Shop Lithium Battery Cells by Size

United Lithium Solutions

Find the Right Lithium Battery Cell Format

Compare cylindrical lithium-ion battery cells by physical size, pack-design requirements, power demand, runtime goals, and intended application. Browse current ULS inventory in the two most widely used formats: 18650 and 21700.

Physical Dimensions Capacity Discharge Capability Pack Configuration

Compare Cell Sizes → Shop by Brand

Multiple Cell Formats Shop current 18650 and 21700 inventory

Technical Guidance Application and model-selection support

Commercial Quantities Project and volume purchasing options

U.S.-Based Support Commercial service from the ULS team

Cylindrical Cell Formats

Battery Cell Size Is the Starting Point—not the Entire Specification

A format such as 18650 or 21700 describes the approximate physical dimensions of the cylindrical cell. It does not, by itself, define chemistry, capacity, discharge capability, cycle life, charging limits, or suitability for a particular battery pack.

Shop Current Inventory

Shop Lithium-Ion Cells by Size

Select a cell format to view available manufacturers, models, product specifications, pricing, and current purchasing options.

Compact Cylindrical Format

18650

Approximately 18 mm × 65 mm

The 18650 remains a widely used lithium-ion cell format for compact battery packs, established pack designs, tools, electronics, mobility applications, and industrial equipment.

Smaller cell diameter for compact pack layouts
Broad selection of high-power and high-capacity models
Common in mature battery-pack designs
Available from multiple established manufacturers

Larger Cylindrical Format

21700

Approximately 21 mm × 70 mm

The 21700 format provides more internal volume than an 18650 and is widely used in newer high-capacity and high-power battery systems, including mobility, drones, industrial equipment, and energy applications.

Greater per-cell energy potential than smaller formats
Can reduce the number of cells needed for comparable pack energy
Strong selection of performance-focused models
Common in modern mobility and industrial designs

Specialty and Future Inventory

Looking for Another Cylindrical Cell Size?

Availability for larger cylindrical formats may depend on manufacturer, chemistry, quantity, lead time, and project requirements.

26650 Battery Cells Approximately 26 × 65 mm. Used in selected industrial, high-current, specialty, and LiFePO4 applications. → 32700 Battery Cells Approximately 32 × 70 mm. Often associated with larger cylindrical LiFePO4 and stationary-energy applications. →

Cell Format Comparison

Compare Common Cylindrical Battery Cell Sizes

Use this table as an initial format comparison. Final selection must be based on the exact manufacturer datasheet and complete battery-system requirements.

Cell Format	Approximate Size	General Design Characteristics	Common Application Categories	Shop or Inquire
18650	18 mm × 65 mm	Compact cylindrical format with a broad selection of power- and energy-focused models.	Battery packs, power tools, e-mobility, electronics, medical equipment, and industrial systems.	Shop 18650
21700	21 mm × 70 mm	Larger internal volume with strong high-capacity and high-power model availability.	E-mobility, drones, robotics, industrial packs, power systems, and energy storage.	Shop 21700
26650	26 mm × 65 mm	Larger cylindrical can used in selected specialty and industrial battery designs.	Industrial equipment, specialty packs, high-current devices, and some LiFePO4 systems.	Request availability
32700	32 mm × 70 mm	Large cylindrical format commonly associated with selected LiFePO4 designs.	Solar storage, backup power, stationary systems, and industrial energy applications.	Request availability

Dimensions are nominal format references. Actual dimensions, tolerances, terminal construction, capacity, current ratings, and chemistry vary by manufacturer and model.

Selection Process

How to Choose the Right Battery Cell Size

Cell size should be selected as part of a complete battery-system design—not as an isolated purchasing decision.

Confirm the Physical Envelope

Determine the maximum pack length, width, height, weight, spacing, insulation, enclosure, and mounting requirements.

Define Pack Voltage

Determine nominal and maximum pack voltage, series count, charging voltage, equipment compatibility, and BMS requirements.

