Hi,

I have am building a project that requires 12v power and to do this I will be making a battery pack out of 3 LIPO Polymer batteries. Each battery has a protection circuit on it. My question is simply do I need to add a 12v battery protection board on top of this to protect the battery pack as a whole, and stop each cell being overcharged, or can I simply connect the batteries in series?



Is there any advantage to have a 12v board? Perhaps in terms of charging, since you have 3.7, 7.4 points across it? I'm no expert on how these things work, as I usually build battery packs with 18650 batteries that don't have protection and I always add a BPB, so any advice appreciated.

Thanks.

 

You need a 3S1P BMS (Battery Management System) that includes balancing.

The LiPo protection boards are not a BMS,

 

You can buy modules that only do balancing; look for 3S balance. The usual ones are resistive, but there are active ones as well. Active is mostly for off-grid applications where every watt is precious.

I'm a little wary of using three protected cells in series, but I can't say for sure it's a bad idea. The one thing I will say is that protection boards do not manage lithium charging, they only protect from overcharging. You need a charger or brick that is explicitly made for lithium charging; for 3S it'll be 12.6V and have a two-colour LED to indicate charging/charged. There's also some solar charge controllers that include lithium charging modes, modules with buck converters to charge from higher voltage DC sources (MAX745 for example), or that boost from 5V USB C.

 

That's very helpful. Thanks for your replies. I have some 3S1P BMSs that I have used in projects before. I hadn't noticed the protection circuits on the batteries themselves then, so it's not hassle to add the BMS on top. Thanks.