On November 11, 1998, approximately 1240 mountain standard time, a Piper PA-28-161, N8236Z, was destroyed by fire while taxiing at Tri-County Airport, Erie, Colorado. The commercial pilot, the sole occupant in the airplane, was not injured. The airplane was owned by the pilot and operated by Air West Flying Club of Broomfield, Colorado, under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country flight which originated approximately 20 minutes before the accident. No flight plan had been filed. The pilot took off en route to Jeffco Airport. Approximately 15 minutes after takeoff, he began to smell something like "ether." The pilot stated that the smell got stronger, and the engine began to run rough. The roughness of the engine increased, and the pilot decided to divert to Tri-County Airport, Erie, Colorado. The pilot said that after landing and taxiing off the end of runway, he began to smell raw fuel. Simultaneously, he became aware of smoke outside the airplane and in the cockpit. The pilot evacuated the airplane. He further stated that "by the time I turned around, the cockpit was engulfed in black smoke, and there were flames coming from the pilot's side of the engine [aft of the fire wall] and wing root area." The airplane was destroyed in the ensuing fire. The pilot described the events leading up to the accident as follows: He began his preflight inspection of the airplane that morning by turning the master switch on. He noted that the navigation lights illuminated and he heard the turn-coordinator gyro begin to spin. He noted that one of the airplane's wings had snow on it and that the airplane had been sitting on the ramp for 7 days (this was to be the first flight since the last 100 hour inspection on November 4, 1998). Airport personnel said that "the last 2 or 3 days had been very cold, with temperatures in the high teens and low 20's at night." The pilot attempted to start the engine and the "propeller barely turned over." He requested assistance in starting the engine and ramp personnel brought out a battery power cart. The Piper External Power (PEP) plug was located on the right side of the fuselage aft of the baggage door. Ramp personnel stated that "the PEP plug did not work" and the decision was made to "jump" the battery. The back seat was removed and the cables were connected to the battery. The engine was started, and the rear seat was replaced. The pilot took off and flew to Ft. Collins-Loveland Municipal Airport, approximately 30 minutes in duration. After landing, he remained on the ground for 15 to 20 minutes. When it came time to leave, the engine stated without difficulty. A Piper representative stated that "a dead or depleted aircraft battery should not be charged in the aircraft." The Pilot's Operating Handbook (POH) does not caution the pilot against charging a depleted aircraft battery in the airplane. Airworthiness Directive 81-23-05, which required the installation of a wooden buffer between the rear seat springs and the battery post, had been complied with. Post-fire examination of the area around the battery failed to disclose any evidence that the battery had ruptured or exploded. Piper Aircraft Corporation Service Bulletin #836A, dated August 26, 1986, which recommends that the aluminum battery cable be replaced with a copper cable, had not been performed. The original aluminum battery cable, which extended from the battery (under the right rear seat) to the starter and the alternator via the bus, was still in place. Representatives from Piper and Gill (the battery manufacturer) said that the aluminum battery cable had "a tendency to change its electrical properties with use." They stated that the cable's resistance increased with age, flight time, and flight cycles. The airplane was manufactured in 1980, and the owner estimated that it had accumulated more than 18,000 hours of flight time at the time of the accident. The airplane's maintenance logbooks indicate that on June 27, 1998, the airplane received a 100 hour inspection at which time the battery was serviced. At the next 100 hour inspection, on August 8, 1998, the mechanic noted that the battery terminals were "cleaned of corrosion." The last 100 hour inspection was completed on November 4, 1998, and again the battery terminals were cleaned of corrosion. The owner of the maintenance shop that performed the 100 hour inspections reported that he "knew the battery was getting weak." The airplane has two main fuel tanks, one located in each wing. The right wing's fuel moves through an aluminum line, across the fuselage, to the left wing root. From there, it proceeds forward to the fuel selector located by the pilot's left knee. The left wing's fuel enters the fuselage and travels forward to the fuel selector. Coincidentally, the battery cable proceeds from under the rear seat to the left wing root and then forward to the firewall. In the vicinity of the fuel selector, the battery cable is 4 to 6 inches above the fuel lines. This is the same area described by the pilot where he first observed the fire.