I have had some strange electrical problems the last week. Battery dead last week after i moved truck 50ft and 20 mins later dead. Dead the next morning, had batteries checked 2 different places each said other battery bad, alternator tested fine. Sat for 2 days and was dead in the morning. Ran fine for 3 days - starts in am and all day. weds cleaning truck for 2 hours and battery dead.

I am assuming i have a power draw somewhere but don't know how to test. Is there a way i can test myself and does anyone have an idea of where to start.

I have the 6.0 engine if that helps.

 

In many cases if you have a short you will have other items like accesories that don't work or are not working properly or a little wacky.

If you have a DVM (Digital volt meter) you can disconnect the positive lead of your battery and put the meter in line (positive lead at source, DC amps max scale prob. 10amp) and see how much quiescent current your drawing. (all accessories off) I can't remember how much the steady state current is but it may be in the 200-400 ma area. If you have a short, enough to kill the battery your probably will be well up over that.

DO NOT attempt to start the vehicle or turn on any higher current accessories (lights/heater etc..) as you can damage the meter (or blow it's fuse) as well as possibly starting a fire.

If you do in-fact have a high current draw you can do process of elimination and pull fuses/relays one at a time.

Others have done this and they may be able to clarify the quiescent current draw.

 

I came upon this thread while trying to answer to the question: "What should I expect the quiescent (or standby or parasitic) current draw to be for my truck (2005 F250 6.0L TD Lariat)? Context: Batteries were drained after truck sat for about 8 weeks (thanks to good weather and my other toy - BMW R1200RT motorcycle). I found pieces of useful information on several threads - this seemed to be most recent so I am posting summary of my finding here.

1st off, I could not find, anywhere, an "official spec range" for this measurement. I initially measured nearly an amp and then watched as the current dropped (presumably after some electronics reset and went back into sleep mode) to around 450mA, which still seemed high. Then I found a post that said you had to wait for up to an hour to let various things (fuel heater?) cut in and then off, to get to the real steady state (quiescent) condition.

So I tried it. I was skeptical but wow - here is what I measured. I did this twice just to be sure. Timings are estimates - I did not use a stopwatch, just watched the clock.

1. Initial current was about 1A, for about 5 to 10 seconds, when it dropped to around 450mA.

2. It stayed at the 450mA level for between 15 to 30 minutes (I wasn't standing there watching - just checked back periodically while doing other work in the garage), then it dropped to around 260mA.

3. After about 45 min to an hour (!), it dropped to 18mA !! Held steady at that for at least another hour. This seems to be the "true" steady state current draw.

I am sure the details will vary greatly depending on equipment installed, but the main lesson I learned was that you have to wait for "stuff to settle down", and wait for much longer than I would have guessed. Curious what is taking so long to "shut off" after initial wake-up. I tried opening and closing the door - this seemed to set it back to the 450mA level again (after shutting door to turn off interior lights - the initial draw w/ door open was over 4A).

Details: I disconnected ground wire from both batteries, and hooked my DMM in high-current range mode (10A, fused) between ground post and ground wire on one battery. I tried again with second battery (for 15 min or so) to see that I got same basic result which I did (as expected).

Hope this is useful - I would have appreciated this info at the start. Wish I could find an official spec range to reference. Oh - after charging up both batteries with a bench charger, I discovered that one them had a dead cell. That was primary cause of my problem.

 

Was the 18ma before you replaced the bad battery? I do hope that you did
them as a pair. Replacing one in a set will give you an unbalanced set
and the old one will drag the new one down to the lower state.
18ma is about the power to light an LED. Did you happen to retest after the
replacement?

Thanks for posting what you found

I have a very good YouTube video on how to test this problem.

Sean

 

Why is this thing double posting.

Sean