When troubleshooting batteries, it is important to always check the voltage at the battery terminals with a multimeter. Then you can try charging the battery using a battery charger and charge it up fully. When the battery is fully charged, you should let the battery sit without using it for about an hour, and then check the voltage of the battery again using the multimeter. If the voltage has dropped after not using it for a period of time, then there may be an issue with your battery. Typical issues with batteries include bad cells, deactivated BMS if the battery is a lithium battery, loud or bubbling noises, rapid discharge, and not being able to hold too much of a steady charge.