I assume you want a way to discharge the cells to find the culprit?
Get something like this.....
250watt 0.1 ohm Resistorhttp://store.evtv.me/proddetail.php?prod=250wresistor
and one of these because you can hook up to a PC and record the data with time
stamps.
TekPower TP4000ZC PC based RS232-Interfaced Auto RangingDigital Multimeter,
MS8220R
Alikehttps://www.amazon.com/TekPower-TP4000ZC-RS232-Interfaced-Ranging-Multimeter/dp/B000OPDFLM
You can do groups like Cor said to narrow it down. You should see a significant
difference in voltage drop under load if you have a bad cell. You can also use
this meter to easily calculate amp hours in or out since you can save the data
to an spreadsheet format.
You could also buy a powerlab 6 because they will discharge as well. Or a
regular battery load tester.
They make them for lithium chemistries. Something like this should work.
https://www.amazon.com/Tenergy-Intelligent-Capacity-Discharger-Resistance/dp/B0178P8H9U
Unless I misunderstood what you are asking.
In addition to how fast the voltage drops you can measure the resistance of the
cells and the speed at which the cell recovers voltage after removing the load.
You should be able to spot one out of family.
From: Mike Beem via EV <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thursday, June 23, 2016 1:02 PM
Subject: [EVDL] Lithium Battery Testing
I spent some time looking through the archive, but couldn't find what I'm
looking for--> I think I have one weak cell in my 40 cell 100 Ah pack; I'm
getting a low battery signal (mini BMS) under load when there is more than
sufficient range left on the charge. These are CALB batteries which I
installed in December 2012. I recently tried going through and individually
charging each one to 3.5v (after charging the whole pack to shut-off point)
with my variable power supply, and at 2 amps maximum, it took me almost 2
weeks of not driving the EV (http://www.evalbum.com/4181) to get all the
way through, so I used a timer, which of course, would defeat the whole
process by not being able to WAIT for 3.5v on every one...
When I first started driving it with the new pack in 2012, it did have the
40 mile range I aimed for when I put this together. I have only driven it
to the limit of the pack once since then, and it was in a colder winter
than we usually have, so I wasn't surprised to have much less range.
I need an easy to put together load I can use with a voltmeter to test
cells, and a range for what voltage drop on these CALB cells would be
normal or weak. I got fairly good at this with lead acid, both flooded and
AGM, but don't have the experience or science to know if, 1) this is a
reasonable way to proceed, and, 2) what those voltage-drop decision points
would be, and, 3) what components to use for the load?
Thank you!
Michael B
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20160623/fd3e157a/attachment.htm>
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20160623/dd0840c1/attachment.htm>
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
