Four months ago, I replaced my battery because it was dead and would not hold a charge. Almost four months later, I go to start my 2004 F150 and it is dead again. I got a jump and drove to auto store where I purchased the battery 4 months ago. They checked the charging system and said it seemed fine. I am wondering if anyone has experienced similar issues. The mechanic wanted to check voltage output when I turned the engine on....it charged at 12.5V right away and then increased to 14.4V a minute later. He said it should have charged at 14V immediately but was not postive it was an alternator problem. possible intermittent alternator??? If anyone has any ideas, please let me know where to start looking. Thanks.

 

IMO, the charge should be over 13V to 14.+V most of the time when the motor is running. You should only drop into the 12's when the truck is shut off and all draw is then on the battery. You may have a charging system issue but then again, a "new" battery going bad in 4 months is always a possibility. If you have a digital volt meter available, jury rig a connection so you can plug it into your 12v dash port and watch it while driving....... My radar detector has that feature built in and I always leave it in that monitor mode... It is always in the 13.7 to 14.4 range.... Let us know how you make out.....

 

Ideally yes the alternator should be regulating over 14v right after the engine is running. However, if you have any other loads on plus the alternator is trying to recharge your "dead" battery, it could take a minute for the current load to drop and voltage to come up. A dead battery in warm temperatures can easily suck in 60+ amps for 10 - 20 seconds and then decline to 0 over a matter of several minutes, maybe 20 minutes or so.

Just a note, you cannot check the condition of your battery when it is basically dead, it needs a healthy state of charge to draw current out of it to check for voltage drops. Your drive from your jump spot may or may not have put enough juice back into the battery for it to be checked properly.

You might have a key off load issue which is draining your battery. I would have your alternator bench tested and if good, check your your key off loads. After that, use an external battery charger, fully charge your battery then have it load tested.

 

The battery was under warranty so I replaced it with a brand new one yesterday. What the auto store mechanic told me to do do is digitally read my battery voltage (not running) every hour to see if I noticed any drop in voltage. So, my first reading was 12.75v. One hour later, I was at 12.63v. Another 1/2 hour later, I was at 12.57v. At that point, I removed the negative battery cable and read the battery directly and watched the voltage climb back up to about 12.65v after 15 minutes. I checked the grounds at the starter, frame and chassis and all connections were great. At this point, not sure what else to check. Do I start pulling fuses on all electronic devices? Any more suggestions would be greatly appreciated. Thanks for your help.

 

It sounds like you have a battery drain and it could be from a multitude of sources. Use the ampmeter function on your meter. Connect your meter between the negative battery cable and the battery negative post. You will want to do this after all your lights are off in the vehicle otherwise it will pull too much current and blow your meter fuse (depending on model) so a small battery disconnect switch works well. Otherwise make your connection before pulling the cable off the battery to perform checks.

From there, I would probably pull the alternator B+ cable first. The alternator regulators can go bad and still function but pull a drain. After that, start pulling fuses until you find the circuit with the culprit.

 

Under hood and glove box lights are notorious for staying on when they shouldn't (defective or mal-adjusted switches) and running down your battery. Those lights are easily checked by removing the bulbs, but the start pulling fuses approach is next on the list. Good luck.