Battery Drain Check Specifications

Keith Browning · April 25, 2018

Also called parasitic drain testing, the test helps you identify and diagnose electrical drains that discharge the battery. For many years the WSM has stated that the maximum current draw on a battery should be no more than 50 milliamps and to this day the current WSM's state this. But I have noticed lately that on late model vehicles like a 2015 F150 and a 2017 Transit, the battery draw after shut down is around 170-185 milliamps. Batteries do not discharge for the amount of time the vehicles are in for service, sometimes for weeks.

So what have the rest of you been seeing for amperage draws?

Here are some of the notes from the Battery Drain Test Procedure:

NOTE: No factory-equipped vehicle should have more than a 50 mA (0.050 amp) draw. Check for current drains on the battery in excess of 50 mA (0.050 amp) with all the electrical accessories off and the vehicle at rest for at least 40 minutes. Current drains can be tested with the following procedure.

NOTE: Many electronic modules draw 10 mA (0.010 amp) or more continuously.

NOTE: Typically, a drain of approximately 1 amp is attributed to an engine compartment lamp, glove compartment lamp or interior lamp staying on continually. Other component failures or wiring shorts are located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading falls to an acceptable level.

NOTE: To accurately test the drain on a battery, use an in-line ammeter between the negative battery post clamp and its respective cable. Use of a test lamp or voltmeter is not an accurate method.

Bruce Amacker · April 25, 2018

Keith:

Are you allowing ample time for all of the modules to "time out"? I've done this test hundreds of times on a variety of cars and trucks teaching our electrical troubleshooting class, and many vehicles take minutes or hours for the modules to time out. Some Chryslers are a couple of hours to get the TCM to clock out and come down to 50ma or less. I commonly see 100-200ma for 30+ minutes while waiting.

PS you can do the math using the amp hour rating of the battery to see how long it will last, IIRC 50ma is several months to run a battery dead. (amp hour/amp draw= hours.-------- A 100 amp hour battery at 50ma is 83 days)

Keith Browning · April 25, 2018

1 hour ago, Bruce Amacker said:

Keith:

Are you allowing ample time for all of the modules to "time out"?

Of course I am. Ford states 40 minutes. The reading on the meter above? 24+hours.

1 hour ago, Bruce Amacker said:

You can do the math using the amp hour rating of the battery to see how long it will last, IIRC 50ma is several months to run a battery dead. (amp hour/amp draw= hours.-------- A 100 amp hour battery at 50ma is 83 days)

Interesting - never thought of that. Would be useful for determining the discharge time for the customer. Unfortunately Ford does not publish amp hour data anywhere I can find.

The battery in this particular truck is a Motorcraft BXT-48H6-610

Bruce Amacker · April 25, 2018

Wow, 178ma after 24 hours is way too much in my opinion, and I assume these are bone stock trucks without added aftermarket BS. I know you're pressed for time, in a perfect world you'd isolate stuff and find out where the draw is. I have a feeling if you talk to Hotline you'll be educating them rather than the other way around, but that's probably where I'd start.

A couple of quick tests would be to use an amp clamp around the alternator wires (one at a time) looking for draw and do a voltage drop across the fuses. A fuse with a 100ma load on it will have a vdrop of a few thou of a volt.

178ma can be picked up by most DC inductive clamps on the battery cable, BTW.

Good Luck!

KDS · April 25, 2018

Might be a good place for a thermal imaging camera

Bruce Amacker · April 25, 2018

On the last page of this PDF it calls for a 2016 Transit to have a 70 amp hour battery:

https://www.fleet.ford.com/truckbbas/topics/2016/16_Transit_SB.pdf

A similar PDF shows the F150 to have either a 70 or 80 amp hour battery.

70/.178= 393 hours, which is only 16 days?

Kevin's idea is a good one, too.

Keith Browning · April 25, 2018

I think it's too high as well but I have heard other guys saying they have seen more then 50 mA and the hotline tells them its okay. So that is why I am asking.

This is a police paddy wagon by the way with whirligigs and sirens, a PC and a two sided prisoner module in the back. Time has nothing to do with it, fixing the truck is the priority so I have plenty of time to complete the isolation process.

Bruce Amacker · April 26, 2018

A lot of ambulances and fire equipment I train on are plugged into shore power when it's parked because they know there's too much draw and it will run down the bats. See if this is the case......?

