Legal Removal Request

Post: Thanks for the swift response. I'm pleased to hear about the compatibility as the 3A+ is so economical to buy and runs at quite low power. The common ground is certainly consistently there except that, as I mentioned there is an offset of about 20mV because essentially the battery measurement is made using conductors carrying negligible current (milli amps at most), whereas the supply to the Pi probably carries a good fraction of half an amp, leading to the measured voltage difference. The offset of 0.53V is not on the measurement of the ADC. Both +ve and -ve inputs of some channels of the ADC are elevated. They are happy to be connected together and the ADC correctly reads a differential of zero but when I measure the pair's voltage to ground with a DVM (~10Mohm input impedance) I find this figure. It is not there for all channels and I think it changes after a Pi reboot. e.g. yesterday, channels 3 and 5 were 0.53V above ground and the others all within 1mV of ground. Today it is channels 1 and 5 in that state, with the others at ground. None are currently connected to the dividers because I don't want to risk blowing up another board until I have understood why it happened last time. Whilst out walking, it came to me that I could put a moderate rating resistor, say 25kohm, in the connections between the divider and the input on both +ve and negative legs to limit current flow with only a 1 or 2% effect on the voltage reading which I can calibrate out. I know this wouldn't protect against an accidental application of 12V, but I'm quite confident that that isn't what happened. I should also have mentioned that I have two ADCDifferentials again now, and that both of them exhibit this, both on a Pi4B as well as on the 3A+. Currently the one on the 4B has the 0.53V on channels 1 to 3. Bonding the -ve to earth might solve it if the capacitive explanation is true but until I just thought of bonding via a 25kohm reistor I haven't dared.