I have a AUTOLITE 27 retro battery made by Axion power battery manufacturing co, 5 years old, 70 amp hours 78 plates, TURBO START.
The battery was in the car when I acquired it 3 years ago. I removed the caps and added water to the cells as my first maintenance procedure, boy we're they thirsty!. During the first year the battery was constantly spitting acid out of the vents and was not due to an overcharge condition. I called the manufacturer and spoke to an engineer to inquire why the battery was spitting acid.
The engineer seemed surprised that anyone would do such a stupid thing as to add water to their battery. They added a lifetime supply of water, or moisture as he called it, during the manufacturing process. I asked him if the battery was airtight and he said no, there are vents in the cap. I said that it makes common sense that a few drops of moisture a year might be needed to keep the battery maintained. He said that's not possible because the caps are glued on. Why don't you tell your customers to add moisture, I asked. Because they might damage the battery and add too much, besides, the lifespan is 4 years, he said.
To make a long story short, my battery was never short on capacity other than the acid spitting out of the caps. I inverted the thing and drained the water and reinstalled it. It's been two years now and that battery is just fine. In fact, it performs better than any other battery I have tested. It acts differently that a traditional acid lead battery. I left my headlights and high beams on for 45 minutes, the battery went from it's latent charge of 12.1V to 11.0, and the car started with a snap pulling down to 10.5V. Next, I charged it with my battery charger, a 10 amp Schumacher, and watched the charger go from 8 amps to 2 amps in 30 seconds while the voltage across the battery terminals climbed to 13V. After an hour the amp draw was 1 or less and the voltage was 15.8V. When I disconnected the charger the battery voltage dropped to 13 in 30 seconds, and the next morning it was at it's usual, 12.1V.
A friend did the same thing by accident and his lasted 15 years.
I wondered why the caps we're so darn hard to remove! If I hadn't done such stupid thing as to add water to my battery it would have shriveled up like a dead leaf and left me stranded somewhere.