Running Dometic fridge from 12v leisure battery (1 Viewer)

Oct 31, 2017
543
1,213
Kent
Funster No
51,209
MH
Carthago T149
Exp
Since 2016
I have fitted another 200w solar panel and have a 230a Fogstar battery, I intend to fit another battery along side. I would like to run the fridge on 12v for periods of the day when the sun shines but when I press the 12v button on the Dometic 10.5 fridge it shows an error message. Our previous Swift van did run from the leisure battery when the gas run out ( found out the hard way :rolleyes:) I assume this van is wired differently, is there a relatively easy way to resolve this ?

PS the fridge works fine when the engine is running

Thanks Roger
 
Feb 19, 2020
1,453
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North Ayrshire
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68,864
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Adria Matrix 670SC
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Newbie
There's different ways they can operate, some have a relay triggered by the d+ from the alternator others like my Thetford have the D+ wired to the fridge so when the d+ is live it switches to the high current 12v feed. You could gets yours to work by fooling it with a false D+ to operate the relay or signal the fridge to work on 12v. It will depend on how yours actually works but be aware a 3 way absorption fridge is very inefficient on 12v and can draw a lot of current maybe as much as 15- 20 amps.
 

TheBig1

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Nov 27, 2011
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It depends if your van is wired to power the 12v to the fridge from the engine battery when the engine runs D+, or the leisure battery as some are. If the former, it will need to have the supply added for the leisure battery. Newer fridges have it as an optional connection anyway
 
Feb 14, 2021
3,718
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Milton Keynes, UK
Funster No
79,219
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Burstner Lyseo 727G
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19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
It depends if your van is wired to power the 12v to the fridge from the engine battery when the engine runs D+, or the leisure battery as some are. If the former, it will need to have the supply added for the leisure battery. Newer fridges have it as an optional connection anyway

Or, like mine - it runs off the leisure battery but still only when the engine is running as it is fitted with a Schaudt booster which charges the leisure battery when the engine is running.

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May 17, 2022
298
603
Stelling Minnis, Canterbury, UK
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Since 1998
Give Steve a call. He can advise and sort it if possible.



IMG_20231011_082510094.jpg
 
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Roger S
Oct 31, 2017
543
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Carthago T149
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Since 2016
Or, like mine - it runs off the leisure battery but still only when the engine is running as it is fitted with a Schaudt booster which charges the leisure battery when the engine is running.
That is how ours works
 

RedFrame

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Sep 2, 2017
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I have fitted another 200w solar panel and have a 230a Fogstar battery, I intend to fit another battery along side. I would like to run the fridge on 12v for periods of the day when the sun shines but when I press the 12v button on the Dometic 10.5 fridge it shows an error message. Our previous Swift van did run from the leisure battery when the gas run out ( found out the hard way :rolleyes:) I assume this van is wired differently, is there a relatively easy way to resolve this ?

PS the fridge works fine when the engine is running

Thanks Roger
I did this with our last van.

If you're adept with 12v it's fairly straightforward to fit a 12v timed momentary switch to deliver 12v to d+, this tells the fridge to operate on 12v, on an AES you don't need to change over on the front panel.

I set the timer to 3 hrs as we were rarely away from the van for that long, I didn't have to remember to switch it off, and if it was still sunny I could always press it again.

The back-light on the momentary switch was lit up when the fridge was running on 12v as a visual indicator, pressing the switch whilst on would cancel 12v and return the fridge to gas.

I only ever used it if Solar was able to yield more than 20A as I was on lead acid at the time.

I think there's a few on here that have done similar (funflair , Lenny HB ?)

Edit: As TheBig1 says, it's important to make sure your fridge is drawing from the leisure not the cab side.


Cheers
Red.
 

funflair

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Dec 11, 2013
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I have fitted another 200w solar panel and have a 230a Fogstar battery, I intend to fit another battery along side. I would like to run the fridge on 12v for periods of the day when the sun shines but when I press the 12v button on the Dometic 10.5 fridge it shows an error message. Our previous Swift van did run from the leisure battery when the gas run out ( found out the hard way :rolleyes:) I assume this van is wired differently, is there a relatively easy way to resolve this ?

PS the fridge works fine when the engine is running

Thanks Roger
I ran our Dometic fridge from solar using the AES out of the Votronic regulator to trigger the D+ on the fridge, basically it thought the engine was running with the Votronic regulator keeping an eye on the battery level, not perfect in that when it comes off every 30 minutes it waits 15 minutes as it thinks you might be in a fuel station 🤔
 
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Roger S
Oct 31, 2017
543
1,213
Kent
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51,209
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Carthago T149
Exp
Since 2016
I did this with our last van.

If you're adept with 12v it's fairly straightforward to fit a 12v timed momentary switch to deliver 12v to d+, this tells the fridge to operate on 12v, on an AES you don't need to change over on the front panel.

I set the timer to 3 hrs as we were rarely away from the van for that long, I didn't have to remember to switch it off, and if it was still sunny I could always press it again.

