Lithium Battery Calculator Guidance

A professional, cost-performance lithium battery pack solution can increase sales and boost brand value. CMB can provide you with professional custom battery packs using our sophisticated lithium battery calculator. If you’re a newcomer to the field and struggling with a lithium-ion battery calculator, don’t worry! Here is some guidance to get more knowledge about lithium batteries.

Understanding Battery Capacity, Voltage, and Wattage

To begin with, it’s essential to determine the capacity, voltage, and wattage of your battery pack solution. Without this information, we won’t be able to proceed to the next step.

The battery capacity calculator is the amount of energy that it can store. A battery’s capacity is named in amp hours (Ah), which is a measure of electrical current over time. One amp hour means one amp of current flowing for one hour. The higher the Ah, the longer the working time the battery will last.

Use the following formula for lithium battery amp hour calculator:

Watt-hours ÷ battery voltage=discharge current x time (hours) x voltage

For example :

The voltage of the battery is 36V and it should support the device’s work over 2 hours. The continuous discharge current is 10 amp and the peak continuous discharge current is 20 amp. For battery ah calculation:

The minimum capacity is the continuous discharge current 10amp X 2 hours = 20Ah.

Or the watt of the bike is from 24V 350W ~450W and it should support the device work over 2 hours.

The capacity is 450W ÷ 24V X 2hours=37.5Ah.

If you would like the battery with a longer lasting time, the Ah can be increased.

Battery Size Calculator

The battery size calculator is how much energy is stored. The common lithium cell size data as below:


Different brands of lithium cells have different size scopes.

The battery pack size calculator depends on the capacity.

For instance, if you require a 43.2V 40Ah 12S10P 21700 lithium battery for the electric surfboard, the battery Pack Dimension is calculated as follows:

21700 electric surfboard battery

43.2V 40Ah 21700 Battery Pack for the electric surfboard

  • Length: 14 x 21.3mm = 298.2mm
  • Width: 10 x 21.3mm = 213mm
  • Height: 72mm (Add red paper)

Based on the above calculations, the complete battery size calculator is 305X238X72(mm).

Battery Consumption Calculator 

Each battery has a consumption rate, which is typically between 0.2% and 5% for lithium batteries. To ensure optimal performance, it’s crucial to charge the battery pack every 3 months. Factors such as battery pack design, BMS, materials, and storage environment affect the battery consumption calculator.

1A=1000mA, 1mA=1000μA

For example, a 5Ah battery with a daily consumption rate of 500μA would last approximately 250 days before being fully depleted.


When the battery capacity is less than 50% before the storage, we should charge the battery every 3 months; When the battery is less than 90% before the storage, we should charge the battery every 6 months.

Battery Discharge Time Calculator 

The battery discharge time calculator helps determine how long a battery will last during operation. The formula is as follows:

Discharge time (hours)=Battery Capacity (Ah)÷Load Current (A)

Please note that the working temperature and environment can affect the load current and, consequently, the battery discharge time. To account for these factors, use the adjusted formula:

Discharge time (hours)=Battery Capacity (Ah) x 0.8(Cardinal Ratio) ÷ Load Current (A)

For instance, for a 12V 100Ah LiFePO4 battery pack with a load current of 50A and an environmental temperature of 35°C:

  • Discharge time (hours) = Rated capacity x Rate discharge capacity x  (1 + 0.006 x Temperature cardinal ration x (Environment temperature – Standard discharge temperature))÷ Load current
  • Discharge time (hours) =(100Ah x 0.8) x (1 + 0.006 x 1 x (35°C – 25°C)) ÷ 50A
  • Discharge time (hours) = 1.696 hours


  1. In the actual discharge process, the load current gradually increases and is not constant. The discharge duration must be different from the calculated one. The current is larger, the discharge time is shorter under the same capacity.
  2. The battery capacity will decrease and should be calculated using the actual capacity after long use. In the initial stage, rated capacity can be used for calculation.
  3. If the battery is not fully charged due to the various discharges, the calculated time will be different.

Battery Charge Time Calculator

Use the following formula to calculate charging time:

Charge time (hours) = Battery capacity (Ah) ÷ Charge current (A) x 1.5 (Cardinal Ratio)

18650 battery

For example, if you have a 3.7V 2600mAh high-temperature li-ion battery with a capacity of 2.6Ah and a charge current of 1A.

The battery time is 2.6Ah÷1A x 1.5=3.9 hours.


  1. When we charge the lithium-ion battery, it is best to choose the dedicated li ion charger from the factory, otherwise, it will affect or damage the li ion battery packs.
  2. The lithium-ion batteries are generally equipped with corresponding constant current chargers. This lithium-ion battery charger controls the charging time of the lithium-ion battery by using a full power indicator light. When the battery is fully charged, an alarm signal will be emitted.
  3. Lithium-ion battery charge temperature range: 0~45 degrees Celsius. If you have a special charge environment, please share your specific charge temperature with the battery pack manufacturer.
  4. Lithium-ion batteries must be prevented from overcharging during the charging process. Overcharging of lithium-ion batteries will cause serious damage to battery performance or even explosion.

Lithium-ion batteries are one professional industry and product. The working of custom battery packs is deadly serious because the lithium-ion battery calculator will affect the li ion battery pack performance and cost. Effective communication between customers and battery pack manufacturers, including sharing specific requirements and battery knowledge, is key to obtaining reliable and long-lasting solutions.

Our Team provides professional lithium battery calculator guidance. Contact us for guidance on customizing battery packs.


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