A word of advice for those who remove the battery for the winter!I installed a new battery in 1999 and have always charged it before installing it into the car in the spring. This year was no different, however the battery would not hold a charge. I had it tested and it was bad. Testing person said I should have charged it about once a month through out the winter months or put it on a trickle charger or it would eventually not hold a charge.
Live and learn.

Battery Tender- worth every penny.

Left my battery in the car fully charged with the screw knob battery disconnect disconnected. Took it out last week and put it on the charger to see what kind of charge it needed...FULL 100% charge. Stuck it back in the car and she cranked right over.

I haven't had any problems like you've mentioned although I have heard the same facts from others. Remember Murphy's law...

I do know however that you have to watch where you store your battery as well. Placing it on concrete is a no-no. It is also better to store it in above freezing ambient temp as the cold of a garage will suck the life out of it as well when it is not in use.

I'm sure others know more out here than I do.

I've heard the same thing about a cement floor. This was in the basement on a wooden shelf all winter.

Not just concrete, anything damp. Dry concrete won't hurt. But concrete completly dry is almost impossible if there is dirt under it. New batteries are much more resistant to this than older ones, but it can still happen. Constant trickle is not necessary. Wood is dry. Warm is better.

But if the battery is good, and fully charged just disconnecting the cables should do it. Still warm and dry is better.

I used to work for a company that sold batteries...the information I was given was not so much wet or dry concrete, but the problem was from old design batteries with a hard rubber case...the design was porous allowing the charge to drain. Modern polypropelene battery cases should not suffer from this, but anything is possible.

In my three old cars I left the batteries hooked up all winter in each car with no problems at all. In my '78, I have one of the Optima spiral cell construction batteries...a bit more expensive ($99 at Costco), but awesome compared to conventional batteries. Smaller in size and more cranking amps and reserve capacity than the oe size battery, plus they can be mounted in any position without leaking. Since the battery in our C3's fits in the car's interior, I wanted a battery with less chance of leaking or gassing.

FYI:
The battery disconnect works great. Just loosen the knob and remove. Then in the spring. Just install the knob and tighten it. You are ready to drive.
I also have 4 pieces of 1/2" plywood, sized to the tire footprint. This keeps the tires from coming in contact with the floor.

I have to pull the battery out of "The Toy" when I park it in the fall (a requirement of the storage facility). I've been storing it in our well room over the winters on a wooden pallet so it is up off the concrete floor.

This spring I thought of swapping the old DieHard for the newer Interstate that was in my 'BowTie' truck. After hooking it up the truck fired right off. Drove it for a couple of days before deciding that I really liked the carrying strap that is built into the DieHard for lifting in and out of "The Toy's" battery compartment, so put the Interstate back in the truck.

The ol' DieHard worked perfectly when called upon to fire-up "The Toy" for the drive home from the storage facility a couple of weeks ago.

I've also made it a habit to lay down a sheet of clear poly to park "The Toy" on while it is stored. That provides a vapor barrier for anything seeping up through the floor and also works as a drop cloth for any miscellaneous fluids that may decide to leave their mark on the floor. And because the fluids can't soak in it makes it easier to identify what they are (oil, anti-freeze, etc).

I disconnect the ground side and charge it up and forget about it until spring.