The back-light on the momentary switch was lit up when the fridge was running on 12v as a visual indicator, pressing the switch whilst on would cancel 12v and return the fridge to gas.

I only ever used it if Solar was able to yield more than 20A as I was on lead acid at the time.

I think there's a few on here that have done similar (funflair , Lenny HB ?)

Edit: As TheBig1 says, it's important to make sure your fridge is drawing from the leisure not the cab side.


Cheers
Red.
That sounds interesting, and not too complicated (y)

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Lenny HB

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Oct 18, 2007
54,059
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On the coast in West Sussex
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658
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Hymer B678 DL
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Since 2008 & many years tugging
You can fit another relay or change the existing fridge relay to a changeover relay.
The relay is switched by the D+ the normally closed contact is connect to the hab battery and the normally open contact connected to the starter battery.
Its a fairly standard way to wire a fridge on German vans, all 3 Hymers we have had have been wired like that.

Also you can make use of the S+ terminal on the back of the fridge, applying a 12v signal switches the fridge to 12v.

My plan when I get the new van is to fit a BMV 712 Shunt/battery monitor it has a programable relay which I will probably set to turn on at 90% SOC & off at 50%. Then feed a 12v signal via the relay to a timer to the S+. I'll probably set the timer (depending on time of year) to come on at 7am then off 60min later and back on 30min later until 6pm. This avoids over discharging the batteries.
 
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Roger S
Oct 31, 2017
543
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Kent
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Carthago T149
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Since 2016
You can fit another relay or change the existing fridge relay to a changeover relay.
The relay is switched by the D+ the normally closed contact is connect to the hab battery and the normally open contact connected to the starter battery.
Its a fairly standard way to wire a fridge on German vans, all 3 Hymers we have had have been wired like that.

Also you can make use of the S+ terminal on the back of the fridge, applying a 12v signal switches the fridge to 12v.

My plan when I get the new van is to fit a BMV 712 Shunt/battery monitor it has a programable relay which I will probably set to turn on at 90% SOC & off at 50%. Then feed a 12v signal via the relay to a timer to the S+. I'll probably set the timer (depending on time of year) to come on at 7am then off 60min later and back on 30min later until 6pm. This avoids over discharging the batteries.
Thank you but hat sadly is beyond my ability :(
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,059
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On the coast in West Sussex
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658
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Hymer B678 DL
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Since 2008 & many years tugging
I strongly advise against running an absorption fridge on 12v from battery banks.

Yes, it is possible. But it could cause big issues and leave you with no battery power.
Not if done correctly as in my post above. My current van has a Votronic Solar Regulator that has a AES output which sends a 12v signal to the fridge S+, when the batteries are charged and plenty of solar. It does it in 30 min blocks so as not to over discharge the batteries. Can't do that on the new van as I will be fitting Victron as they work better with Lithium hence the way of doing it in my post above.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,059
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On the coast in West Sussex
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658
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Since 2008 & many years tugging
If you're adept with 12v it's fairly straightforward to fit a 12v timed momentary switch to deliver 12v to d+, this tells the fridge to operate on 12v, on an AES you don't need to change over on the front panel.
Far better to use the S+ terminal if you use the D+ for safety you need a changeover relay so you don't feed 12v back to the alternator.
 

RedFrame

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Sep 2, 2017
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Far better to use the S+ terminal if you use the D+ for safety you need a changeover relay so you don't feed 12v back to the alternator.
Yes agreed, it's been a couple of years, I forgot about S+ :wasntme:

Cheers
Red
 
Jun 23, 2017
9
7
UK
Funster No
49,135
MH
Overcab bed Motorhome
Exp
Since 1985
I have the Dometic 10.5 fridge in our Pilote 626.When in Auto mode it only selects Battery when engine is running. However I noticed that I can overide this by manually setting it to Battery. It does not care if the engine is running or not. It takes about 18-20A though. I am a bit old school and don't use Auto as I always turn the Gas off.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,059
152,510
On the coast in West Sussex
Funster No
658
MH
Hymer B678 DL
Exp
Since 2008 & many years tugging
I have the Dometic 10.5 fridge in our Pilote 626.When in Auto mode it only selects Battery when engine is running. However I noticed that I can overide this by manually setting it to Battery. It does not care if the engine is running or not. It takes about 18-20A though. I am a bit old school and don't use Auto as I always turn the Gas off.
Fairly standard every van we have had has been like that.
 
Feb 20, 2023
196
319
South Yorkshire, UK
Funster No
94,113
MH
Carthago E line 50 D
Exp
2005
I have the Dometic 10.5 fridge in our Pilote 626.When in Auto mode it only selects Battery when engine is running. However I noticed that I can overide this by manually setting it to Battery. It does not care if the engine is running or not. It takes about 18-20A though. I am a bit old school and don't use Auto as I always turn the Gas off.
I will try that, as at the moment I just put mine on auto and switch the inverter on, but appreciate it may not be the most efficient way.

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