Calculate Current Demand

Review continuous current, peak current, duty cycle, voltage sag, conductor sizing, busbars, and thermal load.

Set Runtime and Energy Goals

Define target watt-hours, expected runtime, usable depth of discharge, reserve capacity, and parallel-cell count.

Review Thermal and Safety Needs

Account for cell spacing, cooling, charging conditions, temperature limits, BMS protection, fusing, and enclosure design.

Confirm Supply and Documentation

Consider manufacturer availability, production consistency, lead time, testing, datasheets, shipping eligibility, and long-term sourcing.

Application Categories

Cylindrical Cells for Commercial Battery Systems

The correct format and model depend on the system’s power, energy, mechanical, environmental, and commercial requirements.

Battery-Pack Manufacturing

Cell sourcing for prototypes, production packs, replacement programs, and OEM systems.

E-Mobility

Battery-cell options for e-bikes, light electric vehicles, mobility systems, and performance applications.

Commercial Drones

High-power and high-energy cell selection for demanding flight, payload, and operational requirements.

Robotics and Automation

Power solutions for mobile robotics, automated equipment, research platforms, and industrial systems.

Energy Storage

Cylindrical cell options for selected backup-power, portable-energy, and stationary battery designs.

Industrial Equipment

Cells for tools, instrumentation, heavy-use equipment, specialty electronics, and field systems.

Research and Development

Cell access for engineering evaluation, product development, laboratory programs, and performance testing.

OEM Product Programs

Cell and battery-program support for manufacturers developing commercial lithium-powered products.

Important Technical Note

Cell format alone does not determine safety or performance. Always use the exact manufacturer datasheet, observe charging and discharging limits, use an appropriate battery-management system, and incorporate suitable electrical, mechanical, and thermal protection. Loose lithium-ion cells are components intended for properly engineered battery systems.

Battery Size Questions

Frequently Asked Questions

What do the numbers 18650 and 21700 mean?

The numbers indicate approximate cylindrical cell dimensions. An 18650 cell is approximately 18 mm in diameter and 65 mm long. A 21700 cell is approximately 21 mm in diameter and 70 mm long. Actual dimensions and tolerances vary by manufacturer and model.

Is a 21700 cell always better than an 18650 cell?

No. A 21700 has more internal volume, but the correct choice depends on the exact model, pack dimensions, current requirements, runtime target, weight, thermal design, cost, availability, and application. A well-selected 18650 can be more appropriate for some systems.

Can I replace an 18650 cell with a 21700 cell?

Not as a direct physical replacement. A 21700 is larger in both diameter and length. Changing formats can require a redesigned enclosure, cell holder, busbar arrangement, insulation system, thermal plan, BMS configuration, and production process.

Which cell size is best for an e-bike battery?

Both 18650 and 21700 cells are used in e-bike batteries. The correct choice depends on required voltage, watt-hours, discharge current, enclosure dimensions, weight target, thermal conditions, charging system, and the specific cell model.

Does a larger cell automatically have a higher discharge rating?

No. Physical size alone does not determine discharge capability. Two cells with the same dimensions can have very different capacity, current, temperature, cycle-life, and charging specifications.

Can ULS help identify the correct cell format?

ULS can review information such as pack voltage, target capacity, current requirements, application, available dimensions, expected order quantity, operating environment, and project timeline to help identify suitable options for further evaluation.

Can I purchase battery cells in commercial quantities?

Commercial purchasing may be available depending on the manufacturer, model, inventory, quantity, shipping destination, and project requirements. Contact ULS with the desired format, model, quantity, and timeline.

How are cylindrical lithium-ion cells shipped?

Shipping methods and eligibility depend on the cell classification, quantity, packaging, destination, carrier requirements, and applicable hazardous-material regulations. Shipping availability must be confirmed for each order.

Commercial and OEM Support

Need Help Choosing Between 18650 and 21700 Cells?

Share your application, required voltage, target capacity, continuous and peak current, dimensional limits, expected quantity, and project timeline. United Lithium Solutions will review the requirements and help identify appropriate next steps.

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