Battery monitor + combiner/isolator. How does it work?

[Fffrank]

I'm using a Renogy battery monitor with a 500a shunt (https://www.renogy.com/500a-battery-monitor/)

It seems to work fine when I'm using it as intended -- monitoring the usage/drain on my fully charged batteries.

But how does it compensate or work when my batteries are combined? Either when the genset is running the charger or when the alternator is charging the battery banks (and the BIRD isolator senses charge volatage and combines.)

[astrocamper]

The shunt is between the negative battery terminal and ALL DC negative connections. It monitor NET amp flow in/out of the battery. It doesn't matter that there may be multiple charge or discharge sources involved. It only shows the resultant flow of amps as a positive (charging) or negative (discharging) number.

[Fffrank]

Originally Posted by astrocamper

The shunt is between the negative battery terminal and ALL DC negative connections. It monitor NET amp flow in/out of the battery. It doesn't matter that there may be multiple charge or discharge sources involved. It only shows the resultant flow of amps as a positive (charging) or negative (discharging) number.

I understand that -- but this is in a Class A and the chassis battery bank has a different ground. And there is a system that combines the banks during charging events. See my confusion?

[astrocamper]

I just read the manual regarding the Renogy battery monitor. It appears not to have any additional connections related to monitoring your chassis battery bank. If your Class A has a way to combine the chassis and house bank while charging it should be a connection beyond the shunt so it will still allow the Renogy shunt to monitor the net current flow in/out of the house bank. It doesn't matter if some of the charging sources are also flowing to the chassis bank.

If you have any DC connection to the negative terminal of your house bank, the Renogy shunt will not be able monitor the total flow in/out of the house bank.

[twinboat]

It is only monitoring the house batteries.

What ever goes to the chassis battery, while on shore power, isn't measured.

It makes no difference to the condition of the house battery.

What goes to the chassis battery isn't measured, while the alternator is charging. Only the amperage that's going in the house battery is measured

In both cases it measures what's going in and what's comming out of the house battery bank.

If the alternator is charging the house battery and your using house light and pumps, the alternator handles that. Nothing is coming out of the house battery, and what's left may be going in, unless the house battery is full.

[Fffrank]

Originally Posted by twinboat

It is only monitoring the house batteries.

What ever goes to the chassis battery, while on shore power, isn't measured.

It makes no difference to the condition of the house battery.

What goes to the chassis battery isn't measured, while the alternator is charging. Only the amperage that's going in the house battery is measured

In both cases it measures what's going in and what's comming out of the house battery bank.

If the alternator is charging the house battery and your using house light and pumps, the alternator handles that. Nothing is coming out of the house battery, and what's left may be going in, unless the house battery is full.

Got it. So combining the two banks while there is charging happening is not throwing off or causing the monitor to become out of sync.... correct?

[astrocamper]

Correct. If the house battery has nothing on the DC negative connection but the shunt it should work fine.

[Fffrank]

Originally Posted by astrocamper

Correct. If the house battery has nothing on the DC negative connection but the shunt it should work fine.

Only negative connections on that bank are through the shunt. Thanks for explaining this to me!

[paul65k]

Originally Posted by Fffrank

I understand that -- but this is in a Class A and the chassis battery bank has a different ground. And there is a system that combines the banks during charging events. See my confusion?

When adding a battery monitor shunt you need to separate the grounds from the Chassis and the house batteries, even if they were wired together from the factory, as mine were.

This is as easy as only putting the house batteries on the "Load" side of the shunt and putting the chassis batteries on the other side of the shunt which will then go to the chassis grounding point.

When I first installed my shunt it was installed incorrectly and I did get some erroneous readings but this was remedied when I got the wiring correct

[Fffrank]

Originally Posted by paul65k

When adding a battery monitor shunt you need to separate the grounds from the Chassis and the house batteries, even if they were wired together from the factory, as mine were.

This is as easy as only putting the house batteries on the "Load" side of the shunt and putting the chassis batteries on the other side of the shunt which will then go to the chassis grounding point.

When I first installed my shunt it was installed incorrectly and I did get some erroneous readings but this was remedied when I got the wiring correct

My chasis grounds go from the batteries to the frame. My house batteries go from the shunt to the frame. This is what you describe, right?

[astrocamper]

Originally Posted by Fffrank

My chasis grounds go from the batteries to the frame. My house batteries go from the shunt to the frame. This is what you describe, right?

This is correct. Just verify there are no other connections to the negative side of the batteries except through the shunt.