Anyway, I'd like to know if this is a normal situation on late Fords. Something tells me it isn't.

Keith Browning · April 26, 2018

9 hours ago, Bruce Amacker said:

A lot of ambulances and fire equipment I train on are plugged into shore power when it's parked because they know there's too much draw and it will run down the bats. See if this is the case......?

The back story is that this unit does not see daily use and it may go as long a 10 days before they need it. There was mention of the dash being seen illuminated out in the lot by officers walking by. If this is true it indicates something is going on which is what I am monitoring for at the moment.

9 hours ago, Bruce Amacker said:

Anyway, I'd like to know if this is a normal situation on late Fords. Something tells me it isn't.

Hence my post because this is not the first time I have seen this draw. One of the next steps is to check a stock unit to see what a bare stock Transit shows as a shut down draw. If this turns out to be related to any of the upfit equipment I will suggest either an isolator switch or a charger/shore line be implemented depending on what I find.

RyanG · April 26, 2018

Just had a 16 Transit cutaway with a service body. Complaint was battery goes dead after couple days. With all doors and hood open and latches in a closed position after an hour It was showing 10 milliamps. Let it sit over the weekend and still no draw, battery was new. Customer picks it up next morning, battery dead. :facepalm: Didn't get a chance to find the draw but I would suspect all the shit tied in to it or whatever was plugged in to the DLC drawing intermittently.

Keith Browning · April 27, 2018

My test on a stock unit revealed the same results! 185 mA draw after 40 minutes which was still 183 mA this morning. I left the test set up overnight. I contacted the Hot-Line. I want to see what they say. The plot thickens.

Keith Browning · April 28, 2018

The more I think about this I am beginning to wonder if my meter is off. This is now three vehicles in the last month that have given me essentially the same reading with this test. I am going to borrow a meter and see what I get. It may be time to send my meter off to Fluke to be checked and calibrated if it is off. Boy if this is the case I am going to be pissed about the wasted hours spent diagnosing this.

Bruce Amacker · April 28, 2018

Or borrow a meter and check a known draw, like a 194 (or LED) bulb and compare it to yours. I have LED interior bulbs in one of my cars that draw 30ma. Or it looks like you're using an 88, put the red lead in the MA port (next to the A port) and see if you get the same reading. I think MA goes up to 2a (2000ma).

Keith Browning · May 1, 2018

I can wrap this one up.

Borrowed a meter, which gave much different readings than mine.

Changed the battery. Nope.

Removed and tested the fuses. My 10 amp was blown so why was I still getting a reading? :banghead:

New fuse, starts a 900 mA and then drops to 8 mA after 20 minutes.

forddieseldoctor · May 2, 2018

Do you know how to test fuses in the meter without opening it up? I check mine everytime before I start testing.

Keith Browning · May 2, 2018

10 hours ago, forddieseldoctor said:

Do you know how to test fuses in the meter without opening it up? I check mine everytime before I start testing.

es I do now. Bruce told me to connect to the mA connections and place the dial on voltage... if the meter beeps the fuse is good.

forddieseldoctor · May 2, 2018

If you set the meter to ohms and put one lead in the ohms/volts port and the other one in the amps port. The meter will read ol if the fuse is failed.

Brad Clayton · May 3, 2018

I hook the meter to the battery and turn the park lights on.

8WA Sman · May 3, 2018

On Tuesday, May 01, 2018 at 7:42 AM, Keith Browning said:

Removed and tested the fuses. My 10 amp was blown so why was I still getting a reading?

Must have been a "fluke" :haha2:

Bruce Amacker · May 4, 2018

Been out of town-

When we do this test in class, I always say to "check your work" while the test is running. That means open the door or turn on the interior lights while you're running the test, the reading should jump up 1-2a and then back down after the BC sleeps......

Keith Browning · May 5, 2018

I guess it comes down to that anyone at any time can accidentally blow their fuses. This even applies to the most confident and competent of us because that usually leads to complacency. Yes, I assumed that since I am the only person using my meter and "I know what I am doing" that it didn't even dawn on me to suspect the meter's fuse. But I am am still confused as to why I was still getting a reading. I would think that the meter would not show anything at all. Live and learn... even after 30 years you can still make mistakes. :blush: