Inverter draw from battery for residential fridge

[Campinfan]

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.

[JRscooby]

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 ?

I second this question. And assuming the 2 are on separate 120V circuits, would 3,000 watts be available?
How much more would be wasted compared to 3000 watt inverter?

[wanderingbob]

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 ?

[MitchF150]

If you only have a single 12v battery I can't see that lasting very long without some additional charging the whole time it's running?

Look into the LI batteries out there now.

You say you don't have room for a second battery? Humm... 41 foot TT should have some room on the tongue for more batt capacity?

My little 26' TT has 2 batts from factory. I can add more if needed, but my needs do not require that at this point.

Good luck! Mitch

[wa8yxm]

One of my favorite 120 volt tools is my Kill-A-Watt meter. it's about a thousand dollars worth of meters.. in a thirty dollar, give or take, box

You read the WATTS draw and divide by 10 (yes I know that's not the battery voltage but by the time you factor in the conversion loss in the inverter 10 works real good) so if the fridge draws 100 watts running the inverter draws 10 amps

Or you can read the amps draw. the Power factor (you can do things to improve that) and other stuff... Power factor is zero to one (one means you are using 100% of the power) and is the cosine of the relationship between voltage and current... Ideally it's ONE. It's also the difference between VOLT-Amps and Watts. It's possible to have something drawing say 150 Volt-Amps (Which is what you pay for) and only using 100 Watts. (PF .6666666)

Kill-a-watt on Amazon

[JRscooby]

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?

[pianotuna]

Campinfan,


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

[Campinfan]

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.

[rk911]

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.

[ktmrfs]

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 12V

If it lists watts current =watts/12

that 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.