Battery protection for 2S2P battery pack

Thread Starter

pmd34

Joined Feb 22, 2014
507
I need to make a battery pack 2 batteries in parallel x 2 in series (ie total 4 batteries) using some 18650 cells (without built in protection). I have found a suitable 2S cell ppreotection IC with cell balancing, over current, over / under voltage etc. that looks good, but I guess I need to have individual cell protection instead or as well, as if one of the cell fails for example, the charge discharge current could end up being handled by one cell alone.
What would peoples recommendations be? There seems to be a vast number of ICs out there but non of them seem to do everything, they might do single cell over / under voltage, but no current limit, they might do 2S cells but have no cell balancing (and its a pain if I have to do this with a separate circuit its hard to make a circuit that doesn't consume power while not in use, and in a way it is bypassing the under voltage protection!)
 

Yaakov

Joined Jan 27, 2019
1,612
There are quite a few small 18650 protection boards designed for direct mounting on the cell itself, would that work?
 

Thread Starter

pmd34

Joined Feb 22, 2014
507
Hi Yaakov, its sort of the way my thoughts are heading, but then I should still have some cell balancing in, so I could end up with a lot of duplicated functionality, and also lots of FET switches causing additional power loss... it just feels.. "messy"!
 

Yaakov

Joined Jan 27, 2019
1,612
Hi Yaakov, its sort of the way my thoughts are heading, but then I should still have some cell balancing in, so I could end up with a lot of duplicated functionality, and also lots of FET switches causing additional power loss... it just feels.. "messy"!
It might not be ideal but I wonder how much loss you’d experience with the directly mounted boards. The duplication itself isn’t so bad, redundancy in safety is a good thing. I suppose, cheap as they are, you could but
Y a few examples and test.

You remind me I had intended to do just that. I have quite a few salvaged 18650 cells and would like to use them singly in a simple way.
 

Thread Starter

pmd34

Joined Feb 22, 2014
507
The DW01 looks ok but it still needs some FETs to disconnect the battery thats the advantage of the KC05111. The size is no trouble, some solder paste and a cheap re-flow oven, but its not a very cheap IC.
 
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