Testing cells before pulling packs apart

Oz18650

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Oct 2, 2017
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As dismantling packs is a slow and difficult process, why not test cells before time and effort is spent on extracting and cleaning up cells, only to then reject them after all the effort?

I have access to a number of 7s1P packs which have balance leads on a plug which was connected to the controller board on the device the pack was in.

I checked a pack just now, and between the main + wire and the first connector on the balance plug, is the voltage of one cell.
between the plug wire 1 and wire 2 is a cell voltage.
etc, etc.

I think I might be able to charge and test all the cells via the existing main wires and balance lead plug, before putting in the effort to dismantle the packs and clean the cells.

Can anyone see any flaws in this idea?

Does anyone test cells before dismantling packs?

I think there may be an issue doing this with laptop battery packs as
a) there are cells in parallel, so a test would find capacity of 2 cells.
b) there is usually circuitry within the battery pack which may interfere with this process (eg doing anything to balance the cells would ruin test results)

With cells in parallel you may still get useful information, eg if 2 cells in parallel shows 1000mah, they are going to be rejected by most people, and a result of 4800mah is going to mean both cells are going to be usedfor most people.
 
If its without BMS i always test before dismantle. Especially large packs.
 
When i get an ebike pack which will be hard and time consuming to take apart (like those that are engulfed in rubber /silicone) i always expose 1 cell or 1 parallel block and attach my imax b6 with magnets to check the cells.
Normal ebike packs are quick to take apart and mostly perfect in my case so far so i dont bother with prechecking those.

U could also write a 1 on one pack, 2 on the next and take out one cell of each to test. Then u can assign the cell to the pack it came from. Might be quicker then rigging up a tester to use with the balance leads or some other jig for that purpose.
Thats how i did it with the laptop packs.
 
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