Wh × 1,000 / V =
0.00 mAh
Conversion formula: mAh = Wh × 1,000 / V
What Is Watt-Hours?
Watt-hours (Wh) is a unit of electrical energy, which may also represent the energy storage capacity of a power source.
When watt-hours are used for energy-consuming devices, it describes how much energy they consume.
What Is Milliamp-Hours?
Milliamp-hours (mAh) is a unit of electric charge. It represents the power capacity of a power source over a given period and measures the amount of electric charge (current) flowing through a circuit for one hour.
Milliamp-hours is typically used to describe battery capacity. It gives users an idea of how much charge a battery can store.
Besides milliamp-hours, amp-hours and watt-hours may also be used as units of battery capacity. But of all three options, milliamp-hours measures in smaller magnitudes. So, milliamp-hours are more commonly used for mobile power sources.
How to Convert Watt Hours to Milliamp Hours (Wh to mAh)
Watt-Hours to Milliamp-Hours Calculation Formula
- To derive the watt-hours to milliamp-hours calculation formula, we need the formulas for electrical energy (in watt-hours) and power:
\(\small{electrical\ energy, E = power\ (W) * time\ (h)}\ (1)\)
\(\small{power = voltage\ (V) * current\ (A)}\ (2)\)
- Representing (1) and (2) with their corresponding units:
\(Wh = W * h\ (3)\)
\(W = V * A\ (4)\)
- Next, we’ll substitute W for V x A in (3)
\(Wh =V * A * h\ (5)\)
- We can rewrite (5) as :
\(Wh =V * Ah\ (6)\)
- Since:
\(Ah = \displaystyle{\frac{mAh}{1000}}\ (7)\)
- We can replace Ah with mAh/1000 in (6):
\(Wh = V * \displaystyle{\frac{mAh}{1000}}\ (8)\)
- Finally, we’ll make mAh the subject of (8):
\(mAh = \displaystyle{\frac{Wh}{V}} * 1000\ (9)\)
Going by our watt-hours to milliamp-hours calculation formula, we can do a Wh to mAh conversion by multiplying watt-hours by 1000 and dividing by battery voltage. Of course, you can just enter the values in our Wh to mAh calculator & Wh becomes mAh.
Doing a milliamp-hours (mAh) – watt-hours (Wh) conversion is pretty much the reverse of the Wh to mAh conversion. We multiply mAh by voltage, then divide by 1000. Of course, an mAh to Wh calculator would make it much easier to convert mAh to Wh.
Conversion Examples
Example 1
If you have a 5V solar generator that discharges 15W of electric charge from one of its ports for up to 18 hours, what is the milliamp-hours rating of the power bank?
To estimate the mAh capacity of this generator, we’ll first calculate how many watt-hours it discharges:
\(\small{capacity\ in\ watt\mbox{-}hours\ (Wh) = power * time}\)
\(= 15* 18 = 270\ Wh\)
Next, we’ll convert the Wh capacity to mAh:
\(\small{capacity\ in\ milliamp\mbox{-}hours\ (mAh) = \displaystyle{\frac{270}{5}} * 1000}\)
\(= 54\, 000\ mAh\)
Example 2:
A 24 v battery powers a 450 W solar refrigerator for around 8 hours before it runs out of electric charge. What’s the milliamp-hours (mAh) rating of the battery?
As before, we’ll start by calculating the energy in watt-hours (Wh) used by the refrigerator:
\(\small{refrigerator\ in\ watt\mbox{-}hours\ (Wh) = 450 * 8}\)
\(= 3\, 600\ Wh\)
The energy used by the refrigerator tells us the battery’s capacity in watt-hours (Wh).
After that, we’ll estimate the battery capacity in mAh by converting watt-hours (Wh) to milliamp-hours (mAh):
\(\small{milliamp\mbox{-}hours = \displaystyle{\frac{1500}{24}} * 1000}\)
\(= 62\, 500\ mAh\)
Why Convert Watt-Hours to Milliamp-Hours?
