The factory installed amp gauge indicates the amount of current flowing to or from the battery, not the current being generated by the alternator. If your alternator and battery are both in good shape you will not see current flowing into or out of the battery, the alternator is supplying the needs of the electrical system. It is normal to see charging after starting but shouldn’t take more then a few minuets to recharge the battery. If the alternator is not meeting the system demand you will see current flowing out of the battery (discharging). If the battery is weak you will see constant charging. Furthermore the Amp rating of an alternator is how much it can generate. It will only generate the current needed by the load. If nothing is on it will be supplying only a few amps, however if you have the bright lights on, the AC on high, the 200 watt stereo blasting, and the electric fan running the alternator will be generation 50- 60 amps whatever the demand is. The amp gauge will see little or no current flow in either case.