E-Meter questions

[StorminN]

Hi folks,

I'm an EV newbie, trying to help a friend that just bought an EV. His truck has an E-Meter in it, and I was over there trying to help him with it the other day.

I'm wondering... for the E-Meter, do most of you folks enter the actual Ah capacity of the battery bank into the E-Meter, or do you adjust (fudge) the settings one way or the other? For example, his battery pack is twenty 6V Exide GC-135's in series, which equals 120V @ 226Ah @ a 20 hour rate. Would you then enter this into the E-Meter as 220Ah, and then just adjust the Peukert, or would you enter a different Ah capacity into the E-Meter, like a one hour rate? Also, would you set the E-Meter "fully charged" conditions to 132V, or higher, or lower?

Currently, his E-Meter fully charged conditions are set to 132V, 5A (2% slightly rounded up), 220Ah

Thanks in advance for any help...

-N.

[leitmotif]

Norm

Thinkn on it maybe we you me Bruce should have done all the discussin on this list instead of EV list?

Moderator can you put everything here if Bruce and Norm go along with it?  = please??

Dan Bentler

[StorminN]

I'm fine with that...

-Norm.

[StorminN]

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On Oct 13, 2008, at 9:14 PM, Bruce Sherry wrote:

Hi guys,

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
Bruce Sherry Designs
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Hi Bruce,

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...

Thanks,
-N.

[leitmotif]

Norm

Ahhh a dyno
I have the instrumentation   two Fluke data loggers 21 channel each.
I'd be interested.

What readouts does the dyno have
Calibrated or just darn good instrumentatiom (more important in my mind)

Dan Bentler

[StorminN]

Hi Dan,

Fluke data loggers... nice. We need one of those here at the factory to figure out what the heck is going on with our three phase power (I suspect it's not even loaded), we get some weird stuff burning up now and again.

Not sure what readouts the dyno has, I'll have to walk over there and take a look. This is the place:
http://www.dynosources.com/

-N.