Earthing a Dual Battery System with VSR

[oncoarse]

I'm fitting a dual battery system to my Fibreglass boat. The system includes a Voltage Sensitive Relay, which has an earth lead attached. Could anyone offer advice as to which earth terminal I should attach the lead to - the starting battery, or the aux battery. Or is there no difference? Thanks.

[John Buoy]

I'm fitting a dual battery system to my Fibreglass boat. The system includes a Voltage Sensitive Relay, which has an earth lead attached. Could anyone offer advice as to which earth terminal I should attach the lead to - the starting battery, or the aux battery. Or is there no difference? Thanks.

Neither Ideally the VSR earth wire needs to fitted to the house negative buzz bar.

Regards Frank

[foxx510]

The earths of the two batteries will be connected together, so it doesn't matter.

[Spaniard_King]

For the VSR to be activated it needs to complete a circuit with the charging supply +. Having said that for the second batter to charge it also will require a circuit to be completed withyt he charging battery therefore both negative terminals of both batteries should be connected via suitable battery cable and then either batteries earth can be connected to the VSR

[John Buoy]

This might explain it a little easier
Top is VSR bottom is Battery Isolator Switch.
The earth lead you desribe is the one hard wired to the VSR
which on the Diagram goes to the Buzz Bar but as staed above shouldn't really matter.





Regards Frank

[oncoarse]

Thanks for the replies guys, Frank's diagram just about sums it all up, thanks Frank. Just for convenience, I'm going to take the earth lead straight to the Battery - terminal.
Cheers, John.

[driveon]

Hi oncoarce, all VSR use the earth as the reference point for their cut-in and cut-out settings.

If the batteries are close together then just pick the easiest negative terminal to connect to.

If the auxiliary battery is located a fair distance from the cranking battery, try to mount the VSR as close to the cranking battery.

While no damage will occur if you mount the VSR and auxiliary battery a long way from the cranking battery, you could find that if your auxiliary battery is fairly low, while the motor is running, the VSR may continuously cut in and out and stop your auxiliary battery from charging properly.

[oncoarse]

Thanks Driveon, I'm going to sit the batteries next to each other, so that should be fine. Thanks heaps for your (and everyone's) advice.