17670 Batteries: How to Choose, Use, and Compare

17670 batteries are cylindrical Li‑ion cells measuring 17 mm in diameter and 67 mm in length. They’re most common in flashlights and specialty electronics that need a narrow cell and can run on a single 3.6–3.7 V Li‑ion. They are a practical rechargeable alternative in some lights that otherwise use two CR123A primaries, provided the driver is rated for one Li‑ion cell.

Key Specs at a Glance

• Size: 17×67 mm (protected/button‑top versions can reach ~69–70 mm)
• Nominal voltage: 3.6–3.7 V (4.2 V full charge; typical cutoff 2.5–3.0 V)
• Typical capacity: 1500–2200 mAh
• Discharge capability: ~2–10 A depending on the specific cell (check datasheet)
• Terminals: flat‑top or button‑top
• Protection: available in protected and unprotected versions

When to Choose a 17670

• Your flashlight or device explicitly supports a single Li‑ion cell and has a tube closer to 17 mm ID (tight for 18650).
• You want more runtime than a 16340 (RCR123A) without increasing diameter.
• You have a light originally designed for 2×CR123A that the manufacturer approves for 1×Li‑ion operation.

When to Consider Alternatives

• 18650: More capacity (typically 2500–3600 mAh) and higher current; choose if your device accepts 18 mm diameter.
• 16650: Slightly narrower (16 mm) for very tight tubes; moderate capacity (~1700–2500 mAh).
• 16340 (RCR123A): Much shorter; lower capacity (~650–900 mAh) but fits compact lights.
• 2×CR123A primaries: Non‑rechargeable; long shelf life and good cold performance; use if your device requires ~6 V and is not rated for Li‑ion.

How to Choose Within the Category

• Protected vs unprotected: Use protected cells if your device lacks low‑voltage cutoff or you prefer extra safety (over/under‑voltage, short‑circuit protection). Use unprotected cells only if the device has built‑in protection and space is tight or higher current is required.
• Button‑top vs flat‑top: Many flashlights and devices with recessed contacts need button‑top. Flat‑top can be fine where spring pressure is strong and contacts are flush.
• Capacity vs current: For high‑output lights (draw >3 A), favor cells with a higher continuous discharge rating; for lower‑draw applications, prioritize capacity for longer runtime.
• Length tolerance: Measure available space; some protected/button‑top 17670s are up to ~70 mm long and may not fit all battery tubes.
• Quality & testing: Prefer reputable manufacturers and distributors that publish tested capacity and discharge curves.

Runtime and Charging

Quick estimate: runtime (hours) ≈ capacity (Ah) × 0.85 ÷ device draw (A). The 0.85 factor accounts for typical efficiency losses.

• Example: A 2000 mAh (2.0 Ah) cell in a 1000‑lumen light drawing 3 A → ~2.0 × 0.85 ÷ 3 ≈ 0.57 h (about 34 minutes).
• Charging: Use a Li‑ion charger to 4.2 V. Charge at 0.5–1 C; for 2000 mAh, 1 A is typical. Expect ~2–3 hours from ~10% to full.
• Storage: 30–60% charge at 59–77 °F (15–25 °C). Top up every 3–6 months.
• Cycle life: Often ~300–500 full cycles to ~80% capacity; gentle use (cool temps, moderate charge/discharge) can extend life.

Compatibility Checklist

• Device explicitly supports a single 3.6/3.7 V Li‑ion cell.
• Inner diameter fits 17 mm, and length allows up to 70 mm if using protected/button‑top cells.
• Contact style (button vs flat) matches your device’s requirements.
• If replacing 2×CR123A: confirm the manual states 1×Li‑ion compatible. Do not assume cross‑compatibility.
• Required current draw is within the cell’s continuous discharge rating.

Safety Notes

• Use only in devices designed for Li‑ion. Never substitute in equipment requiring ~6 V unless approved for 1×Li‑ion.
• Do not use damaged, dented, or swollen cells. Recycle at end of life.
• Charge with a quality Li‑ion charger; stop at 4.2 V and avoid over‑discharge (<2.5–3.0 V).
• Do not carry loose cells; transport in a plastic case to prevent short circuits.
• Do not mix cells (age, brand, capacity) in series/parallel packs.

17670 vs Common Alternatives

Cell	Size (mm)	Typical capacity	Best for	Notes
17670	17×67	1500–2200 mAh	Narrow‑tube lights needing single Li‑ion	Good middle ground vs 16340; check length tolerance
18650	18×65	2500–3600 mAh	Most modern flashlights and electronics	Higher capacity and current if diameter allows
16650	16×65	~1700–2500 mAh	Very tight battery tubes	Less common; verify fit and contacts
16340 (RCR123A)	16×34	~650–900 mAh	Compact lights	Shorter runtime; smaller form factor
2×CR123A (primary)	17×34 each	~1400–1700 mAh each	Emergency kits, cold weather	~6 V total; non‑rechargeable; long shelf life

FAQ

Can I replace 2×CR123A with one 17670?

Only if the device manual states it supports a single Li‑ion cell. 2×CR123A provide ~6 V, while a 17670 is ~3.7 V nominal (4.2 V max). Some drivers work with either; others will not.

Should I choose protected or unprotected?

Choose protected unless your device has reliable built‑in protection and you need maximum current or the shortest possible cell length.

Button‑top or flat‑top?

Pick button‑top for recessed or flat positive contacts (common in flashlights). Flat‑top works where spring pressure is strong and contacts are raised.

How long will a 17670 last per charge?

Divide usable capacity by current draw. A 2000 mAh cell at a 1 A draw can provide roughly 1.7 hours (accounting for efficiency), while at 3 A it’s about 30–40 minutes.

Are 17670 batteries suitable for power tools?

No. Power tools typically require multi‑cell packs with high current delivery and battery management systems. Use only the battery types specified by the tool manufacturer.