Battery charging and fridge operation whilst towing.

[Phillipcharnwoodforest]

Hiya every-one,
I have had a look at the charge/battery condition meter in the caravan when the car is conected and the engine running, and fridge set to 12v. The meter is down to the orange when the fridge is on 12v so switching it off and running the engine again had another look and it's the same. Is this because I have to switch something in the van on the zig unit or even turn the zig unit off . I have never taken any notice of the gauge before and have always cooled the fridge down on 240v for a few days before going away and the wife can load the fresh stuff thats to be kept cool in the fridge at her leisure before we go.

Any ideas guys.

Phillip.

 

[Phillipcharnwoodforest]

Sorry forgot to put this bit, when I dissconnect the car electrics and the zig unit is connected the gauge remains in the green, and the same when I dissconnect the mains suppy also.

Phillip.

 

[RogerL]

It probably indicates an excessive voltage drop - if you have access to a digital voltage meter (DVM) check the voltage across the car battery while connected to caravan with engine running and fridge operative - then check the voltage across the caravan battery in the same circumstances.
The nearer you get to 14.0v at car battery and 13.0v at caravan battery the better.
Voltage drop is caused by the length of cable from car battery to caravan battery and back via earth return - ideally, the car cables should be 50A, or 2x 27A despite only supplying 10-12A as cable size and length cause the voltage drop - the caravan cables should be 25A but many 12S and 13-core cables aren't full spec.
It takes an anorak to ensure that the car is wired properly as well as the caravan - the usual shortcuts are the reason many caravanners complain their 12v fridge operation isn't good enough.

 

[colin-yorkshire1]

hi Phillip,
to be honest i have never checked the gauge while hooked up to the car, so this phenomium may be correct, I know the car charges the battery when under tow as well as keep the fridge cool, and thats about it no anoraks here,
all I do after hitching up, it make sure all the 12v is off and the fridge is on "12v. via the red switch", with 240v off "green switch"
at this point there is no power to the fridge so the red switch is not lit, after starting the car it lights up, and the fridge is on,
after using the mover the gauge sometimes drops to the amber, but after a run to the site or home the gauge is back in the green.
thats it really, what it does in the mean time I have no idea as I am usually sat in the drivers seat

 

[Phillipcharnwoodforest]

Thanks for the ideas both of you, I have never had a look at the gauge before so like you both it's a new one on me, coz' I like to be in the driving seat when the engines running just like you Colin

.

I think I will have a look at some other stuff to see whats what with it. I only want to know out of interest really as every thing seams to be working as it should. There isn't a switch to change over to 12v from 240v except on the fridge so I don't have to switch the 240v off as such, but I wonder if I should be turning off the zig unit, and if so where the devil do I do it.

If and when I can find more info I will get back to you.

Thanks again.

Phillip.

 

[TonyH1]

Hi Phillip,
The 12v supply for the fridge should be a direct feed from the car and would only be live when the engine's running and your alternator is charging. It shouldn't have anything to do with your zig unit. Not sure why your meter is orange while on charge from the car but I'm pretty confident in saying it's not directly because of the fridge. It may possibly be indirectly caused by the fridge if the earth returns can't handle the level of current.

Regards
Tony

 

[SirRogerFFS]

Good points there Tony the Fridge should only work when the engine is running. Just to clarify when the engine stops the relay cuts power to the fridge . Surely the Zig is the mains side not 100% here as I havnt used a Zig for years.So Now I think the thing to check is to see if the power at fridge drops off when stationary no engine running and also check to see where the grey plug gets its earth from and make sure both earths are sound Im a bit vague on the plugs as we have been on 13pin for a few years now.
Sir Roger.