AN ATR42-300 IN CRUISE AT 15000 FT DECLARED AN EMER AND DIVERTED DUE TO LOSS OF ENG DC ELECTRICAL PWR INCLUDING MAIN SHIP'S BATTERY; SWITCHED TO EMER BATTERY PWR.

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15000 FT CRUISE FROM TPA TO MIA IN VMC CONDITIONS WHEN THE DC GENERATOR #1 FAULTED. REFING THE QRH CHKLIST FOR THE FAULT ALLOWED FOR A RESET OF THE GENERATOR. ONCE THE GENERATOR WAS RESET; THE ELECTRICAL SYS WENT 'BIZERK.' ALL BELLS; CHIMES AND WARNING LIGHTS IN THE COCKPIT ACTIVATED SIMULTANEOUSLY; AS WELL AS LIGHTS IN THE PAX CABIN. WE DECLARED AN EMER AND INITIATED A DSCNT TO BELOW 10000 FT DUE TO LOSS OF CABIN PRESSURE. THEN WE PROCEEDED WITH DUAL DC GENERATOR FAILURE CHKLIST. MAIN BATTERY PWR (WHICH SHOULD HAVE LASTED APPROX 43 MINS) WAS LOST WITHIN 1 MIN. THE FLT ATTENDANT CAME TO THE COCKPIT AS SOON AS HIS CABIN LIGHTING STARTED MALFUNCTIONING. WE CONTINUED WITH THE CHKLIST; SELECTING OVERRIDE/UNDERVOLTAGE PER THE QRH IN ORDER TO GO TO EMER BATTERY PWR. THE FLT ATTENDANT WAS BRIEFED IN PERSON. CONTACT WITH ATC (WHICH HAD BEEN LOST WITH THE MAIN BATTERY) WAS NOW RE-ESTABLISHED AND WE WERE GIVEN VECTORS TO RSW. WITH THE INTEGRITY OF THE EMER IN QUESTION; WE ELECTED TO PERFORM A NO FLAP LNDG. THE LNDG WAS ACCOMPLISHED WITHOUT INCIDENT; WITH EMER BRAKING BEING SATISFACTORY. CFR TEAM AND ACFT OPS PERSONNEL MET THE ACFT AS IT EXITED THE RWY AT TXWY A6. THE FIRE MARSHALL ASKED IF WE HAD EXPERIENCED A MAIN BATTERY THERMAL RUNAWAY. NOT HAVING A BATTERY TEMP GAUGE; WE TOLD HIM THAT WE HAD NO WAY OF KNOWING. HE CHKED IT (HE WAS ALSO AN A&P RATED MECH) AND SAID THE BATTERY WAS HOT AND SHOULD BE REMOVED IMMEDIATELY. THE PAX WERE EVACED FROM THE ACFT AND THE BATTERY WAS REMOVED TO THE GRASSY AREA ADJACENT TO THE TXWY. THE ACFT WAS THEN TOWED TO THE CARGO RAMP TO AWAIT INSPECTION BY THE MAINT DEPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE NTSB AND THE FAA HAVE INTERVIEWED THE CREW RECENTLY. THE RPTR SAID THE EXACT CAUSE AT THIS TIME IS UNKNOWN BUT THE FOLLOWING COMPONENTS WERE REPLACED: BOTH ENG DC GENERATORS; L ENG GENERATOR WIRE HARNESS; THE L GENERATOR CTL UNIT AND THE MAIN SHIP'S BATTERY. THE RPTR STATED AT NO TIME WAS ANY ELECTRICAL ODOR OR SMOKE PRESENT IN THE COCKPIT.