Tube Battery Adapter for 18650 cells. Do I need discharge protection?

[timhester81]

I wanted to refit my old 3D Maglite so I made this holder for 2 18650s. It's a drop in replacement for the 3 D cells. I also replaced the incandescent bulb with an LED replacement from Amazon that works from 4v~24v.

I have the batteries wired in serial. I don't intend to charge the batts while in this, this is simply a holder for loose cells. I've gotten some feedback that I need discharge protection. On the one hand I'm using salvaged cells that were pretty cheap to me, but I certainly don't want to risk anything dangerous.

BTW; this is up on Thingiverse Tube Battery Adapter for 18650 with STLs for 2~7 D cells, and 2~7 C cells. It's designed in OpenScad and the source file is there also.

 

[floydR]

There are 2s bms's, battery protection boards. Probably would be smart to include one in the design.
later floyd

 

[Oleksii]

Those springs (which I always don't like) should have at east 100mR (milliOhm) resistance. So it increases resistance on cell itself 2-7 times, depending how high-drain cell is.
Just keep that in mind.

 

[cak]

If you are charging outside the holder I would think at minimum you would want a low voltage cutoff. Realistically the most likely effect of not having protection is that you would overdraw the cells and damage them.