battery switch

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barryg

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I have a battery switch on my new boat marked 1/2 and both is 1 & 2 dedicated to the starter on one position and the domestic on the other and should I assertain which is which and stick to that for start up and what is both for?Is it that whichever is the engine start one to be used to start up then go to both? Everything seems to work on any position including starting!
 
1 domestic battery 2 engine battery. All will work on either. Point is to isolate engine battery to make sure it doesnt die so you can start up even if domestic is drained. Only turn to 1+2 for charging, not normal use, as the drained one will then charged by healthy one. Hope this explains it.
 
Thank u for that just to confirm, get on boat switch to no 2 start up engine then switch over to no 1 for domestic if I switch off engine and want to restart I switch back to no 2 for restart
 
Barry,

1) Go on board and switch to domestic battery.
2) when you are off out with the engine running switch to both and leave there (it will charge both batteries)
3) when you get where you're going and have the anchor down then switch back to domestic only - the engine start cannot then be run down.
4) repeat process!

Remember never to switch the switch between selectors via the "off" section when the engine is running as otherwise you'll kill the alternator (knacker the diodes because the generated power has nowhere to go). Switch to "Off" when you leave the boat

rob
 
Switch to 'engine' battery to start. Engine on, switch to both(1+2). Engine off switch to 'domestic' only. This leaves your engine battery fully charged at all times. Engine batteries have different characteristics to domestic batteries.
 
Having read the other replies I'm confused!

Decide for yourself which battery (bank) is to be for starting the engine, and which for domestic use.

This may be down to the batteries fitted, for instance if one is a small cranking battery and one is a large deep cycle battery, hopefully you will know which is fit for each purpose. If it is not clear you can check which is which either by following the positive leads, or if not visible all the way, check the voltage when charging, the 'active' battery will be 14V or so, the other 12Vish.

In my case each battery is identical for a good reason and I have chosen '1' for engine and '2' for domestics.

Start on 1, charge on Both, use 2 for domestic loads when the engine is off so the engine start battery doesn't get flattened leaving you in a potentially embarassing or even dangerous situation. Never go through the 'Off' position when the engine is running.

Switch to Off when leaving the boat, and close the seacocks too!
 
If you are unsure which of 1 and 2 is your domestic battery then try just switching the radio on and see whether it needs to be switched to 1 or 2 for it to work.

It would probably be worthwhile to sit down with pen and paper on the boat and follow each wire and draw yourself a circuit diagram.
 
[ QUOTE ]

If you are unsure which of 1 and 2 is your domestic battery then try just switching the radio on and see whether it needs to be switched to 1 or 2 for it to work.

It would probably be worthwhile to sit down with pen and paper on the boat and follow each wire and draw yourself a circuit diagram.

[/ QUOTE ]

The radio will work wherever you have the switch 1, 2 or both. Because it should be connected to the common.

You have just really confused everyone ....!!!!
 
Advice from the yard when I chartered a boat which seemed so simple that I've used it ever since.

Daytime leave the switch to both. When you anchor or moor at night (or do a night sail) turn to domestic to save the start battery for the morning.

This way every time you use the engine both batteries will benefit without the inevitable of forgetting to change over when you start the engine for the fourth time in the day.
 
If everything works all the time the chances are the switch is fitted in the charging circuit from the alternator and is not a battery isolator.

It manually sends a charge to either 1 or 2 or both whichever you select.

It could be easily replaced with a split diode unit which would then be automatic.
 
This post perfectly demonstrates...

This post perfectly demonstrates why I have a hatred of 1-2-Both switches! Just look at the confused responses. Why don't boatbuilders just fit 2 simple on/off switches? One for the start battery; one for the domestics. It solves all the problems. No wonder the RAC, sorry RNLI, has so many callouts to "save the lives" of yotties whose engines won't start.
 
Re: This post perfectly demonstrates...

[ QUOTE ]
This post perfectly demonstrates why I have a hatred of 1-2-Both switches! Just look at the confused responses. Why don't boatbuilders just fit 2 simple on/off switches? One for the start battery; one for the domestics. It solves all the problems. No wonder the RAC, sorry RNLI, has so many callouts to "save the lives" of yotties whose engines won't start.

[/ QUOTE ]

Oooohhhh ... It's not the swqitch that's at fault - it's the users who assign daft roles or add to it.

First thing I did when I got my boat was to disconnect one battery positive connection ... then switched to 1 ... then 2 ... to see which position was which battery. I then took a marker pen and marked the batterys accordingly.

While batterty compartment was open - I looked at the batterys to decide which was Heavy duty high CCA to be start battery and other leisure or lesser CCA job to be domestic.

Simple. Small sticker by switch says ... 1 = Dom 2 = engine

Simple system of use ... Arrive at boat ... switch to 2 and start engine. Leave marina / pontoon ... after reasonable period say 20 - 30 mins cahrge should have been replaced - switch to 1 and give charge for last bit of engine run before stopping engine. Sail with switch at 1 .... arrive at destination and start engine on 1 or 2 - up to you ... once started switch to both ... motor in and tie up. Stop engine - switch to 1 for domestics ...

easy .. and once got into habit of ... no problem - it becomes automatic.
 
Re: This post perfectly demonstrates...

You say it "becomes automatic", I say it's unnecessarily complex. I just have 2 simple on/off switches on my boat. If the engine switch isn't on, the engine doesn't start. If the domestic switch isn't on, nothing else works. Switching one or the other off when it should be on doesn't affect anything. You can't accidentally discharge the start battery. Well-meaning family & friends can't mess about with the switches and cause problems. The 1-2-Both switch is a throwback to those ancient times before the invention of sensible 12v electrics, and has no place on a boat in the 21st century.
 
Re: This post perfectly demonstrates...

I don't really understand your post.

What are the differences in what you are proposing are better, apart from a slightly more complex 1-2-both-off switch system?
 
Are we really helping the original poster?

- I would certainly be a bit confused if I were she or he. People have offered all kinds of advice based on the principle that 'this is what I do on my boat'. At least one post seems implicitly premised on the idea that the engine will be on all day. Not if it's a sailing boat and there's a bit of wind surely?
My point really is that battery systems using these common 1-2-both-off switches can be wired in a number of different ways and the starting point should be to discover exactly how this one is wired. I have been on boats where only one (or both obviously as they are then paralleled) of the batteries can be used to start the engine, for example, and others where either can be used.
 
Re: This post perfectly demonstrates...

I've got the same, turn them both on when I get on the boat, turn them both off when I leave the boat. Two seperate circuits that don't affect each other.
 
Re: This post perfectly demonstrates...

I have two of these switches on my boat (3 batteries) and can't really see the use of them. They are rather large, ugly, orange, and could surely be done away with by fitting a relay and blocking diode so that all batteries charge but the engine start battery is isolated if the ignition is off.

That's the system I have in my camper, is there any reason why it couldn't be used in my boat?
 
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