Topic: Reversed the polarity by accident. What might have been damaged?

[Kframe]

Jumping from a running car = bad.

Any electrical theory or data to back that claim?

I have not found the claim to be factual.  But, as an urban myth, quite prolific.

In fact, I have jumped my CB550 from a running car/truck several times with no damage.  I was very careful with polarity connection.

Just because you've done something several times without a problem doesn't mean it's okay to do.  Most of the tech sites on the net that give instructions about jumping a bike warn to have the car off.  The reason cited is that the car's alternator puts out too much current for the bikes system to handle. 

Why would you even want to risk it since the car battery by itself can provide ample current?
-K

[bucky katt]

i would be unwrapping the covering off of the entire harness and check for melted wires/insulation. i'd be surprised if there wasnt more damage in there someplace.

[Gordon]

Just because you've done something several times without a problem doesn't mean it's okay to do.  Most of the tech sites on the net that give instructions about jumping a bike warn to have the car off.  The reason cited is that the car's alternator puts out too much current for the bikes system to handle. 

Why would you even want to risk it since the car battery by itself can provide ample current?
-K

An alternator only provides current, it does not push it or force it on the motorcycle's electrical system.  The motorcycle will only draw as much current as it needs.  

The tech sites you speak of are just perpetrating the myth.  There's plenty of misinformation out there that keeps getting passed around because it just sounds good, but has no basis in reality.  

[Kframe]

Just because you've done something several times without a problem doesn't mean it's okay to do.  Most of the tech sites on the net that give instructions about jumping a bike warn to have the car off.  The reason cited is that the car's alternator puts out too much current for the bikes system to handle. 

Why would you even want to risk it since the car battery by itself can provide ample current?
-K

An alternator only provides current, it does not push it or force it on the motorcycle's electrical system.  The motorcycle will only draw as much current as it needs.  

The tech sites you speak of are just perpetrating the myth.  There's plenty of misinformation out there that keeps getting passed around because it just sounds good, but has no basis in reality.  

Right, but certain components of the bike may draw more if it's available and through wires that aren't heavy enough, frying wires and/or components. 
Cycle sites (not forums) wouldn't likely have started putting out this warning if it had zero truth.
I appreciate that you have a different opinion, and you can risk your bike if you want, but the main point is why would you even start your car to jump your bike?    Any car battery has hundreds of available CCA and doesn't need to have the car running.  Are you going to play russian roulette because you know someone that lived through it?  It's foolish to take the risk with old electronics that are expensive and scarce, or to recommend that someone else take that chance.  This forum is by enthusiasts that have some interest in helping other enthusiasts, so why tell someone there is ZERO risk when you have no chips in the pile and can't guarantee the outcome?
-K

[TwoTired]

Just because you've done something several times without a problem doesn't mean it's okay to do. 

Agreed.  It is usually me that points out such.  It was merely posted as an example, not a proof in itself.

Most of the tech sites on the net that give instructions about jumping a bike warn to have the car off. 

Please cite your referenced tech sites.

A charged motorcycle or car battery is capable of putting out several hundred amps for short periods of time.  They have to, in order to drive starter motors that draw 600-700 amps for cars and about 120 Amps for our bikes.

The average car alternator puts out 30-60 amps, the latter if it is heavy duty such as a police option that expects lots of electrical loads.  This is far less than what is available from the battery, even the motorcycle battery.  If your bike is going to fry with a car alternator, it is certainly going to fry simply by hooking up a fully charged motorcycle battery.

The reason cited is that the car's alternator puts out too much current for the bikes system to handle. 

This is simply bogus reasoning, as the using device is what determines the current draw, (assuming it is available from the source).  It doesn't matter how much the alternator is capable of making, it won't make it unless there is a demand and then only to it's capacity limit.

Why would you even want to risk it since the car battery by itself can provide ample current?

Trick question, as you assume there is risk where none is inherently there.

Why is it you fear something your don't understand?

[Gordon]

I appreciate that you have a different opinion, and you can risk your bike if you want,

This isn't a matter of opinion. 

[TwoTired]

Right, but certain components of the bike may draw more if it's available and through wires that aren't heavy enough, frying wires and/or components.

Sorta true, if you assume that there is a system fault that the expend in-situ battery is current limited (depleted).  But, then it won't matter if the car alternator is running or not, the current available from ANY fully charged battery will make the faulty component/circuit draw the current it demands.

 
Cycle sites (not forums) wouldn't likely have started putting out this warning if it had zero truth.

You mean like old wives have no reason to start a rumor?  Electricity doesn't operate by the principle of the people's majority vote.  Physics rule this arena, despite what humans desire/believe.

 
I appreciate that you have a different opinion, and you can risk your bike if you want, but the main point is why would you even start your car to jump your bike? 

Based on science and the way electrical things work, your point is moot. 
It also happens to negate your opinion, IMO.

 Any car battery has hundreds of available CCA and doesn't need to have the car running.  Are you going to play russian roulette because you know someone that lived through it? 

You are manufacturing a risk (russian roulette) that does not stand up to reality.  And, you can not prove that there is a risk.  You only offer conjecture and urban myth.

It's foolish to take the risk with old electronics that are expensive and scarce, or to recommend that someone else take that chance. 

I could counter that it is foolish to take advice from someone who has no clear understaning of electrical theory and practice and perpetuate urban myths.

This forum is by enthusiasts that have some interest in helping other enthusiasts, so why tell someone there is ZERO risk when you have no chips in the pile and can't guarantee the outcome?

Right back at you, buddy.  Why tell someone there is risk when you can't possibly know there is a risk, because you have no understanding of the actual factors involved?

