Open up fan. Put 1-2 drops of sewing machine oil on fan shaft at fan bearings (bronze bushes) and try running fan. If fan runs fine, problem solved. If problem still exists, see type/rating (volts and amp hour) of battery. Probably is 6v or 12 volt, 2 - 4 Ah lead acid battery. Search on web for its price and dealers in Lahore. To test whether battery is dead or circuit has fault, disconnect old battery wires from battery and connect with known good same voltage charged battery keeping note of + and - wires going to right terminals on new battery. If fan runs OK, then problem is either old battery or battery charging circuit (usually a trickle charger). If fan still doesn’t run with known good battery, then problem is with fan motor or circuit.