# What does Ah on the battery label mean?

## Introduction:

Many people tend to confuse the concepts of Ah and Energy. What is the difference between Ah and kWh? What is Ah when we usually talk about kWh? What is the relationship between Ah and voltage? Today, we will figure this out together.

## What does the A in Ah mean?

A, the full name is Amper, a unit commemorating Ohm’s law proposed by French physicist A Ampere in 1820. That is what we often call current. When electrons move in a direction, we call the opposite direction of electron movement the direction of current.

Typically, A is used as a unit of current size. The traditional definition of ampere was proposed in 1820. The constant current physicist Ampere requires to electrolyze 1.1180 mg of silver ions from a silver nitrate solution in 1 second is 1 A.

In 1946, the International Committee on Weights and Measures (CIPM) redefined Amper. The latest definition is that the interaction force of two round straight wires in a vacuum under energization is 2×10* ^{-7}*N, and the current of each wire is 1 ampere.

## What does the h in Ah mean?

h, the full name is Hours, which represents time. Usually, h is used together with A to indicate the capacity of a battery pack.

## What is Ah?

Let us use the scenario of filling a swimming pool with water from a faucet. If the cross-street area of the faucet is defined as A, then h represents hours, which represents a time period, which can be understood as how long we have turned on the faucet of this cross-street area.

Let us think about this question: if we open the faucet now, how much water will be released from the faucet after a period of time? Intelligent people may have discovered that this problem is straightforward. You only need to multiply the volume of water that can be discharged per second by the time of discharging water. Can’t you calculate how much water has been discharged in total?

Yes, we can understand A as the cross-sectional area of the faucet, and h represents the time for the faucet to discharge water.

Ah, can be understood as the total amount of water that can be released when we use a fixed-sized faucet to drain water for a certain period of time. This is what we often hear about 50Ah and 100Ah. Taking 100Ah as an example, we can understand that if it works for 1 hour with a current of 100A, it is 100Ah.

## Is Energy equal to Ah?

Let us continue the above thinking. Assuming we open the faucet for 1 hour the cross-sectional area is fixed, which means that the current size is fixed. If you buy a faucet and install it in your home, will it release the same amount of water in one hour when you turn it on as in your friend’s home?

Not because we ignored a vital concept: water pressure. This is easy to understand. If the water pressure in your home is high, the water flow rate will be greater under the same cross-sectional area, which means that the final amount of water discharged will also be more significant.

Now, you probably realize that if we want to calculate how much water a faucet can hold, we need several parameters:

- The size of the faucet (cross-sectional area)
- Water flow rate (water pressure)
- The time the faucet is opened (h)

In the same way, Energy is understood in this way. If we want to calculate the Energy of a battery, then we need to know:

- Battery discharge current (A)
- Battery discharge speed (V)
- Battery discharge time (h)

Let’s calculate it together, taking a 12V 100Ah LiFePO4 Battery Pack as an example:

Battery voltage is: 12V

Battery capacity is: 100Ah

Energy is: 12V*100Ah=1200V*Ah=1200Wh (Wh=V*Ah)

Since 1kWh=1000Wh

Therefore, we usually say that the Energy of 12.8V 100Ah is 1.28kWh

## What is C-Rate?

Suppose you have 2 12V 200Ah LiFePO4 Battery Pack, A, and B. A’s maximum discharge current is 100A, while B’s is 200A. So, how long does it take for A and B to run out of power?

Since A has a capacity of 200Ah, but the maximum discharge current is only 100A, 100Ah of capacity can be consumed in 1 hour. It will take 2 hours to run out of power.

Since B also has a capacity of 200Ah and the maximum discharge current is also 200A, the capacity of 200Ah can be consumed in 1 hour. It takes 1 hour to run out of power.

Did you find that the discharge current of A is 100A, which is only half of 200Ah, usually called 0.5C? The discharge current of B is 200A, which is precisely equal to 200Ah. Usually, we call it 1C.

