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Thread: jumper cable idea question

  1. #1
    Registered User f14rio's Avatar
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    jumper cable idea question

    not sure how many amps it takes to start an r1200r or similar machine. anyway, i'm, thinking if you have a female cigarate lighter type plug connected directly to your battery and then fabricate a cable with two male lighter type plugs, you could plug one end into a buddy's car lighter plug and then jump start. my car has two lighter plugs one is probably fuzed i think the other goes dierctly to the battery. the advantage of this might be its easier to use and maybe it takes up less space than conventional cables.

    i'm on the second battery (6kmi) with my 2010 bike and the battery monitor i use tells me its down to 31 percent service life remaining. not sure why the bike seems to be so hard on batteries as the bike is usually connected to a smart charger when in the garage.

    any feedback appreciated, even if its just to tell me its a stupid idea.

    thx,
    ed
    "Enemy fighters at 2 o'clock!...Roger, What should i do until then?"

    2010 r1200r, 2009 harley crossbones, 2008 triumph/sidecar, 1970 norton commando 750

  2. #2
    Day Dreaming ... happy wanderer's Avatar
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    This should probably be posted in the hexhead section but anyway I can tell you this is a very bad idea on any BMW bike. The wiring between the accessory plugs and the battery is not heavy enough to carry the amperage required to "boost" a bike and you will fry the wiring. Charging a battery this way is fine but not jump starting. Way too much current needed!

    Jump starting requires the two batteries to be connected directly together with suitable gauge wiring. The best way to get a low battery up is to connect it to a good one and wait for the good one to discharge into the bad one. Leave it sit for about 15 minutes, disconnect the donor bike and try starting. Often this does the trick.

    If not, re connect the donor battery but DO NOT run the donor bike. This is the best way there is to fry the donor bikes alternator and is a very common mistake.
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  3. #3
    Outlander Omega Man's Avatar
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    Actually it's a good idea Ed as these bikes are so reliant on battery voltage. The idea you describe, IMO, will work under a couple of conditions. You will melt or cause smaller gauge wire with much of a jump to glow red hot. When you jump a car to car- the cables are large diameter. To do it with the smaller dia. cables, let the "donor" charge the run-down battery to get some life into it- perhaps 10 minutes- and don't crank for too long.
    If the battery is stone dead- completely gone bad, it will act as a voltage sink and not allow a start, it will have to be taken out of circuit.
    IIRC the computer has to "see" 9.2 volts or it won't work. Sometimes a weak battery that would run the bike- will not start it as the start voltage draws down the voltage below the required computer voltage. OM
    "Well they say.. time loves a hero but only time will tell.. If he's real, he's a legend from heaven If he ain't he was sent here from hell" Lowell George
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    Registered User lmo1131's Avatar
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    I can tell you this is a very bad idea on any BMW bike.
    I'd say it's pretty bad idea on anything!

    The starter motor on our airheads is rated at roughly .7HP and draws something like 320 amps (cold starting). Your 1200 would be similar, if not higher, I suspect.

    That is a LOT of amperage to expect a 14ga wire to survive.

    If you want a real-world, eye-opening, demonstration, rig up your envisioned set up (a battery, 24-36" of 14ga wire, a starter motor) OFF OF THE BIKE (and well away from the bike), and hit the switch.
    "It is what you discover, after you know it all, that counts." _ John Wooden

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  5. #5
    Lucky motorradmike's Avatar
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    I've seen cig lighter to cig lighter "jumper" cables advertised so although it is a stupid idea, you can take comfort in the fact that it isn't really yours.

    OK idea for charging from a buddies working vehicle in a pinch, but no good for jumping.
    If you forget to disconnect before attempting to start, there would probably be trouble.
    Mike Marr
    1978 Yamaha XS750 (Needs rings), 1996 BMW R1100RS, 2004 Honda CRF230F

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    Those "accessory plug" (cigar lighter) jumpers were intended ONLY as a sort of hillbilly battery charger. You plug them in, start the donor vehicle and go for coffee. The charging system of the donor vehicle would then hopefully charge the dead battery. After 20 min or so, you unplug the jumper system and the dead battery should have enough life to start the engine. If that doesn't work, the dead battry is probably NG; go for the large gage jumper cables and do it the normal way.

  7. #7
    Cam Killer marchyman's Avatar
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    Quote Originally Posted by Happy Wanderer View Post
    If not, re connect the donor battery but DO NOT run the donor bike. This is the best way there is to fry the donor bikes alternator and is a very common mistake.
    The "do not run the donor bike" rule goes back a ways and may not be appropriate. The issue used to be with simplistic zener diode voltage regulators. If the regulator on the bike being jumped had a higher voltage than the regulator on the donor bike the regulator on the donor bike could fry. With a modern voltage regulator that is not an issue. The owners manual for my R1200GS, for example, says:

    ÔÇó Start the engine of the donor vehicle and allow it to run for the duration of the jump-start procedure

    I found out the hard way why they recommend this: my bike was left without enough juice to start or bump start after helping a friend with a dead battery.

