Group 27 deep cycle battery + 2000W inverter

A group 27 with how many amp hours fully charged? A 12 volt or120 volt fridge? A full size fridge that uses how many amps when running? If a 120 volt fridge, how efficient is the inverter?

As other will tell you a Group 27 battery is not a "true" deep discharge battery. The only true deep discharge lead acid batteries are 6V golf cart batteries, size GC2. (One marine/RC Group 27 battery has about 80 amp-hours of power @ 12V; 2 golf cart batteries have about 215 amp-hours of power @ 12V.)

There are too many variables to answer your question. Size of the refrigerator and the amount of power it draws is the first one. Ambient temperature is number two.

Assuming that the refrigerator starts fully cooled with fully cooled contents and YOU DO NOT OPEN THE DOOR, maybe 12 hours.

Probably for an overnight stop you will be fine. Assuming the fridge is already full of cold food. Even then if it shuts off you should be good for another 6 hours if you keep the doors closed. Also assumes no use of the furnace and minimum lights.

No one will be able to give you a true answer, not enough information and too many variables.

Group27 battery is pretty light on capacity, that is an obvious fact.

Group 27 can supply enough energy to power your furnace overnight in cool temperatures, but it will be pretty deeply discharged by morning.

Your inverter unless it has a "power save feature" is going to eat up 1 Ahr-2Ahr of battery capacity per hr just doing nothing. That is 24Ahr-48Ahr per 24 hr period.

Home fridges vary widely with how much energy they will use, some pretty light like 90W (.75A at 120V) to upwards of 780W (6.5A at 120V) and may run perhaps 20-30 minutes per hr..

So, no one is going to be able to answer your question.

My suggestion is try a dry run in your driveway or backyard (where ever you park it) and see just how long you can run the fridge..

My bet is you will need more capacity than a group27 if you want it to run more than 12hrs..

For a rough idea, look at the energy star guide for the fridge and see what it says the energy usage per day is. Many are somewhere around 1 kWh per day, very roughly speaking. (I think they give it per year, but it's easy enough to divide by 365 to get the usage per day.)

1 kWh is equivalent to about 83 Ah at 12V. To the fridge's usage, the conversion inefficiency of the inverter needs to be added. Overnight should generally be doable absent any other significant 12V loads, but probably not much more. Deeply discharging a lead-acid battery is pretty rough on it and doesn't lead to its having a long lifespan. Leaving it discharged is doubly harsh.

Bear in mind that if you draw the battery down below a 50 percent state of charge, you are damaging the battery. (I don't know how much it damages the battery, but that is what they say.) So although the battery might be adequate in the short run, it might not be worth the cost in terms of reduced battery life.

Group 31 batteries have a lot more capacity and are about the same size as a Group 27. Much heavier, though -- lifting them in and out of the battery box is great exercise!! ;)

If you are lucky .... an hour Likely less

That inverter needs 400 amp hours of battery support
two pair of GC-2 is recommended.. That's 400 amp hours with 200 usable
your group 27 is 100 (bit less) with 20-25 usable.

The fridge.. Well you did not say but look at the watts and divide by 10. yes 10 that's how many amp hours it will suck off the battery. So if it sucks 200 watts then it needs 20 amps of battery power

Both Dometic. and Norcold at one time made RV-Fridges using a ultra-high effiency compressors. 35-40 watts.. at 12 volts that's a bit over 3 amps. Door closed (Seems strange to have to specify door closed but the interior light adds a major draw)

As pointed out a group 27 is not much of a battery. A pair of group 31s, a pair of 6V GC or a single 4D will be needed to provide necessary AHs to run the fridge for a usable length of time.

Most residential refrigerators that I have measured use about 1.5 kWh per day. If you only drain the group 27 battery to 50% you'll have about .6 kWh to work with. So, my best estimate is that it will run it for about half a day before it needs recharging.

Running time on the one battery will be short as everyone noted. Another thing is with the inverter, you have the low voltage alarm and shut off, which could be triggered by the fridge when it cycles.

You need short fat wires from inverter to battery, and a decent size battery in AH (or one of the new ones that allow high amp draws and keep their voltages up) to handle the fridge's starting surge.

So you could have what seems like lots of battery left in the 27, but the inverter kicks out anyway.