We usually use C-Rate to describe charging speed. We consider the fastest discharge capability of the battery pack, for example:

If a battery can be discharged in the fastest 1 hour and can discharge 100% of its power every hour, then we call it 1C.

If a battery can be discharged in 2 hours at the fastest and can discharge 50% of its power per hour, we call it 0.5C.

If a battery can be discharged in 5 hours at the fastest, it can discharge 20% of its power per hour, which we call 0.2C.

## What is AC?

AC, which stands for Alternating current, usually refers to a current that changes periodically in size and direction. Common electrical appliances in our homes, such as TVs, refrigerators, washing machines, air conditioners, and computers, all require an AC power supply.

## What is DC?

DC, which stands for Direct Current, usually refers to a current whose direction remains unchanged. The dry batteries, storage batteries, and lithium batteries we are familiar with all output DC.

## Does the battery output AC or DC?

It is DC. Standard batteries on the market, such as 12V 100Ah, 12V 200Ah, 24V 100Ah, and 48V 50Ah, have clear positive and negative poles. If they are connected reversely, it may cause serious consequences.

## How to get AC?

Typically, AC power is provided by a power plant. Whether it is a wind power plant, a hydropower plant, or a nuclear power plant, the final form of power generation is the same. It requires a closed coil to cut the magnetic field lines in a strong magnetic field. To produce an induced current that changes periodically in size and direction. We will write another article to explain the specific principles and complex physics concepts later. Still, for now, we need to know that AC is usually provided directly by power stations.

But in our daily lives, we can also obtain AC through an inverter (converter). If you buy an inverter, the clever structure inside can convert DC into AC to meet our needs, but this conversion often results in energy loss.

## What is DoD?

DoD, Deptch of Discharge, refers to the depth of discharge. 100%DoD stands for complete loop, also known as deep loop. Indicates that the battery is completely discharged. For lithium batteries although most lithium batteries support 100% DoD, statistical data shows that 80% DoD is more conducive to the Cell maintaining a high discharge capacity after thousands of cycles.

## What is SoC?

SOC, State of Charge, refers to the state of charge. We can understand it by comparing it with DoD. If DoD describes how much electricity is used, we can understand SoC as how much electricity is left.

For example, if we use 20% of a battery, 80% is left. Then 20% is DoD, and 80% is SoC.

## What size Ah is right for me?

We usually consider this issue based on your actual needs. Do you want the battery you buy to have as long a life as possible? As we mentioned above, to maintain a higher discharge capacity, it is best to control the DoD at around 80%. So you can calculate: how much electricity must you consume daily?

Taking a 12V battery as an example, if you need to use 80Ah a day, then 80Ah/0.8=100Ah. In other words, you can choose a 100Ah battery so that your daily discharge depth can be controlled within 80% DoD. This is the simplest calculation method.

## Should I choose a larger voltage or a larger Ah?

Let us first calculate the power of 12V 200Ah and 24V 100Ah. They are both 2.4kWh. When you are faced with two choices, choose a higher voltage. Or a larger capacity?

Experience shows that it may be better to choose a higher voltage. Why? Under the same power, the greater the resistance, the lower the current. And we can save some material costs.

## Why do we want the circuit current to be better under the same conditions?

First of all, different wires allow different currents to pass through. We usually use AWG to indicate the cross-sectional area of the wire. If we need a larger current, we need a thicker wire, increasing the cost.

In addition, since the heat generated by the circuit is positively correlated with the current, that is to say, the greater the current, the greater the heat, and the greater the energy loss. This is why when transmitting power over long distances, power plants use step-up transformers to convert the current into The reason for converting to a high-voltage state before transmitting electricity because this can minimize energy loss.

### Author Profile

### Thomas Chen

Thomas Chen is a seasoned expert in the new energy industry, with a focus on lithium battery technology. A Shenzhen University alumnus, class of 2010, Thomas has cultivated a wealth of experience through pivotal roles at EVE and BYD. Renowned for his profound insights into the sector, he possesses a unique aptitude for identifying market trends and understanding customer needs. His articles offer a distinctive perspective, drawn from a rich background in the field.

