Battery Capacity Definition

Battery capacity is one of the most important performance indicators of battery performance and is defined as the product of the current flowing into or out of the battery in ampere hours and the length of time in hours. Battery capacity affects the operating time of a device, and in general, the higher the battery capacity, the longer the operating time for the device.

Battery Capacity Units

Battery capacity is usually measured in ampere-hours (Ah) or milliampere-hours (mAh), but in addition to these two units, we often use watt-hours (Wh) or kilowatt-hours (kWh) when measuring high-capacity batteries.

Battery Capacity Formula

Current (I) indicates the current flowing into or out of the battery in amperes (A), and time (T) is the time the battery maintains a specific current, expressed in hours (h).

1. Battery storage capacity calculation formula

Battery capacity (Q) = current I (amps) x time T (hours)

1.1 For example, if there is a lithium iron phosphate battery discharged at a constant current of 10,000 mA (milliamps) for 5 hours, what is the capacity of the battery?

Battery capacity (Q) = 10000mA x 5H = 50000mAh = 50Ah

So the capacity of a lithium iron phosphate battery is 50Ah.

1.2 For example, if there is a lithium iron phosphate battery with a capacity of 100 ampere hours (Ah),which can supply a constant current of 10 amperes, how long can the lithium iron phosphate battery last?

Time (T) = battery capacity (Q) / current (I) = 100Ah / 10A = 10 hours

So lithium iron phosphate battery can be used for 10 hours.

2. Battery capacity formula

For example, a device can support 12V, can also support 24V, with a 12V (30AH) lithium iron phosphate battery power supply, can provide two hours, then with two series connection will become 24V (30AH) which ampere hours did not increase, but the duration will be twice as long, so the capacity of this time should be taken into account for the power held by the battery, and can not be considered purely for ampere hours.

W (work) = P (power) × T (time) = I (current) × U (voltage) × T (time)

2.1 For example, if there is a 12V lithium iron phosphate battery that can be discharged for 10 hours at a discharge current of 10 amperes, what is the work done by the battery?

W = 10 (current) × 12V × 10 (time) = 1200J

So the work of the lithium iron phosphate battery is 1200

Factors affecting battery capacity

1. The effect of temperature on battery capacity

Battery capacity will vary with the temperature, the lower the temperature the faster the capacity of the battery will fall, the higher the temperature the capacity of the battery will also fall. Due to the difference in the type of battery, different types of batteries have different temperature temperature adaptability, for example, lithium iron phosphate batteries have a strong high temperature adaptability, lead-acid batteries have a greater impact on high and low temperatures, so we need to avoid extreme temperatures, to mitigate the impact of temperature on battery capacity.

2. Impact of battery type on capacity

Different types of batteries have different characteristics, the capacity of the battery will be different, for example, lead-acid batteries have a discharge depth of about 50%, lithium iron phosphate batteries have a discharge depth of 100%, lithium iron phosphate batteries have a higher capacity, which can be used for a longer time for electric equipment. And improper maintenance of the battery will also cause a decline in battery capacity, the traditional lead-acid batteries have a greater impact, lithium iron phosphate batteries are maintenance-free, the impact factor is smaller.

3. Discharge rate on the impact of battery capacity

In different discharge rate, the capacity of the battery will be different, the capacity of lead-acid batteries as the discharge rate increases and decreases, generally lithium iron phosphate batteries can be used for a long time under high discharge rate, the use of lead-acid batteries will be greatly reduced.

4. The influence of electrode plate on battery capacity

The larger the area of the electrode plate, the more active substances that can participate in the electrochemistry, the greater the capacity. Under the same conditions of the battery shell, the use of thin electrode plates can increase the number of electrode plates and increase the porosity of the active material, which can improve the capacity of the battery. In addition, the thickness of the battery electrode plate and the height of the battery electrode plate will have an impact on the battery capacity, the thicker the electrode plate the lower the battery capacity.

5. The use of conditions on the impact of battery capacity

The use conditions of the battery will also affect the battery capacity, such as overcharging, over-discharging, etc., will make the battery capacity decline, when the battery is not in use when the battery is placed in a dry, ventilated area and regularly charge the battery, you can ensure that the capacity of the battery will not decline.

Conclusion:

Battery capacity can be calculated using ampere hours, but in our daily life often use watt hours to determine how much work the battery can do, when choosing a battery, we recommend that you use lithium iron phosphate batteries, lithium iron phosphate batteries have lower external influences and can be used for a longer period of time.