Switching Charge To Vehicle Battery

Hi

On our 2007 Nuevo we have a touchscreen control panel above the hab door.

To swap the charge when on EHU from the hab battery to the veh battery, I just press the ‘CHARGE’ button and it changes.

But when I then check the voltages on a different screen, the hab battery is still charging and not the veh battery. At the time the hab battery was at 12.6v and the veh battery was at 11.8v.

Am I missing something?

Thanks for your help...

Nick.

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.

I agree with Roopert. You need to check the charger. My Sigma which most probably has the same charger and control unit (MES) as yours, sometimes exhibits these symptoms. So far I have fixed by flicking the charger switch on and off until I hear the charger fan start, which it will do if charging a battery at 11.8v.

Hi

Thanks for replying.

Its a PDU 4M charging unit. When standing, on the screen of the control panel, the hab battery is on 12.8v and the vehicle battery 11.8v. When I turn the PDU 4M on, the hab battery goes up to 13.5v irrespective of whether it is on hab or veh selection on the touchscreen control panel. Also, I cant get the fan to come on on the PDU 4M. Could this be it is cold out at the mo or should it work all the time?

I will go and purchase a battery charger later today or definitely take it a good run out tomorrow to charge the vehicle battery. Luckily we have a solar panel that charges the hab battery so that should be ok...

Thanks again

Nick.

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?

Thank you.

I will purchase a battery charger tomorrow and follow what you say. What sort of ampage of charger would you suggest? Or what about a portable solar panel just for the vehicle battery?

In the meantime I will contact an auto electrician.

Thanks.

Nick.

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

Hi

We bought the motorhome last April, our first one. Although I have learned quite a lot so far, I’m still a novice regarding the electrical side so no modifications.

Have bought a charger this afternoon and hooked it up to the vehicle battery. When switched on, the voltage goes up from 11.8v to 13.4v on the panel readout and proves that the reading it gives is fairly accurate and responds to the charge.

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?

Thanks again

Nick.

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.

On mine which ever battery I decide to charge the fan on charger cuts in & gives a good charge.
If you have a volt meter you can check if your charger is working,

Thanks guys.

Peter, we live in Ball Green/Norton.

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.

nick1962 wrote:..... Also, I cant get the fan to come on on the PDU 4M. Could this be it is cold out at the mo or should it work all the time?

Based on my experience with the same PDU 4M and MES controller the charger fan appears to be controlled by 'rate of charge' rather than ambient temperature. So I would expect it to come on if charging the vehicle battery at 11.8v but not necessarily if charging the habitation battery at 12.8v. I should add that the fan, when operating, is intermittent, in shortish bursts typically less than a minute duration.