More jumping batteries

[Trip]

First, to clear up any confusion, the thread was killed because of something else besides this topic. This topic wasn't what caused it to go away.

Originally Posted by Rsv1000R

I've thought of a way you might fry your bikes electronics while jumping the bike, and jumping it from a car could increase the chance of it happening. And figured it deserved a separate thread, as opposed to hijacking the other thread again.

There's 2 parts of this, couldn't tell you if effect is actually strong enough, unless you take what zed's seen working on bikes.

So if you take a long cable, it starts looking inductive, batteries look a bit like capacitors. Connecting the last cable up can spark, and that could cause come ringing, and could cause a voltage spike.

The other effect, is if you dump a lot of current through a long cable it'll create a magnetic field, and when the current drops, will collapse, making a voltage spike.

I also know that for instance cmos ic's, when an input or output is pulled to a higher voltage than supply can inject current into a parasitic scr, and if it turns on, will short the supply until power's removed or something burns out.

Now I suspect a fully charged motorcycle battery, would do the same thing, But it is working with 1/2-1/4th the current into a completely dead battery a car battery could provide.

I will do some measurements on the inductance of a set of cables and study the electric fields through them, but I doubt I will find much. The standard cable is much too short for any of these to be a real factor. Just a quick guess in my head, the max spikes I could see would be in the milliamp/millivolt range. We are talking a few feet here. If we were running a cable 50 feet, I would might take a closer look into impact of the cable.

[Mr Lefty]

oh lord... here we go again

[Rsv1000R]

Originally Posted by Trip

I will do some measurements on the inductance of a set of cables and study the electric fields through them, but I doubt I will find much. The standard cable is much too short for any of these to be a real factor. Just a quick guess in my head, the max spikes I could see would be in the milliamp/millivolt range. We are talking a few feet here. If we were running a cable 50 feet, I would might take a closer look into impact of the cable.

Cool, And most jumper cables are like 12' or longer, and my "concern" is for current spikes in the few hundred amps+, like you might get connecting an auto battery to a 2 or 3v dead cycle battery.

In cmos, there's a reverse biased diode between in/out pins and pwr/gnd. When I worked on this problem for Harris Semi we'd see problems when injecting 20-100ma into these scr's depending on the specific design. So if you started getting voltage spikes of anywhere between about .4v's and 1 volt you might have a possible cause for what zed's seen.

Oh, and don't forget when getting connected, jumper cables almost always spark, which does funny things with voltage.

BTW, if you consider the last connection as points, the jumpers as the inductor, and the battery as a sort of capacitor, the circuit starts looking a lot like a points ignition system.

[Trip]

Originally Posted by Rsv1000R

Cool, And most jumper cables are like 12' or longer, and my "concern" is for current spikes in the few hundred amps+, like you might get connecting an auto battery to a 2 or 3v dead cycle battery.

In cmos, there's a reverse biased diode between in/out pins and pwr/gnd. When I worked on this problem for Harris Semi we'd see problems when injecting 20-100ma into these scr's depending on the specific design. So if you started getting voltage spikes of anywhere between about .4v's and 1 volt you might have a possible cause for what zed's seen.

Oh, and don't forget when getting connected, jumper cables almost always spark, which does funny things with voltage.

BTW, if you consider the last connection as points, the jumpers as the inductor, and the battery as a sort of capacitor, the circuit starts looking a lot like a points ignition system.

Even if the cable were 20', I wouldn't put much hope into the inductance of the line playing a great effect in the circuit of this nature. I would look more to weaknesses in the circuit before I went this route.

An arc flash however, could expose a weakness in the insulation and act as a short.

[derf]

I jumpez my biketh from mesa truck when its bee deader than dead

Seriously if my bike needs a quick jump because I forgot to pull the key when I left it last a car is easy and it's there. As long as the car isn't running you should be fine.

[ZUKIMON]

I'd like to add something into the mix, if I may.


How would jumping a bike from a car battery be any different to the electronics than jumping a car from another car/truck? The electronics inside the ECM/PCM are the same in either, are they not? I mean, a circuit is a circuit, a capacitor is a capacitor, a microprocessor is a microprocessor and so on. How would either of the two be any more fragile than the other?

I understand that you are looking at the AH of each battery and all, but afterall, they're both 12v systems and they work the same. How do motorcycle dealers jump off a bike if they need to do so quickly? It may be worth a call to a dealership just to see what they say.

[Mr Lefty]

Originally Posted by ZUKIMON

I'd like to add something into the mix, if I may.


How would jumping a bike from a car battery be any different to the electronics than jumping a car from another car/truck? The electronics inside the ECM/PCM are the same in either, are they not? I mean, a circuit is a circuit, a capacitor is a capacitor, a microprocessor is a microprocessor and so on. How would either of the two be any more fragile than the other?

I understand that you are looking at the AH of each battery and all, but afterall, they're both 12v systems and they work the same. How do motorcycle dealers jump off a bike if they need to do so quickly? It may be worth a call to a dealership just to see what they say.

that's what Trip and Fatburg are getting at... 12v is 12v is 12v

[ZUKIMON]

That's true. I guess I just like to write things in a way that is understandable to me just for giggles.

[Cutty72]

Originally Posted by ZUKIMON

I'd like to add something into the mix, if I may.


How would jumping a bike from a car battery be any different to the electronics than jumping a car from another car/truck? The electronics inside the ECM/PCM are the same in either, are they not? I mean, a circuit is a circuit, a capacitor is a capacitor, a microprocessor is a microprocessor and so on. How would either of the two be any more fragile than the other?

I understand that you are looking at the AH of each battery and all, but afterall, they're both 12v systems and they work the same. How do motorcycle dealers jump off a bike if they need to do so quickly? It may be worth a call to a dealership just to see what they say.

From what I've seen, dealerships use another bike/bike battery, or a jump box.

[Smittie61984]

Originally Posted by Cutty72

From what I've seen, dealerships use another bike/bike battery, or a jump box.

I grab two high tension power cables from the Nuclear Plant and charge my bike for 5hours before I ride. My head lights catch trees on fire