26650 LiFePO4 Battery 3.2V 3000mAh | IFR26650 LFP Cylindrical Cell

26650 LiFePO4 Battery — IFR26650 3000mAh 3.2V Cylindrical LFP Cell

The 26650 LiFePO4 battery (model IFR26650) is the power format of the cylindrical LFP range: 26 mm in diameter, 65 mm in height, 3000 mAh at a 3.2 V nominal platform — roughly 9.6 Wh and twice the capacity of an IFR18650 in the same length. Where the 18 mm formats serve sensors and small packs, the 26650 exists because some applications need current, not just energy: engine starter batteries, UPS blocks, solar storage strings and AGV drive packs that draw 10 A to 30 A from a single cell. It keeps the LiFePO4 advantages those buyers actually specify for — 2000+ cycle life, no thermal runaway propagation, a flat 3.2 V discharge curve — in the largest cylindrical LFP format in regular production. CMX Battery supplies it with per-lot capacity, IR and OCV test data, OEM branding, and a downloadable datasheet.

Table of contents: Specifications · What Is a 26650 LiFePO4 Battery? · IFR26650 vs IFR18650 · Charge & Discharge · Cycle Life & Safety · Applications · Certifications · OEM/ODM & Ordering · FAQ

26650 LiFePO4 Battery Specifications

Typical values below reflect the production standard for this format across established manufacturers; final parameters ship against the CMX controlled product specification.

What Is a 26650 LiFePO4 Battery?

A 26650 LiFePO4 battery is a rechargeable cylindrical cell whose designation encodes its geometry — 26 mm diameter, 65 mm height, cylindrical format — with lithium iron phosphate as the active chemistry. The IFR prefix is the IEC convention for cylindrical LFP cells (I = lithium-ion, F = iron phosphate, R = round), parallel to the INR prefix used for cylindrical NCM cells. At 26 mm it is the largest cylindrical LFP format in regular production; the same 65 mm length as an 18650 with 46% more diameter delivers roughly twice the capacity.

The cell is a sealed steel can with a CID safety vent; welding is permitted only on the top cap and bottom end, never on the side wall. Its flat 3.2 V discharge curve holds voltage nearly constant across most of the capacity range, so a 4S string (12.8 V nominal) delivers a stable input to 12 V nominal devices — engine starters, UPS blocks and solar lighting controllers — through most of the discharge.

IFR26650 vs IFR18650: Choosing the Cylindrical LFP Format

Both cells share the 65 mm length and the 3.2 V LiFePO4 platform, so the choice is diameter, capacity and rate. Use this table to confirm fitment before sampling.

For the compact 18 mm format, see the IFR18650 page. For the full small-format cylindrical lineup (14 mm and 18 mm families), see the small cylindrical lithium cells overview.

IFR26650 Charge and Discharge Profile

Charging follows CC-CV on the LFP profile: constant current at the standard 0.2–0.5C rate until terminal voltage reaches 3.65 V, then hold at 3.65 V until current tapers below the cut-off threshold. Maximum charge current is 1C (3000 mA) on standard grades. Never charge an IFR26650 with a 4.2 V li-ion charger — the 3.65 V ceiling is a hard chemistry limit, and exceeding it damages the cell. Charge temperature is specified 0–45 °C; below 0 °C, limit current or skip charging.

Discharging is rated 3C (9 A) continuous with 5C (15 A) pulses on standard grades; high-rate grades reach 10C continuous (30 A) with 20C (60 A) short pulses for engine-cranking and AGV drive duty. The high-rate grades trade some capacity and cycle count for current — specify your duty cycle and peak current and we will confirm the right grade.

IFR26650 Cycle Life and Safety Performance

Cycle life is specified at 2000+ cycles to ≥80% capacity retention at full depth of discharge — several times the cycle count of a standard NCM cell — with 3000 to 7000 cycles available at reduced depth of discharge depending on grade. In a UPS or solar application cycling daily, that is five or more years of service.

Safety testing covers over-discharge, overcharge, external short circuit, thermal abuse, drop, vibration and temperature shock — all with no fire, no explosion, no leakage. The LFP chemistry’s higher thermal runaway onset temperature makes it the lower-risk choice for engine compartments, occupied spaces and densely packed strings, and removes the propagation concern in multi-cell series configurations.

26650 LiFePO4 Battery Applications

Engine starter batteries (12 V / 24 V). The flagship application. A 4S IFR26650 block (12.8 V nominal) with a BMS replaces lead-acid starter batteries in motorcycles, marine outboards, golf carts and light equipment: maintenance-free, no acid, roughly a quarter of the lead-acid weight, and cranking current inside the high-rate grades’ envelope. High-rate grades deliver the 20C-class pulses cold-cranking demands.

UPS and data-center backup blocks. Long service life plus a flat discharge curve keeps backup rails stable without conditioning stages; per-lot test data simplifies incoming QC for regulated deployments.

Solar storage strings and off-grid packs. The 3000 mAh capacity in a standard 26650 holder simplifies DIY and OEM storage assemblies; 2000+ cycles at full DOD match the daily charge-discharge duty of an off-grid installation.

AGV, robotics and electric mobility. High-rate grades (10C continuous class) deliver drive and steering current, with the chemistry’s thermal stability simplifying pack thermal design in enclosed chassis.

