Shelf life of car battery



What is the shelf life of a lead-acid battery?

If a lead-acid battery is left on a shelf for, say, 5 years, will it be usable?


Dry, or wet? If it’s a dry battery that has never had acid added it should be fine. One that has acid in it would probably need an occasional charging to keep it up to snuff and then it should be OK. If you left it just sitting without charging odds aren’t good, but you might get a few months/years out of it after a charge up.


Yeah, wet.

I had a battery that was being charged at 17V from my overcharging alternator. One symptom was that the battery had no(!) charge one day. A trickle charge restored the battery but, well, I was scared to leave that battery in the car.

I bought a new battery. The battery dealer was just fine with me keeping the old battery but he said it should be charged every couple of weeks in order for it to be usable. Every couple of weeks seemed like too much of a hassle so I left it there.

I drove hom wondering if I made a mistake.


You have to charge batteries every once in a while or they degrade. They also like being “exercised” periodically.

The easiest way to do this is to find a UPS that takes a 12v battery (look for old ones discarded due to bad batteries). Then replace the small battery in the UPS with the car battery. Use the UPS as usual. It will keep the battery charged and provide emergency power as needed.

Note that overcharging might have damaged the battery. But first check to make sure the electrolyte levels are correct (top off with distilled water if needed).Then use your charger to charge the battery and then try powering a load while measuring voltage.


What’s a UPS?


A stored battery should last longer than an identical one under the hood if it is kept in a cool place and kept charged. You should ideally have a float charger hooked to it. If it becomes discharged, the plates will sulfate. It may be recovered with a relatively high tech charger. Discharged batteries are also subject to freezing.

Small UPS (Uninterruptible power supply) chargers are designed for some sort of sealed or valve-regulated (recombinant) battery, gel cell or AGM (absorbed glass mat). They do not have the correct float voltage for a flooded cell automotive battery and are not ideal.


Five years, unused, sporadically charged, I wouldn’t give you more than $2 as a trade in on a new one. It’s probably shot. Going FLAT is very hard on a battery. Going flat repeatedly is even harder. That’s why there are deep cycle batteries for use in boats and RVs. Those are designed to go flat and come back with a good charge. Even they have a fairly short shelf life, two years tops in my experience. I’ve gotten several new ones on a three year guarantee.


Some parts places send them back after one year. The bad places try to sell them after a longer time. The thing is that you don’t have to buy it if it is over nine months old. You should always try for as new as you can get. Don’t feel bad about leaving the five year old one behind. At least it might be recycled.


L/A batteries self-discharge at a rate determined by temperature and battery condition. When kept cool, below 50 degrees, the rate is about 5 or 6% a month. 90 degrees and above, the rate climbs to 15 or 20 % a month. So unless the stored battery is maintained by charging (choose your own method) it will slowly die. Once completely discharged, it quickly becomes scrap lead.

Even if kept charged, L/A automotive batteries have a 5 or 6 year shelf life. They simply degrade over time…


Get a trickle charger, like made by ‘Battery Tender’ These chargers use a low-amp charge to keep a fully-charged battery in good working order. They sell for $40-80, depending on the features. Designed for boat batteries and classic cars that sit around for a while.


Don’t know where Tester is anymore on the new board but I think he said not to buy a battery that has been on the shelf more than 6 months. Check the mfg date and pass on it if it has been sitting too long.



I can’t imagine why you would want to keep a battery that has been overcharged by a badly regulated alternator and clearly is self-discharging over night. It’s a bad battery now . . . no matter how long you leave it on the shelf. Unless you want to try to use the old battery and keep the new one on the shelf, but that makes even less sense to me. Give the old battery to the parts place for recycling. There is nothing to be gained from keeping it.