If a battery is being charged properly there will be a heavy surge of current as the load of running the starter is recovered. That means the ammeter will show full deflection or close to it and the charging system voltage will be somewhat low. The state of charge of the battery controls the voltage, at least until full charge is reached. As the battery approaches full charge, the terminal voltage goes up and the charge current (ammeter needle deflection) goes down. The right way to check for full charge is by measuring the voltage at the battery posts (not the terminal connectors) after a drive, with the engine running at a fast idle. A 6V battery should indicate 7.5 volts at that time. A 12V battery will show 14.5 volts or slightly more. Checking terminal voltage with the engine off is not a good way to assess charging system performance.
Jerry
