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Battery tender

Discussion in 'Servicing & Maintenance' started by alain bruneau, Sep 25, 2017.

  1. alain bruneau

    alain bruneau Active Member

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    I am thinking that in about 6 weeks, the season is over in my area.
    I went to the dealer today and he try to sell me the BMW "specially made" battery tender.
    I have a charger that works at 1.5 amp and has been doing the job for my previous motorcycles
    over winters. My concern is that it is written on the box of the charger " lead acid battery".
    It is an automatic charger which when fully charge, is floating keeping the charge.
    Am I taking a chance using this charger since the RS battery is AGM ? I sure don't want to damage the electronics.
     
  2. wessie

    wessie Well-Known Member

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    AGM is lead acid - just the electrolyte is held in a fibreglass matting. These batteries need a special charger if fully discharged - they were originally designed for deep discharge use in wheelchairs etc. and need a constant current charger to overcome the inrush current. Using a set of jump leads from a fully charged battery can help to overcome this in an emergency, just to get your basic charger past the initial load test.

    If your battery is at a good charge level then there is no problem using your current (yay!) charger - just connect it direct to the battery (or offset post on the RS). Your charger will keep the battery at a decent level ready for its next use.

    I have used an Optimate 2 (a very basic charger compared to the current Optimate 4 designed to be used with a canbus socket) on all sorts of bikes with an AGM battery. AGM batteries do not discharge very quickly unless you have a load like an alarm. For a bike not used in winter, I find one top-up charge over one weekend per month is usually adequate.
     
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  3. James Bagley

    James Bagley Well-Known Member

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  4. alain bruneau

    alain bruneau Active Member

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    Thanks for this good info. I want to charge the RS once a month with the alligator clamps from the right side of the bike.
    I want to connect on the negative on the battery and on the positive on the boosting positive pole. Is that a regular procedure
    that won't create problem ? Electricity is not my strong pointé
     
  5. MrVvrroomm

    MrVvrroomm Well-Known Member

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  6. wessie

    wessie Well-Known Member

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    yes - this is the way to do it - you may find once every 2 months is adequate - check the voltage display on the dash now and then in a month. I would not bother connecting the charger unless the display is below 12V
     
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  7. Bob Ain't Stoppin'

    Bob Ain't Stoppin' Member

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    One fun way to set this up automatically is to plug the battery tender into the garage opener light. Thus, each time you open the garage door you get 5 minutes of charge. Works great!
     
  8. Mr. 36654

    Mr. 36654 Well-Known Member

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  9. alain bruneau

    alain bruneau Active Member

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    This all start with the sales guy at the BMW dealer telling me that with the BMW battery you need this intelligent charger that cost $140 that will not wreck your electronic which I realize with the help of this forum that this is all BS. I will use my charger as I did in the last numerous winters and everything should be fine. Thanks for all your feedbacks.
     
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  10. Mr. 36654

    Mr. 36654 Well-Known Member

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    There's a small shred of truth in what he told you..
     
  11. alain bruneau

    alain bruneau Active Member

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    And what would that be ?
     
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  12. Mr. 36654

    Mr. 36654 Well-Known Member

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    If you want to charge your battery thru the accessory port, you'll need the BMW (or similar) charger that functions with the CanBus controller. Or, just install a fused pigtail and use any conventional trickle charger.
     
    Last edited: Sep 27, 2017
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  13. Phinj

    Phinj Active Member

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    My dealer installed the Tender pigtail, directly to the battery, I have the wall charger.

    I don't think I will need it for charging. There are USB and assorted accessories for charging/powering accessories for $13.
    Lead acid/AGM, both acid, no difference really, Lithium Ion and others, yes.
     
  14. Beatlunch

    Beatlunch New Member

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    Question: Is that red cover in front of the battery the positive terminal - and if so, can I connect the battery tender lead there? Thanks for your input.
     
  15. Beatlunch

    Beatlunch New Member

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    problem solver - tender added - battery charged. pays to check the owner's manual...
     
  16. Stef

    Stef Active Member

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    You only need a specific charger if you want to charge via the can-bus managed connecter on the right side. If you charge directly on the battery poles, e.g. via a simple extension, any charger will do. It will however not have the BMW-icon on it, and will be cheaper. Which for some could be unacceptable.
     
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  17. runnerhiker

    runnerhiker Well-Known Member Contributor

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    I agree with MrVrom, not just buy the battery tender jr, but use the supplied pigtail directly to the battery and leave it connected all winter. Done. Don't over think it.

    I gather what you have is not a "tender" but a "charger", at least you always use the word charger. A tender is the way to go, plug it in and leave it. They are not the same thing, you can leave the tender plugged in all the time. My current RS is my third BMW with an AGM battery where I have used a standard tender with zero problems.
     
  18. alain bruneau

    alain bruneau Active Member

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    I bought an Optimate 4 dual programs Can Bus. Just plug it in the bike connector and let the charger / tender do the job.
     
  19. Stef

    Stef Active Member

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    Seemed the best option to me last year. Cost some 70 EURO. Brougth the RS without problems through the winter. :)
     
    Last edited: Oct 14, 2017
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  20. Martien

    Martien Member

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    Also use an Optimate 4, last winter for my F700GS, now the RS is hooked up. Plugged into the power outlet on the side, so easy to use.

    One thing I noticed, when the charger is on the front DRL lights up as well, is this normal? Power is completely off, of course, and alarm is switched on, so why does the light go on?
     

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