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BMW 3-Series (E90 E92) Forum
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Increased Battery Discharge
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06-19-2018, 04:06 PM | #1 |
New Member
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Rep 16
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Increased Battery Discharge
No Battery Issues before accident...
Body shop that fixing my car replaced my battery (They said it was old and insurance was paying for it ). They didn't check to see what battery I had prior and replaced it with a non-AGM battery. My car kept dying overnight (I noticed the Push-to-Start button would stay on). 2-3 hours after the car was locked. They replaced the battery with an AGM Battery but my car still says that there is "increased battery discharged". I reset the battery settings via MHD. The car hasn't died since the AGM Battery was put in HOWEVER the car still says that there is a"increased battery discharged" Only electrical mod is a back up camera that is powered via the reverse light. I've been monitoring my battery level via my P3 Gauge, and it is always ~14 ± .5 |
06-19-2018, 04:36 PM | #2 |
Art Collector
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Just to confirm, when you say you reset the battery settings, you mean that you coded the car to tell it an AGM battery was installed, right?
I'd probably start by hooking up an amp meter in series with the ground cable on battery, locking the car and waiting until it goes to sleep, and then observing what kind of current draw exists. You seem to be saying that it isn't actually going to sleep... So the amount of current drawn 20 minutes post-locking might lend a clue as to what might be responsible for parasitic drain, if any even exists. It could be something else that is causing the warning to come on; I have no idea. Just a thought. Others may have more specific diagnostic methods given your issue, but this has worked for me in the past. |
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06-19-2018, 06:56 PM | #3 |
cdmontgomery
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Careful checking parasitic draw using the connections back at the battery - if the trunk is open the car wont go to sleep (unless you can figure out how to defeat the open/close switch) - also a disconnected battery means no electric trunk actuator (either from inside or via the remote). For us unfortunates without the mechanical trunk lock (I have a 2011) a disconnected battery with closed trunk can be a huge issue. Your parasitic loss should be in the 10 - 20ma range (1/100 to 1/50 of an amp). Should go to sleep (start button LED off) in a few seconds with doors locked and a few minutes with doors unlocked. Try measuring via the under hood connectors. In my experience the battery loses about .01 volt per day - so if you start at a nice 12.6 v (at around an hour after shutdown) you should be able to still start the car 60 days later with 12.0 v available. Personally I wouldn't go this long - figuring on a month as the maximum (I had mine drop to 11.9 v once when doing work on the car and it would not crank at that voltage) (not sure how the IBS is intended to function but in that case it did not shut down secondary loads to conserve starting reserve). To check parasitic draw under the hood (my 2011 has no hood open/close switch so the hood can be left open - I think this applies to all E90's but I'm not sure):
> take a healthy extra battery > hook it up to under hood jump connectors - as if doing a jump start > let the system sit for a few hours to allow both batteries to equalize in voltage (since one might start a 12.6 and one at 12.4) > put your amp meter between the jump battery negative and vehicle ground > current reading in ma will be 1/2 the actual parasitic draw (because two batteries in parallel at equal voltage will share any load) > if you read above 5 - 10ma try disconnecting your backup camera (+) connection and see if the draw drops |
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agm, battery, discharged |
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