Isolator switch?

[for sail]

wondering if anyone could point me in the direction of a diagram of how to wire up an isolator switch using two batteries, one for the engine and the other a leisure battery. Any help would be much appreciated!

Cheers.

 

[VicS]

wondering if anyone could point me in the direction of a diagram of how to wire up an isolator switch using two batteries, one for the engine and the other a leisure battery. Any help would be much appreciated!

Cheers.

If you are not thinking about dedicated house and starter batteries, just a switch to select one battery for use nad charging or the other it is easy.

Battery negatives connected together.

One battery positive to one terminal (1 if so labelled) the other battery to the other terminal.(2?)
All circuits to be supplied via the switch to the common terminal.

Some will say dont use one of the rotary 1,2,both,off switches but use two separate switches. If you do use one make sure its a good one .. not cheap tat.
Remember never switch to Off while the engine is running.

If you have to ask such a basic question I suggest you take a look at the Boat Electrical Notes at http://www.tb-training.co.uk/index.htm
you will find a diagram in there

 

[William_H]

Isolator switch

It is not practical to use just one isolator switch for 2 batteries. best IMHO is to have 2 isolator switches one for engine battery and systems and one for the domestic services. Or as said this can all be done in a rotary 1,2,both switch. (multiple switches in one case)
Using separate switches you then have a choice of keeping one battery for engine of a type optimised for high cranking current and another battery for domestic service optimised for deep discharge cycling. You then keep the engine and domestic circuits isolated eexcept for common negatives. You would however need another switch for connecting the 2 circuits (+ves) together for charging or for emergency jump starting the engine off the services battery.
The alternative is to have 2 identical batteries compromised in design for both deep discharge and high engine cranking current. The two circuits engine and services are not isolated but common. So you can turn one battery on and use it for charge and discharge or turn both on for charge and discharge. Note here however that if you always operate with both batteries on for engine start charge and domestic discharge as many do you lose the advantage of reserving one battery against flattening the other. You can in fact discharge both and you are stuck. So you need discipline to charge both with engine running and turn off one to isolate it against discharge.
IMHO opinion the former arrangement is best with an automatic voltage sensing relay (VSR) which will connect the service battery to the engine battery when engine is charging but will isolate the services when engine stops charging. Some VSR can also carry enough current for engine emergency jump start or you fit an extra jump start switch or carry a jumper lead. Be careful of sparks and explosion if you use a jump lead however. There are variations of the latter option using VSR to ensure charging of battery not connected. good luck olewill

 

[VicS]

Here is a diagram ( taken from the instructions for fitting a "Blue Seas" switch)

 

[for sail]

that seems pretty simple cheers

 

[SHUG]

that seems pretty simple cheers

Not so fast my friend !!!!!!
Some 1....off...2 switches also have a connection for the alternator field coil so that you don't blow the diodes between switching positions. Worth checking.