battery change

Mine is a DELTABELX 3 Existing battery is ORBITPOWER 7.2volts 250mah-NiMh. there is a jumper to set to either default-inernal Batt, Or ext batt. The Ext battery connects to the bottom screw terminal of the 11 terminal strip; and the - ground as the 12v -ve (lets call it T2 ). I don't see any...