First, to calculate the voltage and capacity of a lithium battery, we need to understand the voltage of different cathode materials to calculate the rated voltage.
II. Lithium battery packs are composed of individual battery cells connected in series and parallel.
1. Series connection (S): Increase voltage, capacity remains unchanged.
For example, a single ternary lithium battery has a rated voltage of 3.6V and a capacity of 2600mAh. If 10 ternary lithium battery cells are connected in series, the battery pack voltage will be 3.6V × 10 = 36V, while the capacity will remain unchanged at 2600mAh. The final result is 36V 2600mAh.
For example, a single lithium iron phosphate battery has a rated voltage of 3.2V and a capacity of 4000mAh. If 10 lithium iron phosphate cells are connected in series, the battery pack voltage will be 3.2V × 10 = 32V, while the capacity will remain unchanged at 4000mAh. The final result is 32V 4000mAh.
2. Parallel (P): Increases capacity without changing voltage.
For example, a single ternary lithium battery has a rated voltage of 3.6V and a capacity of 2600mAh. If 10 ternary lithium battery cells are connected in parallel, the battery pack capacity is 2600mAh × 10 = 26000mAh. The voltage remains unchanged at 3.6V, so the final capacity is 3.6V 26000mAh.
For example, a single lithium iron phosphate battery has a rated voltage of 3.2V and a capacity of 4000mAh. If 10 lithium iron phosphate cells are connected in parallel, the battery pack capacity is 4000mAh × 10 = 40000mAh. The voltage remains unchanged at 3.2V, so the final capacity is 3.2V 40000mAh.
3. If the battery cells are connected in both series and parallel, calculate the voltage and capacity using the same method as above.
4. Lithium battery pack capacity WH = Rated voltage of battery pack V × Capacity of battery pack AH.
For example: 48V 15AH ternary lithium battery pack
Voltage: 3.7V × 13 = 48.1V ≈ 48V
Capacity: 2500mAh × 6 = 15000mAh = 15Ah
Power consumption: 48V × 15Ah = 720Wh
III. How to calculate the number of strings
Taking a ternary lithium battery with a rated voltage of 3.6V and a 48V rating as an example: 48/3.6 = 13.3 ≈ 14 series.
Taking a ternary lithium battery with a rated voltage of 3.7V and a 48V rating as an example: 48/3.7 = 12.9 ≈ 13 series.
Taking a 48V lithium iron phosphate battery with a rated voltage of 3.2V as an example: 48/3.2 = 15 series.
In other words, ternary lithium batteries with 13 or 14 cells in series both represent 48V, and the appropriate charger must be selected; lithium iron phosphate batteries with 15 cells in series also represent 48V.
Taking a 48V battery as an example:
Example: Calculate using a ternary monomer at 3.7V:
13 cells connected in series (13 * 3.7V = 48.1V) Charging voltage: 13 * 4.2V = 54.6V
14 cells connected in series (14 * 3.7V = 51.8V) Charging voltage: 14 * 4.2V = 58.8V
Example: Calculate based on a single lithium iron phosphate cell at 3.2V:
15 individual units connected in series (15 * 3.2V = 48.0V) Charging voltage: 15 * 3.65V = 54.75V
16 individual cells connected in series (16 * 3.2V = 51.2V) Charging voltage: 16 * 3.65V = 58.4V
At room temperature, it is charged at a constant current rate of 0.5C to 4.2V (for lithium iron phosphate, it is charged to 3.65V), and then switched to constant voltage charging.
IV. How to calculate the quantity and
Taking a 20Ah lithium battery pack as an example
The rated capacity of a single battery cell is 2500mAh, 20Ah/2.5Ah = 8 parallel cells.
