The issue about electric bike battery for bike kit

We purchased a electric bike kit including motor controller, hub motor wheel, throttle, brake lever and with 36V 12AH Lithium Ion electric bike battery that used for testing 36V solar charger from one supplier, not from leaf motor. After charging this electric bike battery for 10 hours by better solar power, full charged, we rode the bike, but hub motor wheel only run about 8km. Then we use 110-230Ac charger to charge this electric bike battery and full charged it. After test, we found this hub motor wheel is still lasted for around 8km.
We use a amperemeter in series to electric bike kit system, powered on and rode it. We got the current is about 5A. The RPM is 257RM.We use 26” hub motor wheel.
We calculate the speed is about 32Km/per hour.
See below formula:
（3.14×26”×0.0254）× 257RPM × 60 minutes ÷ 1000 (m-Km)=32km
If this is 12Ah battery, per hour lost 8ah.We can use 1.5 hours.
See below formula:
12Ah ÷ 8ah/per hour= 1.5hours
We think full charge this electric bike battery per time, the hub motor wheel can run about max 48 km. 32km/per hour × 1.5 hours = 48 km
There is definitely a problem with this electric bike battery, I’m not sure whether electric bike kit is because of the solar charging or our testing, or if it has a fault. But I need a replacement electric bike battery asap, because we don’t have any more 36v electric bike battery, and we sold 1 set of electric bike kit with li battery last week. I think BMS inside this electric bike battery no problem. The problem comes from the li battery cells. Maybe this electric bike battery had stayed in warehouse for a long time and haven’t charged it. It will make the electric bike battery cut down the achieve distances and use life.
So if solve this problem and let my hub motor to work asap, only replace all cells or replace new electric bike battery.
We are angry with our supplier, sent them many emails and no any reply.
Thank you, leaf motor. Help us found the electric bike battery ‘s problem. We are going to order leaf’s products in near future.
Hub motor, electric bike battery, electric bike kit supplier: Leaf Motor Technology Co.,Ltd
Website:https://www.leafmotor.com