I have two 6V batteries in series to provide 12 V. This is a common setup for deep-cycle batteries used in RVs, golf carts, etc.
It would be really useful to be able to measure the voltage of each battery independently, but the reference ground of the other battery is different.
I guess I could measure the first battery from ground to plus, then measure the total voltage in series and subtract to get the voltage of the other battery.
But is there a way to use the Arduino A/D not referenced to chip ground?
cptdondo:
I have two 6V batteries in series to provide 12 V. This is a common setup for deep-cycle batteries used in RVs, golf carts, etc.
It would be really useful to be able to measure the voltage of each battery independently, but the reference ground of the other battery is different.
I guess I could measure the first battery from ground to plus, then measure the total voltage in series and subtract to get the voltage of the other battery.
But is there a way to use the Arduino A/D not referenced to chip ground?
No, the voltage to a arduino analog input must be referenced to the AVR chip's ground pin so the external voltage negative terminal must wire to an arduino shield ground pin.
There are threads on these forums that describe how to measure the voltages of individual cells in a large stack, mostly involving additional processors and opto isolators. For a stack of 2 it is much simpler and sufficiency accurate to measure the total voltage and the mid point voltage.