Boat electrics/battery/solar

[Tony Brooks]

1 hour ago, Chris Debois said:

Morning all. I'm going back to the boat probably today with a clearer mind, I hope.

 

So, if the starter motor is faulty and not charging to the correct voltage, the splitter/VSR will not then be able to switch the charging to the leisures?

 

If you wire the VSR as I suggest then the alternator will try to charge the domestics. Whether it will to any degree or not depends upon what voltage it is producing. If that voltage is above about 13.4V it will charge but at such a low rate as to be considered unserviceable. It will not however charge the engine battery.

 

If the charging voltage goes above the relay activate voltage (say around 13.6 to 13.8) then the relay will close and both batteries will charge in proportion to their degree of discharge but if the alternator is faulty so the voltage never climbs to about 14.4V the charging will never be satisfactory.

 

To try to make its simple, if you wire it in the way I suggest:

 

If the alternator is faulty the domestic battery might charge but probably not enough. The engine battery is unlikely to charge.

 

The only way the relay will not be able to switch to charge the leisures is if you wire the alternator to the engien bank as Alan has suggested. Your call but I would try to reduce the risk to the relay contact doing it that way involves.

[Tony Brooks]

I realise the above may not seem definite enough for someone not familiar with the intricacies of alternators and charging but a perfectly serviceable alternator may produce anything from just over 13V and about 14.5 volts or more depending on the state of the batteries' charge. A faulty one, depending upon the fault, may produce anything between zero volts and a something below 14 volts depending upon the fault. This means a fault alternator can in the right circumstances charge a battery but it will do it very slowly and not as fully as a good alternator can.