. By 3.65 volts it has gone pretty nearly verticle.
If you examine the graph of the 40Ah cell at 3C or 120 amperes, the CURVE is identical. But it is DISPLACED in voltage. Now we rapidly increase to about 3.40 volts and THERE we find the first charge knee. Then a long flat period to 3.65 volts where it is not only not straight up, but it is JUST starting to bend upwards.
This is ENTIRELY consistent. At a higher current level than normal, our voltage will be higher than normal as well.
We talk about charge voltages a lot. I have repeated over and over and over that they are not real and in fact do not matter at all in and of themselves. In the CONTEXT of a procedure, given a specific set of circumstances, we use voltage because it is EASY to measure. But it is NOT state of charge and you might think of it as more of a PROXY for state of charge – all other things being equal.
Which of course in this case they are not. Our procedure assumes a standard charge rate (1/3C) and a standard temperature (25C). If you change that, the meaning of the voltage goes out the window.
The manufacturer recommends 3.65 volts. Now understand that historically, these same sorts of LiFePo4 cells recommended for a long time 4.2v per cell. At some point, after we determined that the KNEE was pretty much done at 3.65v, this was dropped to 4.0v per cell. Still later, they came to 3.65v per cell.
But even that is as an example. And it again assumes 1/3C current rate. At 126 volts, we were lucky to have 30 amps from our little chargers into 180Ah cells. That’s half of 1/3c. More like 1/6th C. And at 1/6th C, you are going to result in a higher state of charge than you will at 1/3C – charging to the same proxy voltage of 3.65.
And so you find Jack the Wide One recommending 3.55v per cell as the target voltage. Extra safety? Well actually a bit of extra reality. We’ll be at about the same point charging to 3.55v at 1/6C as we would be at 3.65v and 1/3c. It is easiest to explain this by saying that we are already at the steep end of the curve and there is no real range to be had here. The CURVE matters. The voltage really never did.
Here’s another example. This is the DISCHARGE rate comparing the discharge curve of a CA180Ah cell at 88F and at 0F. In this case, the curves are NOT identical, but more importantly, the voltage is again displaced. Normally, we would consider 2.80v as being very nearly 100% discharged. But we can see from the chart that we are pretty much there at the BEGINNING of discharge if we are at a temperature of 0 degrees.
All of this long wind is to introduce you to the result graph of our 3C testing of CAM72Fi cells. These are the SAME chemistry as the CA series, but manufactured to optimize for size and weight. And while 3C at 40Ah is 120 amps, for a 72Ah cell this is 216 amperes. And so it displaces the VOLTAGE further. But again it does NOTHING to the charge curve itself.
In this event, we begin charging at a known SOC based on a very measured 2.76volts per cell. In fact all three carefully balanced to 2.76v. By ONE MINUTE of charging, putting in about 3.5 Ah of energy, we are already above 3.60 volts. We see the usual notch as the cell warms up a bit, and then we do in fact turn the knee and see a long flat period of around 3.55v per cell. We should be done charging right?
Not quite. We cut it off at about 3.7v. But we had put in about 69.1 Ah at that point. And as you can see from the curve, we had JUST started to bend the upper knee of the charge curve. Indeed, after charging, we disconnected the cells and within just a few minutes they were done to 3.33v. We normally looke for 3.37 or 3.38 static in a cell we consider “fully charged.”
We actually have a lot of head room to play with here. Recall that we can charge these batteries to 4.2v.
We have recently been discussing CHAdeMO fast charging for the DIY custom conversion cars and we are bent on doing it. But it is a different world at 125 amperes than it is at 11 amperes, and this test illustrates why.
We recently had a forum discussion where a couple of live Leaf drivers in Europe were reporting that some CHAdeMO charge stations would give them 80% charge, while others seemed to cut off early. And they were certain the EVSE was doing it. No matter how I explained that the charge process was entirely a function of the software in the car, they “proved” me wrong by noting different charge times at different charge stations despite pushing the button a lot. When I inquired as to voltages and CAN message data, they actually accused me of demanding that they do my work for me. I was actually hoping for some data rather than grandmother observations of the weather and what it means. I don’t like reading messages from God in cloud formations.
I think if they check again, they will find that the short charging stations are putting out a higher level of current (perhaps 50kw) than the stations that appear to give 80% charge (at 25kw). I’m just guessing.
The issue is that the Nissan Leaf uses LiMN2O4 cells. They are nominally 3.7v charged to 4.2volts – identical to our Renault Influenza packs. Again, the software in the car advises the EVSE of the target voltage. The EVSE actually DOES advise its MAX current. But if the firmware in the car does not take that as an input and calculate the charge voltage based on the charge current, you will get a different termination at high currents than you will at more modest ones.
