battery terminals

If you have the engine running and you disconnect the positive terminal, and the engine keeps running, what are you going to mess up in the car and engine if it keeps running without the positive cable on?

You can fry the alternator.

Hear this. My POS battery terminal broke off of the battery once while the car was shut down. I jumped it while holding the terminal to the battery. I drove my 1996 Buick riviera about 5 miles , stop and go traffic withoumy battery with no problems. I did see current variations and lights were periodically dimming a little bit, but besides that everything worked fine. The car will run, but it will put too much pressure on the alternator and perhaps fry it, just like TheSilentChamber stated.

What usually happens is the diodes in the alternator fry. I'm not an expert on alternators, but the way it was explained to me was that without the battery hooked up, there is no field generation and therefore no voltage regulation. Basically you're making juice but have nowhere to put it and it fries the diodes.

If you can understand that, you're smarter than I am. What the heck is "field generation" aside from what protects the death star from a rebel attack?

nothing, nothing at all. Your engine draws current, your stereo draws current, yourassesories draw currennt, your AC draws current when it runs. Once the battery chargesit doesnt take any more current...if disconencting the battery fried the alternator so would a long drive with no stops.

The alternator doesnt run at full load all of the time ;)

Hear this. My POS battery terminal broke off of the battery once while the car was shut down. I jumped it while holding the terminal to the battery. I drove my 1996 Buick riviera about 5 miles , stop and go traffic withoumy battery with no problems. I did see current variations and lights were periodically dimming a little bit, but besides that everything worked fine. The car will run, but it will put too much pressure on the alternator and perhaps fry it, just like TheSilentChamber stated.

the voltage variatios was from a sudden change in load with your regulator taking more time to react. Normally the battery will cushin these voltage variations but since you dont have a battery... When the alternator isnt flowing any current there is no pressure...its just a magnet spinning in a coil of copper wire with current in the coil moving back and forth with engine RPM...put a load on the other end of the regulator and it gets filtered to DC and current flows from the coil to the diode, and if the current is flowing in the right direction it will flow to the load and if not it stops.


Edit:

The regulator CAN fry without a battery, however, from thoes sudden load changes (from the AC/Stereo/throttle or engine load increase) because the regulator has to double time it to keep up. However a capasitor bank to cushin voltage ripples would work just the same.

The alternator doesnt run at full load all of the time ;)


Iv been thinking exactly the same thing.
Iv know rally cars to complete several hundred kms of running on only the alternator and a push start because the battery jumped out on the first stage and is still sitting in a forest somewhere.
Lots of single seater race cars here run with out a battery, with no ill effects on standard alternators, and Iv done it myself, run a car home with out a battery in it.


Its possible the battery helps with current regulation, when its fully charged I know it helps keep a constant voltage, basicly buffering voltage spikes from the alternator running at differnt speeds.
I can't see how running with out it is going to fry anything.

Exactly, it isnt good for the regulator if you are running on a cheapie OEM internally regulated alternator to have all the voltage spikes, but it inst going to fry the alternator in any short ammount of time either.

A good external regulator should be able to handle it EASY, especially if all you are ruinning is the engine.

Just like moppie said, some race cars run just the alternator and some run just a battery. Running without an alternator helps with paracitic drag on the enginer, running without a battery helps with weight. I didnt even think about rally races...i imagine, even if the battery doesnt get tossed, that conventional starter batteries wouldnt last all too long in a rally race.

What usually happens that leads to frying the alternator is the possative terminal comes off and starts flopping around and eventually makes good ground.

Well, if that happens, yeah you kinda are going to overload your alternator...which is why you fuse your leads children.

However if you physically took it off you should be smart enough to wrap it up in electrical tape and secure it somewhere where it wont short out or flop into the engine's assesory belt or into the radiator fan.

Also, if the (+) battery terminal is disconected the (-) should be as well. In fact you are sapposed to disconect the (-) fist.

Most alternators are not fused.

A good external regulator should be able to handle it EASY, especially if all you are ruinning is the engine.



If I have normal voltage readings from battery and alternator and I am still experiencing minor voltage spikes, does this mean I need an external regulator? The alternator I have is stock and is probably on its way to the grave. What are my options?

Thank you.

Most alternators are not fused.

Every car ive dont audio work on had a fused alternator positive run except for one. Every big 3 Ive done Ive fused. Not fusing can be very dangrous, especailly if it shorts out on the alternator end.



As for your alternator question. Most alternators are inernally regulated. You can buy an external regulator but this is only needed if you plan on running over the normal 13.8-14.4 volts in which case you can bypass the internal regulator and use your external one.

Most aftermarket HO alternators have decent to good regulators. Most stock replacements do not. If you are just looking to replace your stock alternator and you are not putting a major load on your alternaor (lots of off road lights/high current car stereo/winch/ etc...) and you dont plan on running without a a battery (you shouldnt for a daily driver :lol: ) a stock replacement is fine for your needs.

If you want a high ouput alternator look into MeanGreen, HO alternators, and Ohio Generators. Otherwise Autozone stock replacement will do. :)

I work at a NAPA store. A few years ago we got a bulletin saying that running the car with the + cable disconnected, and reconnecting it while the car is running, could possibly spike the ENTIRE electrical system, including the ecm (computer). In 13 years, though, I've never actually seen or heard of that actually happening. Just something to keep in mind.