Battery not charging and alternator producing 50+volts

[Rob Verner]

Hi , the problem started when we couldn't start the plane shortly after a flight. Opening the engine cover I noticed the positive cable had broken of from the alternator at the lug. We charged the batterie and put a new lug on the the cable and reconnected it to the alternator. When we started back up we noticed the batterie wasn't charging. A minute or two later we smelt something ellectric fry. We shut the engine down and called an sparky who tested the system. We have since replaced the voltage regulator , the alternator and the transponder that wouldn't power up anymore. The batterie still doesn't charge and the alternator produces 50+volts with the engine running. Has this happened to anyone else? What could be damaged and where do I start finding the problem. The field is getting just under 12v with the engine running.

 

[bisham]

May not be the problem, but our airplane had one side of the alternator circuit breaker wire loose. Tightened the screw (about a full turn loose) and everything was perfect again.

 

[DNeuf]

Something to check. The "battery sense wire" is a lead to the regulator that the regulator uses to determine the system's state of charge or actual voltage in your electrical system. The battery sense wire may have a high resistance or may be open. If there is a resistance in this circuit, the regulator increases the excitation voltage to the rotor in the alternator to bring up the voltage to around 13.7.
High resistance in this circuit can cause high voltage output from the alternator since the regulator sees less than the actual voltage. An open circuit may shut the regulator down.