Check the voltage of Battery with multimeter. Connect load to it terminals. Now check voltage .If it is constant for some time like 5-10 seconds. it is working. if it is not constant. Charge it once by keeping constant voltage across battery. after some hours check it once by doing same as earlier. if even it is not working. battery may damaged.
note: while testing take care of battery terminals. those terminals should not short. ie., dead short.