Battery problem??
 

My car won't start.

My car is sitting in the garage for winter and once a week I'm turning on the car. But I didn't do it for 2 weeks and my battery was dead. I charged it. and the car barely start. I fully charged the battery(as per my charger) and the following week the car won't start again unless I jump start it.

Do you think the battery is the problem and I should change it or it is the alternator? or something else?

Everything has been fine for the last 2 years. and every week when I start it until I was away for 2 weeks.

I don't know how old is the battery?

Voltage on my volt meter is 12.5v

I'm in Montreal Canada. What type of battery should I buy?
1983 911sc Cabrio

Can't sleep without my car running....

Have you checked the electrolyte levels in the batt (if it not's a sealed type) and refilled with distilled water if low? When you get the car started, what does the voltage read across the batt terminals without any accessories running? How much with headlights on?

What is the condition of the battery terminals? How about the trans to body groundstrap at the front of the transmission?

Keep in mind that if all you do is start the car and let it run a few minutes, you're running down the battery each time you do this. I've read you need to drive the car about 8 miles to recharge the battery after a cold start. That number is highly subjective, but just starting and running for a minute or two in cold weather will kill a battery after awhile if you don't take it for a drive,

ianc