Hello, first check whether the battery has swollen, swollen then the battery is broken, need to be replaced, do not use again, more dangerous. If not, unplug the charger power, and then plug it in to see whether the charger turns the lamp, if the lamp turns, the battery is short of water, need to add water maintenance, you can add an appropriate amount of distilled water in each cell of the battery, or pure water, generally not more than 10 ml, you can inject with a new syringe. But don't add tap water. Finally, use a multimeter to check whether the charging output voltage of the charger is normal. Generally, the charging voltage of the 48V battery is about 55.6V. About 41.7V of 36V. If the charger is normal, check the battery charging port voltage (that is, battery voltage), whether it is normal, possibly the battery is broken. Use the above methods to eliminate, hope to help you.