Leisure Battery to blame ? (1 Viewer)

NorthernIsler

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Feb 24, 2023
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Trying to figure out the reason I only get about 4 hours out of my diesel heater before it dies on me. On cold nights we only use it for short periods trying to maintain 21degC. Its a 5 yr old VWT6.....will a replacement battery fix things ?
 

pappajohn

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They use up to 10amp to start but once running only around ½ amp hour.
If you're on hookup the battery will remain charged so the heater may be at fault.
If you're off grid it could be the battery on its way out
 
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NorthernIsler

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Feb 24, 2023
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Thanks for the replies guys, yes its when off grid, any recommendations for leisure batteries, any brands reckoned better than others ?
 
Apr 27, 2016
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Trying to figure out the reason I only get about 4 hours out of my diesel heater before it dies on me. On cold nights we only use it for short periods trying to maintain 21degC. Its a 5 yr old VWT6.....will a replacement battery fix things

They use up to 10amp to start but once running only around ½ amp hour.
So to calculate your usage, 10 amps for 1/2 hour is 5 amp-hours (Ah). Then 1/2 amp for 24 hours is 12Ah. So you are using a maximum of 5 +12 = 17Ah per day. Your battery is probably about 100Ah,and you can use about 50% of that without causing problems, so that's 50Ah available. That should last you 3 full days. So yes, looks like the battery needs replacing.

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Sep 13, 2016
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21.5 degrees seems very warm to try to maintain over a cold night in a van!
 

Hoovie

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May 16, 2021
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The first thing to do is repeat the process - heater on all night - but hooked up. Then you will know if it is the heater or the electrical supply to it.
If you have already done that, you have answered the question already.
 
Jul 28, 2008
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The heaters pull >20A on start up/shut down - not 10A. The 10A comes from the fact the power is pulsed so the meters only display an average of their delta, so show around 10A. The fact its 20A and the chinese heaters come with thin wires, mean many installs suffer from high voltage drop during this period and the heater drops out. Branded heaters also suffer but tend to be installed better. This is a large reason for startup issues.

In this case, once running (assuming its not on an on/off setting, rather than a run constant low) its likely to be either a duff battery or something else. The easiest way to check is turn it on in the morning with some lights on and see what happens. If it struggles to start and the lights dim/flicker - its almost certainly battery. If it starts, lights fine, and it (and other stuff) runs for an hour or two then look elsewhere,

I am aware of some branded heaters removed from commercial van have a 4hr (IIRC) timeout on them.

If it is your battery, find out make/model/size and get a comparable. Yes, some are better than others but thats a bigger debate :)
 
Sep 29, 2009
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Just as a mater of interest do you have an electric fridge and inverter as well? All power hungry.
 
Dec 17, 2016
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A temporary fix would be to run the van engine when you start the heater so the alternator is boosting the battery voltage. Not feasible if it keeps cycling on and off however.

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Feb 9, 2008
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Why not turn the heating off once your heating temp is reached. I found by putting my diesel heater on for 25 minutes in the morning was enough to heat the motorhome up and then maybe a couple of hours at night max. The m'home insulation is quite good and retains the heat for quite a while and once under the bed covers body heat was more than sufficiant, The batteries would then get topped up during the day by solar of hook up and this has worked well for us for quite a number of years. If you are going to change your battery and you charger is fixed to a lead acid charging profile. You may want to consider this battery as it has a lead acid charging profile and is rated at quite a few thousand charging cycles. Can be discharged below 50 % and very quickly recharged to a full state.

 
Dec 2, 2019
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The heaters pull >20A on start up/shut down - not 10A. The 10A comes from the fact the power is pulsed so the meters only display an average of their delta, so show around 10A. The fact its 20A and the chinese heaters come with thin wires, mean many installs suffer from high voltage drop during this period and the heater drops out. Branded heaters also suffer but tend to be installed better. This is a large reason for startup issues.

