Refrigerator fan/battery

[77domer]

We have a 2017 25Ft international. We are on our 3rd set of batteries. The first replacements I chalked up to the fact that the dealer was not keeping them charged. Replaced with interstate deep cycle batteries and installed 100 watt solar on the roof to keep the batteries charged when storing. Noticed that when we were boon docking the batteries would be down to 50% by morning and we were not running only furnace which is propane. Was careful to keep all things electric off. After about a year the batteries would not keep a full charge. Replaced them with some inexpensive deep cycle batteries from AutoZone and went out for a couple days. This time had nothing but the refrigerator which is running on propane and then the fan. Same thing began happening. Since we have had the trailer the fan for the refrigerator runs about 80% of the time. I wonder if that is the culprit? Should the fan be running that much? We have the refrigerator set to #3 which is mid cooling point.
This is our first airstream/trailer experience so any help would be very much appreciated.

[mikeinca]

A couple of thoughts.

I think it's unlikely that the refrigerator fan alone, if it's working properly, would cause the battery depletion you have described. For one thing, the refrigerator fan doesn't (or shouldn't) be running all or even 80% of the time. It's thermostatically controlled and should only run when ambient temperatures are relatively high: the fan in our 2017 Flying Cloud rarely ran at night in cooler climates, for example. Maybe you need to check the little thermostatic switch which controls fan operation. You can test it's function with a cold pack and a hair dryer. It's probably located in the compartment behind the fridge. Of course, when the trailer is in storage the refrigerator and fan shouldn't be operating at all, so if the battery is draining then, your problem is elsewhere.

Also, if I understood you correctly, you mentioned that you didn't expect the battery to drop to 50% overnight when running your propane furnace. FWIW, keep in mind that the furnace fan is a big energy hog and can easily run down your battery on a cold night.

Anyway, I suspect you may have some other culprit which is draining your battery. You don't, by chance, leave your power inverter switched on...? Light left on in an exterior cargo compartment...? Good luck.

[rmkrum]

Out here in the high desert areas of California the fridge compartment gets hot enough in storage with the fridge turned off to click on the fan. I have to unplug it so it stays off. I run vent fans to cool the trailer during the day. Solar charging maintains the batteries and I have to leave the switch in “use” to get fans to run.

Yes, a fridge fan switch with a pilot light is on the improvements list already.

[Spinonedad]

Install a Victron 712 battery monitor
It will tell you how much current you are drawing and how much battery life you have left,
There are many other things in your Airstream that draw current

[polarlyse]

We have friends whose Airstream, with a Dometic refrigerator, had a heating element in the refrig. door gasket. I don't recall just what the purpose was for but it managed to take a bite out of the battery rather quickly. Look carefully and try to find out if your's may also have this. The solution was to trace the wiring diagram and isolate the power source at the panel in the refrigerator compartment and install a switch on that wire so you can selectively disable the power to this function and halt the power drain.

If your's does not have this function then continue looking for the source

[77domer]

Thanks for all the information. Wasn't aware that the furnace fan was such an energy hog, live and learn!