Control panel woes

I wouldn't like to hazard a guess, other than it probably needs a charged hab battery to complete the circuit, but some control panels are mighty complicated bits of wizardry.

If you tell us the make and model number of the controller it might help. Alternatively, an Internet search for that make/model might throw up the answer. I'm assuming you've studied the handbook.

12v electrical items still run off the hab battery when hooked up - they aren't dual voltage - but the mains electric will charge the hab battery via the onboard charger.

We have a caravan, but the system will be similar.  The charger that keeps the battery topped up when on EHU can be switched off, or can fail.  If either of these things happen, and the battery is dead, there will be no 12v power, and as TW said, the 12v items can only use 12v.  

So, in our case that would mean very few lights, no water, no toilet flush, no fridge (its control panel also needs 12v) and no heating (ditto), and we would need to light the gas hob with a match.

Some chargers will supply 12v without a battery in the circuit, but it is not generally advised.  Others will shut off if the battery is missing or unable to take a charge, which could be the case in your MH.

Thank you very much both - we noticed that our hob ignition stopped working last year after a shorter lay up but we didn't recognise the significance and it worked by the time we arrived on site so we forgot about it.  Reassured that as long as the battery is ok it will be recharged from the mains and we are unlikely to suffer loss of everything.

Enjoy your travels 

It sounds as if your battery is goosed.  You should really consider replacing it not least to avoid any damage to your van equipment and van itself but also to life and limb.

Seems strange that you didn’t get your 12 volt services when on EHU. Even if the battery had failed you should still get power via the charger. Are you certain that the charger is working? There are various ways to check. Your battery should be 12.7 volts approx. when fully charged but when the EHU is plugged in and the charger working this voltage should be around 13.7 volts. On a modern motorhome the control panel should tell you what the voltages are of the engine battery and the habitation battery.

It would help to know the make and age of your motorhome, the make and series of the control system and whether it has a solar panel.