You asked a very simple question but I could spend the rest of the day trying to answer it. More information is needed about what kind of use does your battery get? Do you boondock so your battery bank is your only source of power? Or do you stay hooked up in RV parks most of the time? Do you use solar panels to charge your battery? Or is it charged from your truck? When you say your battery doesn't last long, does that mean it dies and you have to buy another one, or does it mean it goes dead to quick?
Basically the batteries that come with RVs are usually the cheapest thing the manufacturers can stick in it just to say that it comes with a battery. If you're serious about keeping your electrical stuff running when you're not plugged in the quickest thing to do is to get two 6 volt Trojan batteries, hook them up in series and get a better way to charge them than from your truck, such as solar panels, or a generator.
Like I say, batteries, what size and how many is a huge subject and the first thing we would need to know is how you intend to use them.
I only ran the refrigerator on LP. So just the fan & controls. Only lasted about 7hr.Also the battery goes dead in about 3weeks parked with the disconnect off! Don't need if for full use. Just got a day.
Sounds like your batteries shot,
Once a battery goes dead it never comes back to full power again. And if your battery is between three and five years old that's about all they last anyway. Probably the easiest and cheapest thing you can do, and you don't depend on your batteries for doing very much, is get two actual deep cycle, golf cart style batteries, these are normally 6 volt so they will have to be hooked in series to produce 12 volts.
Another thing you can do is get a 12 volt AGM battery, this is the best way to go if you don't have room for two 6 volt golf cart batteries.
The brand of the batteries doesn't matter all that much because there's only a handful of companies that make batteries in America so most batteries are just rebranded from the same company.
You didn't mention how your battery is being charged, even the best battery won't work very well, or last very long if it's not being charged properly.
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