BQ24735: is necessary 4s balancing with 18650 battery?

Hello everybody.

I'm evaluation this application:

• battery powered board
• 4x 18650 cells
• single cells has PCM
• I need to put these cells in series
• BQ24735 for charger
• I've onboard microcontroller

Questions:

• is strictly necessary to do cells balancing with 18650? there's a simple IC like BQ29209 that do that for 4 cells?
• what happen if I don't balance cells? problem with operating time? danger behaviour of cells?

I two commercial application I retrofit I found 18650 (with single PCM every cell) placed in series without balance.

So I'm not sure if I need it or not

I didn't find simple balancers for 4 cells in TI portfolio. Something like BQ29209.

So I'm trying to design a MCU managed balancer. Here you are my draft.

I can read single cell voltage (here you don't see analog frontend) and I can apply a discharge resistor to any cell.

Thanks for any reply to my questions.

Thanks

Stefano