C17load

I travel with the military and my F150 sits for 10-15 days. When I return, the battery is completely dead. I replaced the battery 5 months ago because I was told it was bad. On my most recent trip, I disconnected the battery and when I returned, I hooked it up and the truck fired right up. Any ideas on what could be draining the battery? Can a bad alternator cause this? Thanks in advance for any suggestions.

Boooya

Check your draw with an ohmmeter if you have one. This is the only way to check for draw on a vehicle, a good battery should not go dead after 15 days.
You should have no more then .02-.03 amp draw, to check this disconnect your neg battery cable and hook up your neg side of the meter to the neg battery post.
Then hook up the pos side of the meter to the neg battery cable that goes to ground. so the meter is between the neg battery post and negative cable. If you have more then 35 milliamps draw start pulling fuses one by one till it drops. Eg. if you have a 60 milliamp draw and you pull your radio fuse and it drops down then you problem is in the radio circuit. I know this might sound a bit confusiong but its really quite easy to do.

C17load

Thanks. Sounds like an easy way to troubleshoot. I'm not good when it comes to electrical problems.

dplummer87

Mine does the same thing...If I leave it for more than a week...dead...Original battery went bad a year in. I sold the warranty replacement and bought the bigger one from auto zone and it still dies after a week :-(

sjoholm

when you do the draw test wait 10-15 minutes for everything to power down i dont know the kill time on a ford but i know for dodge it is like 10 minutes and then you get a more accurate reading because otherwise it can read wayyyy wrong!

bloodvette

This is good advice, I recently had a similar problem except mine would drain overnight. I actually DID perform the in-series current draw test becuase I'm an electrician and that's right up my alley. and I proved that yes, the current draw seems high for a few minutes, then steps down, then steps down again. I can't remember exactly, but I'm gonna go on a limb here and tell you how i remember it.

With the meter in series and in amp mode, with the key in the ignition, the moment you turn the key off, and remove it... check the current I think it was 8 amps. for the next 1-2 minutes it stays at 8 amps, this is probably the interior lights. then it dropped to something smaller like 3 amps... this is still too much for a battery to constantly supply for weeks. but then after about 10 or 15 minutes, the current drops once more to about 0.25 to 0.5 amps.

My tests concluded that it was infact my battery so I changed it, and yes it solved my problem. I have in the past, seen an alternator's diode's shorted and cause an excessive drain to ground. but that was a 1968 ford 3 tonne grain truck. lol

good luck, let me know how you make out.