And I get the idea that the top balancing adherents are devoted to this concept based on LiMNO and LiCoO2 cells, not LiFePO4. They appear very afraid of going much over the 4.2v. I really just don’t have the direct experience with cells of that chemistry to advise what happens when you exceed 4.2v, but we are just BARELY turning the knee there at all. Really we are NOT on the knee at that point. So I suspect it won’t hurt them actually. But I don’t know that with any authority.
So in devising our software for CHAdeMO fast charging, we need to map what the charge voltage should be based on the charge current. As we can see from the CAM72FI cell, we needn’t bother at all with a tapering current. Just figure out what the voltage is and cut it off there – quite close to 100% charged in 20 minutes.
Of course teh maximum CHAdeMO current is going to be 120 amperes – not 216. And more likely, the maximum current will be something like 80-100 amperes.
I’m actually considering throwing out voltage as a determinant of SOC for fast charging. We could go for a deltaV/deltaT scheme where we monitor how quickly it changes in voltage. For example, when we first go on charge, IF the voltage is LESS than some absolute, we note the change in Voltage compared to the change in time. If the voltage quickly goes over the absolute, we know someone has just plugged in a fully charged vehicle and we terminate.
If it does not exceed the absolute voltage, we simply calculate what the deltaV/deltaT IS and save it. This will diminish as we cross the knee and go onto the flat part of the curve. We simply keep timing/calculating it in a running total, and when it again goes back UP to equal the rate of change we first encountered, we’ll know we are fully charged and terminate the charge process. We can further count Ah to confirm, and check for absolute voltages for example. But if we had a bad cell that went through the roof, it would show up on this deltaV/deltaT and we could detect it before the whole area burned to the ground.
As to the CAM72 cells, we reached a maximum temperature of 42C. As the non-aqueous organic solvents in the cells start gassing at about 80C, I’m pretty comfortable here. The normal advise is to keep below 65C in temperature. The manufacturer’s spec sheet says charging is ok between 0 and 45C and we are within. True, we started at a 56F ambient, and we are not packed with 50 other cells in a box. But there is a lot of leeway here. I do NOT believe from this test that temperature is a limiting issue at charge rates up to 3C.
As to cycle life deterioration, I have to say that while I’m unconvinced, we have also proven nothing so far here and it remains an open question. But in any event, given our use patterns here at EVTV, an 800 cycle life would be more than adequate. Indeed, we have several cars I would LOVE to upgrade to take advantage of these new cells as the ones in the car are so serioiusly obsolete. But how can you do that when the car still runs at very nearly 100% of the original range capacity?
Perhaps I can persuade a couple of our more attentive battery testers to take on the challenge of 3C cycle testing.
66 thoughts on “FAST Charging – Can Our Batteries Take the Charge?”
First Solar Road has been constructed…actually its a bike path, but pretty cool to see.
I was thinking about this the other day. I think that we should put roads like this in national and state parks to promote Level 2 charging. This way to get the benefit of solar without altering the land scape much….
Thanks for all of the testing jack. It really helps see how the cells handle this type of current. I was going to measure the temp of my 180 cells until I realized that they never seem to be more than a few degrees above ambient and lost interest…
I did not think Ed was using 180Ah cells, I thought they were 100’s… That should be some impressive range indeed…
You are probably right. I think Jehu is too. I probably just pulled that out of my ass.
Yes, I think he is using 400v at 100Ah which would be 40kWh and a 100 mile range.
I’m on it. You might recall that I’ve started high rate cycle testing of CA40s: two packs in parallel, one charged at 0.5C and one at 3C (120 Amps). Both discharged at 0.5C. I am having a hugely entertaining time capturing voltage data reliably so the rig is awaiting modifications and is not running as I write, but my observations so far are fairly consistent with yours: terminal temperatures with the high rate pack climb about 20 degrees C above ambient in 15 minutes (I am only discharging about 75%).
Initial results on a very small number of cycles suggest that the high rate pack is losing capacity faster – but not catastrophically so. It looks to me like a trade off: if high rate charge drops your cycle life from 2000 cycles to 1500 (for example – the data are not in yet) then that is a fair trade off for greater usability. After all, 1500 cycles is 4+ years of daily use, and by 2018 we should be paying peanuts for a kW-hr and getting 100 Amp hours out of something the size of a cigarette packet. And if only one charge in 50 is at that rate then my guess is that it shouldn’t make any significant difference.
From what I know I’d slap a Chademo inlet into the Civic without giving it a second thought
I agree completely with Ed Clausen that some of the DC 12 volt legacy motors on our conversions should be optimized for speed with FET switched PWM. The Pierburg already does this internally so only a stout control PWM is need to tame those little power hungry kitties. (I have two) For my conversion I’d have to put three power FETs on the drive board. One for the heater motor and two for the OEM motors mounted on the radiator. Simple open loop control strategies would work quite well. Having actually used my Arduino Due now, I’m a lot less intimidated by the challenge. I’ve used three different micro-controllers now and the Arduino Due is, without a doubt, the easiest.
