I have an 08 5.4L 3V and just recently my battery doesn't hold a charge. If I let it sit for a day the truck won't start even when the block heater has been plugged into it.

The first time I noticed this was after I let it sit for 4 days in -20C to -30C weather. It cranks 2-4 times then you get nothing. I have a gryphon (possible current draw?) and have had it since November and have never had an issue like this in the past whilst I've had it. To me that would rule it out as a being a power draw. Two weeks ago the truck sat in the same weather for two days and fired right up after not being plugged in. Once I boosted my truck I drove on the highway for 20min or so and in town for another 15min so it should have been charged. Right after I shut it off and turned the key to on and the gryphon showed a charge of 12.2V that quickly dropped to 11.6V where it held. After letting the truck sit for a one day I tried starting it again and I got 2 very weak cranks and it quit, just clicking.

The truck has 60,000kms on it and has never had an issue starting in cold weather, -30C not plugged in it never had a problem. Also the alternator is fine, gryphon read out shows between 14.2V-14.6V.

 

Motorcraft batteries are not what they used to be. Had to replace the one in my 07 after only a year. Go to Sears and purchase a Die Hard platinum 65 Series (Re-badged Odyssey) and don't look back...problem over for many years. As far as a draw on the batt, there is a constant very minimum draw on these batteries all the time..not enough to kill them though.

 

My mc battery that came in the truck lasted about 6 years, replaced it with an energizer (yea i know ) but ive had no problems with it since 2006.

 

My old man had his stock battery in his 2000 f150 last over 10years. He changed it out just because of its age. Showed no signs of weakening though but figured it was time.

 

To Alta and the poster above you, Motorcraft batteries were made by a company named Gould National Batteries (GNB) for many, many years.
They were one of the best batteries you could buy. (Made batteries for a ton of companies, but never one with their own name) UNFORTUNATELY, around 2003 they sold out to Excide which quit making the quality batteries that Gould made. So, Ford switched to having their batteries made by Johnson Controls. (one of the largest battery companies in the world, but a VERY mediocre battery. There are those that will disagree, but they've been wrong about other things too. ) That's the reason Ford batteries up till '03 were so good, and not so good after that!

 

I would still check the draw of the Gryphon. It may over time slowly drained your battery until it was too cold/weak to start the truck. And at least the JCI batteries are better than the Excides.

 

Charge up the battery and head over to a parts store and get the battery load tested.

 

 

I should also mention after this last time I couldn't start the truck I turned the key to on to see the battery voltage and could see it drop .1V every 2-3 seconds or so. That is with only the gryphon, dash lights and headlamps on. Too me that shows the battery doesn't got much capability to hold power. You should be able to have it on accessory and with the door open and radio cranked for at least half an hour before needing to start the motor and charge up the battery.