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Thread: New Battery Time - Options have changed

  1. #1
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    Dinan 8

    New Battery Time - Options have changed

    So its seems that the Dinan 8's battery or probably both batteries need replacing. I originally installed a set of Interstate MTP-93 monsters back in 2010 but they are no longer being manufactured, so I need to use something else now.

    I know my decisions come down to 1 or 2 batteries... lead acid or AGM/sealed. I believe that H6's (750CCA) and H8's (900CCA) should both fit correctly.

    What is everyone doing in 2018? Best place to purchase? Costco, Walmart, Advance Auto, Autozone, etc?

    Thanks,

    -JRW
    Dinan 8 Registry - Dinan8.com

    Glacier Blue 1991 Dinan 8 | Chasis CB73392 | 1 of 50 Produced
    Built for PGA Pro Mark Calcavecchia
    Twin Turbo 5.0L V12 w/ Air-to-Air Intercoolers
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    Complete Information and Pictures

  2. #2
    Join Date
    Jan 2016
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    Ca
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    2001 525it
    We installed 2 agms in a Customers car along with 2 battery tenders because the car sits so much

  3. #3
    Join Date
    Sep 2011
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    Vancouver Canada
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    91 850i 91325iC 01 330Ci
    Just checking the Interstate website, they show for a 1991 850i to use their MTP-93/T8 battery. These fit a large range of newer cars, so I am sure you could find this battery available from a local Interstate dealer. / Henry

  4. #4
    Join Date
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    1993 BMW 850Ci
    The interstate option still fits... but the vent hole has been moved from center (like the OEM batteries) to the end. You will need the adapters (that are sometimes supplied with the battery) to get a connection to the stock ventilation tubes.

    Mark in mid-MO
    1993 BMW 850Ci 6-speed
    2011 Cadi CTS coupe 6-speed

  5. #5
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    1995 840Ci, 2013 X5

  6. #6
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    Quote Originally Posted by jclausen View Post
    We installed 2 agms in a Customers car along with 2 battery tenders because the car sits so much
    Maybe your post glossed over something, but it sounds like you just put two battery tenders on the same circuit, as the batteries are wired in parallel. So neither will work properly.




  7. #7
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    Quote Originally Posted by jclausen View Post
    We installed 2 agms in a Customers car along with 2 battery tenders because the car sits so much
    I guess you can hook up 2 chargers to the 2 batteries. I always separate the batteries by undoing the negative cable but I don't believe that is necessary.

    - - - Updated - - -

    Quote Originally Posted by ltbrett View Post
    Maybe your post glossed over something, but it sounds like you just put two battery tenders on the same circuit, as the batteries are wired in parallel. So neither will work properly.


    But the chargers are working in parallel as well. They are both supplying the same voltage. They just supply more amps.

  8. #8
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    Quote Originally Posted by llcarlos View Post
    I guess you can hook up 2 chargers to the 2 batteries. I always separate the batteries by undoing the negative cable but I don't believe that is necessary.

    - - - Updated - - -



    But the chargers are working in parallel as well. They are both supplying the same voltage. They just supply more amps.
    Battery tenders are voltage sensing. With two in parallel, when one is putting out charging voltage, the other senses an overvoltage and stops charging. At best, only 1 battery tender will be working. At worst, their voltage sensing logic will get confused so neither will charge.

  9. #9
    Join Date
    Oct 2008
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    E31 E38 E65
    AGM only..Lead Acid is trash

    I'm currently running 3 Odyssey 31M-PC2150 Batteries..
    *~*Yamaguchi-gumi Syndicate Member #59,005 *~*
    [ Bippu Couture ] ( D_G ) [ FALKEN Tires]

  10. #10
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    1993 850ci 2001 M5
    Single H8 AGM - never look back
    Regards,

    Brian
    Cave Creek, AZ

  11. #11
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    Dinan 8
    Thanks for all of the replies. I ended up going with a single H8 AGM battery from Advance Auto. With a 25% coupon and the core, it was about $150. Not too bad. I might get a second one at some point. She started right up afterwards.

    -JRW
    Dinan 8 Registry - Dinan8.com

    Glacier Blue 1991 Dinan 8 | Chasis CB73392 | 1 of 50 Produced
    Built for PGA Pro Mark Calcavecchia
    Twin Turbo 5.0L V12 w/ Air-to-Air Intercoolers
    525hp - 589ft/lbs tq
    Complete Information and Pictures

  12. #12
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    Quote Originally Posted by bdiefAZ View Post
    Single H8 AGM - never look back
    This is next on my list. The empty battery spot will become audio equipment storage.
    Desecrator of all things Sacred

  13. #13
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    1993 850ci 2001 M5
    I will be using my empty battery chamber for road trip tool storage, 15 inch tool bags work great for this. The extra trunk space will be welcome on long trips.

    Remember - disconnect the battery cross cable during this conversion, it is a necessary step. This cable can be confirmed with a multi-meter.
    Regards,

    Brian
    Cave Creek, AZ

  14. #14
    Join Date
    Nov 2015
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    E31 850iA 1992
    one battery is enough.
    I have only on the right side a 85ah battery. (the +cable from the right to the left in on the right side removed from the +terminal)
    From the trunk to the starter there is only one +calbe. So its equal if there are one or two battereys on this cable.

    The E32 M70 is delivered with 75ah or 85ah. So, this must also be fine for the E31.

    The two batterys have a problem. They are every time loading each other.