The risk of jumping a motorcycle from a car, running or not, is restricted to keeping the jumper polarity correct.


Sometimes electrical training, and over thirty years of experience allows one to gain some knowledge about basic electrical devices.  It's still hard to overcome deeply entrenched urban myths, as it shakes many persons foundations of understanding.

[Spanner 1]

Kframe, consider this, if you will.....look at the size of the wires serving your home, outside above the meter. It's probably 2/0 copper and capable of carrying 200 amps ( usual supply to a modern home ). Now look at the size of a lamp cord on any lamp in your house. With the lamp turned-on, it's drawing about 1/2Amp ( 60watt bulb ). Now why doesn't that massive 200 Amps available on the big fat supply wires
'rush' into the table lamp and fry it immediately...nothing to stop it....but never going to happen as the lamp only demands 1/2 of an Amp.
It's the demand that causes the current to flow, never what amperage ( power ) is available..........seewhatimean?

[shizzomynizzo]

Kframe, consider this, if you will.....look at the size of the wires serving your home, outside above the meter. It's probably 2/0 copper and capable of carrying 200 amps ( usual supply to a modern home ). Now look at the size of a lamp cord on any lamp in your house. With the lamp turned-on, it's drawing about 1/2Amp ( 60watt bulb ). Now why doesn't that massive 200 Amps available on the big fat supply wires
'rush' into the table lamp and fry it immediately...nothing to stop it....but never going to happen as the lamp only demands 1/2 of an Amp.
It's the demand that causes the current to flow, never what amperage ( power ) is available..........seewhatimean?

So if I want to impress someone at the bar, I can lick my finger and stick it into a light socket....Only if I demand 0 amps....then I am guaranteed not to be electrocuted? (since I am demanding no energy)


 

[Spanner 1]

Actually correct, Shizzy !, but only if your a ' perfect insulator ' for 120volts... no current flow= no shock.....

[Fritz]

So if I want to impress someone at the bar, I can lick my finger and stick it into a light socket....Only if I demand 0 amps....then I am guaranteed not to be electrocuted? (since I am demanding no energy)

Be warned! Maybe you'v got a subconscious demand for energy. You might never know until you let all those cute little electrons run through your body

(And what if somebody reversed the polarity in the socket?)

[MötleyRöx]

(And what if somebody reversed the polarity in the socket?)

Instead of frizzy hair they'd all be in-grown... ewwwwwww.

[bryanj]

Ok then, it may have been two dynamo powered cars where you shouldnt have both running, not sure it was 35-40 years ago---#$%* dont time fly. I recently saw an advert in a trade magazine where you can buy an alternator for a recovery truck that will charge at 120 amps and has connections so you can electric weld using it!

[camelman]

Right, but certain components of the bike may draw more if it's available and through wires that aren't heavy enough, frying wires and/or components. 
Cycle sites (not forums) wouldn't likely have started putting out this warning if it had zero truth.
I appreciate that you have a different opinion, and you can risk your bike if you want, but the main point is why would you even start your car to jump your bike?    Any car battery has hundreds of available CCA and doesn't need to have the car running.  Are you going to play russian roulette because you know someone that lived through it?  It's foolish to take the risk with old electronics that are expensive and scarce, or to recommend that someone else take that chance.  This forum is by enthusiasts that have some interest in helping other enthusiasts, so why tell someone there is ZERO risk when you have no chips in the pile and can't guarantee the outcome?
-K
[/quote]

No, they won't draw more amperage if it is available.  I could get into the theory, but you aren't listening to theory, so just think about actual operation.  Your windshield wiper motor does not draw more power than your starter motor, but it does not burn out when hooked up to the battery that powers your starter motor.  The same can be said of your window motors, the tiny little lights that illuminate various parts of your car, the headlights, taillights, turn signals, ad nauseum.  In other words, individual electrical components will only "demand" a limited amount of power no matter the supply.  So, starting a motorcycle from a car will not harm it because it will only demand a certain amount of power that is predetermined from the construction of the electrical components in the motorcycle.

It is good that you are trying to figure this out, but you are focussed on the wrong concept.  You are looking at the supply side.  Electrical components are only concerned with voltage and whether or not minimum current is supplied.  As long as the voltage is within range (anywhere from 6V to 14.4+V for our systems), and amperage is sufficient, they will operate.  If you get too far out of the range, then bad things happen.  If you supply massively higher amperage than is required... then the systems continue to operate as normal because the parts will only draw what their physical construction allows them to draw.

Regards,
Camelman

[Gordon]

If you supply massively higher amperage than is required... then the systems continue to operate as normal because the parts will only draw what their physical construction allows them to draw.

Regards,
Camelman

A lot of times people just like the myth better than the facts because it sounds better, or they don't understand the facts well enough to make them feel comfortable ignoring the myth. 

I'm positive I've been guilty of that on certain issues before. 

[camelman]

Agreed, I'm sure I do too.  The electrical issue is really very easy to understand, except that we don't ever get to see current and voltage in operation.  They aren't visible, and we can't touch them.  The old water hose analogy seems to explain it well though.

If you compare pressure and volumetric flow rate in a garden hose to voltage and amperage in a wire, then it makes sense.  Pressure is equivalent to voltage.  If a garden hose can handle the pressure, then it will not burst, much like if a wire can handle the voltage it will not burn up.  The volume of water available to flow through the hose is the amperage.  If a water-powered device is hooked up to the hose, and can handle the pressure, then it will only flow a given amount of water volume (amperage).  Having more water volume (larger diameter hose) available doesn't make a difference as long as the pressure remains the same because the amount of water flowing through the device is controlled by the pressure (voltage) in the hose.

Anyway, I think we've beat this one to death.

Camelman