I took one of my Better Place Modules to 137.6 or 4.3 volts per cell, originally by accident. I was checking it every 15 minutes and dozed off watching the news. When I got back out, the amps had dropped from the original 18 amps to around 2 amps but the pack was at 4.3 volts per cell. I used some very scientific instruments (my nose, hands, and ears) and did not smell the sweet smell of electrolyte or hear any hissing and the aluminum battery cases felt the same temperature as the surrounding metal in the car. I ran that charge down and did another charge to 4.3 volts, this time being present at the end of the charge. For what it’s worth, they didn’t seem to gas or heat up. If I recall, the charge curve did start to turn up. I had the cells run down pretty low on one of the charges and actually got it to take 60 amp hours.
I know installing pwm for those heater motors look like I gain, but I’m not so sure. All of those resistor rpm reducing coils are always installed in the heater air stream, and what do they do ?? produce heat ??
Now of course if they are also used for cooling, its another story.
Here in Arizona it’s cooling 99% of the time.
On Ed Clausen’s PTC: shouldn’t the PTC be at the intake side of the fans? That way the fans will be pulling air. That’s the usual arrangement I see with impeller fans.
I do believe he has the PTC elements exactly where the original heat exchanger was. I tried using the same elements he had in my conversion, but with much less success. I got hardly any heat out of them. Admittely I was running a lower voltage and less of them. Hopefully he has more success. In my case I just gave up and installed a heater which burns ethanol among other things to get enough heat to handle our below 0˚F winters.
The one thing that jumps out at me from this data is that the voltage curves look identical for the same C rate charge, the temperature rise is quite a bit more for the new cells. It looks like the weight and volume savings has also increased the temperature rise on the cells. The CA cells only rose 10 (73-83) degrees during the charge while the CAM cells rose 52 degrees (55-107). That does not explain why CALB lowered the rating on the CA cells as well as the CAM (that is just odd). Thanks for taking the time to document all this. Love the battery lab episodes!
Just a thought after I posted. Put a set of bottom balanced cells with a CA60 and a CAM72 in series and fast charge about 50AH into it and see if the CAM increases in temperature faster.
The difference in temperature is simply a difference in power. Our tests of the CA series was performed on a CA40FI cell and the current at 3C was 120 amperes.
In this test we did 3C on a CAM72FI cell and so the current delivery was 216 amperes – almost 100 amps more.
The MATERIAL is the same in both cases, there is just more of it in the CAM72. So the diffusion is the same on both cells, but the applied power is much greater – more heat.
I fear if you did 3C on the CA180, 540 amperes, the results would be untenable. But this test was a bit extreme by design. They claimed a temperature problem, but we never even went past the spec charging temperature of 45C.
As a practical matter, for now CHAdeMO is limited to 125 amperes in any event. My conclusion, and really the heart of what we were trying to demonstrate – CHAdeMO fast charging with the CAM 72 or CAM80 cells is a no brainer. It will work great.
You can also see a bit of an advantage all teh way around for LiFePo4 vs. the other chemistries. More headroom voltage wise.
IF you can find a full blown CHAdeMO charge station that will actually do 125 amps at say 370 volts (46,250 watts) a CAM72 equipped vehicle could be essentially fully charged (not just 80%) in 35 minutes.
As we attack the CHAdeMO kit issue, I think you will again be favorably impressed that in our world, you can make it do what you WANT it to do, without the built in “protections” imposed by the OEM who designed your car. We can do 97% instead of 80% with NO damage at all. There is absolutely no need for a “tapered” ending to this thing. We’ll charge to 3.7v per cell and when it hits it at 125 amps, you’re DONE.
I was indeed able to trickle in the additional energy to reach 72 Ah. So we got 69.11/72 or 96% SOC using 216 amperes. I would expect this to be slightly higher at 125 amps.
Also the CAM cells are smaller and lighter, providing less thermal mass for the power dissipated resulting in higher temps.
Also, Jack’s test was a single fast charge in a lab, starting with a cool cell. If one would instead have the cells first gather heat on a hot day, then drive for an hour, fast charge in less than half, drive again, charge and repeat, one MIGHT find oneself in a situation where the heat build-up in the pack would require active cooling. This is the scenario which fast charging is used in. Repeated drive and charge. Bench testing this could be done perhaps by having the pack in 30˚C room, discharge at 1C, charge at 2C and repeated for several cycles. Note that I am not asking anyone to do this, just that it might be worth doing, if someone has the time and the interest.
