Myth busted: Jump-starting your bike from a car battery

[Black Ice]

This is news?  

[ragtoplvr]

Here is my spin, and I work in automotive electrical reman

If you have a serviceable battery,  make sure it has the correct amount of water.  Not a big concern now, but if winter never jump a frozen battery.  It is probably toast anyway.

There is a alternator thing called a load dump.  It occurs when a heavy load is removed, it can be over 100 volts.

Normally a good battery will absorb enough of it.  When your bike battery is discharged it can not absorb it.

Some but not all alternators are protected against load dump.  Some BMW have a protection device on the alternator.  It can be fried by the bigger car alternator.

Some motorcycle regulators will attempt to dissipate excess voltage, usually to their demise.  I know of no list telling which kind you have.

A fully charged lead acid battery will partially charge a discharged lead acid battery, engine does not need to be running

A part way charged battery can absorb spikes and load dump much better than a dead one

A discharged battery can not protect against reverse connection, so OBSERVE the polarity, or do not jump.

With both engines off, keys off ect, connect jumper cables, and wait at least 5 minutes for some charging.  Time is your friend here

Then start dead bike.

Disconnect cables

Find a new to you twisty road.

Rod

[trapp120]

I've jumped numerous street bikes, dirtbikes and quads from car battery - running. Have not seen an issue with the electrical, or any adverse effects.

[chornbe]

"Then you can jump it off a car.  Your starter motor doesn't car about the incoming amerage, it'll only draw what it's designed to draw."

Exactly. Amps are drawn not force-fed. Path of least resistance and all that.

[chornbe]

Forgive my ignorance but.......Your bike has a parking light????

I thought the lights went out when the key was off?

I know I could possibly leave the hazards on but a parking light?

Some bikes have a parking light on a different key position than ignition or aux or off, etc.

[Bjorn Toulouse]

Over the years I've repaired quite a few bikes with damaged electrical components due to jump starting from a car, although jumping from a car is not a big deal. 12 volts is 12 volts.

In virtually every case the problem was traced to a ham-fisted maroon shorting out the + jumper connection. The proximity of frame rails and other grounded bits to the + battery terminal makes the use of car size jumper cables somewhat dicey in many instances.

The "arc weld" marks on the frame rail reveal your stoopidness, and no, it ain't covered under warranty!


Rex

[whoaru99]

...IMO, I think most 'stories' about things blowing up is people simply getting the polarity wrong.  I can't tell you how many times, both cars and bikes, we had to repair damage for that (although they rarely admit it at first)

I agree. It's usually not jump starting per se that caused the problem, it's much more likely that someone screwed up that is the real problem.

[HaChayalBoded]

Here's a tip for your Hawk GT, ALWAYS, put back that stupid little battery cover thingy. Even though its a little light piece of plastic, it apparently offers just enough of a load bearing for the fender to not have the other two tabs crack and break off.


Ask me how I found that out....

[Zerosum]

Here's a tip for your Hawk GT, ALWAYS, put back that stupid little battery cover thingy. Even though its a little light piece of plastic, it apparently offers just enough of a load bearing for the fender to not have the other two tabs crack and break off.


Ask me how I found that out....

   That's interesting... because that part is currently on a shelf in my garage!    I'll have to put it back on!

[Justin]

Bottom line: Unless you like expensive repairs just leave the car off when jumping from a car battery. When the car is on the charging system is putting out a lot more volts than just the battery alone.

[tigertom1965]

I do have parking lights on my R1200RT.

I think you turn off key and then press and hold left blinker (within so many seconds of turning off bike) for so many seconds and on they come.

Or some other such nonsense.

To turn them off you must turn on bike again.

Why do they make it so difficult?

[highside]

It never ceases to amaze me how many people do not know how to jump start a car. Improper technique can damage a car's electrical system. If your jumping a bike from a car the risks of doing it wrong are magnified. I think that is where this myth comes from.

I agree that there is no need for a car to be running to jump another vehicle. A car battery is perfectly capable of starting a car without the engine running.  

[tigertom1965]

I thought you hooked up the positive to the positive and the negative from the car battery to ground on the second car.

You are not supposed to hook up battery to battery right?

[Justin]

I thought you hooked up the positive to the positive and the negative from the car battery to ground on the second car.

You are not supposed to hook up battery to battery right?

You can do it either way. The negative terminal on the battery is hooked up to the chassis ground anyway...

[birdrunner]

You can do it either way. The negative terminal on the battery is hooked up to the chassis ground anyway...

however, by doing this ground last, and onto a grounded part of the car instead the battery pole, any spark that happens, happens away from any gases your battery MIGHT be producing.  It's a safety thing.

[highside]

You can do it either way. The negative terminal on the battery is hooked up to the chassis ground anyway...

Im no electrician so i couldn't explain why, but i have jumped a LOT of cars and I have found that better results are achieved by grounding on the chassis or motor than on the negative terminal, especially when the battery is thoroughly drained.

[Scoop]

Im no electrician so i couldn't explain why, but i have jumped a LOT of cars and I have found that better results are achieved by grounding on the chassis or motor than on the negative terminal, especially when the battery is thoroughly drained.

The only reason for connecting the negative to the chassis is, as was mentioned above, to prevent a spark that might occur on closing the connection from igniting the hydrogen gas produced by the battery.  Other than that safety issue, it makes no difference where you hook it up.

[black hills]

The only reason for connecting the negative to the chassis is, as was mentioned above, to prevent a spark that might occur on closing the connection from igniting the hydrogen gas produced by the battery.  Other than that safety issue, it makes no difference where you hook it up.

+1 if you follow the negative cable on the battery it goes to the chassis or engine

[cworley5150]

I jump start bikes from time with no problems.

[highside]

+1 if you follow the negative cable on the battery it goes to the chassis or engine

Your probably right that it wont make a difference, cept that for most cars I have jumped the battery terminal is so corroded that a better connection can be made elsewhere.