Drove the car (2004 Elantra) yesterday, noticed that the dash lights were dim. I ran in and out of the gas station to get a newspaper and the car wouldn't start. The battery is only a year old, but jumped it anyway, and the car started. As soon as it was in gear, everything started dimming. In the 1 mile trip hope, I'd lost all interior lights, dash/gauges, and the car wouldn't shift out of first. I limped it home, even cutting off the emergency 4-ways and headlights just to have enough power to get home. When I took the battery in to charge it, it was low, but there's no reason it should be, with how new it is. Is this an alternator issue, or something else?

 

Once the engine is running, the alternater supplies all the electrical power, not the battery. If the lights are dimming then yes, it's probably an alternator problem.