Beyonce Knowles

The autozone guy told me it doesn't, all it does is maintain the power wherever it is at. According to him, if your battery drops below a certain level, the alternator will not charge it up so you have to use a recharger to charge it back to working level. Is this right?

BadCo.

He is retarded! It is not good for it tho, a low or near dead battery can cause spikes in the voltage and be a big wear on your alternator. It is best to put a charged one in there and if it needs charged...charge it with an external source.

Z28Nut

If the battery drops below a certain level, the car won't start therefore the alternator can't charge the batt. But yeah, the autozone guy is a 'tard.

The alternator requires power from the battery to begin generating electricity (field circuit??) but once the motor is running (meaning enough power provided to crank motor will also activate field circuit), the alt provides it's own juice no matter batt condition. BadCo is right about very low/dead batts.

tagz

He is correct. I was under the impression that the alternator charged the battery as well. But, the guy at Napa told me the same exact thing, and he knows what he is talking about... compared to the guys at autozone and/or pepboys...

In older cars, the cars were actually equipped with generators. They charged the battery.

Z28Nut

A generator uses permanent magnets to induce a voltage in it's windings. Spinning shaft = power.

An alternator uses EXTERNALLY powered field windings to induce a voltage in it. Spin shaft w/no field voltage = no power. Spin shaft with field voltage from batt/jump/etc. = power. Once the alternator is making power, it is self driving, meaning you can unhook the battery and it will keep the car running. That's why I had to run the batt or charge wire from my alt all the way back to the batt side of my cutoff switch.

Yes the alternator charges the battery or you'd have to charge the battery every couple of days to keep it starting the car. So the Autozone and Napa guys are sorta right and sorta wrong but didn't explain it very well.

tagz

Lets say your battery was dead. Not enoguh power to start the car. You jump it. Your battery may only have 6-8 volts, and gets the rest of its power from the other car you are jumping it with. Once you disconnect the jumper cables, you are back to 6-8 volts. It may have went up a little bit from the jumper cables.

The car will run becuae it is running from the alternator. The alternator is not going to charge the battery the remaining 6 volts. It will keep it at the initial 6 volts it had.

edit- at least that is how the guy at napa explained it to me

BadCo.

oh that aint right!

Z28Nut

Nope, the alternator will be putting out 12-14volts. The battery will take a while to charge so IF you unhooked the battery from the charging circuit (why do they call it that if alternators don't charge???) and checked its voltage right after starting car, voltage will still be low.

Ask the Napa guy if alternators don't charge, why don't we need to get the batteries charged all the time? Why is the alternator part of the 'charging circuit' on vehicles? Why is he a dumba$$?

I've jump started cars with nearly dead batteries and drove them for an hour or two and they've started up fine after that. Where did the power come from? Thin air?

Lonnie Pavtis

Wow, quit talking to guys that only sell parts instead of ones that actually work on cars.

This would mean that if you jump started a car w/ a dead battery, it would never regain its charge. I've done this hundreds of times.

How does an alternator put out 14 volts while it is charging a 12 volt battery? They do it all the time. Alternators always put out more voltage than the battery they are charging, this potential energy difference is what induces the charge. Key word is "charge". From what your are saying this is impossible.

Please find some educated people to get info from or you may one day make a major mistake based on one of their decisions.

shoebox

Would it surprise anyone to know that the actual GM term for that electrical thing powered by the belt is called a generator?

Isn't it kind of naive to think that it does not replenish the battery? How else is the battery going to last for very long? The reserve capaciy specification (the stock spec is like 90 minutes) on the battery is for how long the battery can last (without any charging) with a 25 amp load and the voltage not dropping below 10.5v. If it gets that low, you probably won't be able to start the engine.

Now, if you battery was never charged by the generator (a.k.a. alternator), you would not be starting your car very often without some external help.

Everyone read along from your new Helms manual :
How can anyone at an auto parts store not know this?

mehoffz24

very well said Lonnie, but please take it easy on the parts guys. some of know what we are talking about. just kidding, it is very hard to find people out there that give great advice( such as your self).

Z28Nut

Finding a parts guy that knows his stuff is akin to finding God (for me, anyway, lol). Most of the ones around here at AutoZone or Adv. Autoparts don't know squat or just enough to be dangerous. Just last night the girl at the register at AutoZone was asked by another employee on the phone what head gaskets are made out of. She said cork or rubber.

Lonnie Pavtis

Jack (mehoffz24), not meaning to rag on parts guys.... quit playing on the 'net & get your 700rwhp ride on the road. You have proven to me to be pretty sharp about cars. You were excluded from the comment, along with anyone else, that actually does work on cars.

It is unfortunate that the parts stores have now begun to hire anyone that can operate a computer to lookup parts. But... some of the girls are better to look at, than some old car guy. The local stores, often let me look up my own stuff, as I've lost my patience quite a few times, dealing with someone that doesn't know a rear main seal from the oil pan gasket (my last issue). You want good entertainment, ask some of them to cross reference something in the catalog. Example #2 NGK TR-6's do not exist at Advance. I had to drive home to find the part# (4177) just to order them. No internet access at the store either.

It used to be car guys that got hired to look up parts (that they understood) in catalogs. Computers have made car geniuses out of anyone that can operate one...the internet is another example.

Good luck to all.....