Battery parasitic draw test

[g300d]

I browsed a lot of threads re checking for parasitic draw and they all have good info, I'm ready to jump into it.

The one thing I'd like to know is can I connect the multimeter to the jump terminals in the engine bay and test from there? Or do I have to do it at the battery terminals in the trunk?

[wpoll]

Current draw can only be measured at the battery terminals...

[g300d]

Thank you, Wayne!

[StephenVA]

Details Details...

BMW Vehicle Parasitic Draw Testing
When your car battery goes dead overnight, usually either the battery is at the end of its life span, or you left something on, such as a light. Occasionally something is drawing power that's not of your doing. This is a parasitic draw, and it can cause the same result as leaving the headlights on: a dead battery in the morning.

1. Remove the negative side battery cable from the negative battery terminal.
2. Connect the black wire to the com input on the multimeter and the red wire to the 10A or 20A input on the multimeter. The meter needs to be able to read at least a 2 or 3 amps for this test to work. Connecting the red wire to the mA input on the multimeter won't work and could damage the meter.
3. Attach a multimeter (set the dial on the multimeter to measure Amps as per multimeter’s instructions) between the negative cable and the negative battery post. Wait a few seconds to several minutes for the car to go into sleep mode - i.e. when you make the contact with the ammeter, the cars computer systems "wake up". After a bit of time they will go back to "sleep".
4. If the ammeter is reading over 25-50 milliamps, something is using too much battery power.
5. Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings) last. Perform the same steps for relays found in the fuse panel. Sometimes relay contacts can fail to release causing a drain. Be sure to observe the ammeter after pulling each fuse or relay.
6. Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners' manual or service manual to find what circuits are on that fuse.
7. Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.
8. Repeat steps 1 & 2 to test your repair. The ammeter will tell you the exact numbers.


BMW Battery Draw Testing
If your Shifter light is on, the car is definitely staying awake.
Your Battery will go down within days. If the light is not on you can have a parasitic draw, while the car is in sleep mode. The only difference, is the second draw is from a module which can’t wake the system (not mission critical), and it will take a lot longer to discharge the battery.
Shifter light NOT on: (battery fully charged)
Find the ground cable on the battery, but do not disconnect. (the cable end connected to the body not the battery, is easier to handle.)
Connect the Positive lead from the “Fluke” to the body of the car (good ground)
Connect the Negative lead to the (brown) ground cable (you can puncture it)
Make sure it’s easy to disconnect the (brown) cable from the body, but don’t take it off yet.
Open the glove box and remove and disable the switch so the light will not turn on, locate the fuse box.
Start the car and run at idle, turn EVERYTHING on, and activate all the components (sunroof, windows, a/c, lights …..) run 5 min.
turn the car off and remove the key. Open all doors and trunk, and with a screw driver, close the door locks so the system thinks all doors and the trunk is closed.
Now lock the vehicle with the remote.
The “Fluke” must be set up to “A” not “mA” otherwise you will blow the
fuse in the meter. Remove the nut from the ground cable and remove the cable from the stud. You meter will indicate around (300mA).
Let the car go to sleep. (16 min) minimum, if this is not happening start over.
After the sleep mode is on the draw should not be more then 50mA, if it’s more go to the glove box and start pulling fuses one by one and check the draw after each one, but do NOT re-install the fuse. Pull the fuse and leave it out
There are some fuses under the right cover in the trunk. If you pull a fuse and car wakes up start over (next time ignore this fuse). If you pull a fuse and the draw drops to around 50mA, read the label on the fuse, you will know which circuit is faulty.

Relay locked on - test
Take out your infrared temp gun and measure each relay. The one that is hotter is "on". Simple!

[oldskewel]

And here's another detail / alternative fact regarding the orange light by the shifter ...

https://xoutpost.com/bmw-sav-forums/...in-issues.html

It appears that the orange light is not always a direct indicator of sleep mode.

In my 2001 3.0i, that orange light is on all the time, sleeping or not. I have no battery drain issues. I now have a very direct sleep detector myself: I installed a dashcam up by the rear view mirror, using the circuitry in the map light cluster up there. The power source I got up there turns off after about 16 minutes, which seems to indicate sleep mode. At that point, the green status LED on the dashcam goes out and recording stops. That also coincided with the ignition key charging coil to stop charging, as also experimentally verified recently (discussed in another thread).

Since sleep vs. not sleep is a huge factor in debugging a drain issue, it is important to realize that the orange shifter LED is not always a direct indicator of that state.

And for people doing testing, I can give a strong recommendation for getting a clamp ammeter. Need to make sure it handles DC, which will cost more than the ones that just do AC. With that, there is no concern for fuses, ranges, disconnecting and reconnecting wires (which could trigger a change of state). When my Dad had a problem with his car that I helped him debug remotely, after a little fumbling around with the meter I had previously given him, I just shipped him a new clamp meter and went from there. Incredibly much easier to use if you are not experienced, and even if you are.

[80stech]

Installing a temporary battery switch and waiting for car to go to sleep before opening the switch (mutimeter already connected) to then check the draw eliminates a lot of things that can go wrong and be misleading especially for someone unfamiliar with what they are doing.

If they are making clamp on (inductive) measuring units that are accurate enough for doing this then that is good. Either way though, it's a really good confidence builder to do this test and gain some understanding on a good vehicle before there is a problem.

[Fifty150hs]

There are a couple common causes for parasitic drain. One is the TCM and the other is Nav if you have it. If you are getting parasitic drain, pull the fuses and if you don't have a dead or near dead battery the next day, plug in one of the fuses and wait another day. If it's dead, you found your culprit. If not, you plug in the next one and give it a day. My money is on the TCM if you have one. From the reading and researching I've done and my own experience they are often the cause. Of course my method requires you to have several days to have the truck down.

[jdstrickland]

Disconnect the Negative battery terminal, set your DVM to its Current scale and connect the leads, one to the cable and the other to the battery post. Open all doors and the hood, WALK AWAY for 15 minutes so everything shuts off, then without changing the status of anything, closing doors, etc., then go to the meter and read the display. You want a milliamp scale. 1000 milliamps is 1 amp. You should be seeing loads when the car is sleeping of something about 100 milliamps, this is 0.1 amp, your car should be able to support this kind of load for a very long time.

[bcredliner]

Originally Posted by jdstrickland

Disconnect the Negative battery terminal, set your DVM to its Current scale and connect the leads, one to the cable and the other to the battery post. Open all doors and the hood, WALK AWAY for 15 minutes so everything shuts off, then without changing the status of anything, closing doors, etc., then go to the meter and read the display. You want a milliamp scale. 1000 milliamps is 1 amp. You should be seeing loads when the car is sleeping of something about 100 milliamps, this is 0.1 amp, your car should be able to support this kind of load for a very long time.

An obviously, if the load is greater start pulling fuses. I assume you have load tested the battery even if it is new and verified the output of the alternator.