Fridge not working from battery

[Craig V]

It seems our fridge is not running from the battery option. It doesn’t get cold at all.
When I select run from battery, the battery indicator goes good to low immediately. If I have the roof vent fan on, I hear it slow down when I select run from battery . So something from fridge is drawing current. I also connected battery to charger but same results. With fridge off, charger output 4A to charge battery.
Fridge seems to work fine running from 120V and propane.

So I think battery is shot or something is wrong with fridge.
Battery water level was OK. Battery came with TM so I’m not sure of its history prior to us (bought TM in November).

Thoughts?

[gonzo628]

Originally Posted by Craig V

It seems our fridge is not running from the battery option. It doesn’t get cold at all.
When I select run from battery, the battery indicator goes good to low immediately. If I have the roof vent fan on, I hear it slow down when I select run from battery . So something from fridge is drawing current. I also connected battery to charger but same results. With fridge off, charger output 4A to charge battery.
Fridge seems to work fine running from 120V and propane.

So I think battery is shot or something is wrong with fridge.
Battery water level was OK. Battery came with TM so I’m not sure of its history prior to us (bought TM in November).

Thoughts?

Are you still connected to shore power whilst running the fridge on battery (ie just testing it)? I ask because I thought the fridge was a pretty signficant drain on the battery.. I know you said you see some kind of current draw, so perhaps that answers the fuse question, but "have you checked the fuse"? Also, have you brought the fridge down to temp via another source (A/C... Propane) and seen if the battery can "maintain" that temp? Have you read the battery voltage with a multimeter?

...Just some thoughts.

[Craig V]

When connected to shore power, it runs fine. Haven’t checked the voltage or fuses. If fuse was blown though, I wouldn’t expect the current draw to occur.
Haven’t tried to maintain temp from battery after it’s already cold.

We tried to start running it while traveling from battery but was not cold at all after about 2-3 hours. Fridge fan may have been off during travel.

Not sure it ever worked from 12V since we got it (last year).

[Craig V]

Was not connected to shore power when testing running from battery.

[Bill]

Craig V -

On DC (battery), the refrigerator uses 10-12 amps of current. If your charger will supply only 4 amps, then the refrig will attempt to pull the remainder from the battery. If the battery is discharged or bad, it is not able to supply 6-8 amps, so the refrig does not work.

When you connect shore power, the TM's built-in charger (sometimes called a converter) is able to supply the missing current, so the refrig works.

There are two bottom line lessons here.

1. The refrig cannot operate solely on battery for more than a very short time, even if the battery is good and starts out fully charged. Most TM batteries have a capacity of about 70 amp-hours when new, and it can be discharged about halfway before it starts to incur damage. So if the usable capacity is 35 amp-hours, and you pull 12 amps from it, you will get about 3 hours of operation before the battery is discharged.

2. If you are driving down the road with the refrig set to battery, your tow vehicle is supposed to be recharging the TM battery as you drive. In reality, the tow vehicle can't/won't supply more than about 4 amps, so again, the refrig pulls the remaining 6-8 amps from the TM battery. And again, the TM battery gets discharged, and you will arrive at the destination with the TM battery near dead. In practical terms, this means you can't run the TM refrig on battery as you travel. You can run it on propane, which works but is discouraged for safety reasons (think about an open propane line in an accident). Or you can simply turn the refrig off, and it will function like a simple styrofoam cooler. It actually is a pretty good cooler - we routinely travel for 8 hours, and find it is still cool when we arrive.

FYI, our member Padgett has built himself a system with very large batteries, and the numbers above do not directly apply to him. However, his mod involves considerable expense. Another one of our members (rickst29) has overcome the tow-vehicle-can't-charge problem, again with a fairly elaborate fix. It involves changing the tow vehicle's 12-volt charging line to 24 volts, so it can push more charge current down the line. You can look up posts from either for more detail.

