You have a few things going on. 6 - 6 volt batteries
makes a pretty large bank of batteries and recharging them, back 100% is pretty hard. It's a case where the large bank can be not helping you out.
The fridges don't run off the inverter
when plugged in they run off the charger
. Under way they charge by the alternator
. The Freedom 20 does that too. Nobody should own that many batteries without checking out your charging
system by a pro with a good meter. Also adding a battery monitor
would tell you information you can understand. Think of it like the fuel
gauge in your car. You can understand Amps in and amps out. You can see it everyday and learn to see what really happens.
Your float voltage probably is not the problem but 12 years old golf carts are surely shot. When the tops of the batteries start to bulge you know they are toast. Once one battery goes bad it starts to take the rest of them too. A bad cell fakes out the regulator
into over charging
the battery bank. So that is why you are adding water
so much. It's also a sign something its wrong.
Don't increase the amp hours in the bank unless you can prove you can charge them properly. I doubt you can. Smaller bank might be better and cheaper. Too many batteries could be worse. Two fridges don't require 1000 amp hours in the bank. You would be throwing money
down a rat hole.
Using 2 volt cells or even an industrial 12 volt battery can be a good thing but it comes after you sort out all the rest. Industrial batteries have way thicker plates and can handle more duty cycles but they still need to be treated properly. You have old batteries being abused so you need to fix both sides of the problem. Don't buy new batteries until you sort out your charging and your daily energy loads. It's how you make the $$ work
Have the Freedom 20 checked out as the newer ones are crap. If you don't need an inverter then do not use them as they suck the life out of a battery bank far too fast.