Alternator Sensing Cable connection

[Stork_III]

Being an electrical numpty , where should the alternator sensing cable be connected at the battery banks.

I have VP2030C, with standard VP alternator, VP split charging device, 1 engine battery and 2 house batteries. 2 seperate battery switches.

VP manual shows sensing wire (yellow 1.5mm2) connected to a house battery + terminal. HR in their wisdom have made connection to output side of house isolation switch with 2 amp inline blade fuse. ie if isolator is switched off during engine running sensing will be cut.

Is it better to connect to the input side of house switch? Thanks

 

[Playtime]

Being an electrical numpty , where should the alternator sensing cable be connected at the battery banks.

I have VP2030C, with standard VP alternator, VP split charging device, 1 engine battery and 2 house batteries. 2 seperate battery switches.

VP manual shows sensing wire (yellow 1.5mm2) connected to a house battery + terminal. HR in their wisdom have made connection to output side of house isolation switch with 2 amp inline blade fuse. ie if isolator is switched off during engine running sensing will be cut.

Is it better to connect to the input side of house switch? Thanks

It is more usual for the sensing wire to be connected directly to the house battery positive terminal, as per the VP guidance. In this way it senses the 'real' battery voltage and compensates for any volts drop in the isolator switch or its wiring to the battery.

I guess HR are worried that the sensing wire will remain permanently connected to the battery even when the isolator is off. Inclusion of the fuse removes any serious danger in this. However, if the electronics in the sensing circuit fail there could be a slow discharge through the sensing wire, unless the battery is completely isolated, for instance by an isolator in the negative (like Bavarias).

Before you alter the wiring it might be worth measuring the volts drop between the output of the isolator and battery while the battery is charging. If this is (as I suspect) only a few millivolts, I would leave the wiring 'as is'.

 

[Stork_III]

It is more usual for the sensing wire to be connected directly to the house battery positive terminal, as per the VP guidance. In this way it senses the 'real' battery voltage and compensates for any volts drop in the isolator switch or its wiring to the battery.

I guess HR are worried that the sensing wire will remain permanently connected to the battery even when the isolator is off. Inclusion of the fuse removes any serious danger in this. However, if the electronics in the sensing circuit fail there could be a slow discharge through the sensing wire, unless the battery is completely isolated, for instance by an isolator in the negative (like Bavarias).

Before you alter the wiring it might be worth measuring the volts drop between the output of the isolator and battery while the battery is charging. If this is (as I suspect) only a few millivolts, I would leave the wiring 'as is'.

Thanks for that. The negative is not seperately isolated soyour failure drain might be possible. The cable area is 35mm2 and quite short, about 400mm, so voltage loss should be small, but will check loss as you suggest.