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Thread: Jump Starting with car Battery?

  1. #1
    JohnWC
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    Jump Starting with car Battery?

    My 96 R1100RT seems to always have a battery leak down problem. A few days off the charger and it barely cranks. A few weeks ago it get really low and it would hardly start, but did. Then, of course, the ABS lights showed a default. Normally after riding a few miles I can cancel them by restarting, but not this time. I had the Odyssey 680 battery supposedly load tested and it passed. 12.8 or so volts. It's about three years old. Took the starter off and had it tested, and it met the specs. Just put it back together and tried it, and again, pretty slow cranking, and the ABS lights flashing. I'm beginning to wonder if the battery is the problem after all. I thought I might try jumping it with my car battery to see if it cranks better, and if it then doesn't have an ABS problem, before I go buy another battery. If I do get another battery it will be back to a regular lead acid, which I believe GSaddict says is better for these models. Any thoughts on if I will burn up the electrical system on the bike with the larger car battery?

  2. #2
    Provided you connect the cables correctly and are using a 12 volt battery jump starting with a car battery will not harm the bike. The amount of current that will flow will depend on the draw of the bike's components and not on the capacity of the battery.
    Paul Glaves - "Big Bend", Texas U.S.A
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  3. #3
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    I have jumped a bike with a car- no problem.

    https://forums.bmwmoa.org/showthread...died-yesterday

    I have found when a battery is left in the system, itís difficult to get to the root of the problem. A way to get closer to the problem, with the battery in-line, is to measure the available voltage while cranking the engine.
    If there is a severe draw-down, the battery is suspect.
    If the battery was removed from the system and run off the car......and ran fine, it would be another way to test the starting.
    OM
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  4. #4
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    As Paul says the bike will pull the amount of current it needs from the car battery and not more BUT you should not boost from a car battery in a running vehicle. This is because the regulator in the bike (a crude shunt type in many cases) may attempt to regulate down the boosting vehicle's charging voltage. A shunt regulator will handle the full current output of the bike's alternator but not necessarily that of the boosting vehicle.

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  5. #5
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    No problem to boost from a car but MAKE SURE the car isn't running.

  6. #6
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Never had trouble jumping with running or not running
    I would try to avoid the start cycle of the donor vehicle during the attempted jump. Once the donor vehicle is running, unless there is some problem with the donor vehicle, itís stable.
    I have found that a ďjumpĒ is no problem with a stable power source.
    OM
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  7. #7
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by RadioFlyer View Post
    As Paul says the bike will pull the amount of current it needs from the car battery and not more BUT you should not boost from a car battery in a running vehicle. This is because the regulator in the bike (a crude shunt type in many cases) may attempt to regulate down the boosting vehicle's charging voltage. A shunt regulator will handle the full current output of the bike's alternator but not necessarily that of the boosting vehicle.

    Sent from my SM-T813 using Tapatalk
    Oilheads & Hexheads do not have shunt type regulators. You can safely jump with an external source.

    Waterheads on the other hand, do. It would not be wise to jump from a running vehicle, especially if revving high.
    Last edited by GSAddict; 11-12-2019 at 01:42 PM.
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  8. #8
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    I will make sure the car is no running other wise you have a good chance of burning out the ECM. I seen it happen more the once. You are better of giving the battery a full charge as with a low battery you are putting more strain on the electrial system.

  9. #9
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    Quote Originally Posted by GSAddict View Post
    Oilheads & Hexheads do not have shunt type regulators. You can safely jump with an external source.

    Waterheads on the other hand, do. It would not be wise to jump from a running vehicle, especially if revving high.
    The F bikes also have shunt regulators. I don't know about the S or K bikes.

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  10. #10
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by RadioFlyer View Post
    The F bikes also have shunt regulators. I don't know about the S or K bikes.

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    I was responding to a boxer thread.
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  11. #11
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    Quote Originally Posted by GSAddict View Post
    I was responding to a boxer thread.
    I was just trying to demonstrate thar the earlier boxers are the exception. Shunt type regulators are very common on bikes.

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  12. #12
    Quote Originally Posted by RadioFlyer View Post
    I was just trying to demonstrate thar the earlier boxers are the exception. Shunt type regulators are very common on bikes.

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    Of course, because they're cheaper.
    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://web.bigbend.net/~glaves/

  13. #13
    JohnWC
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    I'm still assembling the wires needed to jump start the bike from a car battery. But before I did that I wanted to check the voltage draw from the Odyssey battery alone. This is it:

    1) Battery voltage reading after being on charger= 13.3 v
    2) With the key switch turned on (headlights, dash lights) =11.8 v
    3) Cranking the engine= 8.2 v
    4) With engine started and running= 14.1 v

    Admittedly, this is when the temperature is a 22 degrees. But as I stated before, this was causing problems at somewhat higher temperatures also. I would guess that 8.2 volts is well below what it takes to trigger the abs fault light. Anyone know what that threshold is? So, a) even though the starter read an 80 amp, and roughly10 volt draw off the bike, on it it seems to be pulling a lot more, so maybe it is actually broken. Or, b) like my 1972 Ferguson backhoe with no glow plugs, these bikes shouldn't be started and run below about 50 degrees. Any thoughts?

  14. #14
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    I would say itís time for a new battery.
    OM
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  15. #15
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by jconway607 View Post
    I'm still assembling the wires needed to jump start the bike from a car battery. But before I did that I wanted to check the voltage draw from the Odyssey battery alone. This is it:

    1) Battery voltage reading after being on charger= 13.3 v
    2) With the key switch turned on (headlights, dash lights) =11.8 v
    3) Cranking the engine= 8.2 v
    4) With engine started and running= 14.1 v

    Admittedly, this is when the temperature is a 22 degrees. But as I stated before, this was causing problems at somewhat higher temperatures also. I would guess that 8.2 volts is well below what it takes to trigger the abs fault light. Anyone know what that threshold is? So, a) even though the starter read an 80 amp, and roughly10 volt draw off the bike, on it it seems to be pulling a lot more, so maybe it is actually broken. Or, b) like my 1972 Ferguson backhoe with no glow plugs, these bikes shouldn't be started and run below about 50 degrees. Any thoughts?
    A properly charged Odyssey in good condition will crank at over 11v.
    The motronic does function correctly at 8.2v
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