How to determine the charging Amps of a battery pack?

[ebike11]

Sorry if this is an easy question for you pros,
but the pack is not my own. Its a Samsung SDI 36V 9 or 10Ah lithium battery pack that my friend bought second hand however
no charger came with it.
I seen that for the most part, chargers that come with ebikes are around 2A charge rate.
This battery came from an ebike but he will use the battery on a different bike he is building.
Is there a way to know the charging Amps in order to purchase the correct sized charger?

Thanks!!

 

[Hillhater]

Ideally, you would determine the actual cells used in the pack, then look up their data sheet on line to find the manufacturers recommended charge rates.
Failing that , you won't go far wrong by choosing a charger that supplies around 0.5 C charge rate.
So for your pack, a 4-5 amp charger would work well.

 

[dogman dan]

I tend to agree, 3 amps charger should be fine. If you need a faster charge, up to 5 amps should work without major problems.

The bms may be the limiting factor in fact, but most will allow up to 5 amps charging.

 

[ebike11]

I think its a 10s pack...36v

 

[DrkAngel]

.5C is the maximum recommended charge rate for many packs ...
However!
.5C rate should be based on the actual capacity ... not the labeled capacity for new cells.
5A would likely be excessively damaging for a used 10Ah pack.
A cheaper 2-3A charger is safer, and better, unless rapid charging is necessary.

My homebuilt 25.9V 25.92Ah Lipo battery began getting warm during 10A charging after actual capacity dipped below 20Ah.
At modest charge rates most Lithium technology batteries charge at near 100% efficiency = no notable heat production!
Lipo getting warm while charging is a bad sign.

Especially, RC Lipo are often "maximum" rated for much higher charge rates but "recommended" (for safety and longer life) is usually ≤.5C.

 

[izeman]

as dogman said: the bms would probably be the limiting factor. small battery packs often except only very low charge rates. so with a 2A charger you should be on the safe side - battery and bms wise.
even cellman's small high quality 18650 packs only take low charge rates.