Bill

[inghamm]

You can test the fridge on DC by plugging into shore power and leaving the fridge on DC. Just keep in mind that it works poorly at best. It may take longer than 2-3 hours to get cool. We always followed the standard advice. Pack it and turn it on AC the day before, turn the fan on and switch to DC just before you close it down. Then the DC just lets it coast so to speak. It HAS to have the fan on to work at all when closed.

That being said, normal for us was arriving with a very low battery. We did it that way for a couple of years. I discovered the UHaul add-on 7 way Bargman we had installed on our TV did not include any charging wire. We tow with a Hybrid that doesn't have an alternator, so remedying that was going to be more complicated than usual. An easier fix was installing Solar panels and switching to a compressor fridge that is way more efficient on battery. We can go days (maybe forever) running the fridge on just solar power recharging our batteries.

[Larryjb]

Didn't Padgett or some one else use solar panels to supply current for the fridge while driving? According to P=VI, 200W of panels should provide up to 16A at 12V. However, I recognize that I have a lot to learn about solar, and I suspect that one never gets the rated wattage from the panels, which depends on angles, weather, etc.

[BrucePerens]

Originally Posted by Larryjb

P=VI, 200W of panels should provide up to 16A at 12V.

On a perfectly clear day; when the panels have been recently cleaned and all bird poop, dirt, and sap has been removed; when the sun happens to be exactly overhead, ignoring any issues of resistance in your wires, etc.

My 400 watts of panels do keep the compressor 'fridge, which uses much less current than the absorbtion 'fridge, running happily, along with fans, lights, and phone chargers. I would not expect them to work with an absorbtion fridge. And this is parking in an open field.

I just figure my panels will run at 1/4 rated capacity in real-world situations. And they hardly work at all when partially shaded. Park in the woods and you'd better have brought your generator.

[Larryjb]

Originally Posted by BrucePerens

On a perfectly clear day; when the panels have been recently cleaned and all bird poop, dirt, and sap has been removed; when the sun happens to be exactly overhead, ignoring any issues of resistance in your wires, etc.

My 400 watts of panels do keep the compressor 'fridge, which uses much less current than the absorbtion 'fridge, running happily, along with fans, lights, and phone chargers. I would not expect them to work with an absorbtion fridge. And this is parking in an open field.

I just figure my panels will run at 1/4 rated capacity in real-world situations. And they hardly work at all when partially shaded. Park in the woods and you'd better have brought your generator.

This has been the most helpful post regarding solar, in some ways. I knew that solar panels would not put out the rated power unless at perfectly ideal conditions. Knowing they hardly work in shaded areas, which is where I like to camp, the initial cost for solar makes little sense for me.

Back to the fridge and battery:
I'll still keep my absorbtion fridge. At night the freezer is enough to freeze cold packs so we can transfer them to the main fridge to keep it cool while travelling. There appears to be little use for running the fridge on battery. I did notice that, even when connected to my truck and driving all day, it wouldn't keep the battery charged with the fridge on.

[ThePair]

Originally Posted by Craig V

When connected to shore power, it runs fine. Haven’t checked the voltage or fuses. If fuse was blown though, I wouldn’t expect the current draw to occur.
Haven’t tried to maintain temp from battery after it’s already cold.

We tried to start running it while traveling from battery but was not cold at all after about 2-3 hours. Fridge fan may have been off during travel.

Not sure it ever worked from 12V since we got it (last year).

The fridge will need more than 2-3 hours to get cool, even on AC, so that's not the best test of function. However, if you stick your hand carefully in the back and feel heat from the heater, then you know it's working -- just slowly! It's that, or finding the proper wires and testing for the voltage. But the ultimate test is if the heater gets hot on DC, then the DC system is "operational". To make sure the rest of the fridge is working is as simple as: does it get cold eventually on AC? If yes, then the whole system works, since the DC and AC use the same heater sleeve and same cooling system. If the heater doesn't get hot at all, then you'll need to troubleshoot.

As others have said -- use AC to get the fridge cool while at home, and DC is more of a "nice to have on the road" mode than anything else--at least for those of us without monster solar set ups.