Residential Fridge Test - Ampere-Hours

[38FLCamper]

Lots of discussion on how well the residential fridge works on battery and how long...

Ok well ran a full test on our Fridge now that we have the Trimetric meter installed and configured.

Equipment: Whirlpool Top Freezer Fridge on 2000W Inverter

Power: 4x6-Volt Batteries (226AH)

Conditions: Powered up and chilled fridge on AC for 12 hours. Switch power off and on to Inverter - Reset Trimetric Meter to 0 AH. ...

30 Hours on DC/Inverter - Total Draw was 182 AH.

Battery bank was drawn down to 88% (Based on Trimetric)

[dmdrj5]

Hi Walter,

Does the fridge maintain temperature as well on battery power? I installed the remote sensors on our unit and found that over the last month our freezer operated in a range from -3 degrees all the way up to 20 degrees. The refrigerator section maintained temps in the upper 30's. This was on shore power the entire time.

Don

[38FLCamper]

Yes fridge operates at normal temps in both Fridge and Freezer, with food in both... The Ice Maker was running as well. No problems at all.

[Brentf]

38FLCamper - thanks for posting that. I have the same fridge but no ice maker. That looks like about 6 amps per hour. I think I read the inverter takes a half amp for itself.

If you are not boondocking but just want to run the fridge while towing that would suggest that you need a
100 amp battery to supply 48 amps over 8 hours or
150 amp battery(s) to supply 75 amps for 12 hours or about the longest you would drive without hooking up. (not counting the trickle charge from the truck).

Or if you had a 150 amp battery you would need to recharge every 12 hours. I am basing that on the recommendation that your batteries last longer is you don't discharge down below 50%.

If you had enough solar to fully recharge during the day and run the fridge then you would need that 150 amp battery to run the fridge overnight (not counting everything else).

I am going to replace my dealer installed marine/rv battery with the biggest trojan that will fit in the battery compartment looks like it is the T1275 which is a 12 volt 150 amp golf cart battery. If that proves too little I'll add a second one to round it out at 300 amps.

I am also trying to figure out if pulling a dedicated 12 volt line off one of my upfitter switches would keep the battery up while towing. The F250 has 2 25amp and 2 10 amp upfitter switches/lines.

[racer4]

38FLCamper,

Thank you for posting your test results.

I am very interested in the refrigerator power usage when running on the inverter/batteries. I am planning to soon buy a Cedar Creek 36CKTS with a residential refrigerator (18 cu ft or 20 cu ft) . We like to camp in National Park campgrounds occasionally and I am wondering how many hours per day the generator will need to be run to recharge the batteries. I will use 4 6V GC2 batteries, probably Trojan T-105 or T-145.

I wonder how much it would use with the ice maker turned off. I imagine the compressor runs a lot more to freeze the water.

Do you know the model number of your refrigerator? I want to compare your actual results to the yellow Energy Guide label specs for a point of reference.

Thanks

Chris

[38FLCamper]

Don't know how much the ice maker being off would help but will test next chance I get.

[racer4]

Thanks for the model number. I made a note of it and the power usage.

I am interested in power usage with the ice maker off. Thanks for offering to test it. If anybody else has experience with this, please chime in.

Thanks,
Chris

[dmdrj5]

Just wondering why the compressor would run "more" to freeze the water? If it is maintaining proper temperature, it will freeze cubes automatically. The only extra power draws would be the solenoid sending water up to the icemaker and the motor that dumps the cubes, which should be minimal.

Since I never use the icemaker with water from the tank, it is not an issue for me. Just as easy to bring ice from home or use bottled water in ice cube trays.

Don

[racer4]

dmdrj5,

My saying "I imagine the compressor runs a lot more to freeze the water" was a poor choice of words. I remember reading that using icemakers caused an increase in electric use. I did not know exactly why. Since Walter (38FLCamper) tested with the icemaker on, I wondered what a second test with the icemaker turned off would show.

Your post prompted me to search for info on icemaker power use.

I found this: "In tests of four different types of new refrigerators, National Institute of Standards and Technology (NIST) researchers found that ice makers increased rated energy consumption by 12 to 20 percent. About three-fourths of that additional energy cost is due to the electric heaters used to release the ice bits from the molds."

The above quote can be found here:
The Heat Is On: NIST Zeroes In On Energy Consumption of Ice Makers
and more is here:
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=907664

I am looking for info to help decide if it is practical to use one of the residential refrigerators offered by Cedar Creek when there is no electric hookup available and a generator is used to recharge the batteries.

If turning off the icemaker actually avoids a 12-20% power increase in real use, that would make a difference when running from an inverter and batteries.

Chris

[dmdrj5]

Chris,

Thanks for the education on ice makers. It was not my intention to be a smart a**. As you can see by my original post, I forgot about the heating element.

I still have a problem drinking any water from my tank, even when filled from my home water source. I trust my home water, but who knows what is floating around in that tank. That goes for campground water as well.

My apologies,
Don

[DickiedooFlagman]

Originally Posted by Brentf

38FLCamper - thanks for posting that. I have the same fridge but no ice maker. That looks like about 6 amps per hour. I think I read the inverter takes a half amp for itself.

If you are not boondocking but just want to run the fridge while towing that would suggest that you need a
100 amp battery to supply 48 amps over 8 hours or
150 amp battery(s) to supply 75 amps for 12 hours or about the longest you would drive without hooking up. (not counting the trickle charge from the truck).

