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18650 capacity test
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drummerdimitri:
I've got some random salvaged 18650's that I'd like to test for actual capacity, however I am not sure to what voltage they need to be charged prior to discharging them and at what current and to what voltage should they be discharged?

Is there some kind of standard for 18650 capacity testing or does every manufacturer go by their own criteria?
sleemanj:
If they are used then even if the manufacturer had a  published standard it wouldn'`t be very useful.

Measure voltage discard any 0v. Charge them fully (using a proper charger, do the bulk charge slowly say 500ma, and preferably in a suitable explosion containmemt container, check after a few minutes to be sure it is accepting a charge), disconnect let sit for a week and remeasure, it shouldn't have dropped too much (testing self discharge), use a cc discharge at 1a and measure capacity down to 3v, decide if that meets your needs or it's too low capacity to be useful, you might go to 2.7v but diminishing returns. 

If it loses more than 0.2v in a week from 4.2v I'd say trash, if it's capacity is less than 600mAh not really worth it, and if it never completes charging obviously trash., but if it charges, holds, and has a decent capacity at 1a, all good, charge it back to a storage level and put it in your stash (suitable explosion containment stash of course!)
Audioguru:
An older 18650 lithium-ion cell is charged at its recommended current (500mA is fine but might take hours) to 4.20V, then it is about 70% fully charged. Then the charging current must be monitored and the charging must be stopped when the current has dropped to about 33mA. If its voltage has ever dropped lower that 3.0V to 3.2V then it is ruined.

Newer Lithium-Ferrous is charged to a lower maximum voltage and newer Lithium-Graphene is charged to 4.35V.
sleemanj:

--- Quote ---If its voltage has ever dropped lower that 3.0V to 3.2V then it is ruined

--- End quote ---

I have quite a few cells with plenty of capacity (up to 2Ah) that were salvaged after having sat at 1v or even less for long LONG periods of time.

As long as you take care when you initially charge and characterise, there's no problem.  Deep discharge (at least as a one-time) on it's own really isn't as damaging as the old wive's tales might imply.
sleemanj:
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