Can I run my refrigerator on batteries for 5 hours?

[GaryS1964]

What I want to do is run my refrigerator with battery power when towing. I have a 8 cu ft Dometic refrigerator. I generally tow for 4 to 5 hours max. I have two 6V 210 AH batteries in series. I have a 2000W inverter. I will pre-cool the refrigerator prior to departure. I have a 190W solar panel to help charge the battery while towing and I tow mainly during the middle of the day. I don't know how much I can rely on the truck to assist with charging the RV batteries.

The Dometic manual says the control panel draws 3 amps which I assume is continuously. The AC heater draws 5 amps which I assume is intermittently. So worst case the refrigerator is drawing 8 amps/hour. For a 5 hour trip that would be 40 amp hours.

I'm not expert on batteries so I don't know if I can add the amp hours together for 420 AH or if I have 210 AH which means I would have 105 AH to use to power the refrigerator allowing discharge down to 50%.

It appears that I have sufficient battery power to run my refrigerator while towing. Am I missing something?

 

[FT4NOW]

You might be a little off on your math. You cant just go off the info on the panel. For example, if the info says 5 amps on AC, that is for AC, not the amount of DC required when inverting to AC. I think a good rule of thumb is 10A of DC for every 1A of AC when inverting. I'm just going off what other people have said about their inverter usage, yours might be different, but it's certainly not a 1 for 1 when using an inverter.

Sent from my SM-G950U using Tapatalk

 

[Cannon07]

If you have 2 6v in series then you have 210ah at 12v. I have the residential fridge and the one 12v battery that came with camper. I have run 12 hrs with no problem connected to truck. I think the residential fridge consumes less power but for 5 hrs. sounds like you would be ok.

 

[orbiker]

What I want to do is run my refrigerator with battery power when towing. I have a 8 cu ft Dometic refrigerator. I generally tow for 4 to 5 hours max. I have two 6V 210 AH batteries in series. I have a 2000W inverter. I will pre-cool the refrigerator prior to departure. I have a 190W solar panel to help charge the battery while towing and I tow mainly during the middle of the day. I don't know how much I can rely on the truck to assist with charging the RV batteries.

The Dometic manual says the control panel draws 3 amps which I assume is continuously. The AC heater draws 5 amps which I assume is intermittently. So worst case the refrigerator is drawing 8 amps/hour. For a 5 hour trip that would be 40 amp hours.

I'm not expert on batteries so I don't know if I can add the amp hours together for 420 AH or if I have 210 AH which means I would have 105 AH to use to power the refrigerator allowing discharge down to 50%.

It appears that I have sufficient battery power to run my refrigerator while towing. Am I missing something?

You will have only 105 AH of usable power. You will have a little power trickling in from the solar, but I don't think the batteries would last more then an hour or 2 with the frig running on electric.
Why not run on propane like it's designed to do? KEN

 

[Cannon07]

You will have only 105 AH of usable power. You will have a little power trickling in from the solar, but I don't think the batteries would last more then an hour or 2 with the frig running on electric.
Why not run on propane like it's designed to do? KEN

I think he was also plugging into to truck which also gives a another battery and alternator. I was comparing to my diesel which gives me two batteries and probably a larger alternator and then I seen his tv is a 150.

 

[jkwilson]

Amps are instantaneous, so the term “amps/hour” has no meaning. 3 amps on the control panel, plus 5A on the AC side means you will need about 53A on the DC. The inverter isn’t 100% efficient , so I’d throw in another 7A to allow for that, making it use 60A. A 60A draw for 5 hours is 300AH.



Your batteries total 210AH when in series, but since you are drawing current out at 60A from each battery, Peukert says the capacity of the batteries is reduced. My guess is your 210AH batteries will only supply about 140-150AH at that rate.

Your 190W solar will help some, as will the tow vehicle.

Too many variables to know for sure other than you will be using a lot of battery power and your batteries will be run down significantly after traveling.

 

[Scramjet]

You have 105 ah of useable power assuming you don’t want to exceed a 50% depth of discharge. I was taught to use watt hours for these types of questions. You have 1,260 watt hours available with your 50 percent DOD limit. Your Ford will provide roughly 90 watts if you are lucky (7 amps x 13 volts). Your solar panel will provide something less than 190 watts. Depending on the weather and sun angle it could be quite a bit less. Your fridge uses about 370-400 watts when on. I think you would be lucky to make it 3-4 hours with nothing else running.

These fridges are much more efficient on propane. I would go that way until you have more battery or more solar.

