[TurnNBurn]

Originally Posted by mechman600

The 2560 has 16 analog inputs. You need 18 if you want to monitor all of your cells, so, a mux shield. But all you really need BMS for when bottom balancing is shutting off the charger, so you really only need to monitor one cell - the weakest one/quickest to charge.

Here is the relay I bought (but haven't used in my car yet):
G8P-1A2T-F-DC12 - OMRON ELECTRONIC COMPONENTS G8P-1A2T-F-DC12 - AUTOMOTIVE RELAY, SPST-NO, 12VDC, 30A | Newark element14 Canada

I must have missed that. I didn't see it only had 16 analog inputs. I got it now.

So I'm looking at the batteries and I have (obviously) the two cables from each pack. These two will go to the analog inputs on the mux shield? And from the mux shield that will be connected to the display?

What worries me is I look at that wiring diagram for that fuel guage and I know there's going to be more parts to this BMS. Transistors, resistors, transducers, etc... I'd need a diagram to study and a full parts list up front before I feel safe tackling it. Do you have a diagram for the BMS? So I can get a feel for what's required for that?