Inverter to warm motorhome while driving? Forums

Phild

Hi all,
My Hymers heater is no good for winter travel. Would it be possible to use 2 110amp Leisure batteries with an inverter (say 1000w?) to power a fan heater of about 400w or 800w or would it flatten the batterys in no time?

My Dad recons I'd be better off running a Honda genny in a box on the scooter rack. Would this be possible?

PS. I'm new to forums so I hope this is ok
Cheers Phil

Drummer

Welcome to the site, PhilD.
Anyone with a Hymer can't be all bad!
Sorry about the heaters inadequacy, I thought Hymers were the dog's doodahs. I may have to reconsider!!! Will keep my eye on this one Laughing

DABurleigh

Phil,

It is certainly possible, however rare, provided steps are taken to maximise the current from your alternator to the inverter. For an 800W heater you would need around 75A, whilst leaving enough to power headlights, demister, etc., so you are probably talking a heavy duty alternator if you don't have one around 110A output fitted already.

Then there are a couple of ways to go, the simplest being 35mm2 welding cable from alternator, via a heavy duty split charge relay or contactor, to the inverter and leisure batteries. High current cable runs should be as short as you can make them.

Or fit a high output alternator to battery digital regulator, most of which require a separate wire connected to the internal guts of the alternator. Sterling do a version where this is not required.

Again, a genny in a rear box will work, provided you think about air supply and exhaust, refuelling, etc, but it is a strange solution!

More common would be to fit a 2nd heater matrix to use heat from the engine, or a separate diesel-fired heater such as Eberspacher, or going low-tech, cab curtains and warm clothing, once you are certain you don't have a fault with your Hymer heater.

Dave

MandyandDave

We had the same problem whilst driving along, the cab heating is not designed for large motorhomes so we bought one of these and changed the plug to suit the 12v in the rear...marvellous!

http://www.mflgadgets.co.uk/motoring.htm

Regards M&D Smile

DABurleigh

Fine, that's only 17A. Though those away from site hookups would still want to check they were sticking a decent charge into the leisure batteries as well while motoring.

Dave

Anonymous

M&D

Looks good, but be careful if using on a cigarette plug, it will draw about 17Amps

Ken

Phild

Thanks for the interest everyone. I thought I should add that the curtains drawn behind the seats works, but don't the kids just moan when we do that. lol
I've seen the diesel heaters Dave and it's the best way I think, but the cost is high and we thought the honda genny would have other uses the rest of the year. I like the Honda EU20i and maybe would be very quiet if we ran it in a well vented box. Maybe quiet enough not to upset others on sites?
Phil

Road_Runner_644

We run a 1000w fan heater in the middle of our 1996 B644 when travelling in colder weather. It runs through a 2000w invertor, via 2 x 120AH batteries, and the hymer panel suggests that about 15-20 amps is being put back in to the batteries by the alternator. As the fan heater switches on and off, its not a continuous cycle, and we haven't had any battery power problems. the heater pulls the batteries down to about 12v and they tend to sit there until the heater switches off, when they soon shoot up to 12.6 - 12.7 again, at which point the alternator backs off to about 5 amps or less. I guess if i took the thing down to the auto electricians i could get them to squeeze more amps into the leisure batteries, by modifying the split charge circuit.

The reason for the heater was the same, i couldn't believe how cold the thing was when we travelled. The kids were putting their coats on, and complaining. I looked for draughts, and poor seals, but finally found out the culprit was the roof vents, which literally just suck the heat out of the vehicle.

The cab heater is ok, but the heat was not being retained in the vehicle.

I never found this problem in our old CI granduca, as when you shut a roof vent, it was completely shut and air tight.

However these vents have some permanent ventilation even when shut, which i suppose is a safety feature, but a great annoyance. Even when parked, in high winds you can feel the air disturbance around them.

I have sealed the ventilation slots in the lower part of the vents with a sliding plastic louvre thing that i bought at the local diy shop, but plan to seal them up in some more permanent way in the future. I'll find some way of manually allowing some ventilation when parked, thats what we were always used to.

Dave

Phild

This sounds great! I take it you have just joined a second leisure battery to the existing leisure battery(?) then connected the inverter to one of them, presumably with proper battery terminal clamps rather than the cigarette lighter plug which comes with smaller inverters?

I've read in Practical Motorhome somewhere where they fitted a device which dramatically increased the power going to the leisure battery from the engine. This did not need any messing about with the alternator. Perhaps one of these would keep things topped up? Has anyone heard of this device?

Keith-n-Deb

Invertor to warm a motorhome !!!!!!!

it will never work you'd need loads of em to produce that much heat... my invertor runs pretty cool really.

Keith n Debs...... Laughing