"jumpstart" starter eliminates the need for a battery charge

How's a battery charger charge a battery?

It puts about 14-15v across the terminals of the battery.

How's an alternator charge a battery?

It puts about 14-15v across the terminals of the battery.

So - why can a battery charger charge a battery if an alternator can't

An alternator, at full field can exceed 24 volts., so can a battery charger. the difference is the capacity in AMPS that the two different machines can produce. a shop charger will put out 250 AMPS without a problem. A heavy duty alternator, which is very exspensive, can put out 140 AMPS. If it detects a low battery at this output of AMPS, then the voltage will climb. I have repaired many a vehicle that was damaged due to overvoltage conditions, due to charging or the attempted charging of a low or bad battery. think of it in terms of Watts required to recharge a battery. ALSO, an alternator is designed to operate continuously at 60% of it's maximum rating. The max rating is it's surge capacity, not running capacity. If anyone wishes to charge their battery using the alternator, then they are a gambler. It's like entering a fenced yard with a sign that says," large vicious dog lives here 3 days a week" the question is, what 3 days, and the question will be with the car, will we get lucky? and while we are on this subject of electronics, please do not disconnect the battery of a running car to test the alternator, this is a related myth to the alternator-charging-a-dead-battery myth.

Scotland to London?Hmmmm seems to be a British forum here. Hello from accross the big pond.

Reply to
Tech&Tool
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Only if it's broken. As is the rest of your argument.

John

Reply to
John Greystrong

Not unless you've disconnected the regulator &/or the load, in which case it can generate rater more than that.

Only a very cheap oversized one

much cheaper than that shop charger

That's a random number you've found somewher

As the alternator & the user can't tell the difference between a fully discharged & a partially discharged battery & almost any modern cars alternator will supply far more current than the battery will take at

14.4V you're either American or clueless.
Reply to
Duncanwood

Tech&Tool (Tech& snipped-for-privacy@echoforum.com) gurgled happily, sounding much like they were saying :

If the voltage regulator's broken.

If it's broken.

And if they are, the battery soon will be.

Yeh, the "UK" in the group's name does tend to bias the group like that.

Reply to
Adrian

Volts aren't the only thing that counts. If there's f*ck all current behind it, you'll not charge a lemon.

Reply to
Conor

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