12v lifepo4 4s to 48v

[polygon]

Hello,

I own 12 x 12v lifepo4 batteries that i want to use in a 4s and 3p
from what i understand the 12v batteries have built in bms can i just wire like on the image bellow the battery bank or do in need anything else?



thank you for your help!

 

[sunshine_eggo]

You need to check with the manufacturers. Some do not permit putting their batteries in series.

If permitted, you definitely want to fully charge all indivual 12V before putting them in series.

EDIT: There are also 12V balancers that monitor each 12V in a string and transfer charge from high to low.

 

[FrankB]

I opened for that reason an 8S BMS. I found a tvs diode with 75V breaking voltage. The Diodeis from "littlefuse.com". So from protection point of view it should be possible ( in my case!!). To be shure, you need to oben your BMS
But netherless i decided to use an 16S BMS for the 48V system. My main concern are the losses, that you have on each protection transistor. So compared with an 16S BMS, you get 4 time the losses with your 4x4S System.

 

[polygon]

I opened for that reason an 8S BMS. I found a tvs diode with 75V breaking voltage. The Diodeis from "littlefuse.com". So from protection point of view it should be possible ( in my case!!). To be shure, you need to oben your BMS
But netherless i decided to use an 16S BMS for the 48V system. My main concern are the losses, that you have on each protection transistor. So compared with an 16S BMS, you get 4 time the losses with your 4x4S System.

thanks you what would happend if i connect the batterie in series without checking the internal bms?

 

[FrankB]

In normal Situation nothing happen. But the short circuit protection wouldnt work. In that case, you get some arcs in the BMS: in the MOSFET and the tvs diode. For an 48V system you need the 75V tvs diode!