Even if the battery and alternator are new, if there is problem with wiring circuit for either one or both, then you still got problems. If you have a digital multimeter, we help you with some testing. Place meter leads across battery posts, everything off. The generic spec for a full charge is around 12.6 volts. Then start the vehicle, take another reading across battery posts, the second reading should be higher than the first, if charging system is working.