M20P PLT HAD GENERATOR FAILURE. THIS RESULTED IN A NO COM APCH IN VMC AT SPX.

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ACFT EXPERIENCED A FAILURE OF THE GENERATOR/CHARGING SYS THAT CAUSED GRADUAL DISCHARGE OF BATTERY. WHILE IN CRUISE; AT 8500 FT MSL; OVER BPT'S TRSA; I EXPERIENCED LOUD FEEDBACK IN THE SYS AND WAS UNABLE TO RECEIVE/XMIT. I WAS UNABLE TO NOTIFY ZHU -- LAKE CHARLES ESPECIALLY; WITH WHEN I WAS VFR FLT FOLLOWING. I PLACED THE XPONDER TO 1200 AND CONTINUED MY FLT INTO PREVAILING VFR. I DSNDED INTO DEST AT SPX AND MADE A NORDO ENTRY AND LNDG TO THE TFC PATTERN. ON ARR; THE FBO ATTENDANT INFORMED ME THAT CTR WANTED TO TALK TO ME. I WAS ON THE GND APPROX XA00 AND MADE CONTACT WITH ZHU AT APPROX XA20. FACTORS INCLUDE: 1) AN AMMETER THAT IS SMALL; AND INDICATES +/- CHARGING INDICATION; WITHOUT NEGATIVE/DISCHARGE INDICATION. 2) MY FAILURE TO DETECT AND NOTIFY CTR OF POSSIBLE RADIO/XPONDER DIFFICULTIES DUE TO DISCHARGING BATTERY WHILE FLT FOLLOWING. 3) I HAD A HANDHELD COM WITH ME THAT HAD INADVERTENTLY BEEN LEFT ON THE DAY BEFORE; DISCHARGING TOTALLY AND BECOMING USELESS. NOTE: IF MY XPONDER WAS NOT XMITTING DUE TO LOW PWR; I MAY HAVE BEEN SEEN AS A 'PRIMARY TARGET ONLY' WITHIN HOUSTON CLASS B MODE C VEIL ON MY APCH INTO SPX.