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Thread: electrical capacity of an r1150rt

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    electrical capacity of an r1150rt

    I want to add about 350 watts of heated gear and lights. Will my 700 watt alternator power both the bike and these accessories? How do I measure the wattage or amps currently required to power the stock bike's electrical load to determine how much I can add?

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    Quote Originally Posted by jsalmon View Post
    I want to add about 350 watts of heated gear and lights. Will my 700 watt alternator power both the bike and these accessories? How do I measure the wattage or amps currently required to power the stock bike's electrical load to determine how much I can add?
    Don't know about your RT, but for my F800 I found a great graphic/chart on f800riders.com that showed exactly how much of the electrical power at specific rpm level goes toward each function (engine running, heated grips, high beams, etc.); then I went to Gerbing's website for a chart of precisely how much power is used by the jacket liner and the gloves. I now have a chart that tells me that I must run at 3+K rpm to produce enough electrical power for all my accessories (the abovementioned heated gear, plus my aux LED driving lights). Therefore, I now know to drive around town--in the winter--in a lower gear in order to run the engine at 3+K rpm.

    You can undoubtedly find similar info about your RT, perhaps somewhere on this very forum. Someone will quickly come along with the precise answer for you. Good luck.
    Royce
    On the coast of Kansas
    2012 F800ST

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    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by jsalmon View Post
    I want to add about 350 watts of heated gear and lights. Will my 700 watt alternator power both the bike and these accessories? How do I measure the wattage or amps currently required to power the stock bike's electrical load to determine how much I can add?
    Yes - mine does. Caveat - I don't do a lot of stop and go riding with full lights and heated gear but highway riding works fine.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

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    Lucky motorradmike's Avatar
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    Quote Originally Posted by jsalmon View Post
    I want to add about 350 watts of heated gear and lights. Will my 700 watt alternator power both the bike and these accessories? How do I measure the wattage or amps currently required to power the stock bike's electrical load to determine how much I can add?
    If you really want to know how much current your bike draws you can do it this way:

    Disconnect the field wire from the alternator.
    Find someone who has a clamp-on ammeter that measures DC.
    Measure the current supplied by the battery.

    I did that and found my bike draws 10A with the low beam on.
    My alternator is marked 50A so I have 40 left for accessories.
    Mike Marr
    1978 Yamaha XS750 (Needs rings), 1996 BMW R1100RS, 2004 Honda CRF230F

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    Quote Originally Posted by motorradmike View Post
    If you really want to know how much current your bike draws you can do it this way:

    Disconnect the field wire from the alternator.
    Find someone who has a clamp-on ammeter that measures DC.
    Measure the current supplied by the battery.

    I did that and found my bike draws 10A with the low beam on.
    My alternator is marked 50A so I have 40 left for accessories.
    motorradmike

    instead of disconnecting the alternator wire, could I clamp the battery lead with the bike running to measure the current from the battery?

  6. #6
    Lucky motorradmike's Avatar
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    Quote Originally Posted by jsalmon View Post
    motorradmike

    instead of disconnecting the alternator wire, could I clamp the battery lead with the bike running to measure the current from the battery?
    If you don't disable the alternator, you will be measuring current from only one of two sources. I suppose you could use 2 ammeters and measure current from both.

    Perhaps I shouldn't have said anything, Paul has already done it and posted results which completely answer your first question.

    The more power you require for accessories, the more vigilant you will have to be to be certain you aren't draining the battery.
    Small problem close to home but a really big problem in the outback.
    Mike Marr
    1978 Yamaha XS750 (Needs rings), 1996 BMW R1100RS, 2004 Honda CRF230F

  7. #7
    Day Dreaming ... happy wanderer's Avatar
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    A very simple way to avoid low battery trouble is to install an inexpensive digital panel meter. This allows you to keep an eye on state of charge.

    I have a small quartz display connected directly to the battery that works quite well.
    If you google "digital 3 digit waterproof panel meter" there are thousands of them out there.


    2013-05-11 12.20.57.jpg
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  8. #8
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    There won't be any problem with what you want to do but you can probably do it with less juice. Your total sounds like you plan 4 halogen lights plus heated gear or about 220W for lights which is not really necessary. As little as 70W total for 4 well chosen LEDs plus a 35W HID conversion (saves a little) is plenty. You can go bigger but its not really needed.

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