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      05-24-2020, 06:03 PM   #1
lime
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Can't Locate Parasitic Draw? Increased Battery Discharge

I'm really struggling to figure this one out. About mid 2018 my battery died so I replaced it and coded it with Carly. Everything worked fine until about a year ago when I started to get occasional warnings about increased battery discharge where the car shuts everything down to preserve enough power to crank the engine. Initially I thought it was probably just not getting enough use or long enough journeys to adequately charge the battery. I started putting it on a ctek regularly and things seemed ok ish. I'm now at a point where the clocks etc are reset basically every time I get in the car, and increased battery discharge warnings are frequent. I decided to check for a parasitic draw and as far as I can tell I followed the correct procedure for this (shutting trunk/door latches, leaving to sit with ca key far away for >30 mins etc) and after connecting my multimeter between the negative cable and terminal it appears the car is drawing about 2.4 amps while sleeping! The next step I took was leaving the meter connected and having someone watch while I pulled every fuse in the glovebox one by one, there was no change. I even pulled the fuses and relays in the engine bay fuse box. I also decided to test the battery so after charging it until the ctek was happy I immediately read the voltage at 12.25 which isn't ideal. After sitting overnight it was down to 12.1v. I started the car no problem at all at that voltage and checked to see what the alternator was putting out which stabilized at 14.4v so it doesn't appear to be a problem there.

I'm a bit stumped really, any ideas on what to check or try next would be much appreciated.
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      05-24-2020, 07:22 PM   #2
ctuna
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When I leave my ctek on for around 6 hours the battery reads
close to 13 volts. (you are suppose to leave the ctek on for multiple
hours not minutes)
A fully charged battery should measure at least 12.6
I am talking lead acid don't know about AGM.
If you put in an AGM it needs more than registering it needs programming.
Programming for battery type and amp hours.
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      05-24-2020, 08:58 PM   #3
lime
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Quote:
Originally Posted by ctuna View Post
When I leave my ctek on for around 6 hours the battery reads
close to 13 volts. (you are suppose to leave the ctek on for multiple
hours not minutes)
A fully charged battery should measure at least 12.6
I am talking lead acid don't know about AGM.
If you put in an AGM it needs more than registering it needs programming.
Programming for battery type and amp hours.
Yeah I believe if healthy the battery should read >12.5v, I left the ctek on for about 8 hours and it was indicating that the battery was fully charged. I changed the type and capacity via carly as well as registering it so shouldn't be an issue there. My assumption is that the parasitic draw over 2 years has been hard on the battery so I'd like to sort out the drain before dropping hundreds of dollars on a new battery only for it to get ruined by the same issue.

Edit: I thought I'd just check with carly and it seems that while the battery capacity is correct, it is showing a non-agm battery registered when the battery is in fact an agm. I don't know how that happened but I guess I must have screwed up somehow when I was replacing the battery 2 years ago and it has fried this battery. I might grab a new battery and see how things look then, but surely that wouldn't impact the drain right?

Last edited by lime; 05-24-2020 at 09:36 PM..
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      05-25-2020, 12:26 AM   #4
ctuna
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If you let the car set or don't drive it that far it bad for it.
These cars are battery hogs.
That it why its good to let it sit on the battery tender a
couple of times over night a couple of times a month.
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      05-25-2020, 01:59 AM   #5
lime
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Quote:
Originally Posted by ctuna View Post
If you let the car set or don't drive it that far it bad for it.
These cars are battery hogs.
That it why its good to let it sit on the battery tender a
couple of times over night a couple of times a month.
I drive it 3-5 times per week and usually at least 1 of those trips are more than an hour of non-stop driving. Still can't hurt to use the tender every now and then, but it really shouldn't need it.
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      05-28-2020, 03:09 PM   #6
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Quote:
Originally Posted by lime View Post
I decided to check for a parasitic draw and as far as I can tell I followed the correct procedure for this (shutting trunk/door latches, leaving to sit with ca key far away for >30 mins etc) and after connecting my multimeter between the negative cable and terminal it appears the car is drawing about 2.4 amps while sleeping! The next step I took was leaving the meter connected and having someone watch while I pulled every fuse in the glovebox one by one, there was no change. I even pulled the fuses and relays in the engine bay fuse box.
Forget about voltages and trickle chargers. You need to fix the parasitic draw; that's the only cause. A draw like that will eat thru replacement batteries pretty quick, because FLA and AGM like to stay at high SoC.

You might run the fuse test again and see if you get a different result. You don't need to close the doors/trunk. Just wait until the trunk light goes out and you know it's asleep. That way you can leave everything open so it won't wake up when you try to get into the car to pull fuses.

