Battery Drain when alarm not on
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    1. #1
      Junior Member
      Join Date
      Jul 2015
      Location
      South Jersey
      Posts
      24

      Battery Drain when alarm not on

      I currently have a 2010 S40 T5 and noticed a battery drain problem. I had the battery replaced last year and with the new battery, I have been keeping a close eye on the drain. While this may not be 100% accurate, I use "Automatic" to track my car's information. One of the features they have under "labs" is the Battery Health monitor.

      Anyway, 2 weeks ago when I park my car in the garage, I stopped alarming my car. Basically, I would just let the car sit in the garage with the alarm "off". I would say the majority of any car owner would do this since the car is already in the house. So I did this for all of week 1. For week 2, I started to set my car alarm to "on" after I'd park my car in the garage. Based on the Battery Health monitor, there seems to be a substantial battery drain when the alarm is "off" versus "on". In the attached picture, week 2 starts on April 14th.

      Can anyone verify that with the alarm "off" or "on" can cause noticeable batter drain while the car is turned off? The huge spike going down towards the 50% mark are times when I parked in the garage with alarm off. For the spikes that are healthy prior to 4/14, they were when I was parked at work with the alarm "on". After 4/14, I continuously set my alarm to "on" wherever I went including parking overnight in my own garage.


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    3. #2
      Isn't the reason for this (at least some people in the past noticed) that because the facelifts have a different key system that actively searches for the key constantly until it is locked by remote, draining the battery.

      Considering a battery is approximately 60Ah, you're looking at approximately 2.5A drain per hour, or about 41mA a minute, which would be consistent with a radio searching for a key at highest broadcast strength. Any wiring short would be much more significant.

      However a flip side of this could be the battery's 100% mark isn't where it should be, and while it may read 100% it only has a small capacity before it's at 50%, whereas it should have significantly more capacity between 50 and 100%.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
      2012 Subaru Outback 2.5i CVT - Slowmobile - CAI only, Powerstop Rotors+Pads.
      1996 HD Electra Glide - Big Bertha 10:1 Pistons; EV13 Cam: Ultima Digital Ignition; Buell Head Conversion; E85 Carb Tuned;

    4. #3
      Junior Member
      Join Date
      Jul 2015
      Location
      South Jersey
      Posts
      24
      Ah. That makes sense now. I did try to look for this topic but was unable to find it. But everything makes sense now. Guess my car alarm will be on wherever and whenever my ignition is off. Thanks.

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    6. #4
      Junior Member 80sGuy's Avatar
      Join Date
      Nov 2013
      Location
      Los Angeles
      Posts
      638
      I never have problems with my battery while leaving the car parked/armed for weeks, even months but thought it was running kind of weak. Just for maintenance purposes I checked the water level and it was pretty low. I then topped it off and all is well. Just unscrew the six little vent caps off with a quarter and top off with distilled water, though I filled mine with reverse-osmosis drinking water.

      edit: that is if you have an OEM Volvo-branded or a 'serviceable' battery.


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