two 8S-BMS - how to connect

[303acid]

Hey,

like in Topic: must i use 2 Wemos for two BMS or is there another wiring trick?
My Idea: Use a ESP32 - it has 2 UART's <- possible?

for generally: can you also build a ESP32-Version? yes, it's overdose for simple tasks but sometimes usefull

[softwarecrash]

there will no esp32 version.
general its a VERRY BAD idea to connect two bms to a common ground, the bms cut the ground when switching the FETs, then you build a ground loop and destroy both bms and the esp

[303acid]

ok, that means i must use two adapters. Will it be OK to power this the 2 Wemos over USB from one power supply like a mobil charger?

[softwarecrash]

no, with one usb charger with two connections to two esp and bms will build the groud loop again, need two seperate powre supplies. have a bunch of user that do exact this and burns the esp and bms.
that will work and run until the bms cuts the discharge FET

[303acid]

oh yes, youre right! maybe a good idea to ues a buck converter from batterypack (24V) to 5V for the wemos?

[softwarecrash]

a buck will work but ONLY when it connected to the battery cells directly. a connection on the bms "output" line give the same behavior.

[303acid]

that was the idea.

what is with a galvanic isolation for RX/TX with optocoupler like for the relay option...?

[softwarecrash]

Tx rx need ground to Work, need a transmit Isolator, that make the communcation instabile, allready tried.