Years ago my brther was following me it was getting dark and his went out, since his alternater was not working I just swapped batteries, so my alternater was charging his battery, got home had to change his alternater, you can run for a short time on just tha battery, you can run on just the alternater unless you have a short in the battery then disconnect the battery and drive on.

 

You know, I'm not sure about that. I have a very, very small recollection that someone way back said our cars will not run on just the alternator (no battery connected). Something built in as a "failsafe" from the computer, maybe. But again, it is just a small nagging....so maybe I don't have it correct.


Maybe ChevyMgr can answer that???????

 

Now lesserdawn, what I would do is remove the battery and externally charge it, for about a day....a digital smart charger would be ideal, if you have one. I'd double check the battery with a volt meter for terminal voltage. Reinstall the battery and let in sit in the car for about a day recheck the voltage WITHOUT starting the car. If the battery still registers 12.6 ( or something very close to what the voltage is before install) or above I'd say the battery is good. However, if it is less than that, you probably have something drawing it down. This is essentially what Boydie mentioned in his first post.

It is entirely possible you have a bad battery, even though new. Also, if it is a battery that has quite a bit of shelf life, it will take some serious charging to use adequately.....as I mention above, the external battery charger.

 

Not sure about today's cars but before computers you could run a car on a working generator or a working alternator with the battery completely out of the car.

I did it many times. But if it stalled or you shut it off it would not start. (with a generator the car would run but just barely because generators did not put out the power (amperage) that alternators did.

We loved alternators when they came out, they will charge a battery enough to start the car in minutes but it took a generator hours to fully charge a dead battery.

Wow I hope this doesn't start a new controversy........................

Boydie Back in the Saddle.............HHR

 

When I ran the car on just the alternater it was many years ago no computer, but when my alternater went out on my HHR I drove about 25 miles on just the battery but then i had a shorted cell so I had it towed to have an alternater in installed and damn expenseive$$$ over $500.00.

 

They are expensive. Even doing it myself on my nephew's HHR the alternator itself was right at $200.

 

Disagree, the output on the alternator should be 14-14.4 volts, not amps. If you have a 140 amp alternator (or whatever your alt is rated at), then it should test pretty close to that.

If your charging a battery with a charger, you charge by amps.

 

Lets agree to disagree.

Does anyone have an amp meter to hook up to an alternator?
It would be interesting to see what they read. Should read what they are rated at but........

Boydie Back in the (debate) Saddle.

 

Amp meter will only show + or - when there is a load either way...volts on the other hand will show no matter what the alt is doing, unless its defective..its possible to produce low voltage and not show any problems except for a battery that doesnt seem to want to stay charged (discharges during normal operation. Most newer cars will not run anymore under a certain voltage, self protection, therefore a batt has to be present for the car to stay running. As far as amps..14,5 is nothing when you have lights drawing up to 10amps PLUS the eng electronics, fuel pump, injectors, ignition pulses,,stereo blasting and so forth..so at full tilt an alt may be producing well over 75 amps. I believe these output around 125 amps stock , at least replacements do. The battery serves 2 functions..buffer for spike alt loads and to start the car ( and accessories). After that all load is on the alt. The old cars at idle will barley show any amp draw. These newer ones..well, I couldnt find a hard number but its probably up there especially if the fan is turning. Also, found that key off, at the batt, you should not be over .035 milliamp draw, anything more and you have a battery drain going on somewhere....

 

Ah ha, so my old brain wasn't fuzzy after all !!