I replaced the original alternator in my 93 prizm yesterday and the 6 mo old battery will not hold a charge. Is the battery dead or is there some wiring problem to the battery from the alternator?
Have the battery and the charging system tested. It’s possible to get a bad alternator, or the battery may have been damaged by the old alternator.
It could be the battery, the charging system or a dark drain (power usage with the car off).
Take it to most any auto parts store and have them check it. Most will do it for free, it is almost always done honestly and the test, while not 100% complete, will identify most problems.