Redilast Mini USB Li-ion Charger Question

I know nothing about battery chemistry or electronics, and I am happy to have this forum.

I bought a TnC Extreme Micro Turbo light and a dozen IMR 15270 batteries (3.7V, 400 mAh) and I am interested in using the Readylast Mini USB charger. My question is: the charger comes in 500, 250, and 100 mA. The seller warns that the 500 mA charger should not be used in batteries less than 500mA. Would the 250 mA charger completely charge the battery? (again, it's a 400 mA battery.)

The light is beautifully machined and impressively bright for such a small light. Bob at Peak LED was very helpful and knowledgable about his products, and easy to reach. If you're in the market for an American made flashlight, I would recomend going with one of the TnC products.

thanks

jayp said:

The seller warns that the 500 mA charger should not be used in batteries less than 500mA. Would the 250 mA charger completely charge the battery?

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Yeah, that's completely fine.

Changes in mA only affect how fast the battery charges. Using 100mA instead of 200mA would about double the time to charge.

Generally and up to a point, slower charging is better for the battery, and charging too fast can be bad.

Charging current is often given as a function of capacity, where 1C for a 400mAh battery is 400mA, 0.5C for the same 400mAh battery is 200mA. Does that make sense?

As a rule of thumb, if you're not sure, stay at or below 0.5C for the battery, so for a 400mA battery, that would be 200mA. Using the available choices for the charger, that would be 100mA, but 250mA is probably also just fine. You could try 100mA first for example, and if you feel it's too slow, try charging it at 250mA, and keep an eye on the temperature of the battery. If you feel it's heating up, keep using 100mA, if it's completely cold, keep using 250mA.

Thanks for the clear and informative answer terjee.