I have three cars that mostly just sit on my property because my employer provides me with a company vehicle that I drive. Well the company vehicle is in the shop, and the batteries in ALL of my other cars are dead, and seem to be damaged to the point that they will not take a charge on my battery charger. I even unhooked them all before I left them to sit, back when they were working good. Two of my vehicles have Optima (yellow top) deep cycle batteries, because this isn't the first time this has happened, and neither of them are taking a charge. Whats a really reliable and durable car battery that's designed to sit unused and also designed to prevent being damaged when drained? Surely such a thing must exist...
Sorry, couldn't resist. Yeah, good question. Maybe something that can accept a trickle charge so it never depletes.
Turns out the batts were OK, the charger was fried. Or partially fried... it would charge just long enough to trick me, then stop. I replaced it. Still wanna find a battery that holds a charge while sitting for a long time...
You use a small trickle battery charger/maintainer for cars when they're stored. They're just left plugged in and hooked up the battery and left. My tipping trailer has a battery. So I fitted one to that, so when I'm not using it for any period, I just hook up the extension cable to it to maintain the battery.
I don't think there's any getting around it..... If you let a battery sit long enough it's going to discharge. Even the best of batteries will require a battery maintainer.
You need to keep lead-acid batteries charged, otherwise they will go and can suffer permanent damage. They should be charged at least every 3 weeks, preferably 2 weeks, and about every 10 days would be best. You also need to make sure you have a good charger that is able to fully charge them, because some of the smaller ones will not be sufficient to keep a battery from going bad after 5 months. Sometimes the best thing is to simply try driving the car and not leave it sitting too long for more than week or two. Sometimes if the alternator (which is a little electricity-producing generator in the car) goes bad, then the battery will fail to charge. There are some car battery options that are not lead-acid, but those are probably very expensive and not so pragmatic. It would probably be very hard for you to even find them.
From the Department of Too Much Information: Best bet is a trickle charger, but I think you know that. You might sniff out a solar one. (Put it inside the car, BTW). 2 amps should do it if you disconnect. Put a voltmeter between battery positive and disconnected positive cable and check for current draw. I think newer cars are always sucking voltage from somewhere. (FYI: 12v x 1amp = 12 watts) BTW, if outdoors, protect your tires by covering them on the sunny side - check out RV places for cheap ideas.
Lead acid batteries are damaged by discharging them beyond about 50%. In addition, if they are discharged they can freeze, which ruins them. In every case, you cannot expect any battery to remain connected in a vehicle for long periods of time and remain ready to go without any maintenance. If I am going to park a vehicle for a while, I will either disconnect and remove the battery and store fully charged it where it will not be exposed to freezing temperatures, or connect a battery tender that automatically keeps them continuously charged. Finally, there are many youtube videos where people revive dead batteries. I've never tried it, but you may have some success there if you're willing to go through the hassle.
There are only like 2-3 companies making batteries these days and all of the different brands just Co tract it out to them.