Hi guys
So I recently bought a 12V SMD (LED60 MR16) spot, meant to be used for indoor lighting with a LED transformer. I decided to make it into a flashlight by powering it with a pack of 3 x 18650 batteries in series. After the first time of extensive use, one of the 18650 cells short circuited. I didn’t think much of it and replaced the battery. But after using it for some hours, without any problems, I measured the voltages of the separate cells.
The left one (closest to the - pole) had lost pretty much all voltage and was at 0.02V, while the right one (+ pole) is still over 4V. I tested it with different batteries and got the same result, the only difference is that the left battery measured out at a voltage very close to 0, but rose over time until it was back to around 4V. The battery I originally measured won’t rise and even has a negative voltage. I’m absolutely lost as what could cause this and what I can do to prevent it.
I hope someone here can shed some light on this mystery.
PS: cells are unprotected, the cheap kind from DX.com