If you’re not living on the edge, you’re taking up too much room. Or so I’ve been told.
This week’s show is almost entirely devoted to watching paint dry. But it’s fast dry paint. We attempted to charge a CA40FI series cell at a 3C 120 ampere rate.
The Chinese manufacturers of the Thundersky, Sky Energy – now China Aviation Lithium Battery Company, have always listed 3C as the maximum charge rate. In the past two years, they have largely not touted that very loudly and in fact it appears to have disappeared from what little they now publish by way of spec sheet. We really don’t have a proper spec sheet from the manufacturer on these cells.They now include a little booklet that appears to have rounded up every myth known to batterydom into one single grossly inaccurate document for your perusal. Please ignore ALL of it.
We have previously not had either a power supply large enough or a cell small enough to accomplish a 3C charge rate, much less charge a car at 3C. I had done some earlier charging at 1C and higher and had a sense of it not being terribly different actually. But we had just never been in a position to test 3C charging.
The Society of Automotive Engineers, largely in response to Tesla’s Supercharger unveiling, hastily released their J1772-2012-10 standard this past month. That rather makes real the concept of a standardized FAST charge ability for the first time.
The Japanese Tokyo Electric Power Company (TEPCO) had in fact installed a number of fast chargers in Tokyo terming their “standard” ChaDEmo. A play on words meaning have a cup of tea and alluding to the fact that you could charge your car in the time it took to take a cup of tea – a common stop in Japan akin to our swing through the gas station for a big gulp soda. But to get a copy of the actual standard you had to join their club at $150,000 and so we never did quite get to read the actual document. I find it curiously annoying that a body such as SAE purports to publish a “standard” actually charges for a copy of it. It’s simply inappropriate. It should seek as wide a circulation as possible if it is held out to be a standard. That they also employ some sort of DIgital Rights Management and FORCE you to actually install the enforcement software on YOUR computer to download it is simply evil and despicable. But the $66 is a little better than ChaDEmo anyway.
A few ChaDEmo charge stations HAVE been deployed in the U.S. One in Oregon, I think one in California, and a couple in Chicago. Nissan had heavily told the story of the devices at ALL Nissan dealers across the country, which would have by itself established a fast charge network, but like all things Nissan, this appears too to be a bit overstated. We’ve seen NONE of them. Indeed, they had announced availability of a fast charge station device at a very modest $9,900. Again, unobtainium nonsense. Carlos Ghosn really needs more of a plaid sports coat look. He dresses to well for his business practices which do border on the used car lot end of the autospace.
If it hasn’t become apparent to some of our newer viewers, I suffer fools and bullshit artists poorly.
As I think all the hype on public charging infrastructure, certainly Level II AC charging, is poorly directed, why the diatribe on FAST charging standards?
There is little advantage to public charging at 240vac 80 amps. You can do that at home. And largely do. And it is a rare instance in a car with 80 mile range to have any NEED for public charging. The only real scenario is when you are traveling non-local distances – such as between cities. And then it is too little too late. An eight hour stop to charge after a one and a half hour drive just doesn’t make any sense at all.
Fast charging, on the other hand, given the touted 20 minute scenario, is somewhat enabling. It would allow you to drive 80 miles and charge in 20 minutes. In reality, it takes 20 minutes to gas your car – not the 5 minutes universally quoted. I’ve NEVER been in and out of a gas station in
five minutes. But 15-20 is normal. If this was extended to 20-30, no problem.
Unfortunately, what SAE adopted is a 200 amp standard. On higher voltage OEM cars, this might indeed do 80% charge in 20 minutes. But it really doesn’t for our cars, which tend to be 200v or less. Our most popular cell size is of course the CA180FI. And at 200 amps, it would take most of an hour to recharge.
But even that would be enabling. It would turn a cross country trek from a total endurance test to mildly annoying. We are not GOING to have a national network of fast charging stations without a fast charging standard. And so while I abhor the 200 amp limit (how hard IS 300 amps), and likewise share Elon Musk’s opinion of the ridiculous charge connector – just an engineering and design mess – I’m pleased to have a standard at all.
But it brings up the question as to what effect fast charging has on lithium battery cells in general, and of course specifically the cells we use in our converted vehicles. From my biased perspective, the China Aviation Lithim Battery Company CA series cells are the only ones that matter.
They are THAT much better than the THundersky, Winston, Sinopoly cells that no amount of discounting by those guys could realistically move me to go to the trouble of a conversion with those earlier chemistry cells.
And so I’ve kind of myopically drilled down to WHAT specifically would be the behavior of the new CA series cells in a fast charging situation.
The key is temperature. So we invested about $600 in a Raytek MI series temperature sensor. This is a very accurate and very quick infrared temperature sensor. We would love to know the temperature of the anode inside the cell, but we can’t get it without compromising the cell. So we settle for taking the temperature of the anode terminal bolt head.
