Switching Charge To Vehicle Battery

Offhand, it looks like neither battery is charging - are you sure that the charger is producing any output at all?

When the charger is functioning it should take the battery voltage up to around 14.4V (these voltages vary a little according to make and other circumstances, but not by much), and when the battery has finished charging it should hold the battery at a "float" voltage of 13.6V, roughly. Are you seeing that?

As you probably know (because you're trying to make the charger work), 11.8V for the vehicle battery is terminally low. If you can't make the built-in charger function, I would temporarily hook up an external battery charger, just to get some power into it while you figure out whether it's a failed charger, a blown fuse somewhere or something else.

Ah Ok - thanks for the update. So it seems the charger is functioning.

I confess I've never owned that type of power unit, but on a power supply that recent (in relative terms) I would expect the fan to be temperature controlled and not running all the time, so at current ambient temps you should probably expect it not to run while the charger is not under heavy load.

A word of warning: If you manage to start the engine with the vehicle battery that low, you will cause the split charge circuit to connect together two batteries in very different states of charge and it may be that, even with the alternator's output, you could still blow a fuse. A better approach is to get the vehicle battery up to a higher state of charge before attempting an engine start.

It sounds as though you may have a faulty relay in the system, but unfortunately I'm not familiar with the touchscreen based systems of that era, so I don't know whether the relay (if my guess is correct) is likely to be internal to the controller or separate.

Is it fair to assume that you made no changes or additions to the van's electrical system before this problem started?

Is it fair to assume that you made no changes or additions to the van's electrical system before this problem started?

nick1962 wrote:Would it be good to assume then that the charger unit doesnt respond to the command from the control panel and therefore the switch/relay is defective in the charger unit itself?

Typically the relay that switches between vehicle and leisure batteries will not be in the charger, but in the power control system itself.

However, I think Peter knows a lot more about your type of power control system than I do, so best to see whether he or one of the others who have actually owned one can advise.

nick1962 wrote:I will purchase a battery charger tomorrow and follow what you say. What sort of ampage of charger would you suggest?

It's not really so critical these days, unless you want to charge a battery quickly. The chargers that LIDL and ALDI sell are reputed to be pretty good, though probably not as reliable as, for example, a CTEK (though I have had to repair one of my CTEKs recently).

CTEK are definitely now a "premium" make, and there are others with slightly less price premium such as NOCO and Ring, and then numerous cheaper Chinese brands.

If you're after something which will charge anything lead/acid that you're likely to have in a motorhome, then you should not really need anything more than a 5A output, which should be good for batteries up to around 110Ah capacity. If you need to charge bigger batteries then usually it will cope fine, but just take a bit longer, within reason.