Cylindrical 21700 High-Power Cell
A123 Systems 21700 S
Cylindrical 21700 cell delivering 2.5 Ah capacity, 136 Wh/kg energy density and 125 A maximum discharge rate.
Overview
The A123 Systems 21700 S is a high-power Li-ion cylindrical 21700 cell designed for applications that demand sustained high current. with the manufacturer based in China, this cylindrical 21700 cell delivers 2.5 Ah capacity and 9.12 Wh of energy at a nominal voltage of 3.65 V, with a maximum continuous discharge capability of 125 A, making it well suited to high-power systems. At 50.0 C its continuous discharge capability is high for a cell of this capacity class.
Key Features
Extremely high discharge rate: 125 A continuous (50.0 C)
Energy density: 136 Wh/kg
Power density: 6810 W/kg
Capacity: 2.5 Ah nominal capacity
Applications: motorsports, drones, e-mobility
Technical Specifications from the Manufacturer
Parameter
Manufacturer
A123 Systems
Model
21700 S
Type
Li-ion
Form factor
Cylindrical 21700
Country of origin
China
Release year
Nominal voltage
3.65
Energy capacity [Wh]
9.125
Capacity [Ah]
2.5
Gravimetric energy density [Wh/kg]
136
Gravimetric power density [W/kg]
10896
Max continuous discharge [A]
200
Volume [cm³]
25.8703
Mass [g]
67
Positive electrode (cathode)
NCA
Negative electrode (anode)
Graphite
Value
Applications & Use‑Cases
The A123 Systems 21700 S is well suited to the following applications due to its 21700 format and high power performance.
Motorsports: Demands sustained high discharge under competitive load profiles, rapid transient response for acceleration, and thermal stability to maintain performance during race conditions.
Drones: Demands high gravimetric power density for thrust and payload capacity, rapid current response for flight control, and stable voltage delivery across dynamic flight profiles.
E-Mobility: Requires balanced energy and power density for range and acceleration, high cycle life for daily use, and robust calendar life to ensure long-term reliability.
General Applications: Suitable for applications requiring reliable lithium-ion performance with proven cycle life, consistent capacity delivery, and operational safety across diverse use cases.
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Performance & Model Data
Below are modelled performance metrics for the A123 Systems 21700 S across key indicators, including constant current behaviour, rate capability, temperature dependence, and available power under representative drive cycle conditions.
Constant Current Voltage
The A123 Systems 21700 S constant-current plots reveal voltage behaviour under steady loads, ideal for analysing efficiency.
Constant Current Temperature
The A123 Systems 21700 S constant-current plots reveal temperature behaviour under steady loads, ideal for analysing thermal response.
Pulse Power Behaviour
The A123 Systems 21700 S pulse power map evaluates short-duration load responses, allowing engineers to determine the maximum available power as a function of state of charge and temperature.
Dynamic Profile Response
The A123 Systems 21700 S mission-profile plots simulate real-world duty cycles, showing how the cell manages dynamic power demands and temperature changes.
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Case Studies
See how we helped McMurtry reduce cell evaluation time by 70% through data driven testing and modelling.
Motorsports
McMurtry Automotive: Faster cell evaluation
McMurtry Automotive used The Voltt and validated cell models to evaluate the transition from the Molicel P45B to P50B during early pack concept development.
Side by side modelling enabled rapid comparison of electrical and thermal behaviour, avoiding lengthy physical test campaigns. This approach reduced cell evaluation time by seven months, allowing the team to lock in cell selection and pack assumptions earlier while lowering technical risk and accelerating vehicle development.
Comparison with Related Cells
Compare the A123 Systems 21700 S with similar Cylindrical 21700 cells offering comparable capacity and performance characteristics.
Model
Capacity
Max Discharge
Typical Use
Access Cell Data
Manufacturer Background
About A123 Systems
Lithium iron phosphate specialist
A123 Systems was founded in 2001 in Massachusetts, commercialising nanophosphate lithium iron phosphate chemistry developed from research at the Massachusetts Institute of Technology. The company focuses on LFP cells and modules built for high power delivery, long cycle life and thermal stability. Its products are used in automotive low-voltage systems, commercial and specialty vehicles, and grid storage. A123 was acquired by the Wanxiang Group in 2013 and continues to operate as A123 Systems LLC with manufacturing in China and the United States. Its position rests on a long production record in LFP at a time when the chemistry is returning to favour for safety-critical and cost-sensitive applications.
Frequently Asked Questions
What is the capacity and voltage of the A123 Systems 21700 S?
The A123 Systems 21700 S has a nominal capacity of 2.5 Ah and a nominal voltage of 3.65 V, providing 9.12 Wh of energy per cell.
What is the maximum continuous discharge capability of the A123 Systems 21700 S?
The A123 Systems 21700 S supports continuous discharge rates up to 125 A, delivering a power density of 6810 W/kg.
How much does the A123 Systems 21700 S weigh and what is its volume?
The cell has a mass of 67 g and a volume of 25.87 cm³.
In which industries is the A123 Systems 21700 S commonly used?
The A123 Systems 21700 S is used across motorsports, drones, e-mobility, applications that demand sustained high current.
What is The Voltt and how does it accelerate cell evaluation?
The Voltt is About Energy's digital cell simulation platform that models electrochemical and thermal performance, reducing evaluation time by up to 70% compared to laboratory testing.
What data can be extracted using The Voltt?
Engineers can simulate and visualise voltage, temperature, and power responses under constant-current or mission-profile conditions, generating detailed discharge plots to support accurate cell comparison and validation.
