When dealing with batteries and power, you’ll often see two terms: Watt-hours (Wh) and Amp-hours (Ah). Both are units that measure electrical power, but they measure different things. Watt-hours measure electrical energy, while Amp-hours measure electrical charge.
So, how do you convert Wh to Ah, or vice versa? This article breaks down the process and explains why that conversion is so important. Whether you’re picking out a new battery, designing a solar power system, or trying to get a handle on how much energy you’re using, understanding the relationship between “wh in ah” is key.
What are Watt Hours and Amp Hours?
When you’re shopping for batteries, you’ll probably see watt hours (Wh) and amp hours (Ah) listed as key specs. Here’s a quick rundown of what those terms mean.
Watt Hours (Wh)
Watt hours are a unit of energy. A watt hour tells you how much power is used over a period of time.
Think of it this way: 1 Wh means you’re using 1 watt of power for 1 hour.
To calculate watt hours, just multiply watts by hours: Wh = Watts x Hours.
Amp Hours (Ah)
Amp hours measure electric charge. You’ll often see amp hours used to describe the capacity of a battery.
One amp hour is the amount of charge you’d get from a current of 1 amp flowing for 1 hour. So, amp hours are a measurement of battery capacity.
To calculate amp hours, multiply current (amps) by time (hours): Ah = Current (Amps) x Time (Hours).
How Watt-hours and Amp-hours Relate
The relationship between watt-hours (Wh) and amp-hours (Ah) depends on the voltage (V). Think of it this way: the same amount of energy (Wh) can be stored or delivered in different combinations of voltage and current (Ah).
Voltage is key here. For the same Wh rating, a 12V battery will have a different Ah rating than a 24V battery. You can’t directly compare Ah without knowing the voltage.
Calculating Watt Hours to Amp Hours
You can convert watt hours (Wh) to amp hours (Ah) using this formula: Ah = Wh / V. “V” stands for voltage.
It’s really important that you use the right voltage value in this equation. Batteries have a “nominal voltage,” which is the voltage they’re supposed to have, but the actual voltage can fluctuate.
Keep in mind that this formula assumes a constant voltage, but that’s not always the case. Things like battery efficiency and how fast you’re discharging the battery can change its capacity.
Example: Converting Watt-hours to Amp-hours
Let’s say you have a battery that stores 100 Watt-hours and you want to know how many Amp-hours that is at 12 Volts.
Here’s how you’d do it:
Ah = 100 Wh / 12 V = 8.33 Ah
Now, what if the voltage is different? Let’s convert 100 Watt-hours to Amp-hours at 24 Volts:
Ah = 100 Wh / 24 V = 4.17 Ah
As you can see, the Amp-hour value changes depending on the voltage.
Watt Hours to Amp Hours Conversion Charts
To make it easier to convert between watt hours and amp hours, here are some handy conversion charts for common voltages.
Watt Hours to Amp Hours at 12V
[Insert conversion chart here showing Wh values from 100Wh to 1200Wh and their corresponding Ah values at 12V]
Watt Hours to Amp Hours at 24V
[Insert conversion chart here showing Wh values from 100Wh to 1200Wh and their corresponding Ah values at 24V]
Watt Hours to Amp Hours at 36V
[Insert conversion chart here showing Wh values from 100Wh to 1200Wh and their corresponding Ah values at 36V]
Watt Hours to Amp Hours at 48V
[Insert conversion chart here showing Wh values from 100Wh to 1200Wh and their corresponding Ah values at 48V]
These charts should give you a quick reference for converting between watt hours and amp hours at various voltage levels.
Other Conversions
Need to calculate energy storage using different units? Here’s how to convert between amp hours and other common measurements:
How to Convert Amp Hours to Watt Hours (Ah to Wh)
Use this formula: Wh = Ah V
For example: To convert 10 Ah to Wh at 12V: Wh = 10Ah 12V = 120Wh
How to Convert Kilowatt Hours to Amp Hours (kWh to Ah)
Use this formula: Ah = (kWh 1000) / V
For example: To convert 3.5kWh to Ah at 24V: Ah = (3.5 1000) / 24 = 145.83 Ah
How to Convert Watt Hours to Milliamp Hours (Wh to mAh)
Use this formula: mAh = (Wh 1000) / V
For example: To convert 12.4 Wh to mAh at 3.7V: mAh = (12.4 1000) / 3.7 = 3351.35 mAh
To Conclude
Understanding the relationship between watt-hours (Wh) and amp-hours (Ah) is crucial for grasping battery capacity and energy use. The key to converting between these units lies in the simple formula: Ah = Wh / V.
Remember that voltage is a critical factor in this conversion. Ignoring voltage can lead to inaccurate calculations and poor decision-making.
The ability to convert between Wh and Ah has practical applications in many fields, including battery selection, solar system design, energy storage solutions, and the development of electric vehicles. This knowledge empowers you to make informed choices about energy consumption and storage.