What battery is it?
I use these in all my devices. At 35 amps, they leave little room for error even when they begin to weaken. Batteries tend to begin malfunctioning near the end of their lifespan. A typical lifespan for a heavily used 18650 is usually about 1 year. And lower Amp cells tends to malfunction more so than a higher Amp cell.
Molicel P26A
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Liion Wholesale is great trustworthy site to purchase them from.