When you are looking to buy electrical devices, batteries, chargers and power banks, you will often be faced with an array of complicated-looking specifications referring to mAh, Wh, V and A ratings. These are all different units of measurement relating to an item’s electrical power and capacity. It can be overwhelming trying to decipher what all these units mean, and how they relate to each other.
In this article, we will not only explain what each of these electrical units measures, but will also show you how you can convert mAh measurements into Wh and vice versa so that you can compare and contrast devices more accurately.
Once you understand how these units work and relate to each other you will be able to better understand the performance abilities of your electrical devices.
mAh to Wh Conversion Formula:
First off, let’s get straight to the nitty-gritty and have a look at the mathematical formula for converting mAh to Wh and vice versa. For those of you who are simply needing to compare specs for two different devices, this formula will serve you well:
Wh = mAh x V / 1000
mAh = 1000 x Wh / V
In longhand: to convert mAh to Wh you simply have to multiply the milliamps per hour by the voltage and then divide the answer by 1000. This will give you the Watts per hour. To reverse this process and convert Wh to mAh you simply multiply the number of watt-hours by 1000 and then divide the answer by the voltage. This will give you the milliamps per hour.
For example, let’s look at how we would convert the charge of a standard C battery into Watt-hours. A C battery is generally 8000mAh at 1.5 volts:
Wh = 8000mAh x 1.5V / 1000
Wh = 12000 / 1000
Wh = 12
To reverse this…
mAh = 12Wh x 1000 / 1.5V
mAh = 12000 / 1.5
mAh = 8000
If you are looking to quickly convert an mAh rating into Wh, here are some standard measures that you might find useful:
- 5000mAh = 19Wh
- 10000mAh = 37Wh
- 20000mAh = 74Wh
- 50000mAh = 185Wh
And here are some common Wh power bank capacities and the equivalent mAh ratings:
- 10Wh = 2702mAh
- 20Wh = 5405mAh
- 50Wh = 13515mAh
- 100Wh = 27027mAh
- 200Wh = 54054mAh
If this is all you needed to know, then good for you. However, if you are still feeling baffled, let’s break things down into smaller pieces…
What Does mAh Mean?
mAh stands for milliamps per hour (milliamp-hour).
It is the unit of measurement used to measure electrical charge.
It is most often used to measure the capacity of small batteries.
It describes the total energy retained by a battery by detailing the amount of current passing through that battery over a specified period (i.e. an hour).
The higher the mAh of a battery, the longer that battery will be able to supply energy to a device.
What Does Wh Mean?
Wh stands for Watts per hour (Watt-hour).
It is a unit of measurement used to compare the charge and energy capacity of power units that have different voltages.
It is most often used to measure the capacity of energy storage systems and power units as opposed to small batteries and cells.
It describes the voltage (v) and current (amps) of a storage system over a given amount of time (hours).
mAh and Wh Do Not Strictly Indicate Power Capacity:
It is important to note that mAh and Wh do not indicate the overall power capacity of an electrical device or battery. Many people make the mistake of thinking that these ratings directly correlate to power capacity, when in fact another unit of measure must be taken into account to truly determine that. This unit is the Voltage.
Volts measure the force required to overcome the resistance within an electrical system and depending on the Voltage of a power supply or battery the power of the device will vary. For example, a 5000mAh power bank will be more powerful if it has a 9V output than a 5V output. The mAh value is therefore affected by this variable and the two ratings should be considered together.
How Many Volts Should A Power Bank Have?
Generally speaking, the batteries used in power banks and battery cells are either lithium-ion batteries or lithium polymer batteries as these batteries retain charge very well when not being used, can withstand many, many discharge cycles and have excellent energy storage capacities. These batteries tend to be 3.7 volts. However, this voltage can change depending on the make and model.
If the voltage of a battery or power bank is less than that of the device it is connected to, then charging will not occur. For this reason, most large power banks possess the capability to run 5 volts as well. Many modern batteries can convert to 9 volts for fast charging purposes. Energy storage systems have to produce closer to 20V in order to charge laptops and larger devices.
Can You Take A Power Bank On A Plane?
The standard restriction for taking power banks on planes set by airlines is 100Wh. Any power bank with a Wh rating of less than 100 can be safely taken on board and used during flights to power your devices.
What Does W Mean?
W stands for Watts.
Watts are the unit of measure used to describe electrical power.
In an electrical system, the wattage or power is affected by the voltage and current. The higher the voltage and current, the greater the power. However, if you have a battery with a high voltage but a low amperage, the power (wattage) will be lessened.
What Does V Mean?
V stands for Volts or voltage.
Volts are the unit of measure used to describe the force that a device is being powered at.
A good analogy is to think of the electrical system as a plumbing system. In this analogy, Volts are the equivalent of water pressure powering water through the pipes.
The volts are the force required to overcome the resistance (measured in Ohms) within an electrical system. You can think of resistance as being the equivalent of the pipe size in a plumbing system.
What Does A Mean?
A stands for Amps.
Amps are the unit of measurement used to describe current within an electrical system.
If we continue with our plumbing analogy, where Volts represent the water pressure, Amps are the equivalent to the water flow rate. The number of Amps per hour reflects the rate at which electrical charge is passed from the negative to the positive ends of the circuit.