# Truma blown air heating. How long on batteries.



## Chudders (Jul 5, 2008)

I usually always use sites with electric hookup but in a couple of weeks I am going away for two nights with no EHU.
I have Truma heating with the fan blowing the air but I don,t know how long roughly the batteries will run it. I know it,s a bit of an unknown and various factors such as tempereature etc will affect it. But those of you that wild camp regularly may be able to give me a clue as to whether I will get away with using it off and on for a couple of days. I could work it out I suppose if I could find the manual on the fan that says the current consumption.
Any ideas appreciated.
Thanks, Dave
PS Batteries are 2 X 110 amp


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## Bill_OR (Feb 6, 2010)

Dave,
Are you sure that your heating system will run off the batteries at all? Our Trauma Combi system will only run off gas or electric hook up.
Bill


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## Chudders (Jul 5, 2008)

Bill_OR said:


> Dave,
> Are you sure that your heating system will run off the batteries at all? Our Trauma Combi system will only run off gas or electric hook up.
> Bill


Thanks for quick reply,
Yes the heating/water will work off gas or mains electric. The fan is however 12volt which only operates when in space heating mode.
Thanks, Dave


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## Jezport (Jun 19, 2008)

We preheat the van at home on mains if it has got really cold inside. This means that the heating wont need to work as hard to build the heat up, thus saving gas and battery.


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## Bill_OR (Feb 6, 2010)

Dave,
Ah! I follow you. So you'll be using gas for heat & hot water but as you will not be on hook up you need to know how long the batteries will run the fan for?

All I can tell you is that we've been off hook up for 2 days using the heating without a problem - and we only have a single leisure battery.
regards,
Bill


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## iconnor (Nov 27, 2007)

As always it depends what else you will be running of the batteries
e.g. TV.
I have one 100amp/hr battery and easily get an evening of TV and hot air blowing. There is always enough in the battery to run the heating fan again in the morning.
I would have thought with your 2 battery set up you will have no problem for 2+ nights, and if you don't use a TV could last for ages.


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## Rapide561 (Oct 1, 2005)

*Heating*

Hi

I do not think you will have a problem with 2 x 110 amp batteries. The fans uses quite a lot of power when running at high speed (gas on full pelt) but on the slower setting it does not take so much drain.

Just prior to parking up, run the cab heater on full pelt for a few moments to put as much warm air as possible into the van.

Russell


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## Addie (Aug 5, 2008)

We lasted about 48 hours with it 0 outside and +18 inside on a 75 amp battery and the heating on constantly. 

We've now upgraded to 2x 86AH batteries and did 4 days without issue so far.


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## Chudders (Jul 5, 2008)

Thanks everyone for the prompt replies.
Hopefully I should be OK. I wont use the heating continually and not at all at night I hope. 
I have just done a quick calculation after looking at Truma web site.
Fan about 0.5 amp
LED lights about 0.9 amps
TV 1.2 amps
other odds and ends perhaps 0.5 amps
Total if all running at same time about 3 amps/hr
So worst case scenarion 3a/hr divided by 220 amp (divided by 50% for battery efficiency) = 110 battery capacity.
36 hours of use for 3 amps per hour if continuous.
Does that make sense I wonder, If so should be OK as not all will be running continuously.
ie lights wont be needed during day. TV for only occasional use etc etc. Fan heating might be used the longest, depends on weather.

Dave


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## Ken38 (Mar 24, 2009)

Your calcs look fine.

I am surprised the fan is only 0.5A though. When they first fire up the fan really blows strongly and then backs off. So perhaps the average will be 0.5A.


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## Jezport (Jun 19, 2008)

If its cold we keep ours on all the time and lower it at night. Otherwise the heating has to work flat out on high fan to get the van back up to temperature.


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## Chudders (Jul 5, 2008)

Ken38 said:


> Your calcs look fine.
> 
> I am surprised the fan is only 0.5A though. When they first fire up the fan really blows strongly and then backs off. So perhaps the average will be 0.5A.


Yes I see what you mean, I will have another look at Truma site and may be able to find the handbook etc to double check.
I don,t reckon to get more than about 50% efficiency from the batteries due to internal lossess, temperature etc .

Dave

Edit, Re checked Truma site and seems to indicate 0.3 to 1 amp. (4 to 13 watts. So perhaps an average is about 0.5 A although calculated exactly it woud be 0.65A. Also realised I have on my control panel a digital readout of current currently (Pun) being used so I should be able to check that as well.


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## coppo (May 27, 2009)

Believe me you'll be absolutely fine with those batteries. They dont use as much as you think if you have a nice steady heat 0.5 is about right.

Paul.


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## Chudders (Jul 5, 2008)

Thanks for your comments Coppo
Dave


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## Boff (May 10, 2005)

Hi Dave,

do not worry about the Truma heater. We have been staying without EHU for 2-3 days in a row, while outside temperatures not exceeding -15 degrees C during the day and going down below -20 at night made us leave the heating on all the time. 

And we have only one single 100 Ah battery.

I would also not recommend to only switch off the heater completely if outside temperatures stay well above freezing. You could of course turn the thermostat down a bit when leaving the van.

Best Regards,
Gerhard


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## Chudders (Jul 5, 2008)

Thanks for your comments, should be OK, I must do more with the Motothome not on EHU.
I ran the heating up yesterday evening and watched the amp meter on the hab control panel. The fan pulls about 3.5 to 4 amps on start up when its flat out but as it warms up the fan slows to a slower tickover speed and seems to remain there and pulls about 0.6 amps.
So it would seem better as you said to keep the heating on low rather than turn off and go through the higher fan speeds at start up again
Thanks
Dave


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## dikyenfo (Feb 16, 2008)

It does not do any harm to make a list of ACTUAL current use with all the current gadgets we have.
Find the fuse from the battery and connect a meter across and switch on and note power in Amps for all relative equipment and then switch off and do the next until all finished.
I tell you what you will be surprised.


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