[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.