Yes, it would be possible, but they'll still not last as long and they cost a lot more per unit of stored energy.

If you're already on the grid you may be prepared to use a smaller battery bank and use the grid for backup instead of using a generator. Effectively you're making a solar-powered uninterruptible power supply. We installed one of those for a major Brisbane data centre about 12 years ago, but it was actually the batteries that were the most important feature. The solar input was more for show than anything.

You'll need a different inverter to the one you're running now, since the PV won't be feeding the grid, just charging the battery bank. the changeover isolator will kick it out of the circuit.

Alternatively, you could set up the solar to feed into one or the other inverter as desired and take power from the grid to charge your batteries if they run low. Lots of possibilities. As I said, get yourself a knowledgeable local RAPS installer, or talk to one of the distributors.

Leave your solar set up as is, connected to the grid. Treat your battery set up as a completely new set up. Add up all the appliances you have as to their watts needed to run. Very important to fit a run start capacitor to each of your fridges and freezers. This cuts the start wattage to 350 watts without any surge. Individual is trying to flog a battery worth heaps, it is up to you. You can get a 6,000 watt inverter for your battery bank for $ 1,795. A 160 watt solar panel just for battery recharge, plus an alternator set up as a windmill. These chargers are permanently connected, and regulated at 14 volts of charge.
2 fridges and one freezer, TV, lights, kettle, you will need 6 12v deep cycle marine batteries $ 900 . Leave the air con directly connected to the grid or buy more batteries, and add another wind mill alternator.

a597 said;
Very important to fit a run start capacitor to each of your fridges and freezers.
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How would such a capacitor be connected ?
Already being single phase motors they are probably capacitor start anyway.
All refrigeration compressors are capacitor start because you
would not want a centrifugal switch inside the sealed compressor.
Shorted turn start motors would not be used in refrigeration as they
do not produce enough torque to start a compressor and anyway there
is no start winding.

I am curious !

Wrong again. there is a butterfly switch inside the motor and there is a start winding. Capacitors are not added to fridges because it ups the cost, besides that it is all to easy to plug straight into the grid where there is plenty of oomph to start the fridge.
A fridge on start up can pull up to 10 times its running current, that is why we use start run caps;.

What i also should have mentioned is you get a Mashmaster.com switch box
this comes complete with a thermostat and delay start up which u set to 9 minutes delay. U install the thermostat about mid fridge and bypass the original thermostat. You set your off and on temperatures on the mashmaster box. $ 50.00
The capacitors are mounted inside a jiffy box from Jay Carr. for $ 7.00
capacitors are around 14$ and 10 $ from Jay Carr
The jiffy box goes in the existing 240v cord. You cut the cord in half and put a plug on each of the cut ends connect in the jiffy box.
I will find the wiring diagram and let you know.

a597;
Yes I would like to see that circuit.
I presume you bring the start winding out to the capacitor in the box.
If it was a centrifugal switch the start winding would not be brought
out of a sealed unit.
Your description sounded like it was just in series with the mains !
What is the capacitors value ?

Compressors I have worked on all had start capacitors, but then they
were larger than domestic refrigerators.
Come to think of it I do not remember my frig's start capacitor.
However I won't pull it out to look.

I will get the caps value and a resistor is fitted also, which i had to bye a box of ten because it was out of Jay Cars line, that cost me $ 5.oo
I am not home to retrieve the diagram yet, will be home tomorrow about 3pm. The system is magic.
There is one site you can have a look at, this is where you get the thermostat from. mashmaster.com $ 50.00