Solar street lights and high-output luminaires. Deeper lantern and street-light bays use the 26650 where an 18650 cannot deliver the required runtime; low self-discharge suits unattended lighting.

Certifications and Shipping Compliance

Every IFR26650 ships against the documentation compliance teams ask for first: UN38.3 (the UN Manual of Tests and Criteria test summary required for lithium transport by air and sea), MSDS, IEC 62133-2 cell safety compliance, CE and RoHS declarations, and REACH documentation for EU-bound programs. UL1642 / UL2054 reports are available for North American programs on request. Lot-level documentation — capacity, internal resistance and open-circuit voltage per cell — accompanies each shipment so incoming QC starts from data rather than sampling. For the full certification scope, see our lithium battery certifications and compliance page.

OEM/ODM Customization and Ordering

CMX Battery supplies the IFR26650 for OEM programs: welded tabs or connectors to your drawing, shrink-wrap or label branding with your model number, BMS integration for pack orders from 12 V to 48 V, and packaging configured to your line. Cells ship at partial SOC with per-lot test data. Samples are available for bench validation before volume commitment; minimum order quantities, lead times and per-lot test-data format are confirmed with your quotation, which comes back within 24 hours. Warranty is one year from date of shipment against manufacturing defects.

Frequently Asked Questions

What is a 26650 LiFePO4 battery?
A 26650 LiFePO4 battery is a rechargeable cylindrical LFP cell (Ø26.3 × 65.3 mm, 3000 mAh, 3.2 V nominal) — the largest cylindrical LFP format in regular production, built for high-current applications.

What is the difference between IFR26650 and IFR18650?
Same 65 mm length and 3.2 V platform, but the 26650 has 26.3 mm diameter versus 18.2 mm, roughly double the capacity (3000 vs 1500 mAh) and high-rate grades to 10C continuous for starter and drive duty.

What is a 26650 LiFePO4 battery used for?
Engine starter batteries (12 V / 24 V), UPS and data-center backup blocks, solar storage strings, AGV and robotics drive packs, and high-output solar luminaires.

How do you charge a 26650 LiFePO4 battery?
CC-CV to 3.65 V with taper cut-off; standard charge 0.2–0.5C, maximum 1C (3000 mA), charge window 0–45 °C. Never use a 4.2 V li-ion charger.

How many amps can a 26650 LiFePO4 discharge?
Standard grades are rated 3C (9 A) continuous with 5C (15 A) pulses; high-rate grades reach 10C continuous (30 A) with 20C (60 A) short pulses for cranking and drive duty.

How long does an IFR26650 last?
Production cells are specified at 2000+ cycles to ≥80% capacity retention at full DOD — in daily-cycling service that translates to five or more years. Reduced-DOD grades reach 3000–7000 cycles.

Is the 26650 LiFePO4 available with OEM branding?
Yes — welded tabs or connectors, custom labels with your model number, BMS integration and tailored packaging are standard services, with per-lot test data on every shipment.

What is the difference between an IFR26650 and a 21700 battery?
The 21700 (21 × 70 mm) is a thinner, longer cell produced mainly in NCM chemistry, where it leads on energy density per litre. The IFR26650 (Ø26.3 × 65.3 mm) is a wider, shorter LiFePO4 cell built for current and cycle life — 3000 mAh at 3.2 V, 3C (9 A) continuous with a 10C high-rate grade, ≤25 mΩ and 2000+ cycles at full DOD. For stationary storage, UPS and engine-starter duty, where daily deep cycling and thermal stability matter more than watt-hours per litre, the 26650 LFP is the standard industrial format. CMX Battery produces the IFR26650 rather than the 21700; the cylindrical battery sizes guide compares the full lineup.

Can I charge an IFR26650 in an 18650 charger?
Two mismatches: most 18650 charger bays cannot physically hold the 26.3 mm can with reliable contact, and standard 4.2 V lithium-ion profiles exceed the IFR26650’s 3.65 V ± 0.03 V end-of-charge limit — a misuse condition for LiFePO4 that shortens cycle life even when current flows. Charge only on a LiFePO4-profile charger or BMS: CC-CV to 3.65 V, 2.0 V discharge cut-off, within the 0–45 °C charge window.

Can I replace an 18650 with a 26650 in an existing device?
Not without redesigning the holder or enclosure. The IFR26650 is about 8 mm wider and roughly twice the mass of an 18650, and forcing the larger can into an 18 mm bay cracks holders and tears the insulating wrapper. Where the 18 mm envelope is fixed, the upgrade path is the IFR18650 (1500 mAh, 3.2 V) in the same 18 × 65 mm footprint; where the housing accepts 26.3 mm, the IFR26650 doubles the energy per cell and halves the cell count for the same pack capacity.

How should IFR26650 cells be stored?
Store at roughly 40–60% state of charge in a cool, dry, non-conductive container away from metal objects, and check open-circuit voltage every few months — recharge toward storage voltage if it drifts toward the 2.0 V cut-off. Keep long-term storage within the cell’s −20 °C to 60 °C band, avoid extended periods at full charge, and ship only under UN38.3 documentation as Class 9 dangerous goods.

Request a Quote

Send your target voltage, capacity, continuous current and mechanical envelope — you will receive a datasheet-matched quotation, sample options and lead time within 24 hours.

Or email sales@cmxbattery.com. Download the typical specifications overview: IFR26650 Typical Specifications Overview (PDF). The controlled product datasheet is issued with your quotation on request.