On Oct 13, 2008, at 9:14 PM, Bruce Sherry wrote:
The trouble I have with peukert, is making it accurate. If I had an EMeter, I would start with some value I could verify. One thing we can be sure of is if we have t-105's in an EV, we will NEVER see 225AH from them in EV service.
I would do something like draining one with a 40A load, and see what I got. Then I would go from there, but I don't really have a way of knowing what to actually set the EMeter values to to make it accurate.
I had a consultant write software for my units that will implement a variety of peukert, but I don't know how to verify that it works correctly. Sure it takes numbers I give it and appropriately regurgitates the numbers I think it should, but what does that do in the real world? I have yet to convince myself that it is correct for anything more than two points on the curve. Yes, it follows what I believe Peukert says, but is it real? Is it any better than the straight Amp/Hours my existing units implement?
With straight Amp/Hours, I can be reasonably sure that what my unit says is near the truth. I don't have the time or equipment enough to verify even a third point on the curve, let alone 5 or 10. Even if I did, it would most likely be just one battery. One thing I do know is every battery is different. Check the latest entry on my blog: http://brucesherrydesigns.com/blog/2008/10/11/jeffs-zenn-2/
Bruce Sherry Designs
Thanks for the reply. I read your blog entry and I like your methodology on testing the Zenn batteries. I believe that this inconsistency between batteries (and cells) within the same pack is probably the root of many problems that Pba EV'ers experience. I'd like to think that battery regulators would help... but ideally we'd be able to charge each 2V Pba cell individually. From what I've read, this is how the NiMh, Li-ion, and LiFePO4 batteries are charged... cell by cell.
In your blog entry, the battery with the least Ah capacity had 52Ah, and afterwards you set the BatMan3-EV to 45Ah... how did you arrive at the 45Ah number? I'm curious, too... what Ah rating is stamped on those batteries?
So putting these things together... if I took a similar load... (0.25 Ohm, 1000W resistor) and did a similar test, and found that the Ah capacity of one of these GC-135 batteries is, say 150Ah, you would then set the E-Meter Ah capacity to, say 140Ah?
P.S. The business next door to ours here in Sequim has a dynamometer... if someone ever wanted to test battery discharge vs. time with the drive train and everything involved...