powering the 12V fridge

[Jestercat]

It's bveen way too long since I was in highschool electronics to remember my formulas.....

I'm looking to run a 12V power line from my TV to power the fridge while in motion to the CG.  Don't see the point of running propane when 12V is readily available.  This power line will be exclusively for the fridge.

Rather than go to all the trouble of running a dedicated wire back from the battery up by the engine, my TV has a cigarette lighter socket at the rear of the vehicle.

It is labled 12V/120W.  Is this circuit capable of handling the power demands of a dometic fridge :confused: This is where my forgotten formula would help :book:

I'm planning on tapping into the hot side of that lighter socket, then a fuse, then the line to the trailer connector.  My thinking is that if the circuit can handle the fridge, I also know it is switched with the TV ignition, therefore eliminating the need to disconnect the power lead if we are stopped for any length of time while enroute.

How far off base am I here??

[austinado16]

I believe the 12v heating element in the fridge is running at 8 watts.  You might check the trailer wiring because the electrical coupling at the hitch is probably already wired to do this......ie, charge the camper's battery while driving and therefor also be able to power the fridge.

[chasd60]

You may find that the electric element is close to 10-25A depending upon refrigerator model.
25A would be around 300W

[oldmoose]

I don't recommend running your frig on 12v. You'll run the battery down real quick. Stick with propane if you're dry camping.Moose

[Jestercat]

I just got a chance to check my manual for the fridge and it says the element is 125W and has a current rating of 10.5 amps....

Sounds like my plan borders on the maximum draw that circuit is designed to handle.

I think I'll take the extra time and run a dedicated 12gauge line back from the battery directly, with a fuse and relay to switch with the ignition for battery savings.

Our PU has an 8 wire plug (like 2 flat 4's stacked together as one) at the trailer side, but only a 7 wire round plug to attach to the TV.  I know that 3 of those plus 1 for ground is the running/turn/brake lights, the others are for brakes/brakeground/dome light/fridge.

What is the point of having the dome light wired to your TV?  I think I'll use that pin on the 7 round connector for the fridge instead.

[mike4947]

Jester great minds think alike. That's exactly how I've wired several TV's and campers. Keeps the fridge isolated from the trailer battery and with the kep controlled solinoid protects the TV battery as well. And by using the center pin you still have pin 4 for battery charging and no "extra" connections.

[AustinBoston]

I just got a chance to check my manual for the fridge and it says the element is 125W and has a current rating of 10.5 amps....

Sounds like my plan borders on the maximum draw that circuit is designed to handle.

I think I'll take the extra time and run a dedicated 12gauge line back from the battery directly, with a fuse and relay to switch with the ignition for battery savings.

This is the best arrangement I've seen for running any kind of aux power to the camper, and there are others here who have done the same.

In the case of a fridge, I would make sure the fridge is then disconnected from the pop-up's 12V power because you don't want a charge line and a firdge line connected at both the pop-up and the tow vehicle.

Our PU has an 8 wire plug (like 2 flat 4's stacked together as one) at the trailer side, but only a 7 wire round plug to attach to the TV.  I know that 3 of those plus 1 for ground is the running/turn/brake lights, the others are for brakes/brakeground/dome light/fridge.

Hmmm...you really only want one ground, capapble of handling all circuits.  I'm not sure if you are describing what is on the 8-wire or the 7-wire connectors.

What is the point of having the dome light wired to your TV?  I think I'll use that pin on the 7 round connector for the fridge instead.

http://firefyter_emt.tripod.com/elec.htm shows the most common use of the pins on a 7-wire connector.  The correct term for this is "7 wire flat," because tghe much less common "7 wire round" uses the same arrangement but the pins themselves are round.  If I was doing the wiring, I would use the center pin (Aux) for the fridge circuit.

Austin