Yesterday I attempted to change the thermostat on the car (and failed - need a 1/4" socket set), during which time I removed the negative terminal on the battery. After failing, I put the terminal back on, went to start the car so I could refill the water and got the classic "click" that the battery is dead. I didn't spill any water on the alternator so that should be fine? I did have to back the car out of the driveway prior and the weather is a bit colder these days so could that have killed it? I took the battery out, attempted to charge it and it didn't take much of a charge at all. It charged for about an hour or so and then said it was fully charged. It still didn't start. I got my friend over to try and jump it with leads on his X5 but his leads were like doorbell wire and didn't do a great deal (I think they're old), it did almost turn over on one try though. Any ideas? I think it's just the battery itself, I have no idea of it's age so who knows. The terminals look OK but wondered if this is a common issue?