Refrigerator doesn't work on 12V

[Reldma]

Vacationing last week and had a refrigerator that would not work on 12V. First 5 days we had shore power and it worked great. We then had to move and electric was not available. Switched to 12V and at first it seemed to be working, but after an hour we noticed it was not cooling. Checked and saw the battery was dead. Checked the battery and it was only at 2.08. Had battery checked and it indicated the battery was bad, so bought a new battery. New battery tested at 12.58 when I installed it.
Turned the frig on 12v and seemed to work, but not sure if it was. Checked the battery and it read 1.08. Something wrong right! Turned the frig off and the battery then read 12.08. Did this a couple of times and the same thing happened. Thought it must be the ground on the frig. Disconnected the ground and it looked good, but still cleaned it and nothing changed.
Also discovered the frig would not work on gas. It would light and burn as long as the pilot was held in. I ordered a new thermal couple for it, but also cleaned the burner in wood alcohol to make sure that was not the cause.
The frig is a Dometic.
The last 2 days of vacation we ate out wife's way of camping. The lights worked as long as frig was not on 12v.
One more thing. When we arrived home I plugged in to shore power and battery charged to 13.8, so I am assuming that the charger is working okay.
Our TM is a 1999 2720SL Yes I know I have it shown wrong below.
Ray

[Bill]

Reldma -

The refrig draws a lot of power from the battery - a bit more than 10 amps, as I recall. Since the lights dim when you turn the refrig on, it means that the refrig is trying to operate on 12 volts, and the fuse for the refrig is good, but the battery won't support the load. This can be because the battery is old and isn't holding a charge (likely your original problem), or because the battery is not fully charged (likely the problem with your new battery). If you fully charge the new battery, and then disconnect shore power, it might support the refrigerator for three hours, but not much more.

Resting voltages on the order of 12.0-12.8 indicate a discharged battery.

If you don't have shore power, the only reasonable alternative for refrig operation is propane. If propane doesn't work, then that is the problem we should be chasing. Hope the new thermocouple does the job. Let us know.

Bill

[Reldma]

I did fully charge the battery and it lasted for maybe 5 minutes before the battery showed it was dead, but when I turned off the frig the battery then showed almost a full charge without being recharged. I keep thinking it sounds like a bad ground, but the ground on the frig is okay. Is there another ground I should be looking for?
Ray

Those numbers don't sound so unusual to me. Like Bill says, the frig draws a lot of current. That is going to show a big voltage drop at the battery and it's not going to take long to deplete the batterys charge.

In an RV the point of having the DC power option on the frig is for going down the road. Obviously 120 VAC is not going to be available while driving, and running it on propane is a bad idea and also illegal in many states.

While your motor is running the alternator is supplying the power/recharging the battery.

So use the AC or propane while camping and save the DC setting for over the road.

You can't run the fridge on 12V for any length of time unless you are connected to a TV that is running.

[Reldma]

Understand use time limits. Guess I am not explaining my problem correctly.
When I switch to 12v setting my new fully charged battery only last for max 5 minutes and then shows battery dead. But after turning off frig a minute or so the battery then shows it is charged. When the frig is on 12v setting nothing that operates on 12v works but if I wait about a minute or so the lights will work.
Ray

[rvcycleguy]

Sounds to me like the battery will not accept the load from the fridge. There are two main elements associated with batteries. Voltage at rest and voltage under load. Are you using a deep cycle battery or a standard car/ truck battery? Is it completely charged? Have you charged it slowly (low amp) over night or over a number of hours? Can you share with the forum the charging procedure you have used? Suggest you have the battery load tested by a qualified technician with the proper equipment. Not necessarily a generic auto parts store on the corner or the local Walmart auto service desk.

[Bill]

Originally Posted by Reldma

When I switch to 12v setting my new fully charged battery only last for max 5 minutes and then shows battery dead. But after turning off frig a minute or so the battery then shows it is charged. When the frig is on 12v setting nothing that operates on 12v works but if I wait about a minute or so the lights will work.

Ray -

What you are describing is exactly what would be expected of an undercharged battery, or a battery that is faulty and won't hold a charge. It is not related to the quality of the wiring, or the quality of the grounds. The need to wait for the effects you see is the key symptom. A wiring problem would show up instantly.

CycleGuy has asked a good question about charge procedure. While you are at it, do you have any idea what the actual charge current is (not the rating of the charger)?

When you say the battery is fully charged, how do you know it is fully charged? The little lights under the sink cannot be relied upon. The ability to wait a minute, and then turn on a light, is not a good indicator, since a light is a small load compared to the refrig.

A battery that is new is not fully charged when it comes from the store.

I would suggest that you buy a hydrometer. You can get a little floating ball hydrometer for a couple bucks from the automotive section of any hardware store, WalMart, etc, though these are notoriously inaccurate. A better alternative is a turkey-baster type of hydrometer with a glass float such as this one
http://www.grainger.com/Grainger/WES...d-Tester-1EFX6
for about $8-10. This would answer your question once and for all. See it described at
http://www.batterystuff.com/kb/artic...ry-basics.html

Sorry not to be more help. But everything you describe says "discharged battery".

Bill

It takes me closer to 30 minutes to kill my pair of batteries.

You should be able to run the fridge for at least 10 minutes on a single battery before starting the generator to recharge the battery..

I know this because my fridge failed one weekend and it would no longer run on propane. I had no shore power, but I did have a generator.

If I recall correctly, I was using the generator for about half an hour every 2-3 hours during the day. I left the fridge off when the generator was not running. Overnight the fridge was off. The fridge kept things cold enough, but I had nothing that would easily spoil, such as milk.

[MudDog]

Originally Posted by PopBeavers

It takes me closer to 30 minutes to kill my pair of batteries.

You should be able to run the fridge for at least 10 minutes on a single battery before starting the generator to recharge the battery..

With no other loads you should be able to get more than that with good, fully charged batteries.

My 2 6V Deep Cycle batteries are rated at 235 amp hours. If the fridge is pulling 11 amps, I should be able to get close to 10 hours before draining the batteries to 50% with no other loads. Even with a 100 amp hour battery you should get 4+ hours with no other loads.

What am I missing?