Battery Switch Position 1 or 2.

[Stubuc]

I have just purchased an old Boat, the battery switch 1 / 2 and both I understand principles.

Can someone advice how to easily check if 1 or 2 switch position is for my leisure battery?

[rusty69]

Put switch in Posn 2. Do cabin lights come on? 

ETA. By leisure battery I assume you mean your "house battery bank" as opposed to your engine starter battery.

Edited April 24, 2018 by rusty69

[nicknorman]

12 minutes ago, Stubuc said:

I have just purchased an old Boat, the battery switch 1 / 2 and both I understand principles.

Can someone advice how to easily check if 1 or 2 switch position is for my leisure battery?

There are a few different ways these switches can be wired. If it switches where the alternator is connected, try this: set it to 1. Have a 12v  incandescent light on and visible from engine controls. Now start the engine and rev a bit. Did the light get slightly brighter? If yes, position 1 is for charging Leisure. If not, stop engine, move switch to 2 and repeat.

Edited April 24, 2018 by nicknorman

[Stubuc]

Sorry yes the house battery. 

[bizzard]

.  Put it on No1, if you have a voltmeter put it on the starter battery terminals and note the voltage, then start up the engine, voltage should begin to rise, if not stop engine and try again on No2  and do the same with the cabin battery. Stop engine and set on BOTH, start up and both the cabin and start batteries voltages should rise  charging. OFF should isolate everything.

[nicknorman]

Just now, bizzard said:

.  Put it on No1, if you have a voltmeter put it on the starter battery terminals and note the voltage, then start up the engine, voltage should begin to rise, if not stop engine and try again on No2  and do the same with the cabin battery. Stop engine and set on BOTH, start up and both the cabin and start batteries voltages should rise  charging. OFF should isolate everything.

If it’s a alternator charge selector, normally (hopefully) there isn’t an Off position.

[bizzard]

3 minutes ago, nicknorman said:

If it’s a alternator charge selector, normally (hopefully) there isn’t an Off position.

Yes, that's why I said the OFF should isolate everthing including the starter. And stop the engine before switching in case its not a ''make before break'' switch.

[nicknorman]

32 minutes ago, bizzard said:

Yes, that's why I said the OFF should isolate everthing including the starter. And stop the engine before switching in case its not a ''make before break'' switch.

I think you miss the point a bit. There are two ways of doing the switching. One is to switch the alternator feed to 1,2 or both (ie starter battery, domestic battery or both). These switches don’t have an Off position because that would simply cut off the alternator, possibly/probably damaging it if done with engine running. The OP doesn’t mention an Off position so I presume it’s this type of switching. There will be separate isolators somewhere.

The other way of doing it is to have the alternator permanently connected to the engine battery. The 1/2/both/Off switch selects the source of power for the domestic circuits. In Both, it takes power from both batteries and thus connects both batteries together for charging. In Off it cuts off the domestic power. There will be a separate isolator for the engine battery. Or as a variation, as  above but with the alternator permanently connected to the domestic battery.

So if there is an Off position, chances are it will be the second arrangement. If no Off, chances are it’s the first.

[Stubuc]

Sorry there is an OFF / 1 / 2 and Both position on the main switch.

 

 

 

[alan_fincher]

27 minutes ago, nicknorman said:

I think you miss the point a bit. There are two ways of doing the switching. One is to switch the alternator feed to 1,2 or both (ie starter battery, domestic battery or both). These switches don’t have an Off position because that would simply cut off the alternator, possibly/probably damaging it if done with engine running. The OP doesn’t mention an Off position so I presume it’s this type of switching. There will be separate isolators somewhere.

The other way of doing it is to have the alternator permanently connected to the engine battery. The 1/2/both/Off switch selects the source of power for the domestic circuits. In Both, it takes power from both batteries and thus connects both batteries together for charging. In Off it cuts off the domestic power. There will be a separate isolator for the engine battery. Or as a variation, as  above but with the alternator permanently connected to the domestic battery.

So if there is an Off position, chances are it will be the second arrangement. If no Off, chances are it’s the first.

Unless I'm missing something, there is at least a third possibility that is neither of these.

The switch is actually selecting what battery banks are connected to everything else, rather than just the charging circuit.

Our last boat was like this.....

1) The starter battery is connected to everything, including the charging circuit, (domestic bank isolated)
2) The domestic bank is connected to everything, including the charging circuit, (starter battery isolated)
BOTH) Domestic bank paralleled with starter battery all connected to everything, including charging circuit.

OFF) All batteries isolated.

With this arrangement.....

Position 1, whilst starting engine
BOTH, as soon as you have and it is running
Position 2, when you have stopped running the engine, and want starter battery protected.

Yes, it relies on remembering, but is otherwise dead simple.

In an emergency, "BOTH" can be used to parallel all batteries for starting, if the starter battery can't manage it alone.

Obviously the switch has to have a sufficient current rating to be able to withstand stater motor current, (which was about 170 amps on our BMC).

14 minutes ago, Stubuc said:

Sorry there is an OFF / 1 / 2 and Both position on the main switch.

This kind of thing?

Edited April 24, 2018 by alan_fincher

[Tony Brooks]

Agree, at least three ways of wiring the switch and although Nick is correct that ideally a charge switching switch would not have an off I bet many do. They should also definitely be make before break but again most are.

Personally I would be tracing cables if faced with this sort of switch to work out how its wired.

[alan_fincher]

4 minutes ago, Tony Brooks said:

Agree, at least three ways of wiring the switch .......

Or six even, given that the role of 1 & 2 can always be swappd around, (the original question, I think).

[Stubuc]

Thanks everyone for your advice, when I go back to the boat in couple weeks I’ll try your suggestions

[nicknorman]

1 hour ago, alan_fincher said:

Unless I'm missing something, there is at least a third possibility that is neither of these.

The switch is actually selecting what battery banks are connected to everything else, rather than just the charging circuit.

Our last boat was like this.....

1) The starter battery is connected to everything, including the charging circuit, (domestic bank isolated)
2) The domestic bank is connected to everything, including the charging circuit, (starter battery isolated)
BOTH) Domestic bank paralleled with starter battery all connected to everything, including charging circuit.

OFF) All batteries isolated.

With this arrangement.....

Position 1, whilst starting engine
BOTH, as soon as you have and it is running
Position 2, when you have stopped running the engine, and want starter battery protected.

Yes, it relies on remembering, but is otherwise dead simple.

In an emergency, "BOTH" can be used to parallel all batteries for starting, if the starter battery can't manage it alone.

Obviously the switch has to have a sufficient current rating to be able to withstand stater motor current, (which was about 170 amps on our BMC).

 

Yes fair enough. I am sure there are at least 3 ways, probably more. I did say "a few different ways" in my earlier post but then got bored with decribing more than 2 (and probably risked bamboozling the OP!)

Edited April 24, 2018 by nicknorman

[WotEver]

So at the end of all that, the answer to...

13 hours ago, Stubuc said:

Can someone advice how to easily check if 1 or 2 switch position is for my leisure battery?

... is “with a multimeter”.