RE: Electrical problems that imply either battery or alternator problems
Annie, you (or your mechanic) needs to put a volt meter on the battery and
see what it reads, should be above 12 volts, preferably around 12.6 volts
after sitting for a while.  Then, with engine running, check the voltage at
the battery.  That should be well over 13 volts, close to 14 volts or
better, if the alternator is doing it's job.  If the relatively new
alternator was a rebuild from the local FLAPs failures are not uncommon.
And batteries can go bad also, I had one fail completely just five months
after the install.