I had the timing belt replaced on my 2005 Chrysler. I drove for a week, and it appears the battery died. I used jumper cables to start the car, but as soon as I took the cables off the engine died. Anyone know what could cause this?
Since the car sat for a year, it is likely the battery is dead. If the battery terminals are corroded, they could also be preventing the alternator from charging the battery. I would try starting the car with a known good battery, and/or taking the dead battery to a parts store to be tested, as you may still be able to recharge and use it. Next time you park the car for an extended period of time, consider using a battery tender.
If the battery does not fix it, it is probably the alternator as you first suspected. Check all fuses and connections between the battery, alternator, and ground points. If there are no problems, take the alternator to the parts store to be tested. It is not unheard of for 'new' alternators to be bad as well, so if you need a new one, have it tested before installing.
In my experience batteries that are not regularly charged will be dead after about 3 months. A car battery after sitting idle for a year most likely not accept a charge. Time to replace the battery.