Panasonic 18650 Batteries

Li-Ion Protected Cells

'Protected' cells have a small protection circuit built into them to prevent them from being over charged, over heated, shorted, or over discharged. Because protected cells are about 3 mm longer than unprotected cells, they do not always fit lights and chargers, so it's important to determine if they are going to work with your equipment in advance.

Fenix ARB-L2S 18650 3400 mAh batteries $21.95

Panasonic NCR18650B Protected Batteries: $16.95

These are the Ferrari of cells, about the best money can buy. They have the highest mAh capacity currently available. The protected version weighs 48g, has circuit protection and is too tall (69.4mm) to run in the power packs, but fits the Spark headlamps and chargers.

Spark Protected Batteries

Spark Li-Ion rechargeable Battery 18650 3100mAh $14.95. This battery is manufacturered from a Japanese Panasonic cell, which along with Sanyo and GP, are considered to be the top 18650 batteries available.

- Capacity: 3100mAh
- Nominal voltage: 3.60V
- Charge voltage: 4.20V
- Charge current: 1650mA
- Charge time (Std.): 3 hours
- Discharge cut-off voltage: 2.50V
- Discharge current: 620mA
- Discharge cut off current: 30mA
- PCB Protection trip curent: Above 10A

Spark Li-Ion rechargeable Battery 18650 2600mAh: $12.95. These are made from Japanese Sanyo cells.

- Capacity: 2600mAh
- Nominal voltage: 3.7V
- Charging voltage protection: 4.2V
- Protect circuit: 5A
- Discharge cut-off voltage: 3.0V
Testing of this battery shows it has very good discharge capacity of up to 2.2 Ah while maintain a minimum voltage of 3.6v at a 2a current draw, making it suitable for the SX5 headlamp.

From independant test site: "This battery uses aSanyo cell, this is a good quality cell and as can be see on the curves the two cells does track very nicely. There will be no problem with series applications of this cell. The high voltage can be an advantage in smaller (i.e. 3-4 watt) lights where the battery replaces two CR123 cells. The PCB current limit is placed about 30% above the cell specification, this is a good value. All in all a very good battery.

14500 Protected Cells

Nitecore 14500: $12.95

These are very good quality cells with built in low voltage cut-off so they cannot be over discharged. Due to the protection circuit, they will not fit into the AA Battery packs for the Wouxun radios.

Cautions:

Li-Ion cells are safe for use if they are handled properly and used in equipment that will not render them dangerous*. That means following safe charging procedures, storing them properly, and using them properly. Before purchasing 18650 batteries it would be advisable to spend a few minutes reading this very informative guide to using these cells safely.

* All the Spark lights have protection circuits built in and shut off automatically at 2.6v in order to protect the cell from deep discharge.

Li-ion cells are named by using a numerical code which determines the size. The first pair of numbers is the diameter in millimetres, the second pair of numbers is the length in millimetres. 18650 cells have a diameter of 18 mm and a length of 65 mm. The last zero means it's a cylindrical cell.

These are some common Li-ion sizes:
14500: The size of a AA cell.
10440: The size of a AAA cell. Never protected. Do not use these without further research.
16340 AKA RCR123: The size of one CR123 cell.
17670: The size of two stacked CR123 cells.
17500: The size of one and a half stacked CR123 cells.
18650: These are the cells used in laptop battery packs. That’s why this size cells is most researched and most developed and these have the biggest capacity / volume ratio.

Just a few examples of some Safety Tips:
1. Never use unprotected LiCoO2 cells in multi cell lights.

2. If you do use them in a multi cell configuration, make sure that the protected cells in a multicell setup have a balanced charge.

3. Use protected lithium cells of known quality.Test them for capacity every 5 cycles with DMM.

4. Never use cells with 'Fire' as part fo their brand name.

5. Do not store Li-Ion cells in warm places, and do not place them away for long term storage fully charged (IE, at 4.2v, they should be stored at 3.6v).