Dometic fridge issue...

[Geek]

Thanks. It's lead acid 12V 110AH Expedition Plus Semi Traction Leisure Battery, using the engine every day at the moment

How are you charging the battery?

 

[Geek]

I have a state of charge meter where all -ve connections have to go via a shunt. Does that restrict the amount of current that can be supplied?

No

 

[benk]

Add

This is a common issue with Compressor fridges, people look at the consumption figures and choose a cable size accordingly but that doesn't allow for the much higher current drawn momentarily when starting up. Sounds like yours is right on the cusp of being adequate. Increase the cable guage, you may get away with doing just the pos or neg only if you do just one and retry it but bear in mind things get worse as the battery voltage gets lower so probably best to build in a safety margin and do both.

thanks Merl, sounds like this is the most likely issue and hopefully not too much of a ballache to resolve! - what type of cable would you recommend using?

 

[merl]

Add

thanks Merl, sounds like this is the most likely issue and hopefully not too much of a ballache to resolve! - what type of cable would you recommend using?

Something approximately twice the gauge as being used currently.
You could semi bodge it by paralleling up the existing with something of a similar size, It'll save you a bit.of dosh..... probably not worth it and could also cause a bit of head scratching when you or someone else has to work on the van.in the future.

 

[merl]

I have a state of charge meter where all -ve connections have to go via a shunt. Does that restrict the amount of current that can be supplied?

Possibly, it depends on the maximum current rating of the shunt. Shunts generate heat, this could become an issue if you run them close to their max rating for long periods. The TR16 type also stop Coulomb counting at about 20% above their max rating, don't know about the blue ones.

 

[benk]

After a bit of head scratching I think perhaps I might have the solution but I am by no means sure! My Victron app is showing the battery has good voltage of around 13.5 volts . On my current set up my I have leisure battery running to a switch panel (a typical 12v inline switch panel) then to the fridge. I am considering changing the existing set up and adding an extra wiring loom directly between the fridge and the battery, bypassing the switch panel.

If I do this would there be any implications for the switch panel? Would it be a case of disconnecting everything from the leisure battery, removing the current wires at the fridge end and capping them and the adding in the new connection directly from the battery to the fridge, and reconnecting everything else?
Rayne automotive sell a loom (link below) which I think looks like what I need . I appreciate it's difficult to comment accurately without knowing what set up I have, I'd normally be heading to a garage for advice, I'm just trying to get a self fix done if possible as I'm in Porto heading off to Morocco quite soon.
Cheers

Ben

Wiring Loom For CRX50 Fridge - Battery Connection

12V Fridge wiring loom for direct connection to the battery Easily install your fridge for smooth efficient cooling, with this heavy-duty wiring loom Pre-terminated at both ends Inline fused to 15A labelled for easy install 6mm2 cables to minimise voltage drop (up to 4M in length) Product...

rayneautomotive.co.uk

Something approximately twice the gauge as being used currently.
You could semi bodge it by paralleling up the existing with something of a similar size, It'll save you a bit.of dosh..... probably not worth it and could also cause a bit of head scratching when you or someone else has to work on the van.in the future.

 

[merl]

Yes, you've pretty much sussed the job out and there'll be no issues with the PDU either.
One thing worth considering. If the current cables between the PDU and the fridge are withdrawable and long enough you could use them and connect them directly to the battery. This would result in a lower resistance route between battery and fridge because the fridge would no longer be using the additional cables between battery and PDU, the difference would probably be enough to give you reliable starting.
I'm not sure what's included with the loom you linked to but it looks like a couple of cables with ring terminals ready crimped on. You should also fit a fuse to the positive cable close to the battery end, you should do the same if you reuse the cables too.
Any Questions just ask.