I have a 1999 buick century 3.1 and the battery light came on I replaced the battery which didn't fix the problem I have since had the alternator tested and it came back good, replaced serpentine belt, and battery terminals, checked the fuses under the hood, and still the battery isn't charging it only drains while running not sitting what else is there?

SOURCE: Here we go. Battery is dieing, had the battery

RAP stands for Retained Accessory Power. It is the circuit responsible for powering accessories when the key is off. Sounds like something is staying on that shouldn't. Hard to say what though with the information here. if this started happening right after you put in the new radio i would check into that. otherwise start checking accessories like power mirrors,seats, locks and see it something is staying on that shouldnt. i good one to check would be the glove box light or the light under the hood. you can unplug them and then test your draw to see if thats where is was.

SOURCE: having problem with draining battery, alternator

Since you bench tested the alternator, and the battery has good capacity (hopefully isn't 5 years old or more), the next logical step is to do a leakage test.

Disconnect one of the battery cables (either one, I'd go with the negative one) and insert a 12 volt test light between the battery and ground of your car. Now, any current draw must go through the lamp. If it is lit with "nothing drawing any current" you can now look further for the offending circuit. Usually simple stuff like aftermarket alarm system, trunk light staying on, that sort of thing.

Even try removing fuses one at a time to localize which circuit to check.

Good luck.

SOURCE: Charging system malfunction under load

If the condition is present for short times only it will not affect anything. It's possible that the crank pulley is glazed and slipping slightly on a hard pull (everything else depends upon that pulley to be properly driven) You can't really duplicate that on a static test. It's also possible that the battery was a bit low when you bought it and needs to have the charge level topped off with an external charger. Otherwise, the only option I can think of offhand would be to obtain an alternator designed for heavy duty service (police version etc) which may be able to deal with the demand.
As your vehicle gets older, resistance in all circuits increases, making little difference during normal operation but can also influence how your vehicle charges. Cleaning / adding additional ground points can help with this.
If it seems that I'm jumping around a bit, I am, but since the charging system is pretty much operational except at that one point, I'm trying to give you some ideas that either in combination, or one alone will be of some help to you.
good luck

SOURCE: Chevy cobalt 07 charging fuse/ alternator has been tested good

i have a 05 cobalt SS Superchaged and i bought it new and had to warrenty two batteries and i put another battery n about 7 months ago

SOURCE: 2007 Equinox battery drain.

You probley have a bad altanitor, You can remove it and take it to Auto zone they ill test it for free.