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Thread: E31 Battery charge

  1. #1
    Join Date
    Oct 2018
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    San Jose
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    57
    My Cars
    1991 BMW 850i

    E31 Battery charge

    Hi, I'm new to this community and I just bought my E31 today.
    The previous owner told me that i had to plug my car into an outlet so that the battery doesn't die.
    Does anyone else do this, or is it just me?

  2. #2
    Join Date
    Jan 2005
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    Japan
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    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    moved to E31 forum
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    We had a custmer with the two battery's we ended up using two battery tenders now it's always ready to go, also we installed agm battery's

  4. #4
    Join Date
    Nov 2014
    Location
    Seattle
    Posts
    66
    My Cars
    1985 M635CSI, 1992 850i
    Yes, a lot of E31 owners use battery tenders - which indeed plug into the wall outlet.
    Mine is under the hood and connects into the posts under there.

  5. #5
    Join Date
    Oct 2018
    Location
    San Jose
    Posts
    57
    My Cars
    1991 BMW 850i
    Quote Originally Posted by Stantz View Post
    Yes, a lot of E31 owners use battery tenders - which indeed plug into the wall outlet.
    Mine is under the hood and connects into the posts under there.
    Is it possible to do a single battery conversion?
    How will it effect the car?

  6. #6
    Join Date
    Feb 2010
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    Hampshire UK
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    99 840ci Sport Indv
    You can use a single Ctek MXS 5.0 on either battery (or connected to the jump-start points under the hood) and both batteries will be successfully charged - you don't need two chargers as the batteries are connected in parallel.

    More information on battery drain here:

    https://www.meeknet.co.uk/e31/E31_Ba...iagnostics.htm

    Information on changing batteries safely here:

    https://www.meeknet.co.uk/e31/E31_Ba...eplacement.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
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  7. #7
    Join Date
    Jan 2014
    Location
    London, UK
    Posts
    49
    My Cars
    Bmw 840
    Quote Originally Posted by Timm View Post
    You can use a single Ctek MXS 5.0 on either battery (or connected to the jump-start points under the hood)
    Listen to you going all American Its not under the hood, its under the bonnet
    1998 e31 840ci Sport, Individual. 2008 Aston Martin DB9. 2016 4.4 SDV8 Range Rover Vogue.
    1959 Triumph Bonneville, 1969 T120R Triumph Bonneville, 1975 T160 Triumph Trident, 1990 Harley Davidson Fat Bot Grey Ghost, 2009 Triumph Bonneville 50th Anniversary model. 2014 Suzuki Gladius.

  8. #8
    Join Date
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    99 840ci Sport Indv
    When in Rome, do as the Roman's do!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
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  9. #9
    Join Date
    Jan 2014
    Location
    London, UK
    Posts
    49
    My Cars
    Bmw 840
    Quote Originally Posted by Timm View Post
    When in Rome, do as the Roman's do!
    Your not in Rome though, you are in Hampshire UK
    1998 e31 840ci Sport, Individual. 2008 Aston Martin DB9. 2016 4.4 SDV8 Range Rover Vogue.
    1959 Triumph Bonneville, 1969 T120R Triumph Bonneville, 1975 T160 Triumph Trident, 1990 Harley Davidson Fat Bot Grey Ghost, 2009 Triumph Bonneville 50th Anniversary model. 2014 Suzuki Gladius.

  10. #10
    Join Date
    Oct 2018
    Location
    San Jose
    Posts
    57
    My Cars
    1991 BMW 850i
    Quote Originally Posted by rodneyngo View Post
    Hi, I'm new to this community and I just bought my E31 today.
    The previous owner told me that i had to plug my car into an outlet so that the battery doesn't die.
    Does anyone else do this, or is it just me?
    What is the best oil for my e31? I live in california, san jose and i was wondering if 10w40 mobil 1 would be fine.

  11. #11
    Join Date
    May 2013
    Location
    Stamford, CT
    Posts
    840
    My Cars
    1991 BMW 850i
    If this is your daily driver, you probably don't need to keep it on a tender (but still good to do every once and while). I do it when I don't drive it for a while during the summer, and through most of the winter (I'm in the northeast and don't drive it in the winter). The car is kept outside under a cover, so it's kind of a pain to run an extension cord across the driveway. In the winter, I park it close to an outlet and keep it plugged in.

    For oil, I that is what I used. But it does depend on your driving. I struggle to put 500 miles on a year, so wasn't that concerned about viscosity, just wanted synthetic.
    My Cars - 1991 BMW 850i - mine for fun, 1993 Saab 900c - mine for fun, 2008 Lexus is250 - my daily driver, 2003 Dodge Durango - my wife's, 1994 Acura Legend - gave it to kid

  12. #12
    Join Date
    Sep 2018
    Location
    Lodi, NJ
    Posts
    11
    My Cars
    2012 BMW 5 Series
    I have been using the black and decker charger which is a lot cheaper than Ctek and it is working fine. There is a how to on this here.

  13. #13
    Join Date
    Jun 2008
    Location
    SF Bay Area
    Posts
    3,774
    My Cars
    Supercharged 850ci
    For battery drain, GM needs to be removed and rebuilt or RM module needs to be replaced.
    Oil is a long discussion, but I like Motul Xcess 5W40

  14. #14
    Join Date
    Feb 2010
    Location
    Hampshire UK
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    My Cars
    99 840ci Sport Indv
    I've tried quite a few oils in the V8, but have settled on this one because of the reduction in lifter noise:

    https://www.meeknet.co.uk/e31/BMW_E3...ter_Change.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  15. #15
    Join Date
    Sep 2018
    Location
    Belgium
    Posts
    307
    My Cars
    1990 850i and 1970 2800C
    i had battery drain with the oem alarm installation. When that was removed , batterys stayed OK ! I even installed now a battery switch to be safe during long parking inside . Switch is in the trunk , where the batterys - connect to the cars body. I only may not forget to not close the trunk...so i have a towel in there , to use to prevent the lock working with the trunk "nearly" closed.
    And yes, they are in parallel... so if one battery go's bad it pulls the other also down.

  16. #16
    Join Date
    Jun 2012
    Location
    Mundelein, IL
    Posts
    837
    My Cars
    840Ci/6 528iT Europa TCS
    I also use conventional oil in my 840. I use Castrol GTX 20w50. I don't drive the car in winter so I don't really car about the low end of the viscosity. I find it interesting that the owners manual also recommends 15w40 which is mostly a weight used for diesel engines. I have considered using Shell Rotella T4 15w40 but only if I can't find the Castrol 20w50. So far I have been able to find it pretty reasonably.

    I also feel pretty safe using the 20w50 on a day like today when I was red lining the motor while driving around like a "menace to society" passing anything and everything. Just sayin'.

  17. #17
    Join Date
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    Santa Barbara
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    91 Dinan860 & 91 850 6sp
    Exide Extreme L5/49/H8 batteries at, believe it or not, Home Depot for $119
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    I just picked up 4 of them.
    '91 Dinan 860 Stage III (new 6L engine)
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    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

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