THE ACFT WAS OBSERVED FLYING THROUGH THE TOP OF A TREE, THEN THROUGH A FOUR STRAND HIGH VOLTAGE PWR LINE. FINAL IMPACT WAS RELATIVELY FLAT IN A SOY-BEAN FIELD. THE PLT LATER STATED THAT HE HAD BECOME DISORIENTED IN FLT AND HALLUCINATED THAT HE WAS IN A PIPER J-3 ACFT INSTEAD OF A PIPER ARCHER. HE SAID HE MUST HAVE LOST CONTROL AS HE REMEMBERED NOTHING MORE UNTIL HE FELT THE ACFT CRASHING. THE ACFT WAS OBSERVED BY WITNESSES FLYING THRU THE TOPS OF SOME SMALL TREES AND CONTINUING ON THRU A SMALL PWR LINE BEFORE MAKING A 'PAN-CAKE' LANDING IN AN OPEN SOYBEAN FLD WHERE IT SLID ON IT'S BELLY FOR 120 FT BEFORE STOPPING. THE ACFT WAS RELATIVELY INTACT AND THE ENG RAN WHEN TESTED AFTER THE ACCIDENT. THE BATTERY HAD COME LOOSE FROM IT'S MOUNTING BOX IN THE BAGGAGE COMPARTMENT AND ENDED UP IN THE RIGHT FRONT COCKPIT ON THE FLOOR. THE PLT WAS FOUND WALKING OUTSIDE THE ACFT AFTER THE ACCIDENT. HE HAD A SPRAINED ANKLE AND LACERATIONS ON HIS HEAD. THE PLT ALSO HAD A HISTORY OF MEDICAL PROBLEMS.