Charging batteries linked by an isolation switch

[victory]

I have 2 12v batteries connected through an isolation switch which has the usual 1,2,BOTH & OFF positions.

If I want to charge just one of these batteries , is it necessary to disconnect that battery from its +ve and -ve cables before hooking it up to the charger?

If not , then what position should I select on the isolation switch so that the charge goes solely to the selected battery and is not shared between both

 

[pandos]

The batteries should only be connected to each other when the switch is in the both position. Thus any other position should suit your stated purpose.

 

[Sixpence]

If it's connected properly , when you select 1 you use the power from 1 or you charge 1 , select 2 the same happens , select both and likewise , so it all depends on are you using power or charging

 

[Rick]

Assuming you want to isolate the alternator from the battery under charge, if it's battery 2, then select either 1 or OFF. I usually charge in that fashion so that I can get max charge into each battery bankl on a regular basis.

 

[Guest]

The position of the switch should not interefere with any charging if done via croc clips / connectors direct to battery. The only extra you get - is if you select BOTH - then connection to one battery will parellel the other and charge both. Problem with position BOTH is many modern chargers that drop to float charge won't like it and may refuse to start charging.

In answer to what position ... OFF is best - as then there is no drain to any residual items ..... but 1 or 2 is perfectly OK ... as you may be using items while charging ... The switch position determines what battery supplies services / engine start ..... NOT what is charged.

There is absolutely no need to disconnect any battery or leads. It is not like on a car - where they advise charging of vehicle etc.

If you have a standard non-float car charger - you can improve your charge system easily by installing a Maplin Charge Splitter which then charges both batterys independently from one source, without diode drop. (About £7 + few connectors and bit of wire !)

 

[RobBrown]

Sorry if this is a slight thread hi-jack, but query is on same lines:

I have same set up as victory and leave a small (1.5 amp) photocell trickle charger plugged into one of the 12V "cigar" sockets between visits to the boat (it has an inbuilt charge limiter). As what I thought was good practice, I always leave the boat with battery switch "off". Does this mean I have not been trickle charging the batteries? If so, presum have to leave swtiched to 1, 2 or both in future as required?

 

[fireball]

If the switch is "off" and it is wired correctly then you have not been charging any batteries ...

Personally I would not use the trickle charger on "both" as if there is a failure you may end up with no batteries ....

I'd be uncertain as to leaving the switch in the "1" or "2" position too ... I'd prefer an independant connection to the battery bank for the photocell - this way you can isolate the drain circuit whilst leaving the battery on charge.

 

[Guest]

Ciggy socket ....

Normally this will be AFTER the battery switch - and therefore if switch is OFF - then charge is going nowhere !

I get round this by - horror of horrors ! - having a ciggy socket direct to battery bypassing the switch - this is also linked to the VHF so that I always have power available to these. I can hear the intake of breath of the "experts".

If you want to have the trickle charger - I assume it's like mine - from local car shop for keeping car battery topped up - then clip on a ciggy socket direct to the battery you want to charge .... as doing it further down line will introduce more resistance and probably destroy the small charge capability as is ... I found that mine wouldn't keep charge up indefinitely - it just delayed it ....

 

[RobBrown]

Re: Ciggy socket ....

Doh!
/forums/images/graemlins/blush.gif

 

[VicS]

Re: Ciggy socket ....

May I add that anything you leave connected to a battery should be FUSED. The fuse should be as close to the battery as possible and should be rated to protect the thinnest bit of wiring in the circuit you are leaving connected and in the case in point should really be no larger than is necessary to carry the maximum current that the solar charger will deliver.

 

[ColinHuggins]

Re: Connecting the two batteries ....

Another hijack, sorry!

Battery One = dedicated Engine Start, Battery Two = Domestic, each has its own on/off switch. There is a third swicth marked Emergency which appears to bring in No 2 should No 1 be too low to wind the 120HP Perkins. I've never had to use it until recently - that's a problem for another post - and it worked. But I've heard dire warnings about switching that link off while the engine is running - knackered alternators haunt my dreams COS THAT'S WOT I DID!
Please put me out of my misery.

 

[Guest]

Re: Connecting the two batteries ....

I would never have a boat without make before break switching ... and certainly never introduce separate switches for the batterys.
I know I blow against the wind saying that I still support the old style 1 - both - 2 - off battery switch - but at least it stops alternator blows by having both batts connected to its make before break system.

I have introduced one little "quirk" to my engine start. The Alternator exciter power is interlinked to the start button energiser power. So nothing happens without switching on exciter switch. This then means that I never forget to have alternator charging !!