u/PrincipleCapable8230

Hello All. I recently (2 months) purchased a Buzz Cerana 2, which I know is a pretty cheap entry level e-bike. I have some questions about battery charging and capacity. When I charge the battery for overnight (or more), it starts at 95%. It then drops quickly and even sometimes goes slightly back up as I ride. This morning I rode 6.5 miles and it was at 26%, which seems like a lot of battery to use. Are my expectations too high? Would a replacement battery get me more range? I am so far loving the bike, just worried about stranding myself. Thanks!