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can a car keep running with no battery?


scottplus
11-17-2003, 07:54 PM
After starting, will a car keep running if you remove the battery? And why(not). Any help.

b's
11-17-2003, 08:33 PM
it should keep on running as long as you don't disconnect the ground. you can disconnect the postive and the car will still keep on running because your alternator act a power supply. it's what charge your battery or supply power to the car. the battery is just there so you can start the car. but if you disconnect the ground than the car would stop running. engine won't run without ground cable connect to battery or without ground at all.

i hope this help

KC Ron Carter
11-17-2003, 09:25 PM
I believe it is a matter of the type of electrical system used.

Cars with generators will continue to run.

Cars with alternators will fail since they require a field excitaion.

Later,

higgimonster
11-18-2003, 09:50 AM
it should keep on running as long as you don't disconnect the ground. you can disconnect the postive and the car will still keep on running because your alternator act a power supply. it's what charge your battery or supply power to the car. the battery is just there so you can start the car. but if you disconnect the ground than the car would stop running. engine won't run without ground cable connect to battery or without ground at all.

i hope this help

once you disconnect the positive cable from the battery it is completely disconnected. You are right that the car needs a ground and that ground is always the chasis of the vehicle, not the negative terminal of the battery. in fact the negative is grounded to the chasis.
I know there a few cars that use a battery to start then run off then alternator. I remember watching some special on ferrari's on speed channel a few years back where they did that.

KC: what to you mean they nead 'field excitation'? I have never heard that before.

KC Ron Carter
11-18-2003, 04:28 PM
Generators are different, permanent magnets and commutators.

All alternators use electromagnets to create the field.

The current that does that is know as excitation.

The regulator modifies that current to control the output.

http://members.roadfly.com/kcroncarter/etm114.htm
http://members.roadfly.com/kcroncarter/bmwetm114.jpg

I hope this explains the issue,

ivymike1031
11-19-2003, 11:02 PM
I believe it is a matter of the type of electrical system used.

Cars with generators will continue to run.

Cars with alternators will fail since they require a field excitaion.

Later,

I've yet to see this happen. The alternator is more than capable of supplying its own excitation current, once it is going. It charges the darn battery, for pete's sake! Electrical current is fungible.
My biggest concern would be that a transient load (current demand) would push the system voltage down to a point where it ceased to function (ignition system or charging circuit), after which it would quit running. The battery stores energy, with a couple of goals - 1) to allow current draw when the alternator is not generating any; 2) to allow current draw (for a short period) greater than what the alternator can provide. Think of it as an electrical bank account, or as overdraft protection for your alternator.

jhillyer
11-28-2003, 07:27 PM
Yes, a diesel with mechanical fuel injection keeps going, and going.
A solenoid fuel injection system cannot drive the injection and ignition without some capacitive buffer to smooth the warble of a common alternator/regulator, or it can frequently misfire or does not run. That capacitance is what I understand [user] IvyMike1031 is correctly describing.

Thanks for posting questions, else we'd feel useless, and the forum would be barren.

antielvis
12-02-2003, 08:24 PM
Maybe some of the newer vehicles are different, but your car should run fine with the battery disconnected, as long as you're careful about not letting the positive cable hit anything it shouldn't. I've done this before with cars that had dead batteries when I didn't have access to jumper cables. I just used a charged battery to start the car, then swapped the dead battery back in with the vehicle running to let it recharge. I've used this method in cars as old as 1959 and as new as 1988. I don't know what kind of effect this could have on the computer and other electronics, though, so you may want to be careful trying this.

The Dude
12-06-2003, 01:30 PM
I've done that same thing antielvis is talking about to drunk people out in the desert before.I think it was a late 80's early 90's Jimmy Blazer. Just gotta watch that positive cable. Muahahahaha

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