Saft LS-17500

Saft LS-17500 (3.6 V Li-SOCl2, A-size) — Long-life primary cell for low-drain devices

The LS-17500 is a bobbin-type lithium–thionyl chloride cell optimized for ultra-long runtime at low average currents. It excels in equipment that must run for years without service, such as utility meters, data loggers, and memory backup.

Key specs

Chemistry	Li-SOCl2 (bobbin)
Nominal voltage	3.6 V (OCV ≈ 3.67 V)
Typical capacity	≈ 3.6 Ah at 20°C (low-drain to 2.0 V cutoff)
Recommended load profile	Very low to moderate continuous current; small pulses with assistance
Typical continuous current	Up to ~100 mA (best efficiency at ≤10 mA)
Pulse handling	Short pulses can be supported with a pulse-assist capacitor; avoid high-peak GSM-class loads
Self-discharge	≤ 1% per year at 20°C (stored)
Operating temperature	−60°C to +85°C
Size	17 mm diameter × 50 mm length (A / 17500)
Mass	≈ 24 g
Terminations	Flat top; tagged/lead options available (consult configuration options)

Best for

• Smart water/gas meters and AMR/AMI endpoints
• Data loggers, environmental and industrial sensors
• Memory/RTC backup in equipment with very low standby draw
• Asset tracking beacons with infrequent, low-energy transmissions

Avoid or consider alternatives if

• Your device draws frequent high pulses (e.g., cellular/GSM peaks ≥ 1 A) — use a high-pulse chemistry (e.g., Saft LSH series) or add a supercapacitor and validate.
• You need rechargeability or energy recovery — consider Li-ion or LiFePO4 rechargeable solutions.
• Average current is above a few milliamps — runtime will be short; choose a larger cell (e.g., LS 26500/33600) or a different power strategy.

Quick runtime examples (rule-of-thumb)

• Average 10 µA: 3.6 Ah / 0.00001 A ≈ 360,000 h ≈ 41 years (limited by self-discharge; plan 10–15 years max in practice).
• Average 100 µA: 3.6 Ah / 0.0001 A ≈ 36,000 h ≈ 4.1 years.
• Average 50 µA: ≈ 8.2 years (derate for temperature, pulsed loads, and passivation; plan 5–7 years).
• Average 5 mA: 3.6 Ah / 0.005 A ≈ 720 h ≈ 30 days (not a good fit for this chemistry).

Note: Real-world life depends on temperature, pulse profile, cutoff voltage, and cell aging/passivation. Validate with your load profile.

Design and integration notes

• Passivation and voltage delay: After long storage, initial load may cause a temporary voltage dip. Mitigate with a brief pre-load, a low-ESR buffer capacitor (e.g., 100–470 µF), and firmware brownout handling.
• Pulse assistance: For radio bursts (LPWAN, sub-GHz), add a local capacitor near the MCU/RF stage. Verify minimum voltage under worst-case cold start.
• Series/parallel use: Use only matched, new cells. Add blocking and balancing where appropriate. Never mix new and used cells.
• Polarity/short protection: Implement reverse-polarity and short-circuit protection. Do not solder directly to the cell body; use tagged versions or holders.
• Storage: Store cool and dry (ideally ≤ 30°C). For longest life, avoid prolonged high-temperature storage.
• Compatibility: Designed for 3.6 V primary Li-SOCl2 systems; do not substitute into chargers or devices expecting rechargeable chemistries.

Alternatives and equivalents

• Same size/chemistry: Tadiran TL-5903, XENO XL-170F, EVE ER17500 (verify pinout and pulse behavior).
• Higher pulse needs: Use a high-rate Li-SOCl2 (Saft LSH series) or add a supercapacitor; validate at temperature extremes.
• More capacity: Consider larger LS cells (e.g., LS 26500 “C”, LS 33600 “D”).

Safety and handling

• Non-rechargeable: never charge, crush, or short-circuit.
• Use only in approved holders or with factory-applied tags; avoid direct heating.
• Observe proper disposal and recycling regulations; do not incinerate.
• Shipping typically requires UN 38.3 compliance; follow applicable transport rules.

FAQ

Can I use the LS-17500 to power a cellular modem?

Not by itself. GSM/LTE modules demand amp-level pulses. Use a high-pulse chemistry and/or a supercapacitor, or select a rechargeable solution designed for such peaks.

Is the LS-17500 rechargeable?

No. It is a primary (non-rechargeable) cell. Charging is dangerous and can cause venting or rupture.

What cutoff voltage should I design for?

Many designs use 2.0–2.5 V as end-of-life under load. Confirm with your regulator and load profile; validate at cold temperatures where internal resistance increases.

How do I handle passivation after storage?

Expect a brief voltage delay on first load. Use a small pre-load, include a low-ESR reservoir capacitor, and implement brownout-safe startup routines.

Are there different terminal options?

Yes. Cells can be supplied with solder tags, axial/radial leads, or connectors. Choose factory-applied terminations rather than soldering directly to the can.