proportional to how fast I drive or how fast the engine revs?
battery charge speed
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JHZR2
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You need voltage to overcome impedance on the battery. Higher engine sped can increase alternator voltage a bit, and then the alternator may supply more charge current.
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
For the most part it doesn't matter. The voltage regulator will control the output of the alternator. At idle, or under very heavy loads, it may not be able to meet the demand however.
Your alternator is really not designed to charge a dead battery if that's why you're asking. It can cause overheating. Put the battery on a proper charger.
Your alternator is really not designed to charge a dead battery if that's why you're asking. It can cause overheating. Put the battery on a proper charger.
Your typical 120 amp alternator could make about 40 amps at idle of which 10-20 are needed for fuel, ignition, etc. You get your full 120 amps at ~2500 RPM.
At running voltage of 14 volts, it's a function of the battery how fast it can absorb the avilable current. If partially/ mostly discharged, its internal resistance will be less and it'll guzzle amps. If it guzzles enough the alternator will be "full fielded" or working 100% and the system voltage will drop slightly.
If you notice dimming lights especially at idle you know you're full fielding it.
Charging a battery this way can make it burp acid from its vents and shorten it's life, so it's best to throw it on a 6 amp overnight charge if you can.
At running voltage of 14 volts, it's a function of the battery how fast it can absorb the avilable current. If partially/ mostly discharged, its internal resistance will be less and it'll guzzle amps. If it guzzles enough the alternator will be "full fielded" or working 100% and the system voltage will drop slightly.
If you notice dimming lights especially at idle you know you're full fielding it.
Charging a battery this way can make it burp acid from its vents and shorten it's life, so it's best to throw it on a 6 amp overnight charge if you can.
Almost all cars today can charge just fine at idle or slightly above. As the engine revs higher, the voltage regulator holds the alternator output constant, so once the engine is spinning the alternator fast enough to reach its rated current output, spinning it faster doesn't speed anything up.
But as others have said, if the battery was deeply discharged, just driving away and letting the car recharge it will shorten its life. It needs to be put on a charger to bring it up slowly without excessive current and then finish off with a cell equalizing charge.
But as others have said, if the battery was deeply discharged, just driving away and letting the car recharge it will shorten its life. It needs to be put on a charger to bring it up slowly without excessive current and then finish off with a cell equalizing charge.
Originally Posted By: JHZR2
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
Why is that so, its expensive to design it that way or you have the issue of other accessories using the +12 while the car is running?
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
Why is that so, its expensive to design it that way or you have the issue of other accessories using the +12 while the car is running?
lots of informed people!
I have a car in garage I don't like to drive anymore but but I don't want the battery go dead before i sell it. Can I just let the car idle 10minutes every two weeks to keep the battery charged or do i need to bring the car out on highway to run for 10 minutes every two weeks?
I have a car in garage I don't like to drive anymore but but I don't want the battery go dead before i sell it. Can I just let the car idle 10minutes every two weeks to keep the battery charged or do i need to bring the car out on highway to run for 10 minutes every two weeks?
the battery would be far better off on an inexpensive maintainer. The last 5% of a battery charge is soft and slow....
but the rest of the car will be preserved better if you drive it every couple of weeks for 20+ minutes. Not idle, but drive. will it matter? probably not too much, in truth, unless this is going to be the mantra for the next few years.
but the rest of the car will be preserved better if you drive it every couple of weeks for 20+ minutes. Not idle, but drive. will it matter? probably not too much, in truth, unless this is going to be the mantra for the next few years.
Originally Posted By: Donald
Originally Posted By: JHZR2
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
Why is that so, its expensive to design it that way or you have the issue of other accessories using the +12 while the car is running?
A bit of both.
There are car management systems that track the state of battery charge and optimize the alternator output voltage. They tend to be a PITA when the battery nears end of life, and especially when you replace the battery. They often require a dealer computer reset ($$$) when the battery is changed.
Originally Posted By: JHZR2
Problem is that an alternator will never perform a true saturating charge in the correct cc/cv fashion.
Why is that so, its expensive to design it that way or you have the issue of other accessories using the +12 while the car is running?
A bit of both.
There are car management systems that track the state of battery charge and optimize the alternator output voltage. They tend to be a PITA when the battery nears end of life, and especially when you replace the battery. They often require a dealer computer reset ($$$) when the battery is changed.
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