Lithium-ion batteries have a certain range of cell voltage. For example, the normal working voltage range of lithium iron phosphate batteries is 2.5V-3.65V, and the normal working voltage range of lithium manganese oxide and ternary batteries is 3V-4.2V.

In the application of lithium-ion batteries, when the total voltage is 60V and below, a battery protection board is required. Above 60V, a battery management system (BMS) is required. The role of these two devices is to protect the battery from working properly.

Note that after the number of strings of the battery pack is determined, the voltage of the battery pack cannot be adjusted arbitrarily. That is, the voltage change of the battery pack can only change within the normal working voltage range: when charging, it rises from the lower limit of the voltage to the upper limit of the voltage. When using electricity, it drops from the upper limit of the voltage to the lower limit of the voltage.

The best solution: make a set of battery packs, equip a suitable inverter, and equip a DC voltage regulator to meet the voltage step-up and step-down requirements of lithium batteries.