I am dealing with a parasitic current draw on a 2001 F150 2WD, Triton V8.

We recently had the experience of the fairly new (purchased in March '14) battery too dead to crank the engine after sitting about 1 week - in the summer.

The dealer gladly took our $95 diagnostic fee and said there was no parasitic drain and recommended their new battery. They said they tested the battery's cranking amps, but tested it without charging it. We took the in-warranty battery back to Sam's Club, who tested the battery and found it within limits, as did our own independent mechanic.

Essentially the people we'd expect to find and fix the problem don't want to fix it and give the excuse that it's just one of those things. The indie mechanic didn't seem to even want to hear what I found (described below).

I watched a Youtube video on diagnosing parasitic leaks. I connected a digital multimeter in series with the battery and I found the following:

When I have the truck closed up and off (no lights on and everything switched off) when I first connect the meter, it jumps to about 2 amps, then quickly drops down to 0.21 amps (~210 MA). I assume there is something that gets energized by the initial battery connection which drops off.

Doing the math, that current drain of 200 MA is about 400 watt-hours of power in one week. I am reading that car batteries hold about 1000 watt hours. So this small drain (which our indy mechanic and a family friend both dismissed as too small) may be what is killing the battery.

Pulling Fuse 14 under the dash (15 amp - according to the manual, controls three relays, including power windows, interior lights, and the "battery saver") results in a relay "click." The meter then drops from 200 MA or so down to about 60 MA (0.06 A.)

Here is the thing, though: after about 45 minutes, that current drops to what looks to be about 0.010 A (10 ma.) After 15 minutes it still read 200 MA and did not drop until 1/2 hour after that.

So I don't know if this is the parasitic draw that is killing the battery or not. I'm thinking that the meter in series with the truck battery is affecting the results I'm getting.

Also, I tracked down the relay being activated to relay #2 under the dash. It was warm to the touch (coil was getting power.) When I pull out that relay, the drain stops (of course, the lights don't work, either.)

What should I do to correctly diagnose this issue? I wish there was something I could connect in line with the battery cable for long periods of time that would correctly indicate whether there was a small power draw.

Also, I'm using a cheap multimeter I picked up at a ham convention. It may be inserting too much resistance or something to get a correct reading.

Thanks for any help

 

In normal operation, the Battery Saver in the GEM module times out in about 35-40 minutes after the last change in power draw from the accessories. Before timeout, a draw of around 1/4 amp is normal, after timeout, the draw should drop to below 50 mA.

Based on your readings, the system is normal.

 

You need to double check your math! One week is 168 hours. 168 hours times .2 Amps is 33.6 Amp hours not 400!

"Here is the thing, though: after about 45 minutes, that current drops to what looks to be about 0.010 A (10 ma.) After 15 minutes it still read 200 MA and did not drop until 1/2 hour after that."

I'm not sure I follow you. Are you saying that current drops to .01 Amp but then jumps back up to .2 Amps?

"So I don't know if this is the parasitic draw that is killing the battery or not. I'm thinking that the meter in series with the truck battery is affecting the results I'm getting."

Umm. No! It's not. Input impedence of typical DMM is 100,000,000 Ohms. Divide 12 (nominal battery voltage) by 100,000,000 and that will tell you how much current the meter draws. Meters and other electrical instruments are intended to draw as little power as possible from the Device Under Test in order to give you the most accurate results.

"Also, I tracked down the relay being activated to relay #2 under the dash. It was warm to the touch (coil was getting power.) When I pull out that relay, the drain stops (of course, the lights don't work, either.)"

Well if you think that truck is drawing your battery down, you could leave that relay out and find out! Or just disconnect your battery and find out.

But frankly, I agree with your mechanic and your dealer, That draw is too small to be the cause of your problem. That's just from my general auto experience. But also according to ProjectSHO89, those numbers are within spec for the F-150.

I re-read your message just to be sure but you never said if the new battery fixed your problem!

Also I'm assuming that your dealer DID find a problem with your old battery since they replaced it.

Personally, I've had a LOT and I do mean a LOT of problems with batteries in the last few years! Based on your symptoms I would BET that it's a battery problem! Johnson Controls has been buying up all of the other battery manufacturer's Including Optima and frankly their batteries are S H I T! But what's more they seem to be to only brand carried by most retail outlets! Ask your retailer who MADE their batteries and see if they don't start getting cagy and saying that they're so and so brand! But try to pin them down on who MAKES them and watch them start looking elsewhere and start trying to duck the question!

 

How did Sam's club and your mechanic test the battery ?

It needs to be charged overnight to be correctly load tested, and the load test is based on the CCA of the battery ( load tests are not one size fits all as autozone does ).

If the battery was killed dead enough to not turn the starter, that sounds like a battery that has been discharged too far to be called OK by any means now.

Each time a battery is discharged below 12V DC, the life of the battery is drastically reduced.
- Not too sure what the battery you have is like in new condition, but now it is very questionable.

You could have a sulfated cell or the battery is just beat now.
- Really not good for the truck's alternator if you jumped the battery and tried to use the alternator to charge a flat battery. It should have been trickle charged over night at least, before using it.

I would start by having someone actually overnight charge and load test the battery ( based on CCA size ) to make sure it can hold a charge. If it cannot take a load test and recover to 12.6 VDC, the battery is shot.

 

My old 97 would go through a battery every 12-18 months. After 6 years of that, it finally got fixed when the whole thing failed a half mile from an O'Reillys. Since I couldn't go to Walmart for yet another replacement, I bought a new one from the auto parts store. Four years later, battery was still running.