Can my dead Lead Acid batteries be reused?

Originally Posted by suzy

I have two 12V 4.5Ah sealed Lead Acid batteries from an old electric scooter. The scooter is a decade old, and packed up a few months after purchase. The batteries were literally left as is for almost ten years, and I am unsure if they were connected to the circuit or not during that time.
Okay, so the one measures 1.1V, and the other -0.6V! The negative voltage is very odd as the batteries were in series and I can't think how that could be physically possible through (dis)charge..
I do not have any desulphation equipment or similar, all I have is an alarm "UPS box", which slowly charges SLA batteries, although it never gets them above 13.4V as that is what it outputs when no battery is connected, also it's all linear - nothing fancy.
Is there anything I can do to resurrect these batteries with the equipment I have, or should I just have them recycled? I have a fair amount of knowledge in electronics if there's anything I could do. Also, are there any dangers hooking it up to my charger or hooking up one with a voltage too low in general?

Sealed lead acid battery's ten years old with plenty of repetitive charging at some point the cells became low on water the exposed plates became sulfated, if you can prise the caps off then refill each cell with deionized or distilled water just until the water reaches a ring located about an inch below the top of the battery case after the cap has been removed this becomes visible.

Once you've added water, wait half an hour, some of that water is going to soak into those dry plates, check and add water repeating the wait time once again.

Some caps from sealed battery's are press fitted while others are glued on.

There are additives on the market used to rejuvenate a battery, I've never used any of these products, so I'm unable to give any pro's or con's of there use.

Now that your satisfied no more water is needed you can hook up a charger, hopefully the battery will take a charge but in my opinion a ten year olf battery has a one way trip to the scrap yard.

Older commercial battery charges were equipped with a feature that would de-sulphate a battery's plates.

Other factors with an aged battery, if you were to disassemble the battery you would find that a fiber glass mat separates each lead plate, in the old days this separator was made from a thin layer of wood. The below the plates built into the case is a sump, this sump is to allow for crap that sheds free from the plates to have a place to settle with out short circuiting plates in the cell above.

Shedding of plate material comes with age and rough usage from driving over rough gravel roads shaking the battery, this is one of two reasons the battery is secured in place the other is to secure it in case of a vehicle roll over to keep the top posts from shorting out causing a fire. Today most vehicles I would think use a side post battery,

In my line of work any battery that went dead was in a machine no easily accessible and had to be packed out for charging by swapping with my truck battery, now the funny thing is that an alternator will not charge a fully discharged battery while a a generator will.

My first car a 1947 Hudson always had a dead battery, because it had a generator the car could be push started even with out a battery installed.