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Thread: Battery draining woes

  1. #1
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    Battery draining woes

    I've been having a heck of a time diagnosing why my battery keeps draining and killing batteries. The last few years my battery has been slowly draining overnight. It'll get worse enough to where the battery no longer functions and I have to replace. I finally got around to diagnosing it, without luck.

    When I say wont stay charged, there is still power in the battery, but not enough to start. The longer I let it sit, the less power it has...obviously.

    Here's the summary:
    - Replaced bad battery (bad cell) with new Napa battery about 2 weeks ago.
    - Replaced trunk wiring harness. I had a few frayed wires so that's all fixed. No luck.
    - Tested alternator voltage and it was reading 14v at the battery.
    - Within 2 days, battery wont stay charged overnight.
    - Within a week, battery wont stay charged after 4 hours.
    - This weekend I tried to figure out what the issue was with my limited electrical diagnosing ability.

    When I first hooked up my Innova 3320 multimeter, it was reading a draw of 0.013amps. I realized this was the trunk light and so I ran wire from the battery out the window so I could have all the doors closed. It still showed a draw of the same voltage with all the doors closed.

    I started pulling fuses to determine what fuse was the issue. Fuse 33 (i think) which is the interior lighting showed as the culprit. I thought this was odd as all the lights were off so I plugged in my test light to see if power was on that circuit. Sure enough it was with the fuse in. The light would stay on after opening a door for over 30 minutes. I pulled all the interior light bulbs out of their sockets and tested again after opening a door. The light wouldn't come on. I tested draw at the battery and it showed no draw.

    However, this morning, my battery was dead again. Maybe I'm not doing something right. Just need some direction.

    Thanks!


    EDIT: forgot to add one more thing. About a week ago I started a CEL for a camshaft position sensor. I replaced the sensor but it didn't seem like it fixed the issue. If the battery drains at all for more than 2 hours, the car will run rough, indicative of the sensor/wiring failing. If I start the car after letting it sit for less than two hours, it runs perfect. Not sure if this has anything to do with the battery drain or if the sensor is just sensitive to voltage?
    Last edited by Xiphos; 10-15-2018 at 11:31 AM.

  2. #2
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    13 milliamps is well within the parameter of an acceptable draw. I'd say that's not the problem.
    I'd get a good meter and a low or medium range inductive amp probe and go hunting with that starting at the battery cables and working out. When you get to the fuse box a Fuse Buddy comes in handy.
    See ya later,

    tony
    '98 M3, '92 Dinan3, '05 R1100S BCR, '07 R1200S, Aprilia T

  3. #3
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    Quote Originally Posted by tjm3 View Post
    13 milliamps is well within the parameter of an acceptable draw. I'd say that's not the problem.
    I'd get a good meter and a low or medium range inductive amp probe and go hunting with that starting at the battery cables and working out. When you get to the fuse box a Fuse Buddy comes in handy.
    I'll get those testers and see what I find. I added this additional data to my first post but figured I'd put it here so you saw it too. About a week ago I started a CEL for a camshaft position sensor. I replaced the sensor but it didn't seem like it fixed the issue. If the battery drains at all for more than 2 hours, the car will run rough, indicative of the sensor/wiring failing. If I start the car after letting it sit for less than two hours, it runs perfect. Not sure if this has anything to do with the battery drain or if the sensor is just sensitive to voltage?

  4. #4
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    I had a similar problem with my X5 last year. AAA came out and replaced the dead battery. Had them return in a week because it wouldn't start -- same AAA tech replaced the battery, saying the first one was a lemon. Similar no-start problems again in the next few weeks. Alternator checked out fine. So, I began to think there was a parasitic drain, and many multi-meter and fuse tests later, thought my radio was the culprit. Long-story-short, I went back to the origin of the problem, and replaced the AAA battery with a high-quality Interstate battery, and it's been fine ever since. Turns out AAA batteries are crap for cold-cranking. I would consider swapping-out your Napa battery.