    If one has 12,31V and the other 12,30V - there is a current.
    If one has 12,305V an the other has 12,299 - there is a current.
    ..and so on.

    The E31 was equipted with 2*65Ah. The compete capcity is not 130ah.

    If someone will goes down to one battery, look to the battery place - there are positosn to handle 3 lengths of battery.

  15. #15
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    95 BMW 850
    The 65ah AGMs were starting to fail too often and the car wouldn't start with only the driver side battery hooked up so I switched them around and I left the positive cable on the left battery but took the short negative cable off completely. Now the car can sit for 2 weeks and still start. The charger shows both batteries are fully charged. I'm not sure of the point of dragging a spare battery around but you never know.

  16. #16
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    not enough
    https://www.bimmerforums.com/forum/s...ght=battery+h8

    both 8ers have H8's from Wally world. Cheap, readily available and reliable. No complaints here.
    CB42366 - 1991 850i 6-speed. Brilliantrot & Black Nappa Leather
    CD00144 - 1994 850CSi. Hellrot & Black Nappa Leather


    My other projects:
    Supercharged Tbirds, V8 Tbirds, V8 Mustang Convertible, Audi V8 Quattro & Audi S8

  17. #17
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    After 12 years my Yellow Top Optimas are dead, They're so bad when i open the trunk the window drops every 20 seconds,) New Optimas in order this weekend.

  18. #18
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    Quote Originally Posted by DriftGirl View Post
    AGM only..Lead Acid is trash
    Hate to tell you, but AGM is still lead-acid technology

    That said, I'm a single H8 AGM convert myself. I'd only have two batteries in an E31 if it was a concours grade show car and had to be 100% OEM original. I think there are way too many drawbacks to two batteries in these cars, which typically only get driven sporadically.

    - - - Updated - - -

    Quote Originally Posted by E31 850i View Post
    If someone will goes down to one battery, look to the battery place - there are positosn to handle 3 lengths of battery.
    Note that not all 8 series have the threaded nut insert in all 3 positions. My 840 only has one. The holes are there for the inserts, but no threaded nut.

  19. #19
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    840Ci/6 528iT Europa TCS
    I have been with a single AGM for a couple of years now and have never looked backed back. No vent tube and 20 less lbs.

  20. #20
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    Out of curiosity, those that have converted to single battery, how many of you have removed the connecting cable for the driver's side battery?
    Regards,

    Brian
    Cave Creek, AZ

  21. #21
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    Quote Originally Posted by bdiefAZ View Post
    Out of curiosity, those that have converted to single battery, how many of you have removed the connecting cable for the driver's side battery?
    Just left it in, bagged both ends with latex gloves (to give the next guy pause) and tucked both ends up above the wheel wells. Did not see any reason to remove it altogether.
    2000 E38 740i Sport (Oxford Green II) FOR SALE NOW
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  22. #22
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    bmw 850i M-tech
    For cars like E31, which are often driven irregularly, its better to use only one battery. One good 85-100Ah agm battery is enough for everything and gets charged to it's full capacity more often than two batteries, which are also often uneven. I don't know why bmw used two batteries but it's completely pointless.
    Last edited by mikae31; 09-02-2018 at 06:52 AM.

  23. #23
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    I removed the cable to the other side. I also added a subwoofer and mono block amp. The amp is wired directly to the single battery and still no issues.
    In winter, or anytime the car is not used for a week or 10 days, I connect a little float charger/maintainer under the hood. I usually leave it for a day or two every other weekend and I always have a charge to start the car.

  24. #24
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    BTW like Rick, I ended up removing the L-R jumper cable from mine a few weekends ago too (although I hadn't originally planned to). I got neck deep in a really crappy phone removal, so I was in the 'remove all unnecessary crap' mode!

    This is just some of the wires that came out along with the phone.
    Last edited by Chamberlin; 10-02-2018 at 10:16 PM.
    2000 E38 740i Sport (Oxford Green II) FOR SALE NOW
    1995 E31 840Ci Canadian (Oxford Green I)
    2004 E46 330Ci 6spd (Oxford Green II)
    2002 E39 525i Sport 5spd (Oxford Green II) FOR SALE NOW
    2001 E53 X5 3.0i Sport (Oxford Green II) NOT FOR SALE YET
    1995 E31 840Ci (Oxford Green Metallic I) FOR SALE SOON
    2001 E39 530i Sport 5spd (Aspen Silver)
    2001 E38 740i Sport (Sahara Beige)
    2000 E38 740i Sport Canadian (Sahara Beige)
    1994 E31 840Ci 6spd (AVUS Blue)
    2000 E38 740i Sport (Titanium Silver)
    2007 E91 328iT 6spd (Deep Green)
    2000 E36/7 M Roadster (Oxford Green II)
    1999 E36 M3 Coupe 5spd (Fern Green Metallic)
    2000 E36/8 M Coupe (Oxford Green II) FOR SALE SOON
    2001 E36/8 Z3 3.0i Coupe 5spd (Oxford Green II)
    2002 E36/7 M Roadster (Oxford Green II)
    2007 E63 M6 SMG (Silver Grey)
    2006 E86 M Coupe (Sepang Bronze)
    2009 E92 M3 DCT (Space Grey)
    2008 E92 M3 6spd (Melbourne Red)
    1997 E31 850Ci (Jet Black)




  25. #25
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    That's a lot of copper. Your car should be even faster now with all that extra weight removed. It was fairly easy to do and I bet now it looks even cleaner. I cut a piece of wood to place over the battery tray on the LHS so I would have a flat surface to store stuff.

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