Originally Posted by cormier
Get a $20 multimeter -- it will make this process a lot simpler
It doesn't crank when boosted? Even when left to charge for a bit?
It could just be your alternator going slowly as mentioned... Or your battery draining slowly...
Try to get it started (roll start, jump, etc) and meter the battery. You'll be able to rule in / out alternator right away if the volts are staying constant or dropping.
When it's even running for a bit and then is shut off, meter again to check if your battery is holding charge.
May be worth investing in an on-car trickle charger to keep your battery nice when it's sitting for periods like that
I haven't tried to boost it with the new battery, but the old one did not crank even when left connected to the other car for 10 mins.
I'm going to take the battery in to where I bought it to get checked out and charged, but will need to give it a boost to get it there - lol!