Lead-acid batteries (like the ones found in cars) dont like being discharged too low, you've got to remember the battery is only there to start your car, after that the alternator should supply more then enough power for all your car systems. It takes a huge amount of current for your starter motor to turn your engine and start your engine firing. Charge voltage is around 13.5-14.5 volts, so if you are reading that (which you are) then that means your alternator is charging your battery, and if it wasn't supplying enough charge current then your "alternator light" on your dashboar would illuminate. -That charge voltage is what is read when your engine RPM is higher than idle...such as 2000rpm or higher. The longer/higher you run your engine, the more power that is generated by the alternator is which to charge your battery.... As i said batteries dont like to be run down to low, if you've read anything less that about 8 volts then your battery cells are possibly getting damaged, so if your battery has spent a lot of time discharged, my recommendation is get a new battery, if you run big stereo's, amps, subwoofers, suggest getting a bigger battery? the dimming lights/"half power electrics" is because you are drawing more current then the battery/alternator can output, so if thats because your idle speed is too low and your battery can't hold a good charge because the cells are damaged. Wind up your idle speed a little and replace battery. Also, a good sign of a dieing battery is "sluggish" starting of the engine, batteries will also perform worse is cold weather than in warm weather.