I’d like to clarify that I my experiences are based on CHAdeMO charging a 2011 Citroën C-Zero (re-branded Mitsubishi i-MiEV), not a Leaf. It only charges to 4.1 volts at all times. Jack’s 3C testing of CAM72FI kind of explains why it cuts down it’s charging current so early, at 120A around 40%. The engineers who built the car have failed to understand you need to go to higher voltage on higher currents. Or they have, but have chosen to leave a greater margin to protect the cells or cycle life. We’ll never know if they had a point, unless someone hacks their i-MiEV to charge to a higher voltage. It would however seem that the i-MiEV doesn’t suffer from as much capacity degradation like the Leaf does, but again it’s impossible to tell whether it’s different cells, lower charge voltage or the active cooling the vehicle has.
In any case, once you start using CHAdeMO you will find that there is certain amount of button pressing involved, whether or not you have full control of the car side of the charging process. Which admittedly is where most of the logic happens, but not without the station’s consent.
I think we’ve pretty much worked out the mystery of the varying charge stations. The EVSE has no “consent” other than it is either in service or not. These devices have to be certified by the CHAdeMO association to carry the label, and they just aren’t going to play loose and juicy with their own specification. They do revise it. But I have the latest which is interestingly the 1.0 version. They had two prior I believe. There really isn’t much “consent” in it for the EVSE.
It does “advise” the car how much current and voltage it is capable of delivering and we may tune our charge curves based on that, charging to a lower voltage for lower currents and a higher voltage for higher currents. The scenario you had earlier described was extremely unlikely, and I think we have probably worked out at this point what was really going on that made it appear that way.
Your mileage may vary. I really don’t know anything about the i-Miev. Kevin Smith bought his wife one and she loves it.
Kevin’s wife is also a fan of the AMC Gremlin. HaHa.
Interesting. Had to look the car up. FR layout. Would make an excellent conversion. I don’t think they have any around these parts though.
Hi Jarkko, The iMiev does use a different chemistry. Yours can charge at faster rates further. The downside was the cost of your cells.
Will be great to see everyone in March. I know I let you guys down badly in August. If anyone has a spare CA180 cell I reckon I can build a sort of reverse spanner tester to push in 3C!
108 CALB/Skyenergy SE100AHA, 100Ah,, 3.30 Volt, Lithium Iron Phosphate
35kWh pack with custom BMS utilizing the now discontinued Maxim 11068 battery management chip, three forced air cooled battery boxes with variable speed 300CFM fans. The pack has been fast charged at 120A, charging 70% in 40 minutes with a maximum cell temperature of 43C. The pack is usually charged at about 15A, resulting in a 6 hour charge time.
Regen should be reduced when the battery is near full charge. If the bus is charged on a hill and allowed to regen brake, the 72Ah battery will be overcharged with hundreds of Amperes. The experts seem to like overcharging batteries.
I wonder how many times the Boeing Dreamliner batteries were overcharged before the problems surfaced. Maybe 800? In the Dreamliner case I suspect the damaged was caused by the duration (hours) of slow over charging. With the bus, hundreds of Amperes into a warm recently charged battery would raise the cell temperatures to damaging levels. I’m just guessing. The bus battery log file should show the temperatures, voltage and currents.
How much regen current does the Tesla Model S use? It feels like maybe a hundred Amps of regen. How many hundreds of Amperes does a bus use for regen braking?
This is essentially nonsense. Where do you get such misinformation.
Jack.You disagree? *** “Regen should be reduced when the battery is near full charge.” ***
If the battery is full, don’t charge it even more with hundreds of Amperes. Maybe the part you don’t understand is “charged of a hill.” If charged on flat land, the regen will never put back the energy that the battery put out, but “charged of a hill” allows regen to overcharge the battery. It is important to avoid overcharging a full battery. The Dreamliner proved that.
“If the bus is charged on a hill and allowed to regen brake, the 72Ah battery will be overcharged with hundreds of Amperes.”
Please tell me why this is essentially nonsense.
The part I don’t understand? I understand very well and have tens of thousands of miles and years of experience with this and I can only assure you that this is TOTAL NONSENSE.
Now I will ask again. Where did you get this fascinating bit of misinformation. Have you personally destroyed a battery pack in a vehicle you owned and drove by overcharging teh battery pack with regenerative braking?
OR is this a one of thing were you directly observed these conditions and effects in perhaps a friends car? And you were able to ascertain with him that this had occurred?
Or is this something you read online?
Or is this one of those things that you “thought through” very carefully and it simply makes logical sense to you?
“If the bus is charged on a hill and allowed to regen brake, the 72Ah battery will be overcharged with hundreds of Amperes.”
This is TOTAL nonsense, and I wouldn’t spend 50 cents trying to avoid this situation.
The first clue that you have no concept of what you are talking about is the “hundreds of Amperes”. Regen is usually 20 amperes. It can rarely be 60 amperes. And it rarely produces energy for more than 15 seconds. The only benefit to regen is very very cummulative. It doesn’t do much at any one time.
