MOONEY M20 PLT LOST ELECTRICAL PWR DURING IFR FLT RESULTING IN DIVERSION TO ANOTHER ARPT AFTER DSNDING INTO VFR CONDITIONS.

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I WAS FLYING IN IMC AT 9000 FT LEAVING THE HOUSTON AREA ON AN IFR FLT PLAN TO HOT SPRINGS; AR. THERE WERE HVY TSTMS AHEAD TO THE N; AND I WAS BEING VECTORED EASTWARD AROUND THEM. RATHER THAN REMAIN CLR OF THE ACTIVITY; I ENTERED AN AREA OF RAIN AND EXTREMELY STRONG UPDRAFT; WHICH CAUSED ME TO LEAVE MY ASSIGNED ALT AND CLB APPROX 2000 FT BEFORE THE ASCENT STOPPED. I IMMEDIATELY TRIED TO CONTACT ZHU FOR VECTORS CLR OF THE WX; BUT THERE WAS A SLIGHT DELAY AS THE CTLR INDICATED THAT HE THOUGHT HE HAD ALREADY 'HANDED ME OFF' TO ANOTHER CTLR. I WAS TOLD TO TURN 'HARD R' AND CHANGE FREQS; WHICH I DID. AS SOON AS I WAS ABLE; I ALSO BEGAN A DSCNT TO MY ASSIGNED ALT. WHEN I ESTABLISHED CONTACT WITH THE NEW CTLR; IT APPEARED HE WAS HAVING TROUBLE RECEIVING MY XPONDER; AT WHICH TIME I NOTICED THAT THE 'RESPOND' LIGHT ON THE XPONDER WAS NOT ILLUMINATING. ALSO; MY ARGUS MOVING MAP HAD TURNED OFF AND I IMMEDIATELY BEGAN TO SUSPECT I HAD AN ELECTRICAL PROB. SOON AFTER; I WAS UNABLE TO REACH ATC AND COULD ONLY HEAR THEIR CALLS TO ME. AT THIS POINT; I PUT 7600 ON THE XPONDER; WHICH WAS PROBABLY INEFFECTIVE AND ASSESSED MY SIT AS BEING VERY SERIOUS. I FELT THIS WAS AN EMER CONDITION DUE TO LOSS OF COM WITH ATC; LOSS OF NAV DUE TO ELECTRICAL FAILURE; AND NOT KNOWING MY CURRENT POS DUE TO THE STORM AND THE SUBSEQUENT DIVERSION. FORTUNATELY; I SAW THE CLOUDS THINNING BELOW ME AND BEGAN AN IMMEDIATE DSCNT AND QUICKLY BROKE OUT BELOW THE CLOUD LAYER. I SAW AN AIRFIELD BELOW ME AS I BROKE OUT; AND IMMEDIATELY HEADED FOR IT TO LAND; AS I CONTINUED TO TRY TO CONTACT ATC. JUST AS I WAS PASSING OVER THE ARPT; I RECEIVED A FINAL CONTACT FROM ATC ASKING FOR MY ALT. I REPLIED THAT I WAS AT 1800 FT AND DID NOT KNOW MY CURRENT LOCATION; BUT HAD AN ARPT BELOW ME AND WAS LNDG IMMEDIATELY. ATC REPLIED THAT THEY HAD A 'PRIMARY' TARGET OVER EVADALE; TX; WHICH TURNED OUT TO BE MY LOCATION. ALTHOUGH IT TURNED OUT THAT EVADALE ARPT HAD BEEN CLOSED ONE MONTH AGO; I MADE AN UNEVENTFUL LNDG. I CALLED FSS ON MY CELL PHONE AND REQUESTED THAT THEY CONTACT ZHU AND ADVISE THEM THAT I WAS ON THE GND AT EVADALE; WHICH THEY DID. WE SUBSEQUENTLY DETERMINED THAT THE BRUSHES HAD FAILED IN THE GENERATOR AND STOPPED CHARGING THE BATTERY. ALL THE INSTS AND RADIOS WERE OTHERWISE OPERATING PROPERLY. AS A RESULT OF THIS EVENT; THE GENERATOR IS BEING REPLACED BY AN STC'ED ALTERNATOR FOR IMPROVED RELIABILITY AND A LOW VOLTAGE WARNING LIGHT WILL BE ADDED TO THE INST PANEL.