10440 Batteries

10440 Batteries (AAA-size Li-ion): How to Choose and Use

10440 batteries are lithium-ion cells the same size as AAA (10 mm × 44 mm) but with a much higher voltage: 3.6–3.7 V nominal (4.2 V when fully charged). Typical capacity is 300–350 mAh. They are suitable only for devices that explicitly support 10440 or 3.7 V AAA.

When to Choose a 10440

• Use if your device or manual specifies 10440 or 3.7 V AAA input (common in select compact LED flashlights).
• Choose when you need higher voltage and power in an AAA footprint, and runtime needs are short to moderate.
• Avoid for everyday AAA devices (remotes, toys, clocks). These expect 1.5 V/1.2 V and may be damaged by 3.7 V.

Key Specs at a Glance

• Size: 10 × 44 mm (protected versions can be longer at ~46–48 mm)
• Voltage: 3.6–3.7 V nominal, 4.2 V max charge (Li-ion); 3.2 V nominal, 3.6 V max (LiFePO4 variants)
• Capacity: ~300–350 mAh (Li-ion); ~200–250 mAh (LiFePO4)
• Typical continuous current: up to ~1–2 A depending on cell; check the datasheet
• Cycle life: ~200–500 cycles with moderate charge rates and shallow discharges

How to Choose Within This Category

• Chemistry:
  • Li-ion (3.7 V): Higher capacity and brightness; best for devices designed for 4.2 V fully charged.
  • LiFePO4 (3.2 V): Lower voltage and capacity but improved thermal stability; choose if your device specifies 3.2–3.6 V.
• Protection circuit:
  • Protected: Includes over/under-voltage and overcurrent protection; safer, slightly longer. Good default for general users.
  • Unprotected: Shorter and may fit tight compartments; only for users with devices that manage protection and who understand Li-ion safety.
• Top style:
  • Button top: Better contact in many flashlights; often required.
  • Flat top: For devices with spring-loaded contacts; check your device.
• Discharge rating vs. capacity: If your device draws 1–2 A, pick a cell rated for that current even if capacity is slightly lower.
• Length tolerance: Tight battery tubes may not accept longer protected cells; verify the listed length.

Runtime Examples

Estimates for a 350 mAh Li-ion 10440 (actual results vary by device and cutoff voltage):

• 0.5 A draw: ~0.6–0.7 hours (35–45 minutes)
• 1.0 A draw: ~0.25–0.4 hours (15–25 minutes)

If you need longer runtime, consider stepping down brightness or using a larger cell/device (e.g., 14500 or 18650 platforms).

Charging and Care

• Use a quality Li-ion charger that supports 10440 size; do not use NiMH-only AAA chargers.
• Recommended charge rate: 0.2–0.5C (about 70–175 mA for a 350 mAh cell) unless the manufacturer allows more.
• Charge to 4.20 ± 0.05 V (Li-ion) or 3.60 V (LiFePO4). Stop charging when full; do not leave on indefinite trickle.
• Avoid deep discharge; recharge before the cell drops below ~2.8–3.0 V (or per datasheet).
• Store at ~40–60% charge in a cool, dry place. Use a plastic case when carrying loose cells.

Safety Notes

• Never mix 10440 with standard AAA cells in the same device.
• Only use in devices that explicitly support 3.7 V (or 3.2 V for LiFePO4) in AAA format.
• Inspect wraps regularly; rewrap or replace damaged cells. Avoid exposure to heat, crushing, or puncture.

Alternatives to Consider

• AAA NiMH (1.2 V): Best for everyday AAA devices; safe drop-in rechargeable alternative to alkaline.
• 14500 (AA-size Li-ion): Higher capacity and current capability if your device fits AA size and supports 3.7 V.
• 16340/CR123A-size Li-ion: More capacity than 10440 in a compact form for devices designed for this size.

FAQ

Can I use a 10440 in any AAA device?

No. 10440 cells are 3.7 V and can damage devices designed for 1.5 V (alkaline) or 1.2 V (NiMH) AAA. Only use where 10440/3.7 V is specified.

What is the difference between protected and unprotected 10440 cells?

Protected cells include a small circuit that prevents overcharge, over-discharge, and short circuits. They are safer but slightly longer; verify fit in tight battery tubes.

How long will a 10440 run my flashlight?

At 0.5 A, expect roughly 35–45 minutes from a 350 mAh cell. High-turbo modes (≥1 A) may run only 15–25 minutes.

Do I need a special charger?

Use a Li-ion compatible charger that supports small cells like 10440 and stops at 4.20 V (or 3.60 V for LiFePO4). Do not use a NiMH-only AAA charger.

Are 10440 and AAA the same thing?

They are the same physical size, but not the same chemistry or voltage. AAA commonly refers to 1.5 V alkaline or 1.2 V NiMH. 10440 is Li-ion at 3.7 V.