Or if you had a 150 amp battery you would need to recharge every 12 hours. I am basing that on the recommendation that your batteries last longer is you don't discharge down below 50%.

If you had enough solar to fully recharge during the day and run the fridge then you would need that 150 amp battery to run the fridge overnight (not counting everything else).

I am going to replace my dealer installed marine/rv battery with the biggest trojan that will fit in the battery compartment looks like it is the T1275 which is a 12 volt 150 amp golf cart battery. If that proves too little I'll add a second one to round it out at 300 amps.

I am also trying to figure out if pulling a dedicated 12 volt line off one of my upfitter switches would keep the battery up while towing. The F250 has 2 25amp and 2 10 amp upfitter switches/lines.

When calculating wire size for a desired amp draw, remember to double the length of wire in the calculation. Here is a website that may be of assistance. Amps and Wire Gauge - 12V Circuit

Unless you use a dedicated correctly sized wire, you can never get a good charge on the trailer battery from the TV.

[camaraderie]

38fl....Thanks for the good test...so a current model 18cuft Fridge uses about 150 amp hours per day in moderate temperatures with the ice maker on... and maybe 120amp hours with the icemaker off. This suggests that anyone running a similar sized fridge + normal 12V loads ought to have around a 400ah battery bank like you do ... and that a "normal" 200amp hour bank is really quite inadequate for even 24 hours of boondocking...though it will get you down the road for a long drive till you can plug in again.
Thanks...valuable information!

[racer4]

Don,

No problems here.

I'm just trying to do my homework on this purchase, so I don't have regrets after buying.

Everyone,

I noticed, based on pictures, 2016 Cedar Creek 36CKTS have a different model 18 cu ft refrigerator. The handles are different, as is the shape of the top. The picture matches model WRT138FZDM on whirlpool.com that uses 22% less power than the model Cedar Creek was using. It is Energy Star qualified. It would be nice if that is what Cedar Creek is now installing!

It is rated 370kWh (vs 475kWh) per year, which I think equates to ~ 102 AH per day. Those ratings are for no icemaker, which I think would be the same if equipped but turned off. The formula I used is 370kWh/365 days * 1000 watts per kWh / 10V = 102 daily AH use. I used 10 instead of 12V to account for about 20% efficiency loss in the inverter. Does that formula sound right?

Chris

[spock123]

I will be installing my 40amp battery charger soon, I don't think CC has a good converter


Sent from my iPhone using Forest River Forums

[38FLCamper]

That was the first thing I did - tear out the WFCO converter and installed new Progressive Dynamics 9260 converter

[OldCoot]

Originally Posted by Brentf

...150 amp battery(s) to supply 75 amps for 12 hours or about the longest you would drive without hooking up. (not counting the trickle charge from the truck)...

Depending on your truck alternator and the size of the charge wire, the factory alternators can put out from 85A-170A (depending on the size alternator) while running down the highway which is more than a trickle charge. Once the initial charging of the battery after starting, there is minimal draw on the alternator to run the electrical system.

[Brentf]

I figure from 38FLCampers' tests to plan on around 145 amp hours a day with an ice maker. I am going to fish my amp meter out of the barn and put it on the wiring to tell what it pulls when the fridge is on. The complication is that you have a lot of 12v loads on the battery (pilots, CO/Propane leak monitor, etc.) and you have the inverter and the wiring losses. Then you have the 'how hot is the camper so how hard does the fridge have to work?'. Guess we are looking for some general parameters.

[38FLCamper]

Yes lots of little draws and items running power on the 12Volt side... From another post I put up...

Here are some numbers of our power usage by device/appliance... These are all measured as 12V power draw (120V AC Appliances as measured through the Inverter use). Inverter power use at Idle is based on nothing plugged into the inverter. All measurements are done using a Trimetric 2030RV with 500Amp Shunt.




Items Amps
12 Volt Use
IDLE - Phantom Loads 0.90

Lights
1 - LED Puck Light 0.20
2 - LED Puck Light 0.40
3 - LED Puck Light 0.70
4 - LED Puck Light 0.80
Dining Light (3 - Incandescent Bulbs) 4.20
Porch/Step Lights (3 - Incandescent Bulbs) 3.60

Appliances
Water Pump 1.20
Fantastic Fan Vent
Low 1.00
Medium 1.40
High 1.70
Heater (Blower) 7.80
TV Riser Motor 6.50
TV Antenna Amplifier 0.10
Rear TV (12 Volt Jensen) 3.40
Sony DVD/BlueRay Player 0.30

AC Power Use
2000 W Demension Inverter
Idle - No draw 0.90
Fridge On - No compressor 1.00
Fridge On - Compressor 12.60

1000 W Xantrex Inverter (Entertainment)
Idle 0.40
TV and Satellite Box (Standby) 2.00
TV and Satellite Box (On) 18.70

[rzrnaz]

Great data, really useful.

One question though

Originally Posted by 38FLCamper

Power: 4x6-Volt Batteries (226AH

30 Hours on DC/Inverter - Total Draw was 182 AH.

Battery bank was drawn down to 88% (Based on Trimetric)

Using 182AH out of a 226AH bank should leave you with 19% left instead of almost 90%, since you used most (182 of 226) of the system capacity.

Is my math off?

[38FLCamper]

Total battery capacity is actually 226 x 2 for a total of 452 ah. The % is based on the Trimetric gauge and it is possible I have programmed wrong...as the math still doesn't work right