From: pooder@msus1.msus.edu
Newsgroups: rec.motorcycles
Subject: Re: car-to-bike jump start
Date: 28 Sep 92 23:36:31 -0600
Organization: Minnesota State University System

In article <20875@drutx.ATT.COM>, car377@druhi.ATT.COM (RogersC) writes:
> In article <1992Sep27.224050.1303@msus1.msus.edu>, pooder@msus1.msus.edu writes:
>> In article <1992Sep25.134037.457@sbctri.sbc.com>, asper@sbctri.sbc.com (Alan E. Asper) writes:
>> > I got on the bike this morning and the battery was dead. Since the
>> > bike's battery is 12 volts, and my car's battery is 12 volts, can I
>> > use the car battery to jump it? The bike owner's manual only says that
>> > a 12 volt booster battery should be used. No mention of amperage, etc.
>> 
>> Done it many times on many bikes.  
> 
> This sort of argument is also used frequently as a reason why a condom 
> or some other form of birth control protection isn't really necessary.  
> "Hundreds and hundreds of times and *nothing* happened!"
> 
>> 12v. is 12v. (or whatever the voltage
>> really is).  
> 
> Yeah, and 200 amps is 200 amps.  Dump 200 amps into a shorted
> motorcycle starting motor (or jammed, approximately the same thing as 
> shorted), shorted wiring harness, or shorted battery and many really 
> *interesting* and *sparkly* things will happen to the bike. And to *you*, 
> if you're standing close enough.  Batteries can and do explode under such
> conditions.  Wiring harnesses melt and/or ignite and burn.  There is
> no fuse in the primary starter motor power circuit.  
> 
> Motorcycle batteries are typically 12 or 14 Amp-hour batteries.   
> They should be charged at no more than 1/10 that rating for reasons
> of safety and battery life.  You may get away with jumping a bike 
> from a car battery, but if you don't, the results can be pretty messy.
> 
>> BUT, leave the car engine OFF.  The car alternator or generator
>> output may screw things up.
> 
> It increases the applied voltage (and therefore the current supplied) as
> well as adding its output to the car battery output,  a bad thing if
> you have a short.  If you must jump a bike battery with a car
> battery, shut off the engine and turn the car high-beam headlights 
> and accessories on to reduce the amount of current available to the 
> bike, just in case you *do* have a short or in case you develop one 
> while attempting to start the bike.  Take all the safety precautions 
> you would if you expected the battery to explode when you push the
> starter button.
> 
> 

He asked about whether or not it can be done, not about under what
cirumstances.  Any time jump starting is appropriate, using a car battery
as a source of electrons is OK.  Your motorcycle won't draw any more 
current from a car battery than it would from its own battery *if it were
working right*.  BUT, there are circumstances under which jump starting
is NOT OK.  In fact, the only time I'd recommend it is when you've simply
run the battery down and it needs help getting the bike going again.  A
jump start isn't for charging the bike's battery.  Let the charging 
circuit of the motorcycle, or an appropriate charger, do that.  And, of
course, observe all the safety precautions you would when jumpstarting
any other vehicle.

Sheesh, do we have to outline all the things that could go wrong and 
deliver a safety lecture every time we answer a simple question?  Will
I be held liable if someone reads this newsgroup and then is injured in
any way any time in the future?  Should I be more paranoid than I already
am?

Pood-a-roonie