Wiring bms in charge circuit only.

[Edguy83]

Hi, in a previous post I wrote about dismantling Volkswagen battery modules to make 24v 7s battery packs. I have successfully dismantled the modules and created 3 7s 24v packs, now i am planning the bms and charging method. As these cells are capable of high amp charge and discharge the cost of three separate high amp bms units is very expensive so I'm wondering if there is any issue buying lower amp bms for example 3 x 20amp bms and wiring them into the charge circuit only, I have read that it's possible to wire the negative wire from an inverter direct to battery instead of via discharge wire of bms so the bms will still work on charging but not on discharge.
Second question is how would I connect a charger to 3 separate bms and if I'm using 3 separate 20 amp bms what size charger would be best?
Thank for any feedback

 

[sunshine_eggo]

Hi, in a previous post I wrote about dismantling Volkswagen battery modules to make 24v 7s battery packs. I have successfully dismantled the modules and created 3 7s 24v packs, now i am planning the bms and charging method. As these cells are capable of high amp charge and discharge the cost of three separate high amp bms units is very expensive so I'm wondering if there is any issue buying lower amp bms for example 3 x 20amp bms and wiring them into the charge circuit only, I have read that it's possible to wire the negative wire from an inverter direct to battery instead of via discharge wire of bms so the bms will still work on charging but not on discharge.

Bypassing the BMS in charge or discharge is just a bad idea. All charge and discharge should pass through the BMS to insure the BMS can protect the battery.

Cheaping out on the BMS is a good way to destroy your investment.