In this case, once running (assuming its not on an on/off setting, rather than a run constant low) its likely to be either a duff battery or something else. The easiest way to check is turn it on in the morning with some lights on and see what happens. If it struggles to start and the lights dim/flicker - its almost certainly battery. If it starts, lights fine, and it (and other stuff) runs for an hour or two then look elsewhere,

I am aware of some branded heaters removed from commercial van have a 4hr (IIRC) timeout on them.

If it is your battery, find out make/model/size and get a comparable. Yes, some are better than others but thats a bigger debate :)
I don’t think so. The main draw on start up and shut down it’s the glow heater plug. By default settings, this plug is set at 90w plus the fan. The heater it’s a resistive load fed by DC, no pulsing, and you should not see a pulsing even with a oscilloscope. If you do, it’s a DC ripple due to high resistance for the draw: thin wires,weak battery etc. The pulsing will be in the 100hz region, with a peak of 0,3-0,8v. This difference in delta, can not account for the 10a difference you mention. I will be interested to know how you got the 20a. Maybe I’m missing something. The loom wire can be cut near the heater, and spiced with 6mm2 to mitigate the voltage drop, which I did.
 

suavecarve

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I am aware of some branded heaters removed from commercial van have a 4hr (IIRC) timeout on them
The 4 hours does seem a constant and a clue. I agree and this needs looking at first to be able to ignore it.

Put heater on at 1800 hrs to same level tonight and see if it goes off at 2200 hrs and yet your interior lights and tv still work will make you have to look for an override.
I d also be tempted to run it for 4 hours during the day at 15 and see what happens
 
Dec 2, 2019
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I would also recommend take a reading after 3-3,5 hrs into running the heater. Check voltage near the heater by the fuse, and compare it to the voltage at the battery terminals. I suspect the loom wire it’s way undersized for its length, and the heater sees a voltage drop and shut down.

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Hoovie

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May 16, 2021
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I don’t think so. The main draw on start up and shut down it’s the glow heater plug. By default settings, this plug is set at 90w plus the fan. The heater it’s a resistive load fed by DC, no pulsing, and you should not see a pulsing even with a oscilloscope. If you do, it’s a DC ripple due to high resistance for the draw: thin wires,weak battery etc. The pulsing will be in the 100hz region, with a peak of 0,3-0,8v. This difference in delta, can not account for the 10a difference you mention. I will be interested to know how you got the 20a. Maybe I’m missing something. The loom wire can be cut near the heater, and spiced with 6mm2 to mitigate the voltage drop, which I did.
Those numbers sound about right to me.

I did a power consumption check on the [chinese] diesel heater I fitted a few years ago in my last campervan. Logged from before start up to after shutdown.
The graph below shows the power consumption for initial firing, running and then shuting down. You can see the non-heater baseline from 14:15 onwards. Take that power off to see how much the heater itself uses ....


Heater Running - Power by David, on Flickr

If you prefer seeing it in Amps and effect on battery voltage ...

Heater Running - VoltAmp by David, on Flickr

Like Raul, I ran a thicker cable than supplied and cut off the great majority of the provided loom. I also, as a precuation to avoid having the heater not work due to inappropriate low voltage errors, fitted a 12V-13.8V voltage booster close to the heater and wired it via a 3-way switch so I could use with the normal battery supply or via the booster. (whilst fitted, I never actually needed to use it though. But for the cost of around £15, it was worth having ready)

I just noticed I also did a consumption test a bit later on (in October, so colder than above as it happens), seeing how much was taken out the battery over a longer period.


Diesel Power Test - Watts by David, on Flickr


Diesel Power Test by David, on Flickr


So 2.3 Ah to start+stop the heater and around 1.5Ah/Hr whilst it is running :)
 
Last edited:
Dec 2, 2019
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Yes those figures I get as well, 10-12 amp peak draw max, depending on battery SOC. You can actually reduce this slightly by going in the heater settings and reduce the power draw of the plug. It doesn’t bother me, I like a fast start up, so plug drawing 90w it’s ok. In fact I may increase that to keep the plug hotter and cleaner.
 

