Charging Trailer Battery Running Fridge While Driving

Question:

I have a 2013 Jeep Wrangler Rubicon used for towing a small camper trailer with a multi power source frig. The frig works well on propane and 120vac. When towing the frig drains the trailer battery even though I have good connection from the Jeep battery to the trailer power system I have heavy gauge wire to the 7pin connector. From my research it seems that I need a dual charging system to ensure that enough charge current is reaching the trailer to supply the frig and keep the trailer battery fully charged for when I arrive at my off the grid location while not over charging the Jeep battery. The Jeep Alternator is specd at 160 amps. Will the CTEK40186 solve my problem? If so can you provide a wiring diagram? Thanks

asked by: Chris F

Expert Reply:

The problem you are having is that anything other than a breakaway battery cannot be charged up through the 7-Way trailer connector. Most vehicle alternators are not strong enough to push back the required current to charge up larger 12 volt batteries. At best they can maintain the charge level but if there is a constant draw on it then it won't be able to even maintain the charge level.

A DC to DC charger such as # 331-BCDC1225D will definitely help but even it won't be able to charge the battery as fast as the fridge draws power. The solution would be to wire up 2 or more batteries in parallel and or get a larger charger. This will keep the output at 12 volts but double the capacity (if using 2 batteries). So for example if you have 2 identical batteries rated for 50 amp hours then wiring them in parallel will provide a total of 100 amp hours at full charge. So if your fridge drew 10 amps constantly then the 2 batteries in this scenario would run the fridge for about 10 hours.

It would still be a good idea to have a charger, so a larger option such as # 331-BCDC1240D is my recommendation. The charger has 2 inputs;one you can attach to the alternator and the other can be used for a solar panel or not used at all. On the output side one terminal is ground and the other is output to the trailer battery or bank of batteries. This unit has a 40 amp output and will charge much faster allowing for your fridge to be powered and still charge your battery simultaneously.

expert reply by: Michael H