Introduction
When you compare the battery capacity of smartphones, laptops, and other devices, you'll see ratings for milliamp-hour (mAh) and watt-hour (Wh). But what do mAh and Wh mean, and how do they relate to one another? And how can you convert these units to each other? To make sense of these confusing battery ratings, let's first look at the definition of a watt-hour. A watt-hour is one watt of power supplied for one hour. A milliamp-hour is 1/1000 of an amp supplied for one hour. So how do we relate watt-hours to milliamp hours? Let's use volts
When you compare the battery capacity of smartphones, laptops, and other devices, you'll see ratings for milliamp-hour (mAh) and watt-hour (Wh).
When you compare the battery capacity of smartphones, laptops and other devices, you'll see ratings for milliamp-hour (mAh) and watt-hour (Wh).
The mAh rating is a measure of energy capacity. The Wh rating is a measure of energy storage.
The mAh rating indicates how much power your device can consume over time; however it does not tell you how long it will last on one charge or whether it has any other limitations like being able to support fast charging technology such as Qualcomm Quick Charge 3.0+ or Samsung Adaptive Fast Charging (SAFC). The Wh rating indicates how much power is stored within each cell inside your battery pack; however this value does not take into account any additional components added during manufacturing process like Li-ion polymer cells which reduce weight but increase cost per unit volume due to materials required for construction methodology used during construction phase instead using cheaper methods like nickel metal hydride batteries found in most smartphones today instead since these tend not only last longer but also perform better under high temperatures conditions where temperatures rise above 100 degrees Celsius before melting down completely leading us back again into square one where we start over again with nothing left but hope that maybe next time around things might turn out differently...
The Wh rating is a measure of how much power is stored within each cell of your battery pack. The higher the Wh rating, the longer your device will last on one charge or whether it has any other limitations like being able to support fast charging technology such as Qualcomm Quick Charge 3.0+ or Samsung Adaptive Fast Charging (SAFC).
But what do mAh and Wh mean, and how do they relate to one another?
The mAh (or milliampere-hour) is a measure of electrical charge. It's like a battery's internal storage capacity, but it's measured in terms of how much energy can be stored.
Wh (or watt hour) is a measure of energy that comes from one unit of time or work—and it's equal to the power output produced by the device being tested during its most recent charge cycle.
So when you see these two terms used together, they're talking about two different things: one refers to how long your phone will last on one charge; the other refers to how much power it will use during that same periodof time.
So while it's tempting to think that the higher your battery capacity, the longer your phone will last without needing a recharge—that's not necessarily true. The amount of power used by your device during its most recent charge cycle is more important than how much energy is stored inside its battery pack.
And how can you convert these units to each other?
To convert mAh to Wh, you need to multiply the mAh by the voltage. For example, if your battery has 100mAh of charge and you're using it at 3V (the standard voltage for LiPo batteries), then its capacity is 300Wh.
Conversely, if you're using a LiPo battery with 2A output and 1V output (a common level for most hobbyist drones), then its capacity is 1.25Wh per amp hour—or 125W per kilogram!
To make sense of these confusing battery ratings, let's first look at the definition of a watt-hour.
To make sense of these confusing battery ratings, let's first look at the definition of a watt-hour. A watt (W) is a unit of power that measures how much energy something can produce in one second. When you think about your car's battery—the thing that powers your stereo, lights and motor—you'll notice that it has an amp rating on it: 12V × 7Ah = 84W. A milliamp hour (mAh) is 1/1000 of an amp supplied for one hour: 12V × 1000mA = 12000 mAh. So now we have a way to relate different powers and capacities when talking about batteries!
Now let's apply this knowledge by comparing two batteries with similar voltage ratings but different capacities:
- A battery with a 12V rating and a 40Ah capacity will supply 40 amps (40A) for one hour, or 20 amps (20A) for two hours. - A battery with a 12V rating and a 100Ah capacity will supply 100 amps (100A) for one hour, or 50 amps (50A) for two hours.
A watt-hour is one watt of power supplied for one hour.
A watt-hour is one watt of power supplied for one hour. It's a unit of energy, and it's equal to 3,600 joules of energy.
A milliamp-hour is 1/1000 of an amp supplied for one hour.
A milliamp-hour is 1/1000 of an amp supplied for one hour.
For example, if you had a battery with 100 mAH and it was discharged to 50%, then you would have 50 mAH left in the battery. If this same battery had 200 mAH, then it would be completely full after charging for an hour (200/100=2).
So how do we relate watt-hours to milliamp hours? Let's use volts.
To convert mAh to Wh, you can use this formula:
- Multiply volts by 1000 (to get kiloamp hours)
- Divide by 1 million (to get megajoules)
(You can use the same formula for amps and watts, too.)
If a battery has a voltage rating of 3.7 volts and a capacity rating of 7,000 mAh or 7 Ah, we need to multiply the voltage by the amperage by the number of hours to get the total energy stored.
To calculate the total energy stored in a battery, we need to multiply its voltage rating by its current rating. To do this, we'll use our knowledge of Ohm's Law:
Voltage = Current * Resistance
We know that 1 volt is equal to 1 ampere or A and that 1 ampere is equal to 2 Coulombs (C). In other words, if you have a battery with a 3.7 volt rating and 7 Ah capacity, then you will have:
Power = Voltage * Current = 3.7 * 2 = 6 Watts
Now let's convert this into watts using our definition of power: Power = Volts × Amps = Potential difference across two points divided by resistance between them.
At 3.7 volts and 7 Ah (which is also 7000 mAh), this battery stores approximately 26,000 mAh or 26 Ah worth of energy at 3.7 volts. This means 26 Wh in total energy stored.
A battery's capacity is measured in watt-hours (Wh). It's the total amount of energy a battery can store. There are several ways that batteries can be rated, but all measure their capacity in some way and then convert this value into Wh.
For example: If you have a standard AA alkaline battery and it has an amp rating of 1A, then it means that one amp will run your device for one hour before needing replacement. So if you want to know how much power is being used by your device when running at full brightness for 4 hours straight, simply multiply its voltage by its current draw (1A x 4 hours = 4A). For example: If your phone has 2050mAh worth of energy stored inside it at 3.7 volts and 7 Ah which is also 7000 mAh then this means 26 Wh in total energy stored!
You can also easily convert mAh to Wh if you know a device's voltage rating. Here's how that looks:
If you know a device's voltage rating, multiply the data by the amperage. Here's an example:
- The iPhone 6 has a 3.8V battery and draws 1 Amp of current through it. That means that if your charger can supply 1 Amp of current for 24 hours, your smartphone will be able to run for an entire day without needing to be recharged!
Conclusion
We've covered how these units are related, but now that you know what they mean, we hope you feel more confident about how to convert between them. If you're interested in learning more about battery capacity, we also have a guide on how to calculate the energy stored in a battery by multiplying volts times amperage (V x A).