Hoovie

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May 16, 2021
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I don't have a Diesel Heater currently in the Motorhome I have now and I find the Truma Gas/Electric very good. I am contemplating fitting one as a backup/alternative, but would want to connect it into the heating ducting for distribution.
I also mean to log the power the fan on the Truma uses on the various speeds to see how much it uses. I have seen lots of comments about how much that drags the battery down, which surprises me so will have to check that for myself :)
 
Jul 28, 2008
822
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Since 2005! 2000+ nights so far...
I don’t think so. The main draw on start up and shut down it’s the glow heater plug. By default settings, this plug is set at 90w plus the fan. The heater it’s a resistive load fed by DC, no pulsing, and you should not see a pulsing even with a oscilloscope. If you do, it’s a DC ripple due to high resistance for the draw: thin wires,weak battery etc. The pulsing will be in the 100hz region, with a peak of 0,3-0,8v. This difference in delta, can not account for the 10a difference you mention. I will be interested to know how you got the 20a. Maybe I’m missing something. The loom wire can be cut near the heater, and spiced with 6mm2 to mitigate the voltage drop, which I did.
I'd check with your scope :) Not 100hz. The 10A ish is an average - and hence the higher current (pulsed) is more susceptible to voltage drop. (Had been discussed in depth on the heater forums). And yes, of course the power cables replaced with something of suitable spec. Only saw the flickering with one particular LED light range (which wasn't voltage sensitive). Anyway, our differing views aren't really linked to the OP apart from ensuring power cables are "severely over spec'd"
 
Jul 28, 2008
822
753
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Those numbers sound about right to me.

I did a power consumption check on the [chinese] diesel heater I fitted a few years ago in my last campervan. Logged from before start up to after shutdown.
The graph below shows the power consumption for initial firing, running and then shuting down. You can see the non-heater baseline from 14:15 onwards. Take that power off to see how much the heater itself uses ....


Heater Running - Power by David, on Flickr

If you prefer seeing it in Amps and effect on battery voltage ...

Heater Running - VoltAmp by David, on Flickr

Like Raul, I ran a thicker cable than supplied and cut off the great majority of the provided loom. I also, as a precuation to avoid having the heater not work due to inappropriate low voltage errors, fitted a 12V-13.8V voltage booster close to the heater and wired it via a 3-way switch so I could use with the normal battery supply or via the booster. (whilst fitted, I never actually needed to use it though. But for the cost of around £15, it was worth having ready)

I just noticed I also did a consumption test a bit later on (in October, so colder than above as it happens), seeing how much was taken out the battery over a longer period.


Diesel Power Test - Watts by David, on Flickr


Diesel Power Test by David, on Flickr


So 2.3 Ah to start+stop the heater and around 1.5Ah/Hr whilst it is running :)
Thats quite different to ours, startup (from power on, to start cycle, to fan/pulse going to "normal" is closer to 5 mins, not timed it specifically, but certain its closer to 5 than 15 or even 10. Shutdown is about the same. Running power depends on fan speed and fuel pump pulse speed of course.

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Lenny HB

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I also mean to log the power the fan on the Truma uses on the various speeds to see how much it uses.
About 5½ amps at full power a bit less than 1 amp at min fan speed with a CP Plus controller and 1¼ amps with a classic controller.
With the way the Truma works by varying the fan speed relative to temperature an evenings consumption will vary depending on conditions,
 
Jan 31, 2022
279
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70s camper,Weinsberg
Trying to figure out the reason I only get about 4 hours out of my diesel heater before it dies on me. On cold nights we only use it for short periods trying to maintain 21degC. Its a 5 yr old VWT6.....will a replacement battery fix things ?
what diesel heater our autotherm lasts for hours with no problems, where is heater internal or underneath?, is your leisure battery under driver seat and getting hot maybe !!
 

Hoovie

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About 5½ amps at full power a bit less than 1 amp at min fan speed with a CP Plus controller and 1¼ amps with a classic controller.
With the way the Truma works by varying the fan speed relative to temperature an evenings consumption will vary depending on conditions,
I will check my own and see how it compares :)
And using the set speed values rather than the auto-variable setting (you can select between the two).
 

