Am I understanding this about charging car batteries correctly?

[theclencher]

This should help: http://www.landiss.com/battery.htm

I don't know where you get your voltage numbers from, but everything I've ever checked while running has been over 14v.

[theholycow]

+1 on both of theclencher's posts above.

[imzjustplayin]

Originally Posted by theclencher

And to think my stuff has been starting with weak batteries all these years

No, scratch that. And to think millions of engines have been starting in all temps all these years with weak batteries

Including the original factory battery in my '94 Ford that's still going strong today! Too bad Ford doesn't know how to make a proper voltage regulator huh.

I don't know what you're getting at... Also, alluding to your '94 Ford doesn't mean anything these days when a lot of owners are finding themselves replacing their batteries after 4 years. I know because I own some older vehicles and newer vehicles and the newer vehicles with their alarm systems and electronics drain the batteries very quickly while the older vehicles, not so much.

As for you "starting with weak batteries", the electrical systems in cars are designed to work as low as 10.5V, meaning cranking the engine and running it. However that doesn't mean discharging a 12v lead acid battery below 11.7v isn't damaging to it. There isn't anything you've said in this thread that I either didn't know or it refuted what I said besides that alternator charging at a minimum of 14v.. You might not be aware but it's within range for an alternator to operate at 13.5v and the voltage you may see with a multimeter isn't its temperature compensated voltage. Temperature compensation is pretty important when charging lead-acid batteries especially if you intend on them lasting for a significant amount of time.

[theclencher]

My battery is now 17 years old. What more do you want? I've never paid it any special attention either.

Fine. No cars have charged batteries. Happy? What do you intend to do about it?

You didn't look at the link did you.

[theholycow]

theclencher's point (as I understand) is that despite all the insufficient charging theory we can talk about, the practical upshot is that people get in their car every day and it starts just fine without worrying about whether the battery is fully charged or not.

[theclencher]

The bottom line is, any higher charging rate and the batteries would boil off their electrolyte, thus making the periodic addition of water necessary. We all know today's motorist can't even be troubled to put air in their tires, so what would happen is there would be mass battery failures due to low electrolyte levels. And even if people did maintain the levels, the vehicles wouldn't start any better than they do now, and the batteries wouldn't last any longer because overcharging brings on failure just as much as undercharging.

[slurp812]

Originally Posted by theclencher

NO, alternators MAINTAIN batteries fully charged BUT THEY WILL NOT charge up a battery from DEAD. It's too much current for them to do that and they may burn out trying. AND alternators work far better than old school GENerators do at low rpms. Some of these comments lead me to believe you guys think alternators don't charge the batteries fully? Nonsense.

Iv charged many car batteries in the car, on many cars. Not sure what you mean. No a car alternator wont fix a bad battery. Car batteries arent designed to be run dead, if they are it will ruin the battery. I know, I did it in a car with a stick. Left the headlights on, a few times. Push started the car, because the battery was dead, lights, nothing worked. Bump started the car, and drove it, never did anything to the battery except drive the car. I eventually did this 5 times to the same battery and ruined it. Every time, I simply ran the car, and the battery was charged up enough to start the car just fine in the winter. However the repeated running dead killed the battery. Never once did I have a problem with the alternator in this car after charging a dead battery 5 times!

[theclencher]

It's not recommended and with the price of alternators these days, I personally wouldn't chance it.

[slurp812]

Originally Posted by theclencher

It's not recommended and with the price of alternators these days, I personally wouldn't chance it.

I had two choices, bump start and drive it home 23 miles, or walk. A tow at that distance would be more than an alternator. After market alternator for a 1996 accord is $112.

[imzjustplayin]

Sounds like you need that buzzer to remind you to turn off your headlights like the civics come with.. Also just because you can start the car just fine, doesn't mean the battery isn't discharged. 10.5V is the minimum voltage needed to crank most cars but 11.7v is generally considered a fully discharged battery and to charge a battery from 11.7v to 12.7v (full charge) requires quite a few amps, something you can't normally do with your car since it would take several hours of highway driving. What your car was likely doing was charging the battery just enough so that you could drive around with it but that doesn't mean the battery wasn't discharged.