🔋 Battery amp-hour, watt-hour and C rating tutorial

Afrotechmods
25 Sept 201406:12
EducationalLearning
32 Likes 10 Comments

TLDRThis tutorial delves into the fundamentals of battery capacity, explaining key concepts such as amps, amp-hours, watt-hours, and C ratings. It clarifies that a battery delivers current based on the load's needs and introduces the concept of internal impedance affecting current delivery and heat generation. The video contrasts a single 1.2V 2Ah battery with a 9.6V 2Ah pack, highlighting the difference in stored energy measured in watt-hours. It also demystifies C ratings, which indicate the safe current delivery capacity of a battery, and suggests resources for further learning.

Takeaways
  • 🔋 A battery's ability to deliver current is determined by the load's requirements, not just the battery's capacity.
  • 🔌 Amps (amperes) measure the rate of electrical current flow, whereas Amp-Hours (Ah) represent the battery's capacity to hold energy.
  • ⏱️ A battery's capacity in Amp-Hours indicates the amount of current it can supply for a specific duration; e.g., 2 Ah supplies 2 amps for 1 hour.
  • 🌡️ The load's resistance significantly affects the current drawn from the battery, which can vary from low-resistance to high-resistance or complex digital devices.
  • 🚫 Batteries have an internal impedance that limits the current they can deliver and generates heat during discharge.
  • 📈 Discharge rates impact a battery's effective capacity and output voltage, with higher discharge rates reducing both.
  • 🔌 Voltage is a crucial factor in comparing battery energy storage; Watt-Hours (Wh) is the product of Volts and Amp-Hours, providing a clear comparison.
  • 🔋 A 1.2V 2Ah battery and a 9.6V 2Ah battery pack do not hold the same amount of energy; the latter has significantly more stored energy.
  • 🅿️ C ratings are a marketing tool to describe a battery's safe current delivery capacity, where a 'C' represents the battery's capacity in Amp-Hours.
  • 💡 The C rating can be misleading as it conflates units; it suggests multiplying the battery's capacity by the C rating to get a current value.
  • 🎧 The Amp Hour podcast is recommended for electrical engineers interested in deeper dives into battery and electrical concepts.
Q & A

  • What is the main topic of the battery capacity tutorial?

    -The main topic of the tutorial is to discuss various aspects of battery capacity, including amps, amp-hours, watt-hours, C ratings, and other important concepts when working with batteries.

  • Why doesn't a battery necessarily supply the maximum current it is capable of delivering?

    -A battery only delivers as much current as the load requires. The amount of current drawn depends on the load's characteristics, which can vary widely from a low resistance load that draws a lot of current to a high resistance load that draws very little current.

  • What is the difference between amps and amp-hours?

    -Amps, or amperes, measure the flow of electrical current, while amp-hours are a unit of electrical charge that represents the capacity of a battery. An amp-hour indicates the amount of current a battery can supply for one hour.

  • How does the battery's internal impedance affect its performance?

    -The internal impedance of a battery limits the amount of current it can deliver and is a source of heat when the battery is in use. High impedance can prevent a battery from delivering high currents and can reduce the battery's effective capacity at higher discharge rates.

  • What happens when a battery is discharged at a higher rate than recommended?

    -Discharging a battery at a higher rate than recommended can reduce its effective capacity, lower the output voltage due to increased internal resistance, and generate more heat, potentially leading to battery damage or reduced lifespan.

  • How can you estimate battery life?

    -Battery life can be estimated by dividing the battery's capacity in amp-hours by the load's current draw in amps. This gives an approximate duration the battery can last under a specific load.

  • What is the significance of watt-hours in comparing battery energy storage?

    -Watt-hours provide a standardized way to compare the stored energy of batteries by considering both voltage and amp-hour capacity. This unit allows for a direct comparison of energy content across batteries with different voltages.

  • What does a C rating represent in the context of batteries?

    -A C rating is an informal measure indicating the amount of current a battery can safely deliver. It is calculated by multiplying the battery's capacity in amp-hours by the C rating number to get the maximum safe current draw.

