leisure battery to starter battery

[khisanth]

I have a split charging system that when the engine is running and the starter battery is charged it charges the leisure battery up..

I have a solar panel that keeps my leisure battery topped up,

However when the leisure battery is charged from the solar panel I want it to top up the starter battery.

What sort of switch relay would I need and how would I wire it up..

Would it be better if the leisure battery is charged the solar panel switches to the starter battery or... The leisure battery switches when full so the overflow of power goes to the starter battery..

Any advice be greatly appreciated

[Bob]

Probably cheapest and easiest to buy a second solar panel for the SB.

Maplins often do them cheap.

[briwy]

Depends if you want it to do it automatically when the LB is full.
If not, a simple two way changeover switch is all that is required. Wire from the solar panel to the switch, one wire to the LB and the other to the SB. I guess a one gang, two way domestic light switch would do it OK.

[khisanth]

i would prefer it to be automatic as i am very forgetful and busy during the winter months

[scanner]

It would be easier just to use the present system - wire the solar panel to the main battery - as soon as that is charged the charge will divert to the leisure battery.

As the main battery should pretty much always be fully charged, especially when you've just stopped driving, the charge will go straight to the leisure battery anyway.

That way will also make sure you always have a fully charged main battery and leisure battery without you having to make any changes.

[Simon Jones]

I think scanner's proposal is the logical solution. It may depend on what sort of regulator you have on the solar panel & the split charge arrangement. For example, the regulator limits the voltage to the starter battery to 13v, but you have a voltage sensing relay that doesn't switch over to 13.5v, then it will never put charge into the LB.

[scanner]

I think scanner's proposal is the logical solution. It may depend on what sort of regulator you have on the solar panel & the split charge arrangement. For example, the regulator limits the voltage to the starter battery to 13v, but you have a voltage sensing relay that doesn't switch over to 13.5v, then it will never put charge into the LB.

I think regulators usually work well above 13volts don't they? - as batteries need to be kept up towards 14 volts to be at their best.

[Diplomat]

I think scanner's proposal is the logical solution. It may depend on what sort of regulator you have on the solar panel & the split charge arrangement. For example, the regulator limits the voltage to the starter battery to 13v, but you have a voltage sensing relay that doesn't switch over to 13.5v, then it will never put charge into the LB.

I may be wrong but I don't think any of the normal switching gizmos for leisure batteries work under unattended conditions. normally, without an ignition key present and turned appropriately, the two batteries are default switched to be isolated from each other.

That is not to say that the requirement could not be addressed with a bit of logic. However, two solar panels might be simpler but only worth the bother if the van is left unused for ages. I have left the Bongo unstarted for over 3 weeks in winter time and even after application of glow plugs there has always been enough power left to start easily.

I've had the Bongo over six years now and still haven't got round to bothering with a leisure battery. I don't watch telly and if I take a fridge for extended camping it goes out in the awning and runs either on gas or site power. I was going to say "Keep it simple", but maybe my approach sounds complicated to others!


Frank

[scanner]

I may be wrong but I don't think any of the normal switching gizmos for leisure batteries work under unattended conditions. normally, without an ignition key present and turned appropriately, the two batteries are default switched to be isolated from each other.

My Willinton does - it has no connection to the "ignition" system whatsoever and simply senses battery voltage and shunts across any surplus. I can't see any reason why you should think it is (or even needs to be) controlled by the "ignition" in any way.

[briwy]

I think scanner's proposal is the logical solution. It may depend on what sort of regulator you have on the solar panel & the split charge arrangement. For example, the regulator limits the voltage to the starter battery to 13v, but you have a voltage sensing relay that doesn't switch over to 13.5v, then it will never put charge into the LB.

I agree Simon, it could be a problem,

Older panels only produce 12v and newer ones up to 17/18v but this may be limited by the panel regulator.

I guess the OP needs to check at what voltage the split charging system kicks in compared to the voltage from the panel at the regulator output.

I'd be a bit wary though because this will put the LB and SB battery in parallel so any current requirements will come from both batteries. If the panel output can't keep up with the drain then both batteries could flatten.

I suppose in theory a "reverse" spit charge system would work.

Alternatively, just leave it and jump start the SB if it goes flat for some reason from the LB.

[khisanth]

if i split the cable from the solar panel to both batteries would this work.

also on that same note maybe a manual switch to disconect the main battery from the solar panel.

[Simon Jones]

If you run a cable to both, you are connecting them in parallel to they will charge together, but then they will both discharge at the same time (which you don't want). To be honest, unless you have something that is draining the main battery, then there is little to be gained in connecting the solar panel to it. If you only do lots of short trips and / or the starter battery or alternator is weak, you shouldn't need to provide additional charging.

[khisanth]

i know the alarm is draining the battery not very.fast but it is.

[briwy]

if i split the cable from the solar panel to both batteries would this work.

also on that same note maybe a manual switch to disconect the main battery from the solar panel.

Might do, bear in mind what Simon has said but it might be possible to put a diode in the wire to the starter battery to ensure current only flows one way, ie to the SB. Make sure it's well rated though and fuse protected.

[scanner]

If the starter battery is OK and needs little charging my solution should achieve the best result with the least cost and upheaval.
I'm puzzled as to what good a panel that only gives 12v is - any alternator that gives that sort of charge would be thrown away so why is it any good from a panel?