1S2P 18650 protection

Hi guys... I am just playing with an idea I have had for a while: modifying a cheap DX zoom headlamp with a dual 18650 battery pack.

Basically it would be 2 18650s wired in parallel, a single Li-ion 1A driver board (3-4.2V) and a single 18650 protection circuit board covering both cells. This would effectively give me around 5 hours of 1A output at 3.0 - 4.2V

Negative terminals of the batteries would connect before entering the protection PCB, same with positive terminals. From there it is connected to the driver... and then the LED itself.

Current should not be an issue as if a short occurs the PCB should save the batteries otherwise it should be around 0.5A from each cell. Is there a danger that the batteries will become imbalanced or will the voltage and/or internal resistance of the cells balance each other as they are drained (e.g one cell has lower voltage so less current is drawn from it until cells are level)?

Any advice and observations greatly appreciated.

Some thing like this ?


They will only fit unprotected cells like the NCR18650A's

Cheers mate. Have a good ANZAC day, least we forget.

I have seen the above before but not any reviews for it, the big negative for the above is that it can not take protected cells, as well as I want to integrate the LED driver board into the holder as well (protection PCB on the end of one cell and driver board on the end of the other, to give me a nice compact design).


I see where your comming from, i have no idea,s to help, i have tested some 3s1p and the protection works.

should be ok. Cells in parallel don't need balancing, so I'm told, so I shouldn't worry about that. I bought a single cell PCB from DX


a little while ago to protect a recycled laptop 18650 for use in a headlamp (just a single 18650, two would be too heavy for the band). Haven't had time to hook it up yet, so the protected cell I have is still in there, but it looks decent and the reviews are good.