It may be that the battery is bad. At 10ah it should last a while. When it is charged, and your bike is using it, does your bike ride fine? If so then I would think the battery is hooked up fine. If you were only getting say 18 volts, you'd know it.
You might try this which has worked for me with stubborn lithium batteries. Put it on the charger until it is charged, take it off for a few minutes and put it back on. Keep doing it over and over and over. Sometimes the charger thinks the battery is charged, but it is not. When you plug it first in, it charges it a little. But taking it off and putting it back on you keep giving it a little more juice until it is 100%. At the point the lithium battery tends to remember it's full charge.
If you can, charge your FIRST battery and check the voltage. Charge the SECOND battery and check its voltage. They should be around the same. If you find that your second battery is LESS than the first battery then you know it's not taking a complete charge.