  8. #8
    Small road corner junkie pffog's Avatar
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    Quote Originally Posted by Happy Wanderer View Post
    .................

    If not, re connect the donor battery but DO NOT run the donor bike. This is the best way there is to fry the donor bikes alternator and is a very common mistake.
    Sorry, this is an old wives tail, no way you will "fry" ahealthy alternator jumping another vehicle.
    2010 F800GS Full Ohlins package, '04 R1100S Replika
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  9. #9
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    Well, in a pinch I have hooked up older BMW through pigtails or sockets fused at 15A and used the donor car/bike as a charger. It works OK if the receiver is just weak and not sulfated/shorted/permanently dead.
    But the idea that one can pass starter current draw on any wires that light is delusional- no chance.
    There is actually a BMW factory jumper part to allow bike sockets on older models to receive current but it also is no where near heavy enough to carry starter draw...

  10. #10
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by pffog View Post
    Sorry, this is an old wives tail, no way you will "fry" ahealthy alternator jumping another vehicle.
    Not a good idea

    The diodes in any alternator are not rated or designed for cranking currents.
    While leaving the alternator idling probably won't damage them, revving the engine may.
    Some Ford alternators are very susceptible to damage. An associate of mine had a starter/alternator repair business and shared that with me.

    Why risk a problem? If the donor battery is healthy, there will be no problem restarting the vehicle.
    '
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  11. #11
    Pepperfool GSAddict's Avatar
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    You will be blowing fuses or melting wires if you try to crank the bike.
    If you allow the donor battery to charge the bike for 15 min and then remove the 'jumper' the bike will likely start.

    Quote Originally Posted by f14rio View Post
    not sure how many amps it takes to start an r1200r or similar machine. anyway, i'm, thinking if you have a female cigarate lighter type plug connected directly to your battery and then fabricate a cable with two male lighter type plugs, you could plug one end into a buddy's car lighter plug and then jump start. my car has two lighter plugs one is probably fuzed i think the other goes dierctly to the battery. the advantage of this might be its easier to use and maybe it takes up less space than conventional cables.

    i'm on the second battery (6kmi) with my 2010 bike and the battery monitor i use tells me its down to 31 percent service life remaining. not sure why the bike seems to be so hard on batteries as the bike is usually connected to a smart charger when in the garage.

    any feedback appreciated, even if its just to tell me its a stupid idea.

    thx,
    ed
    '
    Ufda happens..........

    It's all about the details.

  12. #12
    Small road corner junkie pffog's Avatar
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    Quote Originally Posted by GSAddict View Post
    Not a good idea

    The diodes in any alternator are not rated or designed for cranking currents. ....................
    This is where I have a problem with the premise, the alternator will not produce anymore current that its design allows, a heavy draw cannot "suck" more current than it is rated for. It just can't happen. The diodes can tolerate what the Alternator is capable of producing, and that is all that they will ever get.

    And if it were true, what would be the difference between that, and if it was the bike being jumped, when the cables were removed and the dead battery was calling for all the current the alternator can out out?
    2010 F800GS Full Ohlins package, '04 R1100S Replika
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  13. #13
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by pffog View Post
    This is where I have a problem with the premise, the alternator will not produce anymore current that its design allows, a heavy draw cannot "suck" more current than it is rated for. It just can't happen. The diodes can tolerate what the Alternator is capable of producing, and that is all that they will ever get.

    And if it were true, what would be the difference between that, and if it was the bike being jumped, when the cables were removed and the dead battery was calling for all the current the alternator can out out?
    Its the instantaneous surge current that can short the diodes. Most alternators can handle it, some can't.
    Why take a risk?
    '
    Ufda happens..........

    It's all about the details.

  14. #14
    Debbie's Servant Lee's Avatar
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    Quote Originally Posted by f14rio View Post
    the advantage of this might be its easier to use and maybe it takes up less space than conventional cables.
    I carry a set of motorcycle jumper cables and they're small enough to fit under the rear trim panel along the back on my K1300S seat.
    They're similar to these.

    http://www.motorcycle-superstore.com...er-Cables.aspx

    Lee 2011 K1300S
    MOA # 30878
    Past BMW Bikes, 2003 K1200RS, 1991 K75S, 1987 K75T, 1984 R100RT

  15. #15
    Still plays with trains. tinytrains's Avatar
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    I still say the donor vehicle should not be running when you hit the starter on the dead engine. Some alternators may have short circuit protection, but unless you know for certain, the donor engine should be off. Why risk your alternator for nothing. They are expensive. You can run the donor engine to charge the other battery for a while if needed.
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