A CITATION 650 IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO #1 BATTERY TEMP OSCILLATING AND INCREASING CAUSED BY A CORRODED AND LOOSE BATTERY TEMP PROBE CONNECTOR.

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ENRTE TO TETERBORO FROM WOOSTER; OH; LEVEL FLT AT FL350; I NOTICED #1 BATTERY TEMP BEGAN OSCILLATING AND INCREASING FROM 20 DEGS C TOWARDS 35 DEGS C AND CONTINUING TO INCREASE. WE FOLLOWED EMER CHKLIST PROC BY ISOLATING BATTERY #1 AND NOTICED MINIMAL AMPERAGE DROP. TEMP CONTINUED TO CLB EVEN WITH BATTERY SWITCH IN EMER AND BATTERY RED LIGHT ON BATTERY TEMP GAUGE ILLUMINATED. WE ADVISED THE CTR WE MAY HAVE AN EMER BECAUSE OF OVERHEATING BATTERY #1 AND CANNOT DETERMINE IF ONLY AN INDICATION PROB OR NOT. WE ASKED FOR NEAREST ARPT AND ADVISED WE NEED TO LAND ASAP. THEY VECTORED US TO ILS AT BRADFORD; PA. DURING DSCNT; BATTERY #1 TEMP DECREASED TO 35 DEGS C UPON LNDG. WE CALLED FOR A MECH AND CHKED WITH CITATION SVC CTR AND TOLD TO PLACE HANDS TO CHK TEMP OF BATTERY CASES #1 AND #2. BOTH WERE COLD. THEN WE DISCONNECTED TEMP PROBE CANNON PLUGS FROM BATTERY #2 WITH INDICATED TEMP OF 21 DEGS C AND RECONNECTED. BATTERY #1 IMMEDIATELY UPON RECONNECTION OF TEMP PROBE CANNON PLUG INDICATED 19 DEGS C. MECH FOUND SLIGHT CORROSION ON BATTERY #1 TEMP PROBE PLUG; CLEANED AND LUBED AND REATTACHED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE BATTERY TEMP INDICATOR FOR THE #1 BATTERY WAS AT FIRST OSCILLATING AND THEN JUST STARTED TO RISE INTO THE WARNING ZONE. THE RPTR SAID THE BATTERY IS A NICKEL CADMIUM TYPE AND IS SENSITIVE TO HEAT. THE RPTR SAID THE MECH IN BFD FOUND THE BATTERY TEMP PROBE CONNECTOR CORRODED AND LOOSE AND WAS ABLE TO CLEAN THE PINS. THE RPTR STATED THE BATTERY AND THE BATTERY TEMP INDICATOR HAS WORKED SATISFACTORY SINCE THE REPAIR.