  • How does the discharge rate affect a battery's effective capacity?

    -As the discharge rate increases, the effective capacity of a battery decreases because more energy is lost as internal heat. This means that a battery's stated capacity at a lower discharge rate may not be achievable if it is discharged more quickly.

  • Why are C ratings potentially confusing when discussing battery performance?

    -C ratings can be confusing because they mix units by multiplying the battery's amp-hour capacity by the C rating and then treating the result as if it were in amps. This can lead to misunderstandings about the actual current the battery can deliver.

  • What is the recommended practice for using the information from a battery data sheet?

    -It is important to refer to a battery's data sheet to understand its limitations, such as maximum safe discharge rates and the impact of different discharge rates on effective capacity. This ensures the battery is used safely and efficiently.

Outlines
00:00
🔋 Understanding Battery Basics: Amps, Amp-Hours, and Watt-Hours

This paragraph introduces the fundamental concepts of battery capacity, including amps, amp-hours, and watt-hours. It explains that a battery's ability to deliver a certain amount of current (amps) is dependent on the load's requirements, not a fixed value. The difference between amps (a unit of electrical current) and amp-hours (a measure of battery capacity) is clarified, with the latter defined as a battery's ability to supply a certain current for a specified time. The example of a 2Ah battery is used to illustrate how varying the current draw affects battery life. The concept of internal impedance in batteries is introduced, explaining how it limits the current a battery can deliver and contributes to heat generation. The importance of understanding a battery's datasheet, especially discharge rates and effective capacity at different discharge currents, is emphasized to ensure safe and efficient battery use.

05:02
🔌 Exploring C Ratings and Battery Energy Comparison

This paragraph delves into the concept of C ratings, which is a measure of the current a battery can safely deliver. It highlights the confusion that can arise from C ratings due to their informal nature and the mixing of units. The example given compares two batteries with the same amp-hour capacity but different C ratings, illustrating the difference in the amount of current they can safely provide. The paragraph also discusses the discharge curves and how they are not typically used in marketing due to their complexity. It concludes with a mention of The Amp Hour podcast as a resource for electrical engineers and an invitation for viewers to support the channel through merchandise purchases.

