Fridge Cutting Out - How I Fixed It

[Alanmh]

I just thought I would share how I diagnosed and fixed a little problem we have been having with our battery and fridge while off grid.

I noticed that after a couple of days on battery only, our fridge would start up, then cut out about 10 seconds later. The fridge is a Webasto chest fridge 40litres. Its a really great fridge and I thought it was pretty efficient. Anyway, a little reading of the fridge manual showed that it was behaving like this due to a low battery voltage. I measured the battery, but it was reading about 12.5v not the 10.6v that the manual said that battery protection kicked in.

After a bit of head scratching, I measured the voltage closer to the fridge and on the positive wire it was a whole volt down compared to the battery, the thin wires put in by the converter were causing a 2volt drop (1vin the positive wire and 1v in the negative).

So, a trip to Hafords to buy the thickest wires I could find. After replacing the feed from the fuse box, with 27amp wire (looks like 4mm? ) the voltage drop is down to about 0.25v per wire, 0.5v total.

So in conclusion, thin wires in the fridge feed meant a 2v drop and with the fridge cutting out at 10. 6v, this meant that it cut out when the leisure battery was 12.6v! With the new thicker wires it should be OK till the LB gets down to 11.1v. Time will tel if the solar panel can keep that up!?

Hope this is useful to someone.

 

[Fish]

Good report and solution pal.

 

[Dellmassive]

Great work. Well done. =)

 

[Pete C]

Excellent reminder thanks. We put in dedicated thick wires just to the fridge for this very reason.

Pete

 

[oldiebut goodie]

I have to remind people about this when fitting heaters - I make the leads to go direct to the battery and they change it to a distribution point which has inadequate wiring and get the same voltage drop and wonder why the heater stops!

 

[Vanbus]

That is well worked out. The destructions on CRX50 show a minimum of 2.5mm cable but this of course depends on many factors, one being the length of cable. Longer run requires thicker cable. People often only size cable for current carrying capacity and forget (or dont know) about volt drop.

 

[oldiebut goodie]

I lost 2v in the alternator lead to the battery on my T3 - it is only 12 inches! Corrosion in the factory crimps after 30 years of corroding salt spray from the road was the likely cause.

 

[Vanbus]

I lost 2v in the alternator lead to the battery on my T3 - it is only 12 inches! Corrosion in the factory crimps after 30 years of corroding salt spray from the road was the likely cause.

So many things giving an affect. And certainy a head scratcher sometimes.....

 

[travelvolts]

We see this on so many "converter " vans. I'd have thought that they would have got the message by now!

 

[Alanmh]

We see this on so many "converter " vans. I'd have thought that they would have got the message by now!

Not surprised. It did have my head scratching a bit.

I'm still not happy with the 0.5v drop so will probably wire directly to the battery (with a fuse of course) in the near future. This should take a couple of metres off the overall run.

 

[travelvolts]

They should always be connected directly to the battery via their own fuse. No switches, control panels or any of that stuff and use 6 mm cable up to 4 metres. If longer than that go up to 10 mm on the + and ground locally using a short run of 6 mm.

 

[Alanmh]

Tha is @travelvolts I got the thickest cable I could find in Halfords, it says 27amps. Looks like it's either 4mm or 6? Is this thick enough?

 

[Deaky]

27a will be 2.5mm cable

 

[Alanmh]

27a will be 2.5mm cable

Thanks @Deaky will order some proper stuff. God knows what was on there originally if that is 2.5!!

 

[travelvolts]

More likely 2 mm thin wall if its from Halfords.