Saft LS-26500 (C size) Li‑SOCl₂ Primary Battery

The Saft LS-26500 is a bobbin-type lithium‑thionyl chloride cell designed for long life in low-to-moderate drain devices. It delivers a stable 3.6 V output, very low self-discharge, and reliable operation across a wide temperature range, making it a strong fit for remote and maintenance‑constrained deployments.

Key specifications

Chemistry	Lithium‑Thionyl Chloride (Li‑SOCl2)
Format	C cell, approx. 26 mm diameter × 50 mm height
Nominal voltage	3.6 V
Typical capacity	~7.4–7.7 Ah (low-drain, 20°C, to ~2.0 V cut‑off; varies by load and temperature)
Operating temperature	Approximately −60°C to +85°C
Self‑discharge	Typically ≤1%/year at 20°C (storage conditions dependent)
Rechargeable	No (primary cell)

Note: Exact ratings depend on the specific part variant and test method. Always confirm with the latest Saft datasheet.

When to choose the LS‑26500

• Multi‑year, low‑average current devices: utility meters, AMI/AMR endpoints, leak/flow sensors, data loggers, asset trackers, environmental monitors.
• Installations with limited maintenance access where battery changes are costly.
• Cold or hot environments that defeat standard alkaline/lithium‑ion solutions.

Avoid or modify if

• Your device demands high continuous current or frequent high‑pulse bursts (e.g., cellular/GSM). Use a pulse buffer (low‑ESR capacitor or hybrid layer capacitor) or consider a high‑pulse Li‑SOCl₂ variant such as Saft LSH series (e.g., LSH 14 for C size).
• You need rechargeability, energy harvesting, or frequent charge/discharge cycles — choose rechargeable chemistries instead.
• You cannot accommodate passivation behavior after long storage; plan for a brief warm‑up/load or buffering.

Runtime planning

Estimate runtime as: Runtime ≈ Usable capacity (Ah) ÷ Average load (A). Adjust for temperature, cut‑off voltage, and pulse losses.

• Example A: 30 µA average — 7.7 Ah ÷ 0.00003 A ≈ 256,000 h ≈ 29 years; in practice, plan 10–15 years due to self‑discharge and environmental factors.
• Example B: 100 µA average — 7.7 Ah ÷ 0.0001 A ≈ 77,000 h ≈ 8.8 years.
• Example C: 1 mA average — 7.7 Ah ÷ 0.001 A ≈ 7,700 h ≈ 10.6 months.

For pulsed radios (LoRa/mesh), size a low‑ESR capacitor to handle burst current while keeping the battery within its recommended continuous current. Validate under worst‑case temperature.

Integration tips

• Set device cut‑off voltage per the datasheet (consider voltage delay/passivation after storage).
• Use a low‑leakage holder or spot‑welded tabs; avoid direct soldering to the cell body.
• Include reverse‑polarity/short protection (e.g., series diode/ideal diode, PTC or fuse).
• For series packs, match cells by lot/age; avoid mixing new and used cells. For parallel use, add current‑sharing and blocking elements.
• Validate pulse performance across temperature with the intended buffer capacitor and real firmware duty cycle.

Compatibility notes

• Output is 3.6 V nominal — ensure the device is rated for this voltage (do not substitute for 1.5 V alkaline C cells).
• If replacing another Li‑SOCl₂ C cell, confirm physical size, terminal style (button top, flat top, tabs), and cut‑off requirements.

Safety and handling

• Do not recharge, short‑circuit, crush, or expose to fire. Risk of venting/explosion if misused.
• Store cool and dry (ideally ≤30°C), in original packaging with terminals insulated.
• Transport under applicable lithium metal regulations (UN 3090/3091) and local carrier rules.
• Dispose/recycle per local regulations; do not incinerate.

Alternatives

• Higher pulse demand (same size): Saft LSH 14 (C size, spiral construction) or LS with a dedicated pulse capacitor.
• Higher capacity (larger size): Saft LS 33600 (D size) for extended runtime at similar currents.
• Rechargeable needs: Li‑ion or Li‑FePO₄ packs with appropriate protection.

FAQ

Is the LS‑26500 rechargeable?

No. It is a primary lithium metal cell and must never be recharged.

Can it power GSM or similar high‑pulse radios?

Not directly. Use a properly sized low‑ESR capacitor or choose a high‑pulse Li‑SOCl₂ cell (e.g., LSH series). Test at the lowest operating temperature.

What is passivation and how do I handle it?

After storage, a protective film can cause a brief voltage delay under load. Minimize by storing cool, applying a small pre‑load, or using a pulse buffer. Design your cut‑off and start‑up routine accordingly.

How long is the shelf life?

Typically 10+ years at 20°C with ultra‑low self‑discharge. Actual life depends on temperature and storage conditions.

Are solder‑tab versions available?

Yes. Cells can be supplied with axial leads or welded tabs. Avoid direct hand‑soldering to the cell can.