Tech,
I agree on the voltage measuring but given that it is a LiPo the internal resistance is very low. I think that the short circuit current is 80A so that would give 11.1V/80A = 0.14 Ohms.
It's a good point about the resistor values. However, I calculated that I would drop only 0.7mA ((3.7V/16000Ohms) * 3) which I termed as acceptable as the entire system will be drawing about 10A, thus making this negligible. However, my original design for the voltage dividers was in the region of about 500k but scaled this down after reading on these forums that you don't actually want to exceed much more than 20kish. Presumably the reason is that the arduino input impedance isn't high enough to support such values.
Thanks for your input - it's much appreciated.
Thanks,
Jonathan