If the hill started IN your garage, and was over 7 miles long at a near vertical, in theory this could be a problem. In reality it never will be. It is frankly absurd.
Actually a lot of inverters DO make provisions for protecting from this. I think it is absurd there too.
Test question – at 30 amperes for one minute, how many ampere hours are produced?
Thanks for your thoughtful reply. I feel the passion in your technical writing which helps my comprehension.
Test question answer: 30 amperes for one minute is 0.5Ah
I have driven my 2012 i-MiEV 42,000 miles in the last three years. The max regen my car is over 100A.
The regen on my car is reduced when the SoC is high. The brakes feels differently with no regen. They feel like an ICE car’s brakes.
Since a Tesla MS weighs twice the i-MiEV and the regen feel even stronger, the Tesla regen must be more that 100A. I assume a bus would also weight much more then my tiny car and have much higher regen current.
To answer your questions:
No I have not personally destroyed a battery with regenerative braking. My battery is protected from regen overcharging.
“Or is this something you read online?” What I have read online is how my battery pack is saved from overcharging by reduced regen.
“Or is this one of those things that you “thought through” …?” Yes. JoeS and I are retires electrical engineers and like you, we think about these things and measure them.
“This is TOTAL nonsense, and I wouldn’t spend 50 cents trying to avoid this situation.” We are in agreement here. Since you don’t live on the side of a mountain like JoeS does, you don’t need to worry. What about your EV army? Do any of them live on the side of a mountain? I wonder if the charging station for the bus is on the side of a mountain. That might explain why the battery pack was overcharged.
Now it seems I changed “charged on a hill” to charged on a the side of a mountain, but I feel my car’s lack of regen even on gentle short inclines after a full charge. How much elevation would the bus’ charging station need for regen to significantly overcharge it’s full battery?
Thank you for your passion. It’s exciting.
The i-MiEV limits maximum battery voltage to 361 volts on recharge. If regen tries to push over this voltage, I imagine it will decrease regen too. That doesn’t tell us anything about the batteries though. It tells us how the i-MiEV works. The batteries would most probably be just fine with a little overvoltage. Same as with the QC we could in fact probably charge the car a bit faster, if they had programmed a higher maximum voltage. Alas, they haven’t and since we can’t reprogram the i-MiEV, we’re stuck with what has been programmed in. I drive a C-Zero.
This is kind of a hopeless situation reminiscent of the Leaf guys and their turtle. You have no direct experience with any of this. JoeS Hill has become a MOUNTAIN now and your iMiev generates 100 amps of regen. Incredibly, your iMiev doesn’t even have an ammeter on it capable of tellying you how much regen it does make but you have an authoritative source in an online forum of a knowledgeable party who hooked up a clamp meter and noted that HE got 100 amps, once, for about a second, on HIS iMiev. So surely you and Joe, in free fall at terminal velocity, would cook your batteries were it not for the “protection” which magically and suddenly makes your regen go away.
Fortunately, we are not victims here. We can control our regen here, switch it on and off, adjust its level to whatever we find delightful, and we do not need to depend on the blue needle or the white needle nor how many tick marks they represent. And I can assure you from first hand experience with a variety fo cars and a variety of settings that if your iMiev ever produces 100 amperes, it is for such a brief time that it wouldn’t noticeably do ANYTHING to your batteries.
You can, of course, in your MIND, expand Joe’s moutain to a 14,000 foot peak, suspend the laws of physics, and quadruple the mass of the iMiev by packing it with gold mined from the top of the mountain. I don’t think it will matter then. Even with the “protection” turned off which as a victim of iMiev, you are not priviledged to perform.
If you and Joe are engineers, why don’t you collaborte on a build of an electric vehicle you can control, where you can adjust the regen to whatever you like and properly measure both the current, and the ampere hours accurately and it will become readily apparent that you have a solution in search of a problem.
To damage your cells, and I don’t actually know what chemistry the iMiev uses, you have to hold the overcharge sufficiently long to get the cells to an overvoltage sufficient to gas the electrolyte. As you use energy to get the car in motion in the first place, this is just heroically implausible – mountains and valleys akimbo.
Indeed I HAVE seen reference to this and again, I think this is an easily engineered solution to a problem that was never properly confirmed in teh first place. Essentially all the OEM’s have come to teh same solution when actually required by the State of California to warranty their packs for 8 years or 100,000 miles – they simply limit the charge to signficantly less than 100% and often much less. We advocate doing that anyway to ensure long pack life. But it basically takes any possibility of damaging the cells with regenerative braking off the table.
