# Zak's 160 amp bottom balancer



## Ziggythewiz (May 16, 2010)

I've always said people go to great lengths to bottom balance, but 20' doesn't seem so far 

Have you checked to see how close they stay with varying amounts of time connected after discharging?


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## Zak650 (Sep 20, 2008)

I balanced another set of 6 with 3 (.3ohm resistors) in parallel instead of the rebar as an initial test indoors. After being disconnected for 3 days they are all within a total spread of .06 volts. It took a really long time to drain them down with the .1 ohm load. The rebar hookup initially kicked off at a little over 5 hours, now I'm waiting for the bounceback. I'll leave everthing hooked up overnight and see what they measure. The cells in both cases were pretty well fully charged when I started the draindown.


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## EVfun (Mar 14, 2010)

The downside of using steel as a load resistor is that its resistance changes quite dramatically with temperature changes. You would want to measure, and perhaps try to control, the temperature of the load bearing rebar. (Load bearing in a way the manufacturer never intended!)


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## Zak650 (Sep 20, 2008)

EVfun said:


> The downside of using steel as a load resistor is that its resistance changes quite dramatically with temperature changes. You would want to measure, and perhaps try to control, the temperature of the load bearing rebar. (Load bearing in a way the manufacturer never intended!)


I noticed that after the steel got pretty warm (160 deg F.) my system amperage dropped to 135 amps. But as I'm mainly interested in a cheap high amperage resistor it really doesn't matter the JLD is what really controlling things and it seems pretty consistant.


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## Elithion (Oct 6, 2009)

Zak,
Please wear safety glasses when working with such set-ups. It's a small inconvenience, but it can prevent great damage to your eyes, should something unexpected happen.


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## Zak650 (Sep 20, 2008)

Thanks Davide, good point.

24 hour report:

6 Calb 100 cells, I first notice JLD had turned off the relay a little over 5 hours, rebar was still slightly warm. Left to go out to dinner, it did not show any temperature or activity when I returned so it may have finished draining the cells around 5-6 hours after starting. Left everything connected overnight and disconnected and seperated cells 18 hours after starting draindown. 
24 hours after starting draindown and cells seperated all cells within .03 volt range


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## PStechPaul (May 1, 2012)

You might fold up that rebar and put it in a bucket of water. Then you will at least have some hot water to make tea or take a bath, and it will keep the temperature below 100C. Please don't contribute to global warming (or even local warming) with your bottom balancing!


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## njloof (Nov 21, 2011)

Memo to self: do not drink the tea at PStechPaul's.


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## Zak650 (Sep 20, 2008)

njloof said:


> Memo to self: do not drink the tea at PStechPaul's.


mmmmm, lukewarm rusto latte, just like Starbucks


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## Zak650 (Sep 20, 2008)

Here's some more results and settings:

JLD5740: [email protected] 2.760, [email protected] 2.650

After Draindown 2.75 volts, all cells withing .04 range

Assembled pack charge setpoint 3.425 volts/cell

Peak voltage on the cell with least capacity near end of charge 3.77

Peak voltage on the cell with greatest capacity near end of charge 3.37

Resting cell voltage range after 24 hours (3.34-3.38)

Recharge amount: 100AH

I'm really impressed with this system and the results. I've previously bottom balanced these cells individually with my celllog 8, but using the JLD 5740 and the cells in parallel seems to have arrived at more consistant results.


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## Roy Von Rogers (Mar 21, 2009)

Zak650 said:


> Here's some more results and settings:
> 
> JLD5740: [email protected] 2.760, [email protected] 2.650
> 
> ...


How long did you let them sit before taking the measurement.

Roy


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## Zak650 (Sep 20, 2008)

Roy Von Rogers said:


> How long did you let them sit before taking the measurement.


I think the draindown was pretty much over about 18 hours before I took the measurements. I believe the paralleling of the cells had a significant effect on the consistancy, it was literally like it was one giant 600AH cell that gets averaged out over the 18 hours before being seperated.


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