By max I assume you mean it shows maximum to the Charging side.
One possibility is the battery is very low or has an internal problem.
Put the battery on a charger. Slow charge (2 amps) if its not an automatically controlled charger. If its a traditional battery, check the acid level is over the lead plates. If not add some distilled water. Do this before connecting the charger.
Another possibility is a regulation issue.
Do you have a hand hand multimeter?
If so, a quick check is to measure the battery voltage across the terminals.
Do this engine off, then engine running at slow idle, and engine running at fast idle or something fast.
Engine off, no lights on etc, the battery should be close to 12.8 Volts.
Engine running voltage should be between 13.9 and 14.7 Volts.
Voltage may increase a little with rpms above idle but then should be the same whether its running at 1700 or 2000 rpm. And it should not be above 14.9 Volts.
