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Old 08-23-2016, 06:47 PM   #1
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Residential fridge in motorhome is draining my batteries

When my Dometic fridge died, I replaced it with a Frigidaire FFTR1022QB. I've successfully used residential fridges in other campers but this one is kicking my butt.

I have four 6-volt batteries and a 2000 watt pure sine wave inverter. When I run the fridge off of my inverter, it drains the batteries down in about a half a day.

I bought an amp meter with a clamp that reads both AC and DC amps.

When the fridge is running off of shore power, it reads 1.25 AC amps. Perfect. See picture.

The inverter is connected directly to my batteries. With the fridge running off of the inverter, I put my clamp around the wire coming from the battery and it pulls 8.2 DC amps with flickers (sometimes) up to 15 DC amps. When I shut the fridge off, the inverter pulls just 0.8 DC amps from the batteries. When the inverter is shut off my batteries last forever.

What am I missing?

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Old 08-23-2016, 07:02 PM   #2
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Difference in the amp reading is voltage difference.

1 amp @120 volt would be 10 amp on 12 volt

So your readings sound about right.

How old are your batteries, have you tested them?
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Old 08-23-2016, 07:08 PM   #3
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A refrigerator is not a steady current draw. Suggest to get a Kill-a-Watt meter, about $20. It plugs in-line and will tell you actual device power usage over time.
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Old 08-23-2016, 07:11 PM   #4
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Got ice maker? It pulls more power. I turn off the ice maker of trying to minimize power usage. Is the unit already at temperature? Will of course run more to get up to temp than once there.
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Old 08-23-2016, 07:15 PM   #5
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Quote:
Originally Posted by jacwjames View Post
Difference in the amp reading is voltage difference.

1 amp @120 volt would be 10 amp on 12 volt

So your readings sound about right.

How old are your batteries, have you tested them?
I agree with Jim, how old and what are they rated at in terms of AH?
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Old 08-23-2016, 07:16 PM   #6
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It's called Ohm's Law. Looks like everything is normal from a power draw standpoint.

Ohm's Law Calculations With Power

Your battery capacity is another matter. Appears your batteries are not very good.
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Old 08-23-2016, 07:16 PM   #7
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I would check your batteries for sure... do you have an autostart for your generator? that can give you peace of mind that your batteries wont leave you stranded.
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Old 08-23-2016, 07:18 PM   #8
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Quote:
Originally Posted by vsheetz View Post
Got ice maker? It pulls more power. I turn off the ice maker of trying to minimize power usage. Is the unit already at temperature? Will of course run more to get up to temp than once there.
Ice maker makes freezer to go -4 and draws tons of power TURN ICE off when on inverter and life should be good. Do not open doors unless your really need a cold beer loose cold with doors open.

I can go over 16 hrs with sat tvs on and gen will not auto start until I get ready to make coffee in morning when I dry park overnite.

My coach batteries are fully charged when I park and are 2 years old and the auto start is happy.
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Old 08-23-2016, 07:18 PM   #9
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Are you charging your batteries up to 14.5 volts before tapering down to 13.5.

If your drawing 15 amps for an hour, that's 15 AH. That's with the fridge running steady. They usually run 1/3 the time.

Your batteries should deliver over 400 AH before dead.
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Old 08-23-2016, 07:18 PM   #10
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You could also check what the defrost timer is doing. Assuming the unit is frost free it has a cycle that uses an electric strip heater to pump warm air through periodically to melt off the frost that has developed. When that kicks on it significantly increases power draw. I'd put a switch and pilot light on it to control when it happens. YMMV.
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Old 08-23-2016, 07:22 PM   #11
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Same set up as you. Take mine 24 hrs before batteries get to 11v. Found out accidentally.
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Old 08-23-2016, 07:44 PM   #12
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Automatic ice makers and a defrost cycle will eat power for heating purposes. Need to shut both features off when on battery power.
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Old 08-23-2016, 07:47 PM   #13
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If you want to find out EXACTLY how much power your fridge is using purchase a Kill-O-Watt as suggested by a previous poster.

Run it for a month or more on shore power then look at the consumption figures.

Do the math as suggested by other posters and you will have your answer.

I have a Samsung RF-197 and have done two different analysis coming up with a figure of 1.82 Kwh per day that the fridge uses on average. So that is about 1800 watts per day.

Volts X Amp's = Watts

120 X 15 = 1800

Therefore my fridge uses about 15 amps per day OR about 150 AH's per day from my House battery bank through my Inverter.

My House battery bank is 4 - 6VDC GC-2 Sam's Club batteries with a total AH capacity of 450 AH's.

However, I can only use half of that safely without ruining my batteries. So with 225 AH's available that can easily last me over 8 hours is nothing else is drawing from the same battery bank.

I can usually get through the night without my generator starting up if the battery bank is completely full at Float SOC before turning in for the night.

I hope this helps you in understanding how it all works.

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Old 08-23-2016, 09:14 PM   #14
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Some interesting info being posted. No, I do not have a built-in ice maker. Never thought about the defrost cycle but it makes sense to figure out how to put a switch to shut it off. No autostart on my generator. My batteries are only a couple years old, but am definitely going to test them and double-check how many AH's I have and do some more math.
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