I tried to find something on this issue. I have a truck that sits (parked) for weeks at a time. The battery runs down - drops in voltage charge within 1 to 2 weeks. Drops from 12.8 to under 12. The original battery has the same issues. I replaced it with the best NAPA battery that would fit. Original battery is fine. I use it start a my diesel farm tractor. I had compass/temp//voltage display wired direct to the battery. Thought the small lights in the display were causing the problem. Disconnected. No change. So what causes the battery to discharge in what I think is short time period.? I thought it was the drain caused by all the keep alive electronics? Computer radio etc. NO lights are on. I have not connected an amp meter inline to see what the current draw may be. Only way I can keep the battery charged it use a battery float charger. Thoughts Thanks RR

 

Before you look for a drain, you need to answer some questions. Is the alternator charging the battery? Are the connections to the battery tight and clean? Are the battery cables in good condition? Is the serpentine belt in good condition?

Yes, there be some drain on the system, but a good battery should not die within 2 weeks.

 

And???? when you do drive it, is it long enough to recharge the system sufficiently?

 

Sarge, yes did all that. Charges at 14.4 when running. Drops to 13.8 at idle. Do not think charging is a problem. 2006 with 37000 miles - looks almost new no cable issues no corrosion. I disconnect the ground cable and it stays up over 12.5 for weeks. If I do not keep the battery float charger connected - when all cables are connected- the voltage drops over days. Float charger keeps it at 13.2 I have no equipment connected on the battery hot side of the ignition. I have thought about pulling the ground cable when it sits for more then a week. That resets the radio clock and computer, not the best solution As an aside my wife's F150 2001 has the original battery that holds 12 v plus over a week or longer.

 

Yes, it never goes on short tips. Most runs are over an hour. Then I keep it on the float charger as I indicated above. So the battery is fully charged. I going to connect the amp meter tomorrow.

 

I know this doesn't make it right, but if my truck sits more than about 2 weeks, the battery is nearly dead. It has no electrical issues otherwise, the battery is only a couple years old and the terminals are spotless. I just drive it more or keep it on a float charger.

 

My 03 is in winter storage for months on end and fires right up after , somethings wrong with yours..

 

Go with the ammeter. Anything else is a guess.

 

Bigpipes - yes 2003 not a problem. My 2000 7.3 was fine also.. This is a 2006 So removed the ground from the battery, connected digital 10 amp meter in line. Yep a drain 1.5 amp for about 1 minute- draw to charge up the assorted capacitors?? Then it dropped to .54 amp 1/2 amp. I opened the door - amps jumped to 2.5 Closed door back to 0.5. It does appear the newer trucks have constant draw. Tested the 2002 F150 about 0.1 amp maybe 0.15. Left the meter connected to the 05 for a few hours. Drain was between 0.52 and 0.56. Voltmeter reading when connected 12.2 Disconnected 12.5 So why the 1/2 amp drain. Figure that out 24 hrs = 12 amp drain. 12 amp hr drain per day will surely drop the charge in a few weeks. I have a 1020 cca amp battery at 32* rating. At least I know I have a good battery and good charging system. I could start pulling fuses to see what circuits are causing it, but I am sure it will be the computer and radio. So the solution will be to keep the float charger on when parked. Another driver had the same problem, resolved with the charger also. Not a big deal. I can let the charger connected. Might call the Ford shop - doubt they have a response though.

 

So your saying ford designed a truck That if not started for three to four weeks the battery will be dead ?? Do you have the factory brake controller or aftermarket ? I had an issue with my prodigy controller that killed my battery after a couple weeks , got it replaced under warranty issue gone..

 

As I stated above, no after market equipment is installed. ( on the battery hot side) Any after market equipment is on the 'key on ' power and the upfitter switches. Factory trailer brake controller. Trailer is NOT connected. 'Something' in the stock truck is causing the 1/2 amp dis-charge, by design or defect. Just trying to figure this out. When it warms up some, I will start pulling fuses and disconnecting loads.

 

Good luck , keep us posted if you get it figured out..

 

Does this truck have heated mirrors? Give them a touch next time you get around to it. Just a hunch, see if this is shorted on all the time. couldnt hurt to try.

 

Yes, however I have them discounted, I ran a wire from the fuse block- ( wire that connects to the mirrors) to one of the upfitter switches. No need having them hot all year long. Was too wet cold today to mess with pulling fuses to figure this out.

 

OK, put the ammeter back on, then start pulling fuses, one at a time, until you see the current draw go away or go down. This will at least point you in the right direction.

Don't forget, you also have fuses under the hood.