Hi,
You really need isolation, flying capacitor would be the simplest to use with small low power relays.
OR
Google;
multiple cell measurement I2C isolator
You will find many other methods also look for SPI isolation systems.
Tom.. 
Hi,
You really need isolation, flying capacitor would be the simplest to use with small low power relays.
OR
Google;
multiple cell measurement I2C isolator
You will find many other methods also look for SPI isolation systems.
Tom..