There are mainly two reasons why gate motor might not be charging the battery. The first issue might be caused by a faulty gate motor charger supply. You need to test the charger and confirm if there is enough voltage required for charging the battery. Each gate motor and battery are different so you need to know the size of the batteries and how much voltage required to charge. Secondly, check if the power cables to the battery are tight and no dirt. Thirdly, the batteries might be dead. In a case where there is correct voltage from your battery charger, replace the batteries.