The mco runs the charger. It looks like this

From the top, a 12V to 5v smps module. On the left, supplies from mower run and charger in.

an esp32.

on the left, the beeper. Unused ADC on the right. Too hard to remove.

plug for the SOC gauge on the left. a temperature sensor on the right 

Enable plug for the VMON optoisolators on the left.

any smarts for this board is in the software.