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Thread: Accessory plug & Herr Canbus

  1. #1
    Registered User northsquad's Avatar
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    Accessory plug & Herr Canbus

    I know this has been discussed ad nauseam, but what was BMW thinking when they wired the accessory plug through the Canbus electrical system? Can't charge battery anymore without jumping through hoops, my cycle gadget air pump won't run, heated clothing blows the Canbus. Someone at BMW made a decision to screw with that perfect accessory plug, and I'm trying to understand why. Exactly what can you run on the Canbus accessory plug? I'm sure even in Germany they have heard the expression if it aint broken don't fix it?
    Any thought on why they did this?
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  2. #2
    Cannonball Rider #52 darrylri's Avatar
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    Ôé¼Ôé¼Ôé¼Ôé¼. It saves them a bunch of money on expensive copper and it's cheaper to route the canbus around the bike. Also, it puts BMW in the driver's seat when you have an electrical failure.

    The accessory plug is good for radar detectors, GPSes, and maybe an electric vest.

    But basically, if you're going to do anything really custom, you're going to be going around the canbus anyway.

    Because the canbus forces owners to go around it, if there's an electrical failure, it's pretty easy to decide whether it's part of the OEM wiring or some bodge the user stuck on the bike.
    --Darryl Richman, forum liaison
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  3. #3
    Registered User northsquad's Avatar
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    Understood, and I'm all for anything that helps keep pricing down, but why couldn't they program the Canbus to allow 15AMPS to flow at the accessory plug instead of the 4-5AMPS it can handle.
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  4. #4
    Cam Killer marchyman's Avatar
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    Sigh... you too, Darryl?

    Ôé¼Ôé¼Ôé¼Ôé¼ might be the answer, but it has nothing to do with the CAN-bus. It would be due to the design/implementation of the ZFE.

    The accessory plug is NOT wired through the CAN-bus. It is wired directly to the ZFE. Lights, switches, battery, etc., are not connected to the the CAN-bus. The ONLY items on the CAN-bus are the ZFE, ABS controller, BMS-K, Instrument cluster, and the alarm.

    Quote Originally Posted by apples
    Understood, and I'm all for anything that helps keep pricing down, but why couldn't they program the Canbus to allow 15AMPS to flow at the accessory plug instead of the 4-5AMPS it can handle.
    You mean "why didn't BMW design/program the ZFE to handle more current." I don't know the answer. Perhaps they ran out of room (more current needs more chip real estate). Perhaps the initial requirements were wrong.

    It's easy enough to wire the outlet directly to the battery. You could even wire it through a relay triggered by the original wiring if you want the same key-on/key-off activation. Or add a second connection that goes to the battery. Lots of choices.

    // marc

  5. #5
    Cannonball Rider #52 darrylri's Avatar
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    Sorry, I guess so, Marco. I didn't realize that the unfused links to all of the outlying units weren't considered a part of the bus.
    --Darryl Richman, forum liaison
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  6. #6
    Once there was a Tavern PAULBACH's Avatar
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    There is a spot in the fairing where an accessory plug can be placed. The plastic has a round spot where drilling will be easy. Just put your accessory plug there and run a fused outlet to the battery.

    If you wish to be elegant - make the accessory outlet easy to disconnect. Whitehorse press sells the part as do many other vendors in Owner News.

  7. #7
    Honey Badger Semper_Fi's Avatar
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    I have done 4 things to the bike - which to me have greatly improved its usability.

    1- Front ACC socket put in a disconnect so I can take off the panel easier

    2 - Rear socket - wired directly to Centech fuse panel, selected a 20A fuse can run compressor without ZFE module shutting me down

    3 - yesterday cut off the BMW connector on fancy (expensive) charger and added hook up for direct to battery connection - sweet - no more key dance and the AGM battery is happy

    4 - Have gerbings mounted directly to Centech panel on 15 amp fuse - no issues for getting warm.

    As posted above anythig you want added to the bike you will be going around the in place systems anyway.

    CANBUS - think of as wiring harness

    ZFE is the computer that controls things via the wire harness

    Marc/Darryl - great points in ensuring clear disctinction between the two systems
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  8. #8
    Rally Rat
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    So let me get this straight, if I want to use my heated vest/gloves on the K1200S, I need to add wiring so I don't burn something up? Makes sense...... I'm not a vehicle tech, but from what I am understanding, I can use the circuit that now powers to factory outlet as a key switched power source to energize a 12v relay, and bring hot (fused) and ground legs off the battery to now energize the outlet.

    Is there any advantage to using a fuse block, other than the obvious multiple lines out?

    Thanks!

  9. #9
    Cannonball Rider #52 darrylri's Avatar
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    Quote Originally Posted by john1691 View Post
    So let me get this straight, if I want to use my heated vest/gloves on the K1200S, I need to add wiring so I don't burn something up? Makes sense......
    No, you have it wrong. You need to add wiring and a socket so that you can use your vest. If you plug your vest into the existing socket, the ZFE will turn off the juice to it.

    I'm not a vehicle tech, but from what I am understanding, I can use the circuit that now powers to factory outlet as a key switched power source to energize a 12v relay, and bring hot (fused) and ground legs off the battery to now energize the outlet.

    Is there any advantage to using a fuse block, other than the obvious multiple lines out?

    Thanks!
    Yes, there is another advantage -- you don't end up with lots of wires connected to the battery. It's annoying to take apart and put together, and can lead to high resistance and corrosion build up at the battery terminals. Having a separate fuse block gets around these problems.
    --Darryl Richman, forum liaison
    http://darryl.crafty-fox.com

  10. #10
    Rally Rat
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    Thanks Darryl!

  11. #11
    Registered User northsquad's Avatar
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    Do you need to remove the left side tupperware on an 08GT or can the wires be fished up to the battery behind the panel?
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