You know what this thread needs?
Seriously though, the battery should have at least 12.0 volts with no loads turned on and the engine off. 12.4-12.6 would be better. With the engine running, you should see 13.6-14.4 volts. Anything under 13 while the engine is running means the alternator is probably bad. Or there could be a loose connection or bad ground.
E92 335i/6MT Dinan Stage 3: intercooler, oil cooler, intake, flash, exhaust, LW dual-mass flywheel.
Vishnu PWM methanol custom trunk mount, Diffsonline 3-clutch Salisbury custom diff, Ohlins Road and Track coilovers, Vorshlag camber plates, much more...
E28 M5 w/ buncha stuff, R171 SLK350