Starting the motorhome Engine while on hookup

I had always understood you shouldn't start the motorhome engine whilst connected to the mains. Not sure of the technical details as to why but I understand it can cause serious problems to the engine electrics?

One the other point about the battery being flat. Not all motorhomes have their cab batteries charged whilst on hook-up. One way round this is to have a device like a Battery Master fitted which basically takes any excess charge from the leisure battery (which is charged whilst on hook-up) and pushes it into the cab battery to keep it topped up. I have had them fitted to both my motorhomes and not had an issue starting the motor.

David

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I wired my solar setup to 90% habitation battery and 10% engine, so that keeps it topped up nicely, even with the alarm taking a small amount from the engine battery.

Our solar panels also charge both (not sure of split) and keep them topped up even in this really dull weather we have been having. We have both an alarm and tracker drawing power and as the van is in storage didn’t want to take the risk of a flat battery.

No idea what drains there might be on your vehicle main battery but would be surprised that it could not manage to start after such a (relatively) short time standing. No ideas what others have experienced.

Starting your engine while connected to the mains could have caused a large current surge in the charger/12 DC power supply so I would check that out 

I have started my engine with the electric still connected and not noticed any ill effects! My thoughts are the regulator controlling output from the alternator will kick in and control the current to both leasiure and engine battery. If the electric is connected then the regulator will see the voltage from the on board battery charger and send zilch to the batteries. That is my thinking. If you have any other views I would be interested to read them.

peedee

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ideally, both leisure and vehicle batteries should be charged from all three sources....EHU, solar, alternator.

Heethers, What van do you have?

im with most others, you wont have done any damage but you can check the charging regime by hooking up and putting a volt meter across the cab battery.

of it isnt charging it, i would second others and get a Battery Master fitted. 

On Autosleepers motorhomes there is an interlock to prevent starting the engine if the EHU lead is plugged in so I assume that it would be detrimental. I can think of many reasons for not trying to start the engine whilst on hook-up but the fact that you have no interlock is perhaps a sign that this is allowed and all is well, however, I would suggest trying to avoid in future.