Guess-timate sealed Li Ion pack capacity?

[burpee]

I bought a Magic Shine bike light system with a Li Ion battery pack that is sealed in shrink wrap.

The battery is a 4x18650 package, there doesn't appear to be any PCB attached, and there is absolutely no literature on the sales web site or anywhere else, other than stating predicted run times for the battery.

So is there any way to test the battery to have some idea of the quality of the cells and the theoretical capacity? I mean without opening and dismantling the battery.

So far I do know that it powers the light at "middle setting" for well over five hours.

During this run time test, the voltage dropped to 6.6V from 8.3V. And the current rose from .7A to .85A - apparently averaging ~5.75 watts output for 5.5 hours.

Thanks.

 

[Battery Guy]

Pictures would certainly help.

Given the voltage range you mentioned, it sounds like a 2S/2P configuration.

It worries me that the pack has two parallel blocks in series with no apparent PCB to protect against imbalance, overcharge or overdischarge of one of the parallel blocks.

BG

 

[burpee]

The MS lights are ordered from an unknown vendor in China with DealX acting as an international broker. The light I got looked like it had been "through the wringer." Probably a dealer return or refurbish. The battery was a normal rectangle, in tight black shrink-wrap with a lead coming out the top at 90 degrees. But there was no hint of additional material or objects glued to the top or bottom. (or side)

That got me wondering if the pack was four "protected" cells, as opposed to the use of a PCB. OF course it IS 2s2p and has been charged to 8.5V once. And as I mentioned supplied 5.7 watts for 5.5 hours - which I construe to mean it supplied 30 Watt hours. Which I suppose must mean the battery is a ~32 Watt hour battery. Which I assume means I could use just two of these cells in a carrier and expect nearly three hours run time.

That way I can go on becoming a flashlight freak in the future because now I would have the option buying flashlights that use 18650s.