Even at the power levels you're needing, I think the EIG cells are likely your safest and surest bet, given my results so far, out of the stuff that is available in small quantities from reputable battery vendors or manufacturers. (i.e., isn't seconds, recycled used or discarded or damaged cells, or otherwise completely unknown QC or known-to-be-bad-or-nonexistent-QC)
Apologies to the OP for the OT:
etriker said:
How does one get a NDA ?
What did they give you to keep quiet and not let your ES buds in on the info?
Well, that's the thing about an NDA (Non Disclosure Agreement)--you can't say anything about the stuff unless they specifically say it's ok. I got permission to discuss the technical details and results of the pack, but can say nothing about it's origins.
Regarding NDAs in general, having done beta testing for music-composition/recording-related software/hardware in years past, I can say that sometimes a company will approach a person based on previous experience with other companies, to do alpha or beta testing of stuff, but there is always a NDA involved in which nothing about the entire thing can be discussed. Sometimes after the testing is over and product is released, then technical issues can be discussed, but usually nothign about the beta process or anything else can be discussed, and usually you are not allowed to say anything about having been a beta tester. (though in at least one case we were all given T-shirts stating we were beta testers, and were allowed to wear them in public, yet we still couldn't actually state we were beta testers, so I dunno about some companies. :?). Sometimes products are never released, and you're usually not allowed to ever say anything about them, even to other beta testers *or* other employees in other programs by the same company. That's wierd, but it happens. Sometimes you get the product for free, and sometimes a discount. Usually with hardware it's the latter, software the former, but there are exceptions to both.
Hopefully that answers your question sufficiently, because that's all I can really say.
Regarding the cells themselves, I have the NMC 20Ah cells with their trays. Presently 16 of them are my traction pack, and 3 are my lighting pack, and a couple "spares" that are really part of the traction pack but not presently attached to it and a 4th cell for the lighting pack that I took off because of the lower voltage of my present lighting. While I wish I had more of them, I'm grateful to have just these. I have paralleled them (at pack level, not cell level) with a 16s2p 10Ah RC LiPo pack for some test rides when I had the 4KW+ controller setup on CB2, but there wasn't too much difference in voltage sag even at takeoffs. I don't know the Ri of the RC LiPo but would guess that it is not as good as the EIG, based on the differences in voltage sag in this and other tests.
etriker said:
Did you do a burn down on the grill test of the NDA cells ? What do they do when they get too hot ?
I'm sure that at some point they *would* burn, just like any other cell. But unlike at least some RC LiPo and some other types of cells, they don't seem to have a problem being taken down to 0V and then still be recharged and used "normally" (at least at 1C or less). No puffing, no heat, no fire, etc.
I dont' have enough fo them to "waste" one on such a test, until I manage to damage one beyond usability for my purposes--which so far hasn't happened even with taking 3 of them down to 0V in my lighting pack--they still appear to work just as well as they did before, at least in the lighting pack. If one does fail I will do an overcharge test to see what happens, similar to my RC LiPo pouch fireworks tests last July. Hopefully I'll have better instrumentation for monitoring by then.
However, these cells don't seem to get warm in my typical use on CB2, pulling 2-4C for 3-6 seconds at a time, then 0.5-1C for a minute or two, then nothing for a few seconds to a minute or two, then repeat the cycle (in stop-and-go traffic). I do not yet have temperature monitoring, but I had the bare pack where I could check it by hand for a while. Now it is protected from crash/skid/water in an ammocan with a vent (just in case).
The "damaged" lighting pack does not get warm either, AFAICT, with a constant 0.25-0.3C drain (headlight) and intermittent smaller drains.
999zip999 said:
He needs a safe pack that anyone who plugs it in will be safe. So a A123 with a bms so it is a plug and play pack. Amberwolf are you talking about a EIG pack that you made with a BMS ? Did Jay64 use a BMS ? Who has made a EIG pack with a BMS plug and play. What BMS's are out there for the suport of the EIG cell that wouldn't brake the bank ?
I dunno about a BMS--at first I used the cells just bulk charging and manually monitoring (but there were never any balance issues; there could be once they get older, but not so far).
Now I have an early version of the Methods HVC/LVC on there, but it has yet to be needed. I don't run the cells down very far most of the time (10Ah at most typically before I recharge, sometimes half that or less, sometimes 15Ah or so). I have my CA LVC at 56V, for 3.5v/cell, but have not hit it yet. My charger is set for 66.3V max, but usually only to 66.2V, which is 4.13-4.14V/cell.
I use a Battery Medic from Mdd0127 to periodically check the cell balance at various SOCs; it's accuracy is close enough to see if anything is really bad.
Can someone find the back door for these besides Luke ?
Well, based on what he's posted here and there, I think he was dealing directly with EIG via the front door sales office, along with a lot of other battery manufacturers, when he was picking what cells the Zero was gonna use.
JonesCG and JohnRobHolmes have also used the front door sales office directly thru EIG, AFAICT, and so has at least one other person (sorry I forgot the name). So there's no need for a "back door" that I can see--anyone can purchase the cells, although they aren't as cheap as other options, in the quantities we'd be using here on ES (even a group buy wouldn't bring it down that much, and those things don't tend to go very well, so I don't expect any to happen anytime soon).
