Friday, Dec 17, 2004 at 12:44
Hi David C, your result is correct but what causes that result is actually back to front.
An alternator just produces current determined by the current load present to it, it has no way of knowing if the battery is charged or not.
When a battery is low there will be a larger than normal voltage difference between the battery voltage and the regulator voltage.
The current being produced is the current that the battery requires and as long as the alternator is turning fast enough then it will produce the current the battery will needs.
As the battery charges and it’s voltage approaches the regulator voltage, the current requirements of the battery reduces.
If you had a battery full charged by the vehicle’s charge system at as example ONLY, the battery was about 85% charged and the you increased the vehicle’s voltage regulator from 14.2 to 14.9 and the went for a good drive. You would find that at the end of the drive battery would be close to 100% but if you measured the current coming from the alternator, you would find that at the instant you increased the voltage level of the regulator, the current coming from the alternator increased.
This has nothing to do with the alternator “knowing” how if the battery is charged or not.
Facts are that the battery itself determines how much current it wants, the alternator only knows that there is a demand for current.
The greater the voltage difference between the batteries voltage and the power sources voltage, the greater the current will be going into the battery.
There is another way this could be demonstrated. If you had 50 batteries all fully charged and you connected one battery to the vehicles charge system and that battery pulled 1 amp when fully charged as you connected each new battery to the charge, the alternator would increase it’s out put by one amp for each additional battery.
Also if you have a battery that is pulling 10 amps at a given voltage, It won’t matter if the alternator is capable of producing 10 amps or 1,000 amps, the battery will only pull 10 amps.
Put quiet simply, you have to increase the voltage applied to the battery to increase the battery's charge level.
Cheers
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