Probably not carbons, but from the alternator, maybe.

There's a test to see if your alternator is bad: start your car as you would normally do, then disconnect the negative battery cable. If your car stops running or the idle dips real low, its your alternator. If it keeps running, your battery is fried.

Autozone will also test it for free if you bring it to them. Generally, if the reading is under 13 volts, you have got a bad one.

Good luck!