The CE-2665 is a 3.2V 26650 LiFePO4 cell, 3.4 amp-hours, 10.9 watt-hours, in a steel can 26mm across. It is the step up from the 18650 in the cylindrical range, and it favours rugged outdoor duty over compactness.
Outdoor Duty
Why the steel can matters
A 26650 in a steel canister takes vibration and temperature swings better than a small pouch or prismatic cell, which is why it turns up in equipment that lives outdoors unattended. Navigation buoys and marks, weather instruments, trail cameras and small solar lamps all run cells in this class. The LFP chemistry adds the safety a sealed outdoor enclosure needs and the cycle life a device that recharges from a small panel every day depends on.
Wide temperature tolerance is the other reason. These cells discharge from minus twenty to sixty degrees, so a buoy keeps flashing through a cold night and a hot afternoon on the same pack. Charging still stops below freezing, which a controller or a heater manages on installations that see sub-zero mornings.
Data
Datasheet
| Model | CE-2665 (26650) |
|---|---|
| Nominal voltage | 3.2V |
| Rated capacity | 3.4Ah |
| Energy | 10.9Wh |
| Charge voltage | 3.65V |
| Discharge cutoff | 2.0V |
| Continuous discharge | 10A (3C) |
| Peak discharge | 17A (5C) |
| Cycle life | ≥2,000 cycles |
| Weight | ≈85 g |
| Size | 26 × 65 mm |
| Operating temperature | Discharge -20~60°C / Charge 0~45°C |
| Certification | UN38.3 / CE / RoHS |
Pack notes
| 4S | 12.8V · 44Wh: buoy lamps, outdoor instruments |
|---|---|
| 4S2P | 12.8V · 87Wh: longer-runtime outdoor packs |
| Wide-temp | -20 to 60°C discharge |
The buoy and the monitoring station
A navigation buoy is a good test of the format. It floats unattended for months, flashes a light every night, recharges from a small panel by day, and cannot be allowed to fail or catch fire at sea. The 26650 answers each of those: the steel can takes the constant motion, the LFP chemistry gives the safety and the daily-cycle life, and the wide temperature range keeps the light working through cold nights and hot afternoons on one pack. Coastal and inland marks, data buoys and offshore instruments all run cells in this class for the same reasons. On land the same cell suits weather stations, wildlife cameras and small solar lamps, any device left outdoors that has to recharge itself and stay reliable for years. These sites share a pattern: a small panel, a modest daily load, and years between service visits, which is the duty the steel-can LFP cell holds up under where a smaller or higher-energy cell would not.
Build
Assembling a 26650 pack
Like the 18650, these cells weld into a pack with nickel strip and a BMS rather than bolting. Four in series make 12.8 volts, the common voltage for buoy lamps and outdoor instruments, and parallel groups add runtime for longer nights. Match cells on capacity before welding, which cells from one factory batch already are. Charge to 3.65 volts per cell, hold standby stock at 30 to 50 percent, and every cell traces to its factory test record by code.
The 26650 sits between the 18650 and the larger 32700 in both size and job. It carries roughly twice the energy of an 18650 in a can still small enough to weld into a compact pack, which is why it suits a device that needs more than the smallest cell can hold but less than a prismatic build. A 4S pack makes the 12.8 volts a buoy lamp or an outdoor instrument runs on, and parallel groups add the nights of autonomy a remote site specifies. Delivered capacity meets the 3.4-amp-hour rating, and every cell carries its code to the factory test record.
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