Does anyone know how many amps are drawn by an inverter to convert to AC for a residential fridge. My battery is rated at 175 minutes at 25 amps but I am trying to figure out how many amps are being drawn out. Or can anyone tell me how to figure it out.

look at the fridge nameplate and look for either the power in watts or max current. If it lists max current multiply by 10 to get inverter draw from 12VIf it lists watts current =watts/12that will give you a pretty close estimate of max power draw from the batteries.now to get run time you will need to take into account the duty cycle of the fridge, what % of the time the compressor is running.

ktmrfs wrote:...now to get run time you will need to take into account the duty cycle of the fridge, what % of the time the compressor is running.and, of course, that will depend on how efficient the fridge is; how well insulated it is; its operating environment (is the interior of the RV cool, is the wall against which the fridge is installed in direct sunlight, shaded by trees or an awning); how often you open the fridge or freezer doors, etc.

I am trying to figure out a couple things on this. We have gone to Florida and the fridge stayed on for each day of the trip there. So the truck must be recharging the battery as I drive it, but then on the way home, the battery went low (eventually bad) and the inverter shut off. I did go buy a group 27 instead of the group 24 but now I am thinking I should have gotten the 6 volts or a second 12 volt but I am not sure another 12 volt will fit in the space.

Campinfan,I'd go with a dc to DC charger that has enough capacity to power the fridge.

I'm not a expert, or even very smart. But I think the bigger a inverter, the more it drains battery even when load on inverter. Considering that, and the fact the fridge cycles off and on, wouldn't it be better to have a inverter just large enough to power the fridge, left on all the time, and a second that can be turned on only when need other 120V loads?

Inverter draw from battery for residential fridge

JimmyG_The_One
Explorer
Nov 26, 2023
AC = DC / 0.6360
Soooo...Probably not long.
MNtundraRet
Navigator
Nov 26, 2023
You would be better off with 2 6-volt batteries. Two group 27 12-volt batteries would give less time.
Campinfan
Explorer III
Oct 31, 2023
voodoo101 wrote:
Consider using a kill-a-watt meter from P3. Inexpensive and you can plug your fridge into it for a day or whatever duration you choose. It will give you actual power consumed. Go from there rather than guessing.

Sounds like great advice. Thank you.
lenr
Explorer III
Oct 30, 2023
My residential fridge draws 1.3 amps, 120 volts, when running which is nowhere close to all the time. My battery monitor says my batteries are down to 55% in 8 hours when not plugged into shore power. However, driving down the road they only drop to 90% so I have to believe that the truck hot wire is supplying 80% of the fridge draw. No DC to DC converter is used, just a straight connection.
ScottG
Nomad
Oct 30, 2023
Most new residential fridges use between 100 and 300 watts* (22cu/ft) and while the vehicle is running it will be putting out 14+ volts so the 7 pin would need to provide somewhere between 7~25 amps.

*Momentary start up current not withstanding.
Chum_lee
Explorer
Oct 30, 2023
"Does anyone know how many amps are drawn by an inverter to convert to AC for a residential fridge. Can anyone tell me how to figure it out.

Look for the Manufacturers ID plate attached somewhere to your refrigerator. It will state the load in amps @ 120 volts. Convert that to watts. Watts = Volts X Amps. For example, if your refrigerator draws 6 amps @ 120 volts, the watts equal 6 X 120 = 720 watts actual load. Now add the power draw of your inverter (in addition to the energy required to run the frig) to convert from 12 to 120 volts. If you have a 1000 watt inverter, figure about 5%. So .05 X 1000 = 50 watts. Now add that to the actual load. 720 + 50 = 770 watts. Now convert to battery amps @ 12 volts. 770 / 12 = 64 amps. That's a lot, but it is not continuous. It's based on the duty cycle of your refrigerator.

64 amps @ 12 volts far exceeds what you could reasonably/reliably expect to run through a single pin on a standard 7 pin truck/trailer connector. Your residential refrigerator may draw less than 6 amps (@ 120 volts), but, if it's a high end model with all the bells and whistles, it could be considerably more.

Chum lee
voodoo101
Explorer
Oct 28, 2023
Consider using a kill-a-watt meter from P3. Inexpensive and you can plug your fridge into it for a day or whatever duration you choose. It will give you actual power consumed. Go from there rather than guessing.
deltabravo
Nomad
Oct 28, 2023
Campinfan wrote:
I did go buy a group 27 instead of the group 24 but now I am thinking I should have gotten the 6 volts or a second 12 volt but I am not sure another 12 volt will fit in the space.

One group 27 battery is not nearly enough capacity to run the fridge for more than a few hours.
deltabravo
Nomad
Oct 28, 2023
wanderingbob wrote:
I am just curious since we are on the subject , Two inverters , hooked up the same , one is 1,000 watts , the other is 2,000 watts , both on idle , nothing plugged in . Is the 2,000 watt machine drawing twice as much current as the 1,000 watt one ?

Every inverter will have a different no load draw. Looks at the specs of the two inverters in question so see what their no load draw is.
deltabravo
Nomad
Oct 28, 2023
The amp draw from the batteries via the inverter is dependent on what the AC amp draw of the fridge is. Look at the specs of the fridge to get the amp draw.