Classic/Antique Car Repair: Battery problems

Question
Hi Brad-

Have several old cars, however my latest purchase ('83 Chrysler conv.)is giving me problems with the battery. Bought a brand new battery about 3 years ago, that lasted less then a year. Battery was dead when I got the car out in the spring even though I unhook the neg. cable for storage over the winter. The parts store tested the battery and it was bad so I got a free replacement. Last spring battery was dead again. Parts store tested the battery and it was bad so they gave me another one and checked my charging system. They said my alternator was bad (tested in the car) so I took it to another parts store and 2 mechanics and they all said my alternator was charging a little low but not out of spec.

Putting the car away last fall, filled up with gas, drove a few miles and put the car in the garage and unhooked the neg cable. Went to start it earlier this week as it was a nice winter day and the courtesy lights were dim and the engine would not turn over. Took the battery back to the parts store (now out of warranty) and the clerk explained that batteries dis-charge just sitting there whether they are hooked up or not. I told him I had several old cars and they can sit for months (maybe even a year)and have no issues with the battery losing it's charge. In fact I pulled the battery out of my camper that was last used in Sept. and it started the car just fine. He just repeated what he told me earlier.

Ideas why am I having problems? Is it possible to get 3 bad batteries in a row? If you think it is a bad battery again I will try for another new battery by calling the parts store customer service number.

Jim

Answer
I have had some problems with batteries from a well known parts store when I asked the battery to sit in winter storage. However that said I think the problem might be a little more sinister. If the alternator is not charging up to snuff it will not top off the battery, meaning that it could be only half charged. That means that half of the sulfur in the sulfuric acid in the battery is attached to the plates. That is how the battery stores electrical energy through a chemical reaction tween the acid and the lead and lead peroxide in the plates. Now take the half charged battery and place it in winter storage and the sulfur on the plate begins to crystallize and harden. This is called sulfation and causes battery failure. Without testing the car my best guess is that is what is happening to your car.