REgenerative braking is a not very efficient (30% say) method of converting kinetic energy into electrical energy. If you will graph the current over time on your hill, or your mountain, and tally it all up, which as engineers should be within your grasp even without online forums, an infamous source of EV quackery, it would be very impressive to generate 1.5 ampere hours on a huge hill/mountain. That’s just not enough, even if your cells WERE indeed “fully charge at 100%” to do ANY damage whatsoever.
The gulf here is just too wide. On ANY of our cars, I can and do watch the meter ticking backwards at whim. On a BIG hill, in a much larger car, I might get 3/10ths. Occasionally.
With very strong regen, if you do an entire drive, you might well find that for every ampere-hour you take out, you MIGHT get 0.15 ampere hours back in. That’s as good as it gets. And note that this does NOT mean a 15% efficiency gain. We have done extensive testing of regenerative braking over drives of 50 and 100 miles in mixed terrain and traffic. I usually wind up in negative numbers. That is, I drive slightly (1.5 %) more efficiently with no regen whatsoever than I do WITH regen. Lead foot Mario Noto gets a 6-7% plus.
I have become a big fan of regenerative braking not for energy efficiency, but simply because I like the “feel” of it and we do quite a bit of product development to make it easy to “tune” your car for the perfect “feel” from regenerative braking. It makes driving much more enjoyable for me personally. I found this out AFTER proviing rather indisputably that it is a total waste of equipment and expense to save any energy at all. But driviing on one pedal and coming to a full stop with the throttle is actually a lot of fun. It feels great.
I appreciate the enthusiasm as an iMiev owner. But you have stumbled into a place where all these guys actually build and renovate cars. Passing on mythology you learned on owner forums about turtles and blue bands and the guesses of the new enthusiasts is kind of surreal here at EVTV. You offered a condescending bit of very unlikely wisdom and failed utterly to produce your data. Or actually any data which was readily apparent in your initial comment.
If you read through past comments on this blog and in our actual technical forums, most of us present our DATA and then our QUESTIONS as to what it might mean. We share what we have actually observed, in the hopes that someone can help us explain it. Or in a lot of cases, just connector part numbers and pinouts, which is forever the most crucial part of all electric vehicle technology.
Good article by Fortune about the secret negotiating process for the Gigafactory:
An interesting article with some oh-so-familiar (Ho-Hos and Ding-Dongs) words: “The average driver also stays for about 15 minutes as the car is charged. That means charging locations stand to cash in with other sales. “We’re pretty close to the nine to 12 minutes people spend at a gas station that has a restaurant and a couple of convenience stores on-site,” Jones said.”
Stay away from CHAdeMO chargers.
In a german forum I have read it took the pizza delivery far too long. The i-MiEV was already charged and back on the Autobahn before the pizza had a chance to arrive.
Peter and Karin
Excellent report Jack. I appreciate you tireless efforts to keep them honest.
Thanks David. Actually I hate to rain on anyone’s parade. No loss here if people experiment with power electronics. But there is always kind of a conspiracy of silence on these things. You can see it in Jehu’s report. He’s noted some “anomalies” all along with these chargers. But always optimistic, always dismissing the problem, it’ll all be ok. Finally, after a 125 mile tow, and a year later, he comes clean. It is all NOT so good.
In the past couple of months, I’ve heard from probably 12 or maybe 13 who have “thrown in the towel” on the EV Motor Werks antics. What I guess I was hearing was that they didn’t mind them blowing up, which seems strange to me. But more that the guy wouldn’t do anything about it for two or even four months. An electric car WITHOUT a charger, is kind of a one ride device. This would anger me in extremus.
As I said, you want to buy the kit and party hearty – go for it. But for those expecting to buy an off the shelf charger and have it work reliably, we have to issue a BEWARE. It’s not going to happen from this outfit. And if something goes wrong, they all of sudden go e-mail deaf and dumb.
Note that for those of you who bought one and found it delightful and 100% reliable – that changes nothing. Your good fortune, at least up to now, is your good fortune. That there are others who have lost time, money, and effort on this is indisputable at this point.
The best light I can put it in is its an experiment that for a substantial number of people, did not work out.
If I got the tricky stuff correctly …
CHAdeMO lets you connect directly to your battery. You could use it to power your house or you could use it to eat the power from your solar array.
With that kind of connector you can pull your charger out of your car but still use it when at home. On the road with CHAdeMO there is no more need for your charger.
The i-MiEV has got 2 canbusses. One bus is talking to the CHAdeMO device (charger or power plant for your house) the other bus is talking to the rest of your car. The BMU battery management unit is a blackbox containing BMS and Battery. It is the BMS talking CHAdeMO to the outside or to its built in charger.
We should be able to translate (GEVCU) CHAdeMO to charger CANBUS to use any existing charger to play CHAdeMO. Not much sense at first sight, the cable is far to expensive … but it helps getting a working CHAdeMO without much powerplay.
