Analyzing battery ratings: mAh and mWh.
When choosing a device, battery capacity becomes a key consideration factor. However, regarding battery units such as mAh (milliampere hour) and mWh (milliwatt hour), they often confuse people. In this article, we will unveil the mystery of battery capacity.
MAh: a measure of battery capacity
mAh， Milliampere hour is a unit specifically used to measure the charging capacity of a battery. It refers to the duration for which a battery can discharge continuously at a certain current. Simply put, mAh represents how much energy a battery can release in one hour. At the same rated voltage, the larger the capacity, the longer the battery life. Imagine that mAh is like the amount of water that a reservoir can hold. The higher the mAh value, the larger the reservoir.
Here is a simple formula to explain the concept of mAh: Q=I × t, where:
·Q represents the charge capacity of the battery, measured in mAh.
·I represents current, measured in milliamps (mA).
·T represents time, measured in hours (h).
If a battery has a rated capacity of 2000mAh, it means it can output 2000mA current (equivalent to 2A current) within 1 hour.
MWh: Measurement of battery energy storage
MWh (milliwatt hours) represents the energy generated by the constant power provided by the battery at different operating voltages. In fact, true capacity is closely related to voltage. The voltage of most batteries is not a fixed value and may vary during use.
In short, mWh is like the total energy stored in a reservoir, combining depth (voltage) and volume (capacity). This means that mWh can more accurately reflect the energy potential of the battery.
Let's use a simple formula again to explain the concept of mWh: W=U × Q, where:
·W represents the energy capacity of the battery, measured in mWh.
·U represents voltage, measured in volts (V).
·Q is the charge capacity of the battery, measured in mAh.
For example, if a battery has a capacity of 2000mAh and a voltage of 3.7V (V), its energy capacity would be 7.4Wh or 7400mWh. This means that this battery can provide 7400mWh of energy.
Conversion between mAh and mWh
MAh and mWh are two different ways of measuring battery capacity, and their conversion is based on the voltage of the battery. They can be converted using the following formula:
mWh = mAh×V
This conversion is particularly important in regulations regarding the carrying of lithium batteries in aviation and other fields. Usually, the capacity of lithium batteries cannot exceed 100 watt hours (Wh). But many rechargeable batteries are labeled in mAh units and can be quickly converted to mWh.
Why do most batteries use mAh as their capacity rating?
This is mainly because mAh can more intuitively reflect the battery's usage time. For example, when we know that a power bank has a nominal capacity of 20000mAh and our smartphone battery has a nominal capacity of 5000mAh, we can quickly estimate that the power bank can charge the phone approximately four times. This simple calculation method makes it easier for us to estimate the device's battery life.
MAh is easy to calculate, while mWh may involve complex issues with the discharge platform. And we have become accustomed to this way in our daily lives.
However, in some cases, using mWh rating is more appropriate. Especially when comparing battery capacities at different voltages, mWh provides a more accurate basis for comparison. For example, when comparing a 2500mAh 1.5V lithium-ion battery with a 1.2V nickel hydrogen battery, by calculating their mWh values, we can more accurately determine which battery has a higher rated capacity.
2500mAh x 1.5V = 3750mWh
2500mAh x 1.2V = 3000mWh
Therefore, the rated capacity of a 1.5V No. 5
lithium-ion battery is higher than that of a 1.2V No. 5 nickel hydrogen battery.
Different units need to be used in different situations
High energy consuming equipment
For high energy consuming devices, mWh tags are more suitable. Due to the need for continuous and stable power supply and fast power consumption, these devices often operate at different voltages, and the impact of voltage differences on energy capacity needs to be considered.
Multi battery assembly
When multiple battery units are connected in series or parallel, such as laptop battery packs or remote-controlled toy cars, mWh labels also help accurately represent the total energy capacity.
Different device drivers
The driver program used by the device also determines the choice of measurement units. Linear constant current drivers directly control the current from the battery, making mAh a more suitable unit of measurement. And boost or buck drivers have fixed output power and relatively consistent efficiency, in which case mWh is more suitable.
Application scenarios of mAh and mWh
In home environments, we typically use devices with lower power requirements, such as TV remote controls and wall clocks. The power and current levels of these devices are relatively low, and the frequency of battery replacement is also relatively low, so prioritizing battery life is crucial. In this case, mAh is a more appropriate unit of measurement for current capacity.
For example, a household wall clock consumes approximately 2mW of power per hour. If you use a standard No. 5 battery with a nominal capacity of 3000mAh (rated voltage of 1.5V), it can power a wall clock for up to 2250 hours. This indicates that mAh batteries are very suitable for devices that require long-term use and have low power consumption.
In another scenario, when using a 20000mAh power bank to charge a 5000mAh smartphone battery (usually a 3.7V battery), you can quickly calculate that it can charge the phone four times. Therefore, mAh is used to indicate battery capacity, allowing users to intuitively calculate usage time.
However, in the field of medium to high energy consuming devices, such as VR controllers, wireless microphones, electric toothbrushes, remote cameras, and electric remote-controlled cars. These devices typically require a stable power supply and quickly consume power to provide a sensitive experience. In this case, mWh becomes the ideal unit of measurement.
Some well-known brands label both mAh and mWh on the battery, allowing users to quickly and easily understand information without the need for calculation. For example, XTAR has labeled 4150mWh and 2500mAh on its latest rechargeable 1.5V No. 5
lithium battery.
conclusion
In short, we use various electronic devices in our daily lives, each with its specific power requirements. By understanding the difference between mAh and mWh, we can better choose batteries that meet the energy requirements of the device, ensuring the normal operation of electronic devices.
Whether pursuing long battery life, higher power output, or compatibility with different voltages, the key to choosing depends on the specific application scenario. These measurement units provide us with key information about battery performance and applicability, enabling us to make appropriate choices.