## Introduction:

Many people tend to confuse the concepts of Ah and Energy. What is the difference between Ah and kWh? What is Ah when we usually talk about kWh? What is the relationship between Ah and voltage? Today, we will figure this out together.

## What does the A in Ah mean?

A, the full name is Amper, a unit commemorating Ohm’s law proposed by French physicist A Ampere in 1820. That is what we often call current. When electrons move in a direction, we call the opposite direction of electron movement the direction of current.

Typically, A is used as a unit of current size. The traditional definition of ampere was proposed in 1820. The constant current physicist Ampere requires to electrolyze 1.1180 mg of silver ions from a silver nitrate solution in 1 second is 1 A.

In 1946, the International Committee on Weights and Measures (CIPM) redefined Amper. The latest definition is that the interaction force of two round straight wires in a vacuum under energization is 2×10* ^{-7}*N, and the current of each wire is 1 ampere.

## What does the h in Ah mean?

h, the full name is Hours, which represents time. Usually, h is used together with A to indicate the capacity of a battery pack.

## What is Ah?

Let us use the scenario of filling a swimming pool with water from a faucet. If the cross-street area of the faucet is defined as A, then h represents hours, which represents a time period, which can be understood as how long we have turned on the faucet of this cross-street area.

Let us think about this question: if we open the faucet now, how much water will be released from the faucet after a period of time? Intelligent people may have discovered that this problem is straightforward. You only need to multiply the volume of water that can be discharged per second by the time of discharging water. Can’t you calculate how much water has been discharged in total?

Yes, we can understand A as the cross-sectional area of the faucet, and h represents the time for the faucet to discharge water.

Ah, can be understood as the total amount of water that can be released when we use a fixed-sized faucet to drain water for a certain period of time. This is what we often hear about 50Ah and 100Ah. Taking 100Ah as an example, we can understand that if it works for 1 hour with a current of 100A, it is 100Ah.

## Is Energy equal to Ah?

Let us continue the above thinking. Assuming we open the faucet for 1 hour the cross-sectional area is fixed, which means that the current size is fixed. If you buy a faucet and install it in your home, will it release the same amount of water in one hour when you turn it on as in your friend’s home?

Not because we ignored a vital concept: water pressure. This is easy to understand. If the water pressure in your home is high, the water flow rate will be greater under the same cross-sectional area, which means that the final amount of water discharged will also be more significant.

Now, you probably realize that if we want to calculate how much water a faucet can hold, we need several parameters:

- The size of the faucet (cross-sectional area)
- Water flow rate (water pressure)
- The time the faucet is opened (h)

In the same way, Energy is understood in this way. If we want to calculate the Energy of a battery, then we need to know:

- Battery discharge current (A)
- Battery discharge speed (V)
- Battery discharge time (h)

Let’s calculate it together, taking a 12V 100Ah LiFePO4 Battery Pack as an example:

Battery voltage is: 12V

Battery capacity is: 100Ah

Energy is: 12V*100Ah=1200V*Ah=1200Wh (Wh=V*Ah)

Since 1kWh=1000Wh

Therefore, we usually say that the Energy of 12.8V 100Ah is 1.28kWh

## What is C-Rate?

Suppose you have 2 12V 200Ah LiFePO4 Battery Pack, A, and B. A’s maximum discharge current is 100A, while B’s is 200A. So, how long does it take for A and B to run out of power?

Since A has a capacity of 200Ah, but the maximum discharge current is only 100A, 100Ah of capacity can be consumed in 1 hour. It will take 2 hours to run out of power.

Since B also has a capacity of 200Ah and the maximum discharge current is also 200A, the capacity of 200Ah can be consumed in 1 hour. It takes 1 hour to run out of power.

Did you find that the discharge current of A is 100A, which is only half of 200Ah, usually called 0.5C? The discharge current of B is 200A, which is precisely equal to 200Ah. Usually, we call it 1C.