Regular Charger, local battery pack in the house, it does not hurt if I simply connect my local battery and my car battery in parallel, does it?
There will be a high current for a moment but then those voltages come closer and the current goes down. After that your regular charger will charge both your local pack and the pack in the car. If you want to go on the road again, no problem. Your local charger will charge your local battery while your car is on the road.
Hope I did not type to much nonsense.
Peter and Karin
The development of CAN interface products is coming along quite nicely. Another avenue of development that could be beneficial to the EV movement would be use of CAN controlled OEM electric power steering pumps (EPS). The CAN commands for such units has not surfaced yet….. There are folks that have made use of Volvo EPSs in a default mode which allows the unit to run at full speed. Many of these CAN controlled units have the ability to vary the pump rate according to CAN commands. Implementing an EPS into an EV project would be another step forward in making a refined conversion. Does anyone have a vehicle with an EPS and the ability to capture CAN? Any Volvo fanboys out there?
Mike Schooling had some amusement with the all-electric power steering in his RX8 (burned out a motor I think). He had to spoof some CAN signals. I believe he has a solution specifically for that car.
I am SERIOUSLY considering coming to the UK for the mini EuroCCON as it would quite nicely coincide with the FormulaE race in Long Beach on the way back (4 April). Do you guys have any thoughts for getting everyone together for fun and frivolity in the UK?
Nick – I don’t really do frivolity very well but if your schedule before or after takes you anywhere near Redditch you are most welcome for a meal or whatnot. My cooking is brutal but effective. I’ll be at the event myself of course (hoping to take the Civic)
Interesting developments on the show this week. I have a 98 Ford Ranger that i’m finishing and I keep thinking about canbus applications. I have a JLD-404 in it and have been contemplating what I could do with a JLD-505. I’m glad to hear it’s getting close. And I keep hovering my finger over the ‘buy’ button on the CanDue because I want to experiment with it. The project that remains unfinished in my truck is battery heating. I have four battery boxes and I’ve built a controller using an Arduino Mini, four of those Dallas one-wire temperature probes, and a SainSmart relay board. I elected to (for now anyway) just power the unit from AC when I plug the truck in to charge. If any of the boxes is below 58 degrees it turns the heater on in that box. If any of them are below 40 it inhibits the charger. I had the prototype working months ago but getting it wired up and secure in a weatherproof box (i.e. fitment) has been taking a lot longer than I imagined. That canbus CanDo thing (CanTS) looks very cool and might have made this whole project go a lot faster. I’m imagining a more fully connected vehicle where I can put in better instrumentation to watch temperatures and charging and discharging, etc. Keep up the good work!
Jack, I just want you to know that those of us that build electric vehicles find your show invaluable. Your attention to detail and tenacious testing is not boring at all. It is exactly what a person needs who is attempting to actually build an electric vehicle and I want to thank you and congratulate you on a job well done.
Lightning Motorcycles LS-218 – Jay Leno’s Garage: http://youtu.be/Lz1aTLBKIoQ
Kiss the ring.
Jack the Black floor shows dirt as bad as the white floor… Go NAVY! use battleship grey
I don’t think Jack wants to go back to being a swabbie…
I know wrong blog post, but check it out just finished reading this on autoblog. Sounds very familiar
All you Stateside guys and gals – have a good and blessed Thanksgiving day
Many may have said you’re programs are long, but I have to say this Thanksgiving Weekend, I miss you and your wonderful videos…. They are the cherry on top of my busy week…..
Looking forward to next weekend!
I agree Carl, didn’t know what to do with myself Sunday morning with out a little EVTV to go with my coffee.
I watched the first ones again 🙂
I too watched the 1st one, and found his take on the whole of EV-dom still consistant over these last few years!
He even mentioned that he’d rather give his money to a “failing GM” than China!!! lol On video #1!
I had three EVs on my drive at one point last week: my Ampera, a Leaf my brother has on long term test and the Civic (conversion nearly done – would be finished but I tore some muscles in my back).
BTW we tried the Chademo charger at our local motorway services. When we plugged it in we were around 50% charge and it was sucking 100 Amps. After a leisurely coffee we came out to find it at 90% charge running at 15 amps. I didn’t realise that it would do that.
Restarted my high rate test rig: will do a video segment sometime in the next week or so. Early days still (just less than 250 cycles), but no suggestion of a catastrophic loss of cycle life using a 3C charge rate
Slowly, very slowly, I see more and more of them. Yesterday somebody came out of parking in the forest. He was almost in our way but he took of like a spaceship and was away without making noise. I would not have noticed – but without making noise?
We found him again at a traffic light. It was an Opel Ampera (Chevy Volt).
I dont know if there will ever come a video out of my pc. I am still fighting windmills like Don Quixote, trying do build Gentoo (very customiced Linux) and getting all my hardware like CANBUS and usb-video working. It hopefully will become a second dashboard for our i-MiEV, bringing dashboard, CANBUS log and video together.
