Most ebikes come with sealed lead acid batteries. SLA for short.
These batteries require you to recharge them after every use. Even when they are in storage they require charging at the most every 30 days. There lifespan is around 2 years or 200 to 300 charges.
The reason behind charging after every use is to keep the sulfonating action to a minimum. As you use the battery the sulfonating action works faster creating a layer at the top of the battery. The layer gets thicker as you use them. When you recharge the battery and it becomes full the sulfonating action slows down but you have less capacity because the recharge process can only fill the battery to the sulfonating layer. This is why it is hard to tell if your batteries need replacing because they slowly lose there capacity therefore losing your riding range.
We can test your batteries for you and replace them if necessary.