We usually use C-Rate to describe charging speed. We consider the fastest discharge capability of the battery pack, for example:

If a battery can be discharged in the fastest 1 hour and can discharge 100% of its power every hour, then we call it 1C.

If a battery can be discharged in 2 hours at the fastest and can discharge 50% of its power per hour, we call it 0.5C.

If a battery can be discharged in 5 hours at the fastest, it can discharge 20% of its power per hour, which we call 0.2C.

## What is AC?

AC, which stands for Alternating current, usually refers to a current that changes periodically in size and direction. Common electrical appliances in our homes, such as TVs, refrigerators, washing machines, air conditioners, and computers, all require an AC power supply.

## What is DC?

DC, which stands for Direct Current, usually refers to a current whose direction remains unchanged. The dry batteries, storage batteries, and lithium batteries we are familiar with all output DC.

## Does the battery output AC or DC?

It is DC. Standard batteries on the market, such as 12V 100Ah, 12V 200Ah, 24V 100Ah, and 48V 50Ah, have clear positive and negative poles. If they are connected reversely, it may cause serious consequences.

## How to get AC?

Typically, AC power is provided by a power plant. Whether it is a wind power plant, a hydropower plant, or a nuclear power plant, the final form of power generation is the same. It requires a closed coil to cut the magnetic field lines in a strong magnetic field. To produce an induced current that changes periodically in size and direction. We will write another article to explain the specific principles and complex physics concepts later. Still, for now, we need to know that AC is usually provided directly by power stations.

But in our daily lives, we can also obtain AC through an inverter (converter). If you buy an inverter, the clever structure inside can convert DC into AC to meet our needs, but this conversion often results in energy loss.

## What is DoD?

DoD, Deptch of Discharge, refers to the depth of discharge. 100%DoD stands for complete loop, also known as deep loop. Indicates that the battery is completely discharged. For lithium batteries although most lithium batteries support 100% DoD, statistical data shows that 80% DoD is more conducive to the Cell maintaining a high discharge capacity after thousands of cycles.

## What is SoC?

SOC, State of Charge, refers to the state of charge. We can understand it by comparing it with DoD. If DoD describes how much electricity is used, we can understand SoC as how much electricity is left.

For example, if we use 20% of a battery, 80% is left. Then 20% is DoD, and 80% is SoC.

## What size Ah is right for me?

We usually consider this issue based on your actual needs. Do you want the battery you buy to have as long a life as possible? As we mentioned above, to maintain a higher discharge capacity, it is best to control the DoD at around 80%. So you can calculate: how much electricity must you consume daily?

Taking a 12V battery as an example, if you need to use 80Ah a day, then 80Ah/0.8=100Ah. In other words, you can choose a 100Ah battery so that your daily discharge depth can be controlled within 80% DoD. This is the simplest calculation method.

## Should I choose a larger voltage or a larger Ah?

Let us first calculate the power of 12V 200Ah and 24V 100Ah. They are both 2.4kWh. When you are faced with two choices, choose a higher voltage. Or a larger capacity?

Experience shows that it may be better to choose a higher voltage. Why? Under the same power, the greater the resistance, the lower the current. And we can save some material costs.

## Why do we want the circuit current to be better under the same conditions?

First of all, different wires allow different currents to pass through. We usually use AWG to indicate the cross-sectional area of the wire. If we need a larger current, we need a thicker wire, increasing the cost.

In addition, since the heat generated by the circuit is positively correlated with the current, that is to say, the greater the current, the greater the heat, and the greater the energy loss. This is why when transmitting power over long distances, power plants use step-up transformers to convert the current into The reason for converting to a high-voltage state before transmitting electricity because this can minimize energy loss.

### Author Profile

### Thomas Chen

Thomas Chen is a seasoned expert in the new energy industry, with a focus on lithium battery technology. A Shenzhen University alumnus, class of 2010, Thomas has cultivated a wealth of experience through pivotal roles at EVE and BYD. Renowned for his profound insights into the sector, he possesses a unique aptitude for identifying market trends and understanding customer needs. His articles offer a distinctive perspective, drawn from a rich background in the field.

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