Brian

 

[RV Sailor]

There is something not right about the power usage .

I have a Domestic 8 cu ft 12 volt refrigerator on my sailboat which draws an average of 65 amps per day. I’ve had it for years and am quiet certain of its power usage

Why are these ac reefers with much better insulation using such an incredible amt of power

 

[jkwilson]

There is something not right about the power usage .

I have a Domestic 8 cu ft 12 volt refrigerator on my sailboat which draws an average of 65 amps per day. I’ve had it for years and am quiet certain of its power usage

Why are these ac reefers with much better insulation using such an incredible amt of power

This is a 2 way refrigerator with a several hundred watt heating element. 5A at 120V would be 600W. At 12V, 600W is 50A, and that isn’t including an allowance for inefficiencies in the inversion process.

12V absorption refrigerators don’t use nearly as much power because they don’t do nearly as much cooling. A 12V compressor refrigerator is much more efficient.

The phrase “65 amps per day” has no meaning. If you turn on something that draws 1A, it draws 1A instantly and continues to draw 1A as long as it is on. You may be confusing amps with Amp-Hours which is current multiplied by time. The previously mentioned 1A load would consume 24AH if powered all day. The OP’s refrigerator consumes 48AH per day from the 12V system whether cooling or just operating the control board and that would be true whether operating on LP or AC. Generating heat from electricity takes a lot more battery power.

 

[RV Sailor]

This is a 2 way refrigerator with a several hundred watt heating element. 5A at 120V would be 600W. At 12V, 600W is 50A, and that isn’t including an allowance for inefficiencies in the inversion process.

12V absorption refrigerators don’t use nearly as much power because they don’t do nearly as much cooling. A 12V compressor refrigerator is much more efficient.

The phrase “65 amps per day” has no meaning. If you turn on something that draws 1A, it draws 1A instantly and continues to draw 1A as long as it is on. You may be confusing amps with Amp-Hours which is current multiplied by time. The previously mentioned 1A load would consume 24AH if powered all day. The OP’s refrigerator consumes 48AH per day from the 12V system whether cooling or just operating the control board and that would be true whether operating on LP or AC. Generating heat from electricity takes a lot more battery power.

John thanks for the explaination. I already understood everything after sentence 1. Not confused about ah vs amp. Nit confused how to convert amps to watts either

A commercial refrigerator has a heating element is something I didn’t know. Do they all operate that way? Are they all such energy hogs? When an appliance says 1000 watts does that mean it draws 1000 watts all the time it’s on.

I understand my 12 volt reefer on our 35 ft sailboat. Everything there I convert into a and ah. There is an average of 3-4 amps used which cycles intermittently depending on how hard the compressor has to work to keep the reefer at 38 degrees.
It uses anywhere from 45 - 70 amps per day from our batteries depending on outside temps. There is no heating element

Is what you are saying it would be more efficient to put a 12 volt only reefer in instead of these 110 units ( disregarding the conversion of inverting the loss
of converting 12 v to 110.)

 

[jkwilson]

John thanks for the explaination. I already understood everything after sentence 1. Not confused about ah vs amp. Nit confused how to convert amps to watts either

A commercial refrigerator has a heating element is something I didn’t know. Do they all operate that way? Are they all such energy hogs? When an appliance says 1000 watts does that mean it draws 1000 watts all the time it’s on.

I understand my 12 volt reefer on our 35 ft sailboat. Everything there I convert into a and ah. There is an average of 3-4 amps used which cycles intermittently depending on how hard the compressor has to work to keep the reefer at 38 degrees.
It uses anywhere from 45 - 70 amps per day from our batteries depending on outside temps. There is no heating element

Is what you are saying it would be more efficient to put a 12 volt only reefer in instead of these 110 units ( disregarding the conversion of inverting the loss
of converting 12 v to 110.)

Absorption refrigerators have traditionally been used in RVs, and they use a heat source to boil ammonia. There is no compressor in these units. Generally RV units are two-way (LP or 120VAC), or three-way (LP, 120VAC or 12VDC). Both versions require 12VDC to power the control system and sometimes fans even when they are operating with other heat sources. There are even versions that burn diesel or kerosene, but I’ve never seen them in an RV. The three-way units are not nearly as common as they used to be, primarily because the 12V mode didn’t do much cooling.

So the 12V control circuit draws a steady 2A, and then the heater power used varies by the environmental conditions.

There are also 12V compressor refrigerators on the market now which reduce power consumption some.

Most RVers operate on LP while AC power isn’t available.