Monitoring one set of batteries-what's missed?

[RMo]

So.… I’ve been reading a lot about the impossibility or impracticality of measuring all your battery input/output in systems where there are 2 sets of batteries each with a separate ground. In my case, a 2015 CS Adventurous with two 6v AGMs under the hood that power the fridge, DC outlets and small electricals, and a larger 24v AGM bank that powers the A/C and has an equalizer connected to the front AMGs. The front AGMs are charged by the MB standard alternator (I think) and the rear AGMs by the second alternator, solar, or shore power.

The leading solutions mentioned for measuring usage seem to be: using a shunt on the positive side with a Blue Sea monitor, running a cable to a common ground and using a negative-lead shunt, using two monitors (I got lost trying to understand this one), or just living with it.

My question is: If I attach a monitor to the negative lead on the rear AGM bank (e.g., a BVM 712) and do so according to instructions, what will my monitor readings be showing? In other words, what current will I be missing? Also, will current used to “equalize” the batteries be captured with this set up?

I’m not looking for the perfect solution; I’m just trying to understand what is possible within my abilities and would provide useful information for battery maintenance and use. Thanks for any and all input.

[@Michael]

I ended up with two monitors, one for each bank. I want to know the status of each bank, not the status of both banks combined, so separate monitors are needed.

I ended up with a monitor on the '+' side because one of my banks was grounded in multiple places and was too difficult to re-wire to a single ground point.

Not all monitors are capable of installation on the '+' side.

[Winston]

Originally Posted by RMo

My question is: If I attach a monitor to the negative lead on the rear AGM bank (e.g., a BVM 712) and do so according to instructions, what will my monitor readings be showing? In other words, what current will I be missing? Also, will current used to “equalize” the batteries be captured with this set up?

Although we don't own your model Class B, we think the answer is clear if you place the shunt as the only connection to negative lead of your rear batteries. You will measure the 1) instantaneous current entering or leaving the rear batteries including all charging and discharging currents and including any "equalize" current; 2) the voltage of the rear battery; and, 3) the State of Charge of the rear battery.

We are sold on the value of such monitors and, were we in your shoes, we'd put separate monitors on both battery banks.

[RMo]

Thank you both! I am especially glad to hear that the equalizing current would be measured. I think I'll go for a cheap DC-outlet-plug-in voltage monitor on the front batteries, as I am most concerned about the rear bank.


Thanks again,
Reed