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F150 dead battery mystery

I have a 2013 F150, about 125,000 miles, 5.0L. Replaced original battery less than a year ago. No problems with that to date. It sat for about 36 hours over the weekend, nothing left on. When I tried to unlock it Sunday morning, it didn’t have the juice for even that. When I unlocked it manually, no power to anything. It jumped fine, though, and everything seems fine. I bought a cheap battery check at a local store. The battery level is 100 percent; the alternator check indicates that it’s working. Cranking check is good. Any advice on what to check or what would cause it to go completely dead?

A mechanic can do a parasitic draw test, or Google it. Not real complicated.

Check the under hood light and glove box light.

One of the switches may be stuck on.
If you either open the hood or glove box the bulb should be cool to the touch for about a minute.If it’s hot right away, the switch is bad.

Also check that the cargo light is not on. Sometimes people do not realize that they turned it on.


Well batteries can die (wont take a charge) on you suddenly as they have on me on occasion and for no obvious reason. Perhaps something stayed on without your knowledge? You will only know in time if the batt continues to drop out on you seemingly out of nowhere.

Not sure which battery check device you are using, but those kinds of tools are not all created equal. It would be a good idea to buy a Multi-Meter … They have a ton of useful applications outside just voltage measurements.

With a meter, you can read your batts resting voltage and then compare that to the voltage while the engine is running. Typical healthy batts will read just over 12-12.8 VDC at rest… With the engine running you should see more than the resting voltage all the way up to 14.5-7 VDC is normal… but not much higher than that. The voltage stays fairly constant as well…even if engine rpm’s are increased, it tries to provide the battery with a consistent number to charge itself.

If you see 15VDC or more you have a problem with the alternator and it will harm the batt in short order. You really do need a Multi-Meter to help you with this issue. Also be on the lookout for any items not shutting off in the vehicle obviously…

Let us know what you find…

Thanks. I followed your advice, and everything is in normal. What I haven’t done is search for the parasitic battery drain mentioned in the earlier reply. Guess that’s next.

One last thought; if the top of the battery is dirty it can drain battery also. To check if it is, take a volt meter, red on pos battery terminal and black near neg terminal (not on it). If you see voltage, it is traveling across the battery. Use baking soda and water to clean top of battery. Do not flood the top or let any seep inside of battery.

Dead battery that jumped fine?
Define “jumped fine.” Did it start right up shortly after connecting the donor vehicle? or did it take a while to charge your truck, then started and ran normal?

for a battery to go from so dead that it won’t unlock the doors to starting rather quickly and easily (if that is the case,) I would suspect loose or dirty battery cable before much else. Hooking up the jumpers may have made enough of a connection to get it going.

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