What exactly does a battery isolator isolate - and from what?

[Kantara]

Actually, he's right. It isn't isolating the circuits as you have proved, so it can't be the isolator. It may have been designed to be in the first place, but it is no longer doing what it was supposed to. You need to do some wire following to see what is going on

 

Richard

I'm sorry, but you've lost me. The problem I am referring to is with regard to the domestic isolator - it is clearly connected to the domestic bank, whether or not it works.

 

I wired in a Voltage Sensitive relay exactly as per the instructions supplied, without giving it too much thought.

It was actually on the battery side of the main isolators, I then found that the (quite modest) solar panel was causing the relay to drop in and out, creating some strange effects. Probably nothing to do with what you are seeing, but another indication that things don't always do what you expect them to.

 

Don't you have your panels wired to the battery side of the isolator (via a fuse)? It seems the logical way to me.

 

Tim

 

I'm at a disadvantage here now, in that I am no longer with the boat, since I've returned to land for the winter. I'll keep all of your replies, and check things out when I return. Many thanks. I now have a professional coming to the boat in February to attend to another wiring problem, so I'll probably refer this to him.

[blackrose]

I'm sorry, but you've lost me. The problem I am referring to is with regard to the domestic isolator - it is clearly connected to the domestic bank, whether or not it works.

 

I think Richard means that although the isolator is connected to the domestic bank, it's being bypassed (or it's stuck on).

Edited November 27, 2012 by blackrose

[RobH]

I have replaced two of my isolators because they had failed in the ON position (the key still turned but the circuit remained on even when it was selected "Off"). Try disconnecting one side of the switch (I suggest the output, not the positive feed from the battery). If the lights still work it is a wiring fault and you need to trace cables. If they don't work then the switch has probably failed in the ON position. If you need to replace it get one with a rated capacity well over that of your system, particularly if you have an inverter.

[BlueStringPudding]

I thought I knew the answer to this question, because it seems kind of obvious, but when I switched off my domestic battery isolators today (and the starter battery and the bowthruster battery isolators too) I found I still had domestic battery power available in the boat - the lights could be switched on. What's wrong here, anyone - please??

I had a similar symptom before I rejigged my battery wiring. Mine was the solar panel's small current giving the lights a little power and also the radio (not enough to power it but it would turn on and off repeatedly)

[costalot]

The marine surveyor to certified our new boat informed me the only 12V consumers that do not have to be connected to the domestic battery bank through the battery master isolation switch were the bilge pump and burglar alarm, and these have to be fused separately.

[Arthur Brown]

A lot of wire tracing seems in order! Solar should be connected to the battery via protection but NOT through the master switch so that the panels can charge the batteries while you are away.