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Battery Cell Formats and Chemistries Reference: 18650, 21700, 4680, LFP, NMC, NCA

Purchasing and engineering teams in EV programs constantly compare cell formats and chemistries, and the first questions are usually about size and voltage. This table puts the common ones side by side so you can sanity-check a quote or a datasheet.

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Format or chemistry	Category	Nominal voltage	Typical upper charge voltage	Notes
18650	Cylindrical format	Depends on chemistry	Depends on chemistry	Approximately 18 mm diameter by 65 mm length. Long history in laptops and early EV packs.
21700	Cylindrical format	Depends on chemistry	Depends on chemistry	Approximately 21 mm diameter by 70 mm length. Larger capacity per cell than 18650.
26650	Cylindrical format	Depends on chemistry	Depends on chemistry	Approximately 26 mm diameter by 65 mm length. Common with LFP chemistry in power tools and storage.
4680	Cylindrical format	Depends on chemistry	Depends on chemistry	Approximately 46 mm diameter by 80 mm length. Large-format cylindrical cell introduced for newer EV packs.
Prismatic	Format	Depends on chemistry	Depends on chemistry	Rigid rectangular metal case. Efficient packing, common in Asian and European EV packs.
Pouch	Format	Depends on chemistry	Depends on chemistry	Laminated foil enclosure. Flexible shape, needs structural support and swelling management in the module.
LFP (LiFePO4)	Chemistry	3.2 V	3.65 V	Lithium iron phosphate. Good thermal stability and cycle life, lower energy density, flat voltage curve.
NMC (nickel manganese cobalt)	Chemistry	3.6 to 3.7 V	4.2 V (some variants higher)	Widely used in EVs. Higher energy density than LFP. Several nickel-rich variants exist.
NCA (nickel cobalt aluminium)	Chemistry	3.6 V	4.2 V	High energy density. Used in some cylindrical cell packs.
LCO (lithium cobalt oxide)	Chemistry	3.7 V	4.2 V	Mostly used in consumer electronics rather than vehicles.
LMO (lithium manganese oxide)	Chemistry	3.7 V	4.2 V	Good power capability, lower cycle life. Sometimes blended with NMC.
LTO (lithium titanate anode)	Chemistry	2.3 to 2.4 V	2.8 V	Very fast charge and long life, lower energy density and higher cost.
Sodium-ion	Chemistry	About 3.0 to 3.1 V	Varies by design	Emerging alternative without lithium. Check supplier data for actual figures.
400 V class pack (NMC example)	Pack architecture	About 355 V at 96 cells in series	About 403 V at 4.2 V per cell	96 cells in series times 3.7 V nominal gives about 355 V. Parallel groups add capacity.
800 V class pack (NMC example)	Pack architecture	About 710 V at 192 cells in series	About 806 V at 4.2 V per cell	Doubling series count doubles voltage. Insulation and clearance design must follow.
State of charge window	Concept	Not applicable	Not applicable	Manufacturers usually limit the usable window to protect cell life, so usable and gross capacity differ.

Voltages are typical values for general planning. Use the cell supplier datasheet for actual nominal, minimum and maximum voltage and temperature limits.

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How to use the table

Search by format name, such as 21700, or by chemistry, such as LFP. Cylindrical, prismatic and pouch rows describe the physical format, and the chemistry rows describe the electrochemistry and voltage. A real cell is one of each, for example a prismatic LFP cell. Use the pack architecture rows to estimate series count for a target voltage class and export the filtered rows to Excel for a sourcing comparison.

Format versus chemistry

Format controls how the cell is packaged, cooled and mounted. Chemistry controls voltage, energy density, safety margin and life. Because they are independent, the same chemistry can be supplied in several formats. Compare like with like when evaluating suppliers: an NMC pouch cell and an LFP prismatic cell have different voltage, so a pack needs a different series count for the same system voltage.

Format: cylindrical, prismatic or pouch
Chemistry: LFP, NMC, NCA, LTO and others
Series count equals pack voltage divided by cell voltage

Worked example for series count

A 400 V class pack built from NMC cells at 3.7 V nominal needs about 108 cells in series for 400 V nominal, or 96 in series if the target is around 355 V. With 4.2 V maximum, 96 cells reach about 403 V at full charge. An LFP pack at 3.2 V per cell needs about 125 cells in series to reach 400 V nominal. These numbers show why chemistry choice changes the bill of materials and the battery management channel count.

Common mistakes

Do not use the nominal voltage to size insulation or clearances. Use the maximum charge voltage, plus margin. Do not compare energy density figures taken at different levels, cell, module or pack. And do not assume that a format name guarantees interchangeability, since tabs, venting and terminals differ between suppliers even for the same nominal size.

Frequently Asked Questions

Which cell chemistry has the highest nominal voltage?

Among the common ones, NMC, NCA, LCO and LMO sit around 3.6 to 3.7 V nominal, higher than LFP at 3.2 V and LTO at about 2.3 to 2.4 V. Higher voltage per cell means fewer cells in series for a given pack voltage.

Why does a 4680 cell matter?

It is a larger cylindrical format than 21700. Larger cells reduce the number of cells, tabs and connections per pack, which can simplify assembly. Performance still depends on the chemistry and the supplier design.

Is LFP safer than NMC?

LFP is generally regarded as more thermally stable, but pack safety depends on the full design: cell quality, the battery management system, cooling and propagation protection. Use supplier test data, not the chemistry alone.

Can I use these voltages for design sign-off?

No. They are typical values for estimating. Always design from the cell supplier datasheet, which gives the exact nominal, minimum and maximum voltage and temperature limits for the specific cell.

Tracking cells, lots and supplier data across ERP and quality systems is a common pain point. Netray can discuss a private assistant that answers these questions from your own records.

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