This stainless bolt conducts electricity or course, but also conducts heat rather well. The actual charge current goes from the copper terminal lug of our charge cable to the copper flat of the anode terminal. The bolt just holds it in place. It may pickup a little heat from this interface under current, but not much and it really shouldn’t be conducting any current at all if our interface is clean. It will however conduct heat from the anode pretty well and so we think it represents anode temperature pretty fair. As it radiates somewhat better than the anode foils, it will be smidge lower than the true anode temperature. But the relationship should be pretty linear.
Why the anode? In charging a cell, this is where the heat shows up. As lithium ions diffuse into the graphite anode, there is a heat gain. And so you will observe higher temperatures at the anode in charging than on the cathode.
Of course, the question of cell damage is really a question of heat. While I am somewhat blase about the ambient heat of Phoenix and its possible effect on the cell, internally generated heat is pretty much an indication of wear and tear on the cell. Ambient doesn’t HELP this situation, but it really isn’t entirely related. We’re interested in the effects of high current charging on the cell and that means the cell internals really.
We have done some casual temperature measurements of cells while charging and discharging before. Usually by taping a probe to the case or shooting it with the DeWalt infrared. But we really weren’t focused on it much. I had kind of a sense of WHEN the temperature rise occurred during the charge cycle, but had never really tested it in any methodical fashion.
So we had questions on two points:
1. What level or percentage of charge could be accomplished with a 3C charge? This goes to a very tricky question. In order to charge fast, you have to have maximum current. We can do that up to our Constant Voltage switch point. After that, we go into Constant Voltage phase and as the energy level in the cell rises, the current MUST diminish to maintain that voltage. That inherently reduces the charge rate and so extends the charge time. Fast charge is about FAST so there is no point sitting there charging at lower rates. If you charge at max current up to the CV voltage, what percentage charge do you accomplish. The common myth is 80%. A very believable number since in normal charging that is about where you are when switching to CV.
2. Does fast charging damage the cell? This would best be answered by doing cycle tests for 100 cycles or more to 100% discharge while charging at 3C. Not convenient. So we look for two things – temperature on the anode while/after fast charging, and an immediate retest of capacity after fast charging. Any serious damage should show up there with one or the other indication.
This doesn’t mean that without temperature or capacity decrease there is NO damage to the cell. But none that needs be immediately addressed and likely, if it doesn’t show up at ALL there, it is unlikely that it is damage that needs to be addressed – probably at all.
Prior to the test, I would have believed any result except the one we obtained.
In regards to the first point, we APPEARED to have charged the cell to 97% capacity by charging at a steady 3C (120 amperes) to a voltage of 3.65v. This is quite surprising. In fact, I almost fell over. Comparing the amount put IN to the amount that comes back OUT on a subsequent capacity test, and repeating this whole thing 3 times this week, we are getting a very steady 39.685 amp hours in capacity OUT at 30 amps. But we put about 41 and change IN when charging. I think we are seeing normal charge efficiency losses here. And so it really is NOT 97% charged – probably more like 92% charged. That is STILL a very astounding result.
With regards to temperature, even though I predicted that the temperature gain would be greater toward the end of charge, I was absolutely astounded at what happened. FAST charge at 120 amps to that 94% charge level resulted in a temperature gain of 10F (5.5C) from an ambient of 73F to a finished temperature of 83C. No real delay here either. When we shut off the charge, the temperature immediately starts to cool.
But AFTER fast charge, and after cooling back down to 73F. we put the Powerlab8 on to charge an additional 2.5 Ah into the cell in the normal CC/CV fashion at 30 amperes. The temperature peaked at 3.65v and 30 amps at 126F. This represents a 53F gain. This is a FIVEFOLD greater gain than in the fast charge scenario. Slice that, dice that, and discount that to any level you want, it will leave a remainder that is still multiples of the fast charge temperature gain. And even though I predicted it, I did NOT see that coming. I would have guessed 50% gain in the first 90% charge and the other 50% in the last 10% and would have found that DRAMATIC. This was not dramatic, it takes us to an entirely OTHER conclusion.
We are overcharging our cells. Obviously we are at 3.65. But I suspect at lower voltages as well. The last portion of the charge curve is obviously damaging. The further away you are from it, the better. And it couldn’t possibly be overstated given this evidence. Remember we were NOT fast charging at all during the Powerlab8 portion of the charge. In fact we were at 1/4th the current seeing 5x temperature gain.
The apparent voltage while fast charging IS signficantly higher. And so while we would slow charge to 3.50 we can probably safely fast charge to 3.55 x Number of cells and will wind up with about an 83% SOC at that level. That would be our real world FAST charge scenario for these cells. At 200 amps on a 180C, we would probably be back at 3.50 v per cell.
That greatly simplifies fast charging. You simply charge to your normal CC/CV voltage, but then cut it off once it is reached with no tapering charge. And I would at this point rest easy that I could do as much of that kind of fast charging as desired, with no thought to battery cycle life. At this point, I have NO (read zero or below) evidence or even indication of any damaging effect of fast charging on these cells.
