Charging Battery with Alternator - Warning
Maybe i am missing something here, but what is the purpose of a voltage regulator, i thought once the battery was at full charge, and by driving 5 to 10 minutes the regulator steps down how fast the charge is according to the number of things like lights and wipers, if your alternator continued to charge at the same rate any time you started your car, if the regulator don't drop the voltage to the battery, it wouldn't matter if you had a weak battery or not,your battery would explode
I'll give this a shot.
The regulator
tries to maintain the system at approximately 14 Volts.
it controls power going into the alternator's rotor. It's spinning electro-magnet. More current into the electromagnetic, the stronger the magnetic field.
The battery
draws current when recharging just like devices such as a lights or electric motors.
The voltage across the light or battery determines how much current it will draw.
For example, headlights at 14 volts will draw around 10 amps. If they are supplied power at 17 Volts, they might draw over 15 amps (in which case the circuit breaker will trip or the lights will burn out quick).
A battery is different because its draw varies with its charge state.
example 1:
A battery that has just started a car may initially draw 10 to 20 amps when supplied at 14 volts.
After a minute or so, it will draw 5 amps at the same 14 volts.
Within 5 minutes, it will be drawing less than an amp.
Continually subject to 14 Volts, eventually a wet cell car battery reaches an equilibrium where the chemical reaction essentially stops. It has a surface charge of around 13.2 volts, but really only has stored energy at 12.8 Volts. Lots of stored energy. Enough to turn the starter motor and then some.
example 2:
A battery that is fully discharged will draw more than 20 amps when supplied at 14 Volts.
The current must be limited if we don't want it drawing 40 amps.
Reducing the voltage is how its usually done.
Some chargers do this automatically, or we can do this manually by setting the charger to a lower rate.
When there is no charger available, we can take advantage of the limits of the alternator design to reduce current to the battery.
An alternator's capacity to produce power goes up with rpm.
If the alternator speed can be kept down, many alternators simply can not supply 40 plus amps at 14 Volts when the engine speed is under 1000 rpm.
