battery type

Is the 1500 watt inverter 1500 surge and 750 continious? If so it may be a touch small for the usage.
If it's 1500 continious then look at power supply issues, wire size and inverter location as well.
What are the power requirements of the fridge?

It would be helpful to know something about your motorhome. Gas or diesel, year, make, model.

Always use true deep cycle batteries for your house 12V system. Starting batteries are not designed for the constant discharge/recharge cycling. If you already have two 6 volt batteries (deep cycle golf car batteries) I would add two more (since they have to be wired in series creating a 12V pair).

Four good 6volt golf car batteries wired properly to create two 12V pairs should run your fridge just fine. When you are driving down the road, your engine alternator should be charging the house batteries so running the fridge on the inverter should be no issue. When you are parked, the inverter will power the fridge until the batteries get low. Running the generator for a couple of hours at night should keep them charged.

Two six volt deep cycle batteries should be plenty for your refer...got to be another problem.

Battery type. DEEP CYCLE is indicated.. Does not matter if it is Flooded wet
Maintenance free or AGM but it should be DEEP CYCLE

The best deal on DEEP CYCLE is the 6 Volt GC-2 Golf Car battery. you need two of them in series to make 12 volts. and for a 1500 Watt inverter you should have at least two pair in (one pair per 1,000 watts).

You might even go with a 3rd pair for the fridge.

Battery banks should be made of the same type of batteries and preferably installed at the same time. If you have one that does hold up the same as the rest, it will constantly draw power from the others.

I suspect it's the inverter and/or wiring that is your issue. If the fridge takes 1500w to start, that's only 125amps. A pair of 6v batteries wired for 12v should handle that easy. The bigger issue is how long they will handle it.

The two 6 volt batteries and 1500 watt inverter should work. You say they won't start the fridge. They should .. 1- the batteries are dead the 2- ,wires are wrong , or 3- the inverter isn't working. Can you plug in other items and do they run ?
More batteries will increase the run time but 2 -6volt batteries (normally that would be golf cart deep cycle ) are plenty to start a refrigerator. First fix what you have.

Duplicate

I have deal with problems like this a lot over the years, so, I am going to ask one question.

How far is the inverter from the house bank?

This is probably where the problem is. It usually is.

Matt

valhalla360 wrote:
Battery banks should be made of the same type of batteries and preferably installed at the same time. If you have one that does hold up the same as the rest, it will constantly draw power from the others.

Not following this advice will result in short battery life.

True DEEP CYCLE 12V batteries are difficult to find, even in metro areas and expensive. 4 - 6V golf cart batteries is your best bang for the buck.

Matt_Colie wrote:
I have dealt with problems like this a lot over the years, so, I am going to ask one question.

How far is the inverter from the house bank?

This is probably where the problem is. It usually is.

[b[CONCUR !