I was out driving yesterday and after 30 minutes of driving suddenly the car is starting to have poor gas response and sound like it is going to stall while at cruising speed. After about 2 miles where I first turn off the radio which help keep it alive a bit and then turn off the lights it just dies and refuses to start again. The battery was so low that i could hardly get the top up.

I charged the battery at home alittle and got the car back. Over the night i have charged the battery and it isshowing a healthy 12.87 volts. When i turned on the car it jumped to 14.10 which i believe is ok. However after around 5 minutes of idling it fell to 12.74.

Is this normal because it senses the battery is fully charged?

RPM does not affect voltage.
I have MAC UD pulleys on it

 

Altenator has bit the dust, take it off and have it tested to be sure, but driving + battery dead = altenator...most of the time. Battery light on?

 

no, the battery light does not come on now.

 

how many miles? sounds like alternator

 

39k miles.

Anybody know if it is allowed to drop in voltage or if the voltage should be steady once the engine is running?

The engine can run without the negative battery pole connected so the alternator can't be completely dead. Voltage regulator maybe?

 

your alternator may be going, when idling check the voltage, if its under 14 ur alternator is bye bye