Lithium batteries are activated and tested before being labeled and shipped from the factory. There is no such thing as a lithium battery that is not fully charged, it just needs to be fully charged. Lithium batteries usually have a protective plate that cannot be overdischarged or overcharged. As long as the protection plate is attached and no overdischarge or overcharging occurs, there will be no problems and the battery will not be damaged.
The battery should be charged with a balanced charger to ensure that each cell is fully charged to maximize performance. If the performance of one cell is poor, the performance of the entire battery will be poor as well. 64V can be 20 cell 3.2V lithium iron phosphate batteries connected in series. Each of the 20 cells must be coherent and intact. Check if there are any significant cellsdifferent ones and simply replace them.