Protection Circuit

[matt304]

I built a light using 2x 18350 cells which are unprotected cells.

I have a bit of extra room inside the light to place a low-voltage protection circuit.

Where can I find small protection circuits suitable for cutoff of two 3.7V cells that are placed in series?

 

[alpg88]

http://www.batteryspace.com/pcmforli-coli-mn-nibatterypacks.aspx

 

[matt304]

Thank you for the link. A lot of good stuff there.

Unfortunately, I don't believe I can use those.

My light gives me a limitation of about 0.7" ID circular to lay a flat board.

The one chip they show for a single cell would work it appears, but all the chips for 8.4V dual cells are long and will not fit the chamber.

Any other suggestions anyone?

 

[matt304]

Would it be possible to stack two of the circular 3.7V modules, then wire them in parallel input/output?

I'm not sure that would work because even in parallel from the source, they would each still see 8.4V, correct? I believe it's not the voltage that would be halved, but the amperage...

 

[alpg88]

Where can I find small protection circuits suitable for cutoff of two 3.7V cells that are placed in series?

http://www.batteryspace.com/pcbfor74vli-ion1865018500batterypacks7alimit2round.aspx

 

[matt304]

http://www.batteryspace.com/pcbfor74vli-ion1865018500batterypacks7alimit2round.aspx

Yeah, see I only have about 0.7" of space diameter. It needs to be about the size of a coin to work...

 

[alpg88]

Yeah, see I only have about 0.7" of space diameter. It needs to be about the size of a coin to work...

than get 2 pcb, one for each cell, http://www.batteryspace.com/PCB-for-3.7V-Li-ion-18650/18500-cell-Battery-2.0A-Limit.aspx
but it pbly be easier to buy protected cells.