Question: how do you know if your alternator is overcharging your battery?
Answer: High Gauge Reading. An overcharging alternator will cause the voltmeter on the vehicle's dash to read an overly high voltage that may or may not vary with engine speed. ... 
Low Battery Electrolyte. ... 
Burnt Bulbs. ... 
Battery Heating. ... 
Swollen Battery. ... 
Seeping Battery.