  5. #5
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    Quote Originally Posted by M3rocket View Post
    I had a similar problem with my X5 last year. AAA came out and replaced the dead battery. Had them return in a week because it wouldn't start -- same AAA tech replaced the battery, saying the first one was a lemon. Similar no-start problems again in the next few weeks. Alternator checked out fine. So, I began to think there was a parasitic drain, and many multi-meter and fuse tests later, thought my radio was the culprit. Long-story-short, I went back to the origin of the problem, and replaced the AAA battery with a high-quality Interstate battery, and it's been fine ever since. Turns out AAA batteries are crap for cold-cranking. I would consider swapping-out your Napa battery.
    It originally started and went through two interstate batteries before switching to napa. Napa is a bit better on their warranty policy on batteries from what I've found.

  6. #6
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    To kill a battery overnight, you need a typical parasitic draw of 500 mA or more. Check the multi disc CD player in the trunk, radio, amp, and all interior lights. These are the typical culprits.

    If you still can't figure it out, you can always get a priority start (on Amazon) - at least you won't get stranded anymore.

  7. #7
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    I also have a battery drain. If i let the car sit for 2 weeks, it may not start.
    In the winter time, its worse. Maybe 5 days to a week before the battery doesnt have enough juice to cold crank.

    Thankfully, i have a garage and the car is on a battery tender. I also noticed some of the electronics in the car doesnt like it when the battery is low.

    I have had an interstate battery, optima red top battery and currently duralast battery. Having the battery die or leaving it dead for a long time can damage the battery.

  8. #8
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    Quote Originally Posted by RND1 View Post
    To kill a battery overnight, you need a typical parasitic draw of 500 mA or more. Check the multi disc CD player in the trunk, radio, amp, and all interior lights. These are the typical culprits.

    If you still can't figure it out, you can always get a priority start (on Amazon) - at least you won't get stranded anymore.
    Quote Originally Posted by hc1001 View Post
    I also have a battery drain. If i let the car sit for 2 weeks, it may not start.
    In the winter time, its worse. Maybe 5 days to a week before the battery doesnt have enough juice to cold crank.

    Thankfully, i have a garage and the car is on a battery tender. I also noticed some of the electronics in the car doesnt like it when the battery is low.

    I have had an interstate battery, optima red top battery and currently duralast battery. Having the battery die or leaving it dead for a long time can damage the battery.

    My battery will only last maybe 4 hours before its low enough to not start.

  9. #9
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    Are you measuring drain right at the battery?

    I'd get a really cheap Harbor Freight multimeter and compare the two meters, or try the drain test on another car.

  10. #10
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    Quote Originally Posted by marvinstockman View Post
    Are you measuring drain right at the battery?

    I'd get a really cheap Harbor Freight multimeter and compare the two meters, or try the drain test on another car.
    Yes, disconnecting the ground from the battery then testing the drain between the ground and the battery.

  11. #11
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    Then I'd get another meter and compare the two.

  12. #12
    NeilM is offline Member BMW E36 M3 Expert
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    When this happened to me quite a few years ago it turned out to be a failed trunk light switch. Classic refrigerator light problem!

    Neil

  13. #13
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    my oem (dealer added) alpine alarm kills my battery after a week or so.

    https://www.canadiantire.ca/en/pdp/m...3507p.html#srp

    I run a cheap battery disconnect. Often park the car for several weeks so it works for me. Added theft prevention too!

    Doesn't solve your problem, but it might save some daily frustration.

    As others have said, I'd be trying another multimeter.

    EDIT: did you compare the voltage reading at the alternator, the starter and the battery? even if your meter is wack the interesting thing would be the voltage drop. There shouldn't be much if any. I went through a similar diagnosis before finding a rotten connector at the positive jumper lug in the bay. I was losing 2 volts there - and it was melting the inside of the terminal box.
    Last edited by The Producer; 10-23-2018 at 01:09 AM.

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