You can also try disconnecting positive leads from the battery; there are 3 main positives as well as the BMS sensor positive lead. That could help narrow down your search.
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      05-28-2020, 07:30 PM   #7
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^ what he said.

2.4 Amps is really high. IIRC the draw while asleep should be in the few hundred mA range (300-500 mA).

Have a look though this to get an understanding of where the power is routed.
https://www.e92n55.com/wp-content/up...us-systems.pdf

Last edited by Canuck335; 05-28-2020 at 07:36 PM..
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      05-28-2020, 11:41 PM   #8
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http://www.bimmerfest.com/forums/sho...15&postcount=6

draw should be .5 amps when awake less than 80 ma asleep
Its in the electrical pdf posted.

https://www.newtis.info/tisv2/a/en/
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      06-01-2020, 07:17 PM   #9
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Quote:
Originally Posted by ewicky View Post
Forget about voltages and trickle chargers. You need to fix the parasitic draw; that's the only cause. A draw like that will eat thru replacement batteries pretty quick, because FLA and AGM like to stay at high SoC.

You might run the fuse test again and see if you get a different result. You don't need to close the doors/trunk. Just wait until the trunk light goes out and you know it's asleep. That way you can leave everything open so it won't wake up when you try to get into the car to pull fuses.

You can also try disconnecting positive leads from the battery; there are 3 main positives as well as the BMS sensor positive lead. That could help narrow down your search.
Good idea with the positive leads. I just disconnected what I believe to be the IBS, Engine electronics, and junction box and saw no change in the amp draw. My setup looks a little different to the pdf so I'm not sure how to disconnect the B+ to the starter/alternator without disconnecting everything. Is there a better way to test that circuit?

Here is my setup, I disconnected the 3 cables down the right hand side of the power distribution box one at a time:
View post on imgur.com


I've heard that the alternator diode can cause these issues quite often with these cars, how would I test that?
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      06-02-2020, 10:09 AM   #10
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Quote:
Originally Posted by lime View Post
Good idea with the positive leads. I just disconnected what I believe to be the IBS, Engine electronics, and junction box and saw no change in the amp draw. My setup looks a little different to the pdf so I'm not sure how to disconnect the B+ to the starter/alternator without disconnecting everything. Is there a better way to test that circuit?

Here is my setup, I disconnected the 3 cables down the right hand side of the power distribution box one at a time:
View post on imgur.com


I've heard that the alternator diode can cause these issues quite often with these cars, how would I test that?
How are you measuring current with the leads hooked up to the mA plugs on your multimeter? You should be using the 10A plug and COM. Now I'm not even sure I believe the 2.5A draw you measured, based on you photo it might be a miss-measure.
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      06-02-2020, 10:20 AM   #11
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Quote:
Originally Posted by lime View Post
I've heard that the alternator diode can cause these issues quite often with these cars, how would I test that?
If the diode is pulling 2.5A at 12V, that's like 30 watts. It and the things around it would be hot or at least noticeably warm after the rest of the car has cooled.
But ya, you could disconnect your alternator and see if the parasitic draw stops.
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      06-03-2020, 05:58 AM   #12
lime
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Quote:
Originally Posted by ewicky View Post
How are you measuring current with the leads hooked up to the mA plugs on your multimeter? You should be using the 10A plug and COM. Now I'm not even sure I believe the 2.5A draw you measured, based on you photo it might be a miss-measure.
You're right, the 10a circuit wasn't working so I used the other jack and assumed because the scale was amps that it would work. I bought a new multi-meter today and did some testing. Connecting to the car woke it up and drew a peak of about 7 amps then gradually drew less until the meter was reading 0.03. It read the same number on most settings which seemed odd to me. Couldn't get any reading at all using the VΩmA port.

Here are a few photos in order:
View post on imgur.com


First few is just after the car had gone to sleep, after that just trying different ranges but not seeing any change. I'm not an expert in reading these meters so not entirely sure what it's telling me, but looks to me like around 30ma of draw.

It appears that there may not be a parasitic draw after all? Possibly just a damaged battery after having it coded as a non-agm when it is indeed an agm battery? The thing that confuses me is that with my other meter when I connect it using the 200mA range it says overload. Any thoughts?

Last edited by lime; 06-03-2020 at 06:33 AM..
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      06-04-2020, 02:59 AM   #13
ctuna
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It looks like the ma range comes from the other plug that says
ma.
However the 2.6 amp draw I am assuming is when the car
is awake and not running in no bueno . It should be some thing
like .5 amps.
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