running 12v fridge while travelling

ricky vw
There are many ways you can connect a fridge. If you are worried about flattening the AGM because you forget, then if it is connected to the alternator it will flatten the start battery quicker and then NO START.
Some sort of relay/solenoid which is voltage controlled is a sound idea. Called VSR's Voltage Sensitive Relay, which pull in after the start batt has had a bit of charge and it disconnects the two if the voltage gets down to a set level and therefore protecting your start battery.

You don't say what type of fridge it is: 3 way power hungry item or compressor fridge which us about 1/4 of the 3way fridges.
Your needs and wiring cables and any auto safety items will depend on the type of fridge to a large extent.

Fuses? They need to protect the wiring if a short happens to the negative. ie, both ends of the charge cable for safety.
A bit more info and others will have solutions/suggestions.

Get ready for the avalanche.

yes you can take a 12 volt feed to your fridge in the caravan but from the start battery not straight from the alternator you will need 3b&s cable to avoid voltage drop and inefficient cooling and a 50 amp fuse from the battery Then to prevent running the battery flat a fridge switch can be fitted when the caravan stops the fridge switches off after a small delay to prevent switching off at every stop It then starts again when the vehicle is moving again This is the simplist way to get a 12 volt fridge running in the caravan for travelling only then on 240 volt or gas when stopped There are many other ways eg solenoids dc to dc chargers some better some not But this is probably the cheapest and easiest also use Anderson plugs to connect to the caravan fridge not the standard trailer plug as it wont take the current draw causing inefficient cooling and an overheated plug
click on linkcaravan fridge cut off switch
this is s link to one supplier for the fridge switch
good luck
Steve

Ricky,

There's good advice above.

I would add one suggestion. Provide the fridge with its own wiring - both positive and negative - from the engine bay to the fridge. (And include a fridge switch in that line as suggested above.)

Your fridge draws about 12-15 amps continuously when on 12 volts and consequently there will be significant voltage drop in the wiring. If you were charging the auxilliary battery through the same line, this voltage drop would seriously reduce the charging available to your aux battery.

I assume that you already have a voltage sensitive relay and fuse under the bonnet. I'd connect the fridge wiring after that relay and fuse, where the present aux battery wiring takes off. Note that it is important to provide some means of switching the fridge circuit off when stationary, as otherwise the fridge will be permanently connected to the aux battery - a fridge switch would be ideal, or a relay (headlight relay would be good) activated by the ignition switch.

Cheers

John

thanks everyone for your input.it is just what i wanted and all understandable.sometimes it can get confusing (threads).can't wait to hit the road in feb.Ricky.