Battery Charging Switch - Wiring?

[bob_tyler]

I have one of those battery switches (Batt 1, Both, Batt2, Off) which allegedly protects the alternator.

The wiring diagram is quite clear. The feed and battery cables are straightforward positive heavy duty battery cable.

There are, however, two much smaller terminals in the switch to be wired to the regulator. What the diagram does not say is what size wire is required between the regulator on the alternator and the switch.

Am I right in presuming that it is these latter two wires that provide the circuit which protects the alternator and that, without them, there is no protection. If so what size should the wires be?

The switch is marked "AM London" who I can't trace. I bought the switch at the 2004 LIBS but can't remember who from. /forums/images/graemlins/confused.gif

 

[ShipsWoofy]

There is some advise on the website below that might help

Reading college notes

I hope this helps a little.

 

[steverow]

AM supplies are still around. They had a stand at LIBS, and they do a lot of the boat jumbles. They are usually at the Malvern BJ sometime late Feb.
Dunno their web adress though.

 

[pvb]

If it has 2 small terminals...

If it has 2 small terminals, these are intended to break the alternator's field circuit (thus de-energising the alternator) immediately before the main contacts open. The idea of this is that it should avoid any damage to alternator diodes through sudden surges. If you want to wire it up, you'll need to break into the field wire at the alternator and run 2 wires to the switch. There's not much current in the field circuit so, to answer your original question, you can use quite light wire - say 1.5 sq mm.

Having said all that, if you haven't fitted the switch yet, my recommendation would be to sell it and fit 2 separate simple on/off switches instead to isolate the 2 batteries. One battery should be a dedicated starting battery; the other a domestic battery (or a bank of domestic batteries). Take the main output lead from the alternator direct to the engine starting battery, and fit a VSR (voltage sensitive relay) to link the starting battery to the domestic battery to provide charging to both batteries whenever the engine's running. This is foolproof and fit-and-forget, unlike those wretched 1-2-Both switches!

 

[peterb]

[ QUOTE ]
AM supplies are still around. They had a stand at LIBS, and they do a lot of the boat jumbles. They are usually at the Malvern BJ sometime late Feb.
Dunno their web adress though.

[/ QUOTE ]

The LIBS show guide has an "Abel Marine" showing switches, etc., and I assume that this is AM supplies. No web site is given, but their phone number is 020 8651 0868. Address is 7 Mallard Rd, Selsdon, Surrey, CR2 8PX