Hyuandai models like- Xing, prime, i10, sonata enberra, tucson, accent , verna

Interesting theory.alternator. Before you replace it, DO NOT rule out the ignition coil pack; Hyundais are known for having ignition issues on 4cyl engines. Could be a cylinder ''missing'' its spark in the firing sequence.

Simple test for ur alternator:

With the engine running, hook up a volt meter to the battery terminals. It should read at minimum 13.5 volts & maximum 15 volts. If it is below 13.5, ur alternator is not working or is not wired correctly. Above 15 & the regulator is fried, which will destroy ur car is electrical system,

Most of Hyundai is older cars has alternators made by Mitsubishi, not too sure if they still do it that way though. Consult ur local Auto Parts store for details, Autozone has a reputation for selling junk ones as rebuilt, so never leave the store without seeing it tested. My mom got one from the local autozone, they tested it as being fine & it failed my voltage test, so be wary.