Jack, it is a lot of fun seeing your video with fish swimming across the screen and some messages in between. I had to get rid of kde and gnome to get most of the stuff working. My own video is only 640×480 but may by I can show two video sources simultaneously. The fish are an indicator for how much time my little atom cpu has still left and they very often freeze. It is cold outside after all, actually freezing.
Peter and Karin
I have an Ampera. Not that fast on paper 0-60 but flooring it at three mph takes your breath away and you can do it at every set of lights without filling the world with fumes and noise and wearing out your clutch. If someone would just do a conversion to take out the ICE bits, simplify the heater and add Chademo plus enough batteries for a 100 mile range I’d never want another car
The next Gen Leaf seems to fit all those numbers…
When it comes. Hey. seat heaters in Aldi were selling off at like £5~6.
Saw this on the CALB Website…you might want to check for excessive side fumbling on your cells.
“The original CALB CA Battery had a base plate of pre-famulated amulite surmounted by a malleable logarithmic casing in such a way that the two spurving bearings were in a direct line with the panametric fan. The New CAM Cells consisted simply of six hydrocoptic marzlevanes, so fitted to the ambifacient lunar waneshaft that side fumbling was effectively prevented.
The main winding was of the normal lotus-o-delta type placed in panendermic semi-boloid slots of the stator, every seventh conductor being connected by a non-reversible tremie pipe to the differential girdle spring on the “up” end of the grammeters.”
I’ve noticed over the last few days that the EVTV EU Warehouse has disappeared. With this and Jacks announcement of pulling out of the UK meeting next year, is there anything we should know about over here in Europe/UK? Has there been a parting of the ways?
The evtv-amsterdam.eu website redirects to http://newelectric.nl/ might be another clue.
If you can repeatedly measure a voltage between CAM cell case and both terminals, does it mean that it would discharge just a tiny bit by itself?
it remainds me of vacuum tubes. They had 9 terminals. Say 3 for filament, series 200 mA or parallel 6.3 V and a pentode needs another 5. So what to make out of that 9th terminal. They warned it is used internally for mechanical stability and it was not supposed to be connected anywhere. Radio amateurs successfully used it.
That battery case is not isolated but where does it connect to? You might use it for yet another cell of unknown capacity and chemistry. If you really use it you might corrode something that was not supposed to see current in the first place.
The mechanics are easy to guess. You have got two aluminium foils rolled and squeezed into an aluminium cup. Compared to the foils the cup has a very small surface so it cannot have too very much capacity. Some fluid obviously has spilled between the cup and the foils and you do actually have yet another cell but it might be connected in series to both anode and cathode.
As long as it is not there it does not change anything for the two foils, but as soon as you connect it does react with anode or cathode or both.
Peter and Karin
Peter – Vacuum Tubes?? You are showing your age. Even I hardly remember them – and I did my flight training alongside Pontius the Pilate
Myself and an old colleague replaced all those glass fets with plastic ones. Had to pre-solder resistors across the legs first… Oh, after that got rid of the nasty wax covered old caps that used to dry up.
Unlike its glass brethren, it died in a thunderstorm.
Great report and testing. I am a follower of your v-logs on this website and YouTube. Love it so much and thanks for sharing your knowledge.
I came across this website (http://crosspointkinetics.com/) – Crosspoint Kinetics makes a electric hybrid bolt-on product for class 3 trucks (I believe these are delivery trucks). They use capacitors in place of batteries. Wanted to ask what your thoughts are with regard to using capacitors vs. batteries.
I am a bit biased against capacitors. I spent a couple of years and $20,000 on a capacitor module for electric cars. By the time I was done, the ESR of the batteries had fallen below the Maxwell capacitors that were available at the time and so the damn thing appeared to work backwards. Instead of boosting sudden demands for current, it was sucking it up. I think. It got kind of interactive and I never really worked it out.
There was a scam five or six years ago about a guy who had developed a high voltage ceramic capacitor of huge energy capacity. One of the electric car companies actually ceased production of their car and invested all their money from an IPO in this quack scheme, which of course just quietly went away. I think it was called ENERSTOR and it engendered a cottage industry of blogs about evenly split between crackpots that swore it would work and would be out within weeks and detractors who were equally crackpot who dreamed up ways of debunking it.
So the whole genre went copper foil helmet. But I am haunted by the guys in San Diego who came up with a way of creating graphine by painting carbide solution on CD’s and using the laser in a disk drive burner to convert it to graphene. They would make a capacitor the size of a stamp that would hold enough charge to light an LED for 10 minutes or so.
So while it is a long shot, something could come out of left field on this and expand the capacity of the capacitor 10 orders of magnitude or so. That would be a game changer. But not impossible.