The ammeter is measuring the current that's going in or out of the battery. All of the electrical load, ignition, lights, and accessories, is being tapped off downstream of the ammeter if the system is wired correctly. Let's compare the charging system to a water system, with a reserve tank, a well pump, and various demands such as a garden hose, household taps in the kitchen, bathroom, etc., and a sprinkler system to water the yard. As long as the pump is able to produce more water than the system demands, some of it can be used to fill the reserve tank. With no demand, a pressure switch (the voltage regulator) will shut the pump off when the desired pressure level is reached to avoid damaging the pipes from overpressure. As water taps are turned on, the pump will supply the damand, and the remaining volume is used to keep the tank full. In the event more water is demanded than the pump can supply, the reservoir tank makes up the difference, at least until it empties itself.
The volume of water going into the tank (amps) will change according to how much demand is being made on the pump by the system taps because the pump has a limited capacity (controlled by the current regulator, for instance). In the electrical system, generator (or alternator) output is used to supply the system demands first, and whatever excess current capacity that's available, if any, is used for battery charging. The ammeter is wired to show how much current is going into, or out of the battery only- - - -it does not show how much demand is being made by the system unless the engine is not running and/or the generator is not charging for some reason. Yes, the vast majority of the time, the system control is done by the voltage regulator only- - - -the current regulator only functions during periods of extreme demand to prevent overloading of the generator. An alternator stator is self-limiting due to the resistance of its windings, but a generator armature can destroy itself from overcurrent unless its output is controlled by the current regulator.
Are you confused yet?
Jerry
Last edited by Hotrod Lincoln; 08/07/2012 10:25 AM.
