RE: [DML] Re: Car's use of electricty / alternator & battery question

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

Sorry Dave, 
An alternators job is not to charge the battery like the old generators did
but to top them off. If you have a good battery and it's low sure the
alternator will top it off but if you barely can start the car and you think
the battery will be fully charged when you get to the destination then you
may be in for a surprise. 

Now if your going on a drive and it's 200 miles away on a nice day when you
don't need the air condition and lights and you have almost no load on the
system and a low battery and a good alternator then I'll say it will charge
the battery. But normal driving around town day and night radio on ac on and
lights on then tell me how many people had a dead battery when they went in
somewhere and came back out and the car wouldn't start.
Battery chargers take 4 to 8 hours to charge a battery with no load.
 
Any alternator shop or someone that knows the alternators will tell you
that.
As far as the resting period, why do you think the Motorola's are leaking
and burning up. They were trying to recharge the weak or low battery and run
all the high loads of the car at the same time and they finally melt and
gave up. 
Why also do you think isolators are made for duel battery systems.
Everything needs a cooling down period.
John Hervey

  

-----Original Message-----
From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
Dave Swingle
Sent: Sunday, July 08, 2007 4:10 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Re: Car's use of electricty / alternator & battery question

Huh? Sorry - but I can't let this go......

If this statement is true then you should be replacing the battery 
about every week. **Of course** the alternator is made to charge the 
battery (otherwise jump starting a car with a dead battery wouldn't 
work). 

When the car is running the alternator is putting out exactly as much 
current as the car needs to operate all the electrical systems. If 
the battery is low, the alternator will put out more current (up to 
its rated current) until the battery is charged. If it were to put 
out more all the time (seen as too high of a voltage), it would be 
overcharging the battery. If it were to put out less than it takes to 
operate the car's systems, the battery would soon run down. 

The regulator is exactly that, a regulator, and it really isn't 
carrying any load itself, it regulates the output of the alternator 
to a specific output voltage. It doesn't "care" what the load is, the 
load is supplied by the alternator core and the diode bridge in it. 

An alternator should be able to deliver it's rated output current-at-
voltage indefinitely, although the max output may vary a bit with 
temperature. If an alternator delivers a very high output but 
overheats or burns out when run that way for long, the rating is not 
accurate. 

This is all very non-DeLorean specific and should be covered in just 
about any automotive textbook. 

Dave


--- In dmcnews@xxxxxxxxxxxxxxx, "John Hervey" <john@...> wrote:
>
> David Vegas, I agree with what Dave D. Is saying but don't get the
> impression that you can do this indefinitely. The alternator has to 
rest or
> it will burn up the regulator. To drive the car for any length of 
time you
> would have to keep the RPM's to 1500 minimum to also supply voltage 
and
> current to the car. That's why the battery is in parallel with the
> alternator that when it has a chance to rest the battery is running 
the car.
> 
> One other thing, the alternator is not made to charge a battery but 
to keep
> it topped off, again if it had to run all the time with no rest 
because the
> battery was low it would burn up the regulator.



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