I have a feeling you get shocked a lot.

Batteries don't have kinetic energy unless they are dropped on your foot. Kinetic energy requires velocity and mass. Batteries have chemical energy that is used to make an electrical potential (voltage).

There is no "law of electricity". There is a Ohm's law.


Potential energy is stored energy, an alternator stores nothing. An alternator has the potential to make electricity but saying it has potential energy in the context of this discussion is not really true.

I took the battery out of my scooter the other day (because it was dead) and kick started the scooter. I drove it to the pizza shop, turned it off, got my pizza, kick started it again and drove it back without a battery. This may be cheating, I think it has a magneto. It would not start with the dead battery in.

I am pretty sure I hill started my Z car in high school for weeks (I parked way out in parking lots).

Also I am sure I have disconnected the battery on a running vehicle and it does not die.

I will agree that having a battery is better because no battery might cause damage, but saying that it won't work at all is not true. If the battery is completely dead it may be better to disconnect the battery so the alternator is not trying to charge the battery as well as run everything else. I don't know that I would try to prove this for grins on my bike but if it was that or push I would disconnect the battery and try.

 

in a fuel injected car, you cannot run it without a battery, I was not talking about a carb car and as far as bikes I'm assuming it's the same thing... as far as the kinetic and potential, I was I have no idea where that was coming from... made sense to me at the time tho I knew it had no relivence.... you can't disconnect a battery in a Fuel injected vehicle and run it. carb. doesn't count that's cheating.

 

So disconnecting the battery on a running car with fuel injection will kill it? Or you just can't push start it? I wish I still had my Stanza. I don't have a car I want to risk testing this with.

 

No, it will not kill the car, it will keep chugging along like your old Z car did. However, there is a possibility that voltage variations will wreak havoc on the electronics.

 

You're right. If the battery is completely gone, an EFI bike ain't starting even from a push start. Thankfully, things aren't usually that bad. The single largest draw on a battery is the starter, so even a battery that doesn't have enough juice to turn the engine over will generally still have enough power to run the fuel pump and EFI computer.

I have push-started my EFI 1976 914 many times with no problems (yes, it's EFI, not mechanical injection; 1st generation BOSCH D-Jetronic, a speed-density system that operates similarly to the Delphi one used by H-D, though older and cruder).

A stater (for an average 4-cylinder car) will pull 150-175 amps depending on temperature. The fuel pump and ECU combined are definitely not pulling anything close to that, so even when there's not enough juice left to run the starter, chances are that the fuel pump and ECU can still get enough power from the battery.