That said, I am increasingly finding sufficient difference in behaviour in these CA series cells to admonish you that if you run Thundersky or even the SE series from CALB that these results may not apply to your car. Can we duplicate this test for those cells? Frankly, I’ve just lost interest. CALB continues to make the SE cells in a few odd sizes, but their availability has already dwindled. The Sinopoly and Winston cells and High Power and Headway remain available, but frankly we just don’t think they matter anymore. Until they counter the CA series, they are kind of yesterday’s news.
And THAT said, note that SAE Level II DC charging is going to limit most of you to 2C on 100Ah cells and barely 1C on the larger and more common 180Ah cells as well. So I don’t think that at the charging rates AVAILABLE that any of those cells will really have any problem either.
Bottom line, as I’ve always said, the cells can do fast charge now. The problem is getting the power. We’ll see if the adoption of the SAE fast charging standard leads to actual deployment of fast chargers.
Meanwhile WE intend to pursue it. There is not a week goes by that we don’t hear from someone wanting to charge from their own home solar charged battery bank. I think the PulsaR can do that as well as provide us a path to SAE fast charging. Ryan will have to work out this goofy PLC data protocol, but assures me that it really isn’t much more than an annoyance and he’s mostly annoyed at the $150 fee for the specification itself.
As am I.
The other notable element in this episode is a continuation of the sea change shift in the fortunes of the conversion crowd. By upgrading the nature of the builds, at a time when the automaker and battery company fortunes are in shambles, it has become ok to be a conversion shop. Steve Burns of AMP Electric Vehicles stopped by to note that they were really just like us in many ways and Fisker has announced they are showing up at SEMA. Audi has cancelled production plans for their E8 E-Tron with the usual greasy lies about always intending it to be an internal prototype. Nissan is heavily discounting the Leaf to comical levels and indeed rumors about of a DOWNSCALE LEAF if you can believe it for 2013. GM is going the other direction and doing a Cadillac ELR version of the Volt. This was my advice from the beginning two years ago. You can hide the cost of the drivetrain more easily in a car that is already higher in price. And you HAVE to appeal to well heeled early adopters – not the economy shopper. The case for an economic reason to drive electric CANNOT BE MADE until economies of scale come into play and they are NOT going to come into play by building a billion dollar plant in Tennessee to make 150,000 economy cars no one is going to buy. To break a chicken and egg standoff, you have to tap on the egg GENTLY or talk to the chicken PERSUASIVELY. Bludgeoning the two leads
to a messy dinner, but no more chickens or eggs.
I truly believe the number of people willing to pay a significant premium for the advantages of an electric car will grow steadily toward a tipping point. But anyone who wants to be a player has to offer a very desirable car to those who can afford it. In a season where “trickle down” is a dirty word, it is only dirty to those who truly do NOT understand how economies work – or disruptive technologies for that matter. But I see a sea change in the wind. I think we’ll be getting better components here shortly, and the DIY “hobbyist” conversion guys are going to eventually be recognized as the most persuasive and influential key to the puzzle. We are already seeing companies that recoiled in horror at being besmirched with the same brush come around to the reality that they are really just like us, but bigger. And facing the same problems. And the “we only sell to OEM” suppliers have learned a very valuable lesson in marketing. You sell to the guy willing to buy – not to some surreal imagined “target market.”
A 74 year old guy wandered into our shop and wanted to buy a Soliton 1, an 11 inch motor, and enough batteries to light Cleveland, all to run a Chevy S10 pickup truck. I told him I would be happy to sell them to him, but he would most likely hurt himself with such a grossly overpowered beast. He hauled out a 30 inch framed photograph showing him WINNING one of the largest drag races in the deep south with the same truck using an ICE engine. “Thought I might try to do it again in electric” he noted.
Noted. Here, I’ll help you load em up. Valuable lesson repeated. Remind me to practice my “sit down and shut up” moves more often.
As to the CA cells. We are about sold out. Pomona is sold out. I talked to CALB about selling their cells last May and wasn’t certain we could meet their required quantities to be a dealer. We’ve rather become their largest outlet. But there will actually be a bit of a shortage until mid-November. Which is just a couple of weeks at this point. WE are putting in a larger order this time in the hopes of meeting our viewers requirements timely. But the more we examine these strange new cells, the better we like them.
The final thing we learned in this test is just how very capable this Revolectrix PowerLab 8 Battery Workstation is. It has a LOT more utilty when coupled with their really very good software. You can use it to charge at up to 40 amperes. You can not only use it to discharge cells, but can discharge using constant current/constant voltage just as you do when charging. You can use it to perform complete cycles, charging and then discharging or discharging followed by charging. And we actually used it to monitor and graph our progress when using a DIFFERENT power supply to fast charge the cells. It makes beautiful graphs, but better you can export all the graph data for voltage, current, time, etc. to a tab delimited file for later imort into Excel or whatever. This thing is cool.