Mindmap
Keywords
💡battery capacity
Battery capacity refers to the amount of energy a battery can store and deliver before it needs to be recharged or replaced. In the context of the video, it is a central theme as it discusses various units like amp-hours and watt-hours that help estimate and compare the energy storage capability of batteries. The video uses the example of a 2000mAh or 2Ah rechargeable AA battery to explain that it can supply two amps for one hour.
💡amps
Amperes, or amps, is a unit of measurement for the flow of electric current. In the video, amps are used to describe the rate at which a battery delivers electrical current, with the understanding that the actual current delivered depends on the needs of the connected load. The video clarifies that a battery capable of delivering one amp does not necessarily supply one amp to every connected device, as the load's resistance and requirements will determine the drawn current.
💡amp-hours
Amp-hours are a unit of electric charge, used to express the capacity of a battery. The term is introduced in the video as a way to estimate the battery life, where a higher amp-hour rating indicates the battery can either deliver more current for the same amount of time or deliver the same current for a longer period. The video uses the example of a 2Ah battery to illustrate that it can supply two amps for one hour, or one amp for two hours, and so on.
💡watt-hours
Watt-hours are a unit of energy that represents the amount of work done by an electric current. In the video, watt-hours are introduced as a way to compare the stored energy of batteries with different voltages, as it combines the factors of voltage and current (amp-hours) to give a more accurate representation of energy capacity. The video provides a clear comparison between a 1.2V 2Ah battery with a capacity of 2.4 watt-hours and a 9.6V 2Ah battery pack with a capacity of 19.2 watt-hours, emphasizing the importance of considering both voltage and current when assessing battery energy storage.
💡C rating
The C rating is an informal term used to describe the safe current a battery can deliver. It is based on the battery's capacity in amp-hours, with the 'C' standing for capacity. For instance, a 20C battery can safely deliver a current twenty times its capacity. The video explains that a 2200mAh battery with a 20C rating can provide up to 44 amps of current. However, it also cautions that C ratings can be confusing as they mix units, which can lead to misunderstandings about the actual current a battery can deliver.
💡internal impedance
Internal impedance refers to the resistance within a battery that limits the amount of current it can deliver and generates heat when current is being supplied. In the video, it is mentioned that a battery's internal impedance, such as 25 milliohms, acts like a small resistor inside the battery, affecting its performance. This concept is crucial as it explains why a battery may not be able to deliver the high current it is theoretically capable of, and why it heats up during high-current discharges.
💡discharge rate
Discharge rate is the speed at which a battery delivers its stored energy. The video explains that the discharge rate affects both the amount of current a battery can deliver and its effective capacity. For example, a battery may have a capacity of 2 amp-hours when discharged at a rate lower than 400mA, but its effective capacity decreases to 1.7 amp-hours when discharged at 4 amps. This illustrates the relationship between discharge rate, current draw, and battery performance.
💡load
In the context of the video, a load refers to the device or system that is connected to the battery and uses the electrical energy it provides. The load's resistance and power requirements determine the amount of current drawn from the battery. The video uses various examples, such as a low-resistance load that draws a lot of current or a high-resistance load that draws very little, to illustrate how different loads can affect battery performance and life.
💡voltage
Voltage is the electrical potential difference between two points in a circuit, driving the flow of electric current. The video discusses how voltage interacts with current (amps) to determine the power (watts) of a battery and how it affects the overall energy capacity (watt-hours) when combined with amp-hours. It also touches on how the output voltage of a battery decreases as more current is drawn, due to the voltage drop across the battery's internal resistance.
💡energy storage
Energy storage refers to the process of accumulating energy in a form that can be used later. In the context of the video, energy storage is the primary function of batteries, and understanding the various units and factors that affect this storage capability is essential. The video delves into how different battery specifications, such as amp-hours and watt-hours, relate to their energy storage capacity and how this capacity can be effectively utilized and managed.
💡The Amp Hour podcast
The Amp Hour podcast is a resource mentioned in the video for electrical engineers interested in deepening their understanding of topics related to batteries and electrical current. The video encourages viewers to check out the podcast for more in-depth discussions and insights into the field, indicating its relevance to the overall theme of battery capacity and electrical engineering.
Highlights

Introduction to battery capacity and related concepts such as amps, amp-hours, watt-hours, and C ratings.

Explanation that a battery will only deliver as much current as the load requires, not necessarily its maximum capability.

Clarification on the difference between amps and amp-hours, emphasizing that amp-hours are a measure of a battery's capacity.

Example given of a 2Ah battery and how it can deliver different amounts of current based on the connected load.

Discussion on the internal impedance of a battery and how it limits the amount of current the battery can deliver and contributes to heat generation.

Explanation of discharge curves and how they indicate the safe discharge rate and effective capacity of a battery at different current draws.

Comparison between a 1.2V 2Ah battery and a 9.6V 2Ah battery pack, highlighting the difference in energy storage despite the same amp-hour rating.

Introduction of watt-hours as a unit for comparing the stored energy of batteries by converting amp-hours to watt-hours.

Definition and explanation of C ratings, which describe the amount of current a battery can safely deliver.

Illustration of how C ratings can be misleading due to the confusion they introduce with the units of measurement.

Practical application of understanding battery specifications and limitations when working with electronic devices.

Importance of considering battery life and load requirements when selecting a battery for a particular application.

Discussion on the impact of internal battery resistance on output voltage and overall battery performance.

The concept that higher discharge rates can lead to reduced effective capacity and lower output voltage due to increased internal heating.

Promotion of The Amp Hour podcast as a resource for electrical engineers looking to deepen their understanding of battery technology.

Invitation to support the channel and check out new merchandise like t-shirts and mugs.

Transcripts

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