Hello everyone. I hope someone can answer me with a solution to my problem. I have a 2008 Cadillac STS, 3.6 Ltr. engine and generally am very happy with it, save for one problem. My battery voltage reads in the range of 14.2 to 14.6 volts almost all of the time the car is running. It only goes down to a normal range of about 13.0 volts after several hours of highway driving. The battery has been changed twice in the past three years and on two occasions it has been dead after the car had been parked for several days. It has been evaluated at least 6 times by the Cadillac service and they cannot find a reason. The Customer Service Regional Manager has extended my warrantee for two years for the charging/battery system but cannot figure out what is wrong. I am convinced the battery is being overcharged and burned out by the charging system but the dealer service shop cannot find anything wrong. If this isn’t fixed soon I will have to sell the car as I cannot afford to fix it or change batteries after the warrantee runs out next year. Can anyone tell me what the problem may be? Thanks for your help.
Stu
The voltages for the STS are 13.0 to 13.6 and 14…0 to 14.6. The computer controls what range the alternator is to produce and when to do it. They are the normal ranges. This has nothing to do if you need a new battery. I had to replace mine at the 6 year mark. I got my replacement Delco for my car at my local Cadillac dealer.
14.2 to 14.6 volts is normal for your charging system. It settles down to 13 volts after a while because it has charged the battery and does not need to continue to do so at the rate of 14.2-14.6 volts. That does not overcharge the battery. If the battery is dead after sitting for several days then a draw needs to be checked for. Repeatedly replacing the battery will not fix a draw.
The voltages you stated are normal DC voltages. Has the alternator been checked for AC voltage. You should have no more than .1 volt of AC voltage across the battery while the engine is running. High AC voltage will kill a good battery.
There could be a current draw on the system and it is draining the battery. You shouldn’t have more than perhaps 50 milliamps of current draw while the car is parked the systems have gone into the sleep mode. Here is a helpful link for you to look at.