Determining the Best Charging System
Batteries come with a C-rating – a rating system that gives some insight into their charging behavior.
A battery’s C-rate is the ratio of its charge or discharge current to its apparent battery capacity in mAh. By that definition, we can determine a battery’s best (maximum) charge current when we know its C-rate and nominal battery capacity.
For instance, if a battery’s C-rate is 3C and its mAh is 5,000, the maximum charge current of its charger should be:
\(3 * 5\, 000 = 15\, 000\ mA = 15\ A\)
Why is it necessary to know the maximum charge current for a battery? Well, going beyond the maximum charge current of a battery might shorten the battery’s lifespan. There’s also a chance that it can make the battery explode.
Calculating Battery Runtime When Connected to a Device Whose Milliamperage is Known
Normally, we can calculate how long a battery will last using its watt-hours and the total watts of the devices connected to it. But if we do not know the watts of the devices but know the amperage, the amperage could also work.
But then, if we are trying to figure out a battery’s runtime using its milliamperage, we need to know its milliamp-hours (mAh). This is where converting watt-hours (Wh) to milliamp-hours (mAh) comes in.
Here’s an instance:
If a 90Wh, 24-volt battery has a 30W load, it will last up to 3 hours. But then, if we only knew the total milliamperage of the load on the battery, we would estimate the runtime differently.
Say the total load was 500 mA. We estimate the runtime by converting the battery’s watt-hours to mAh:
\(90\ Wh = 3\, 750\ mAh\)
Then divide mAh by the battery’s milliamps:
\(= \displaystyle{\frac{3750}{500}} = 7.5\ hours\)
How to Convert Wh to mAh With Our Calculator
To do a Wh to mAh conversion with our calculator, enter energy in watt-hours (Wh) in the corresponding field. Next, enter voltage. Finally, click the calculate button below the input fields of the Wh to mAh calculator & Wh becomes mAh.
Quick Watt-Hours to Milliamp-Hours Conversion Chart
Here are some quick watt-hours (Wh) to milliamp-hours (mAh) conversions at common battery voltages:
How to Convert Watt-Hours to Amp-Hours (Wh to Ah)
We can derive the formula to convert watt-hours (Wh) to amp-hours (Ah) using the same steps as we did for the watt-hours to milliamp-hours conversion.
- First, we define the formula for electrical energy in watt-hours:
\(\small{Energy\ in\ watt\mbox{-}hours\ (Wh) = power\ (W) * time\ (h)}\ (1)\)
- Next, we define the formula for power:
\(Power = voltage\ (V) * ampere\ (A)\ (2)\)
- Now, we replace power with voltage x ampere in (1):
\(\small{Energy\ in\ watt\mbox{-}hours = voltage * ampere * time}\ (3)\)
- Let’s replace the quantities with their units:
\(Wh = V * A * h\)
\(Wh = V * Ah\ (4)\)
- Now, let’s make Ah the subject of (4):
\(Ah = \displaystyle{\frac{Wh}{V}}\ (5)\)
- So, to get the electric charge capacity of a battery in Ah from the Wh, divide Wh by voltage.
How to Convert Kilowatt-Hours to Milliamp-Hours (kWh to mAh)
To derive the formula to convert kilowatt-hours (kWh) to milliamp-hours (mAh), we need the Wh to kWh conversion formula and Wh to mAh conversion formula:
\(Wh = kWh * 1000\ (1)\)
\(mAh = \displaystyle{\frac{Wh}{V}} * 1000\ (2)\)
Then, we’ll replace Wh with kWh x 1000 in (2):
\(mAh = \displaystyle{\frac{kWh}{V}} * 1000000\ (3)\)
So, to do a kWh to mAh conversion, divide kilowatt-hours (kWh) by voltage, then multiply by one million.