This is what an Imon looks like

Imon is built on a vmon board.  Imon was the result of a mistake, and I needed to complete the project and mow the lawn.

The mower internals partly looks like this. 4 batteries with a current shunt (just a 4 terminal resistor). There is a 48V to 12V SMPS. Nothing special, The negative input connects to the negative output. A converter to 5V runs the mco logic, with an ADC.  When charging, the voltage across the current shunt is positive to the reference 0V net. Which is fine for the ADC on the mco board.  When mowing, the voltage from the current shunt is negative , ie below ground, to the ADC inputs, Which is NOT fine for the ADC. 

So I took a VMON board that I had previously discarded, I stupidly blew it up by shorting 12v on the vmon battery terminal to one of the I2C control wires on the temperature regulator, with a spanner tightening the bolt.   This smokes anything connected to I2C. esp32, 2 temp sensors, ADC.  Sigh.

By powering the repaired vmon, hacking a little, renaming the boioard and giving it a new dose of software. with a couple of new resistors,  wires and hot glue,  and an isolated 12v to 5v power supply module, I could float the logic on the board, and bias the curren tshunt to the mid rail of the imon board .