12v two battery system

[Slinky Spring]

Can anyone point me to a website or advise me on how to wire separate batteries for engine and leisure.
My current set up has 2 leisure batteries in series to run everything. Obviously, this can result in no engine if you leave the lights on all night.

 

[alan]

Have a look at the Adverc web site. They have some descriptions there showing theis alternator regulator ......... but you can just ignore the bits that don't interest you.

Alan.

 

[VicS]

[ QUOTE ]
2 leisure batteries in series to run everything

[/ QUOTE ] You mean in parallel I assume!

The simplest solution is separate isolator switches. Just switch on which ever you want to use or charge. If needed both can be switched on. Just remember not to switch both off while the engine is running.

More convenient to use a 1,2, both,off type switch but it is essential to get a really good one as there is some rubbish about.

Beyond that you are into the realms of separating engine and domestic wiring, but that should be simple , and using split charging either with a diode splitter or a VSR.

A lot of the basics can be found at http://www.tb-training.co.uk/cover.html but look at the sections on split charging as well as on batteries.

 

[davidbains]

I suggest you leave the parrallel domestic bank and just add a smaller starter battery.
Then connect them via a VSR (voltage sensing relay) to charge both.
In fact if your parrallel bank is say 200Ahrs you are unlikely to flatten it enough to prevent starting in one night, as long as your charging arrangements are powerful enough and include either windmills or solar panels or both!!
I've got by like this for years.
But I always switch the fridge off at dusk.
I eventually added a windlass battery but still don't have a starter battery which I know will horrify battery salesmen.

 

[ghostlymoron]

I have 2 battery banks charged through diodes connected to the battery side of the 2 isolators (key switches). This way the engine will charge either or both batteries as necessary with no danger of blowing up the alternator. For engine starting or domestics, turn the appropriate switch to 'on'. Remember that some circuits need to be 'always on' e.g. automatic bilge pumps (although all that this will achieve is to flatten the battery before the boat sinks!) I'm thinking of fitting a smart alternator controller which speeds up battery charging by 400% it is claimed.

 

[jennymckay]

I don't recommend 1-2-both switches because you really need to keep both battery banks totally separate and not simply use one or another.
Isolator switches are the way to go, with maybe a 3rd switch for emergency parallel.
If you're not familiar with battery wiring, I suggest you get a copy of Nigel Calder's book (AKA the Bible!), and read more than you will ever want to about this subject.
I would also strongly advise getting a battery monitor (we use Sterling, but there are many on the market), to tell you exactly what is being pulled from each battery at any one time.

 

[damo]

I completely agree with jennymckay - an isolator switch, and a split charging system with a dedicated engine batt. Emergency changeover can be achieved with jump leads.

And every boat should have a copy of Calder's books IMO /forums/images/graemlins/smile.gif (...and it would save a lot of questions here /forums/images/graemlins/grin.gif)

 

[Slinky Spring]

Thanks for all the advice. I now have a better grasp of how little I know!!!
I will do a wiring diagram next time I'm on the boat to make sense of what I have at the moment, and then look at how it could be improved.

 

[William_H]

You have to choose if you want to rotate the use of the batteries or if you want one dedicated to start only. Leisure batteries are probably fine for engine start but cheaper purpose built batteries can be used for engine only. ie a car battery.
However to use only the batteries you have you can use a 1,2.both switch but as already suggested individual switches are better.
Ensure the swithes are high enough current rating for start current.
Also ensure the negative wiring is heavy enough for start current on both batteries. good luck olewill

 

[Jean]

Keep it simple and go for a quality 1-2-both switch.