Lenny HB

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Oct 18, 2007
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I will check my own and see how it compares :)
And using the set speed values rather than the auto-variable setting (you can select between the two).
I only have a choice of Eco or High.
Eco varies fan speed with temp, high is full blast all the time.
 

Hoovie

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I only have a choice of Eco or High.
Eco varies fan speed with temp, high is full blast all the time.
Sounds quite inflexible?
This is what my fan controller looks like:
iu

Middle is off
Switch on left, you set the fan speed between 1 and 5
Switch on right, you set the maximum fan speed between 1 and 5 and the actual speed will vary between off and the max speed set.

With this, you can use the fan to provide some airflow in the van with the heater off if you want. I would think with yours it would not be possible without having to put up with a very loud fan noise constantly?

5.5A at max seems remarkably high and inefficient. Just as I checked how the Diesel Heater used the battery, I did the same for the Maxxair Extreme Fan I fitted. These are very good and powerful (when you want them to be) fans - more so than the Truma fans I would say and don't use close to 5A at full power.
I'll be graphing the usage of the Truma Fan in the same way as I did the Maxxair (shown below). Information is Power :)

Maxxair Power Consumption
by David, on Flickr

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Lenny HB

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Oct 18, 2007
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Sounds quite inflexible?
This is what my fan controller looks like:
iu

Middle is off
Switch on left, you set the fan speed between 1 and 5
Switch on right, you set the maximum fan speed between 1 and 5 and the actual speed will vary between off and the max speed set.

With this, you can use the fan to provide some airflow in the van with the heater off if you want. I would think with yours it would not be possible without having to put up with a very loud fan noise constantly?

5.5A at max seems remarkably high and inefficient. Just as I checked how the Diesel Heater used the battery, I did the same for the Maxxair Extreme Fan I fitted. These are very good and powerful (when you want them to be) fans - more so than the Truma fans I would say and don't use close to 5A at full power.
I'll be graphing the usage of the Truma Fan in the same way as I did the Maxxair (shown below). Information is Power :)

Maxxair Power Consumption by David, on Flickr
That's not a Combi I thought all the Truma heaters in Motorhomes these days were Combi's
 

Hoovie

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That's not a Combi I thought all the Truma heaters in Motorhomes these days were Combi's
correct. It is not a combi :) And I am pleased it is not.
I have the Truma S3004 with Ultraheat 500/1000/2000 Element and a Truma Ultrastore with 850W Element.
 

Lenny HB

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Oct 18, 2007
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correct. It is not a combi :) And I am pleased it is not.
I have the Truma S3004 with Ultraheat 500/1000/2000 Element and a Truma Ultrastore with 850W Element.
Every van I've had has had a Combi I like them, nice to be able to set the timer and wake up in a warm van. Had caravans with the 3000 heaters.
 
Feb 9, 2008
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Since my post at #11 A funster member has asked questions about this LifePo4 battery that can be maintained with a Lead Acid charging profile. I have read the article and looked at the U Tube clip and I have to say it impressive to say the least.




Overall battery summary at 15.30
 

huck999

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I don’t think so. The main draw on start up and shut down it’s the glow heater plug. By default settings, this plug is set at 90w plus the fan. The heater it’s a resistive load fed by DC, no pulsing, and you should not see a pulsing even with a oscilloscope. If you do, it’s a DC ripple due to high resistance for the draw: thin wires,weak battery etc. The pulsing will be in the 100hz region, with a peak of 0,3-0,8v. This difference in delta, can not account for the 10a difference you mention. I will be interested to know how you got the 20a. Maybe I’m missing something. The loom wire can be cut near the heater, and spiced with 6mm2 to mitigate the voltage drop, which I did.
I put a clamp monitor on my unit for 24hours. I found the initial start-up load was 15amp even with 6mm cables. What I did notice was that as the unit ramped down the current dropped off but when the thermostat called for heat the current again went up to 10-12 amps. I found that the glow plug was kicking in each time and thus hammering the batteries. I cannot say if this was just on my unit, but I have heard of many people waking up with flat batteries after using the heaters over night.

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