Last night my car died from lack of battery power. This past week the lights have kept on getting dimmer and dimmer until last night when I could barely see my head lights on the road. I got a jump and made it another 1.5 mi home and in died again. Tested the alternator (150amp) and the guy said it was over charging at 18 volts. I have a regular 70 amp alternator that is charging at the right level. The battery was drained and is being recharged and tested as I write this. Could the over charging alternator drain the battery somehow? Or would it be something else. I have had that alternator on the car for about 4 yrs now with no issues. And this just started happening last week.

Any ideas as to what could cause this, anything else I should test out, maybe a drain somewhere else in the car.

I have the battery in the trunk, the fuse is a 125amp and its an optima yellow top.

any help would be appreciated this is my DD

 

If the alternator is overcharging the battery, the battery will die eventually.

18 volts is way too high. It should be... somewhere between 12 and 14 if i remember correctly. My old nissan alternator killed a battery and it was only overcharging at 15 volts.

Get a new alt, and get a new battery because yours is probably toast. It wont hold a charge correctly if its been overcharged like that for any length of time.

 

my volt meter usuallly reads about 14...and thats over charging my car...around 13.5-13.8 is where the sweet spot is, i think thats what it is

 

Alight I put in my old alternator which was charging correctly. Took the car back to advanced and had it check. It was charging at 13.8 volts which is good. Now I just have to wait and see if it dies again. I also have a new problem my head unit will not power on. I check all the connections and the red security light flashes when the faces is off but it wont power on. I will be checking fuses today.