Did something dumb - help please
Club Member
Joined: May 2006
Posts: 10,815
Likes: 16
From: Virginia
I guess I got lucky as hell when my bike wouldn't start last year I jumped it with my car. It still wouldn't start so I started the car and revved it up. The bike finally started but I found out the negative battery post was bad from a loose cable shorting out and melting the terminal. Replaced the battery and all has been good after that.
Club Member
Joined: Jun 2007
Posts: 3,435
Likes: 28
From: Living in open carry state :D
I am with you PIg... I have been jumpming bikes with a car for a long time. Never had a problem ... Knock on wood. I also never ran into a person who actually did have a problem when they did it, was a pre-existing problem like this one... They were only passing on what was told to them. Just like placing a battery on a concrete floor will ruin the battery.
Advanced
Joined: Jul 2008
Posts: 79
Likes: 0
From: Leesburg VA
I am not sure I understand why it is not good to jump a bike with a running car. Can someone please explain it to me?
My understanding is that the current is a factor of resistance versus voltage. So the only way that I can see a running car damaging a bike is if the charge voltage of the car is a lot higher than the charge volatage of the bike.
Is that the case?
You cant push more amps than is required so an amp rating of an alternator is the maximum amount that can be pulled by the device that is being connected and not the number of amps pushed out.
Given that the charge voltages are the same, say nominal 14V, then the resistance of the bike battery is going to be static and thus the current will be the same regardless of whether it is the car alternator or bike stator doing the charging.
That is one of the reasons the voltage regulator is there is to keep the voltage steady.
Cheers
David
My understanding is that the current is a factor of resistance versus voltage. So the only way that I can see a running car damaging a bike is if the charge voltage of the car is a lot higher than the charge volatage of the bike.
Is that the case?
You cant push more amps than is required so an amp rating of an alternator is the maximum amount that can be pulled by the device that is being connected and not the number of amps pushed out.
Given that the charge voltages are the same, say nominal 14V, then the resistance of the bike battery is going to be static and thus the current will be the same regardless of whether it is the car alternator or bike stator doing the charging.
That is one of the reasons the voltage regulator is there is to keep the voltage steady.
Cheers
David
Outstanding HDF Member
Joined: Nov 2007
Posts: 2,289
Likes: 22
From: Beautiful Downtown Burbank
Ozzie Dave, in a perfect world, your assessment would be correct.
Unfortunately, life looks at it differently. The regulator is designed to operate with voltage and amperage going one way. When you jump it from a running vehicle, you put reverse bias against it. The regulator dont like that. As long as theres no forward bias, the regulator doesnt care about the reverse. The minute the bike starts and there is forward bias, something has to give. Add to it the magnetic field that collapses around the jumper connection when you disconnect (spiking into the thousands of volts reverse bias), the regulator is going to try its hardest to stop it. If it cant, it goes POOF. If it dont go Poof fast enough, I'll bet you cant guess whats next in line.....
Otherwise, use a piece of 14 gauge wire between the jumper cables and the bikes battery, and you have a 99% chance of not doing any damage
Unfortunately, life looks at it differently. The regulator is designed to operate with voltage and amperage going one way. When you jump it from a running vehicle, you put reverse bias against it. The regulator dont like that. As long as theres no forward bias, the regulator doesnt care about the reverse. The minute the bike starts and there is forward bias, something has to give. Add to it the magnetic field that collapses around the jumper connection when you disconnect (spiking into the thousands of volts reverse bias), the regulator is going to try its hardest to stop it. If it cant, it goes POOF. If it dont go Poof fast enough, I'll bet you cant guess whats next in line.....
Otherwise, use a piece of 14 gauge wire between the jumper cables and the bikes battery, and you have a 99% chance of not doing any damage
Banned
Joined: Oct 2007
Posts: 1,494
Likes: 5
I agree with kk6pg.
If you have a good connection you should not need to have the jumper vehicle running in order to start your bike anyway. You should connect the positive to the BAT and negative to the engine ground, not @ the Batery. On newer vehicles it is very unsafe to jump them either, I have seen many a fried ECM!
If you have a good connection you should not need to have the jumper vehicle running in order to start your bike anyway. You should connect the positive to the BAT and negative to the engine ground, not @ the Batery. On newer vehicles it is very unsafe to jump them either, I have seen many a fried ECM!
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