LITHIUM BATTERY SAFETY
Anyone who is new to lithium batteries must read the following information. Lithium batteries, if mishandled or misused, can pose a serious risk of personal injury and property damage. Most risks can be reduced or even eliminated entirely by understanding how to safely use them.
1. Buy quality batteries and chargers.
- Buy from a trusted vendor who sells only high quality products. There's so many fake rated batteries sold where the capacity and/or current rating is highly exaggerated. Most cheap batteries are recycled and rewrapped, some found to be hollow with a tiny battery inside, packed with flour to increase the weight.
2. Discharging.
- When using your batteries, learn about their charge state by checking with a voltmeter (or with your charger if it is so equipped) whenever you recharge the batteries. I’d recommend targeting 3.5V as the level when to recharge, with 3.0V being “acceptable”. Lower than 2.5V and you are definitely hurting your batteries. If you ever hit 2.5V or lower, you should be very careful whenever you recharge and use this battery. I'd highly recommend disposing them.
- If you have no means of measuring the battery's voltage, then the next best thing is to recharge your batteries as soon as you notice the torch's output declining. Get into the habit of recharging your batteries on a regular basis.
3. Charging. A good quality charger will help prevent overcharging. On the better chargers, digital readouts help you to keep track of the charging process.
- Never charge your batteries when you are not present. While it’s not necessary for you to hover over them while they are charging, you should be alert and close enough to respond to any problems.
- If you need to leave while your batteries are still charging, unplug the charger and re-start the process when you return.
- Always charge on a fire-proof surface.
4. Care and Maintenance.
- Avoid physical abuse.
- Avoid getting the batteries wet.
- Avoid extreme temperatures.
- Never use beyond the manufacturer's specs.
- Discard any dented, deformed, or punctured batteries.
- When not being used, store them in a cool, dry location.
- When storing them for long periods of time, store them at 40% or about 3.5V. The ideal storage temperature should be no higher than 25°C.
- When storing them, make sure that there is no possibility for short circuits. Ensure that there is no way for any loose metal (or jumble of loose batteries) coming into simultaneous contact with both terminals of any battery.
5. Multiple battery applications. Understand that your risks go up exponentially by using multiple batteries. Not only do your chances increase and the potential magnitude increase by the number of batteries being used, but the risks of unbalanced discharge between batteries is introduced. So all the caveats of using a single battery are even more important: don’t overcharge, don’t over-discharge your batteries, and take care of them properly. In addition, the following guidelines have been suggested:
- Use mated sets of batteries. Use the same brand and specific model of battery within a set.
- Always keep the same set for the torch. Don’t mix and match batteries when recharging.
- Always recharge all of the batteries at the same time. Don’t partially charge individual batteries.
6. Protected batteries versus unprotected batteries. Protected batteries have circuitry that provides safeguards against overcharging (usually set at 4.2 volts) and over-discharging (set at somewhere between 2.5V to 2.9V, depending on manufacturer). Do not depend on the protection to work. While they are fairly reliable, they are not foolproof. Consider them as a fail-safe device or measure of last resort.
Other things that you should know:
- Protected batteries are slightly longer than their unprotected counterparts. Most torches can accept either, but some have such tight margins that only unprotected or smaller models of protected batteries will fit.
- Protected batteries, because of their additional circuitry, are limited in providing maximum power. For most torches, this does not make a difference, since the torch's driver is the limiting component in providing power to the LED. However, for some torches, the drivers are direct driven and the limiting component is the battery. Unprotected high-drain batteries are recommended for such torches.
- The protection circuit is sometimes referred to as PCM or PCB (Protection Circuit Module or Protection Circuit Board).
- Besides protected and unprotected types of batteries, batteries may come in either button-top or flat-top versions. Button-tops are the more common variety and fit almost all torches. Flat-tops are suitable for single battery torches that have both head-springs and tail-springs. If you plan on buying flat-tops, make sure that they will work for your particular torch.
7. Low Voltage Protection (LVP). Many torches are equipped with LVP circuits to prevent the over-discharge of batteries. Depending on the specific manufacturer, the LVP circuits may cut off the battery between 2.6V and 3.0V. In some cases, the LVP circuit may merely warn the user about the low voltage by some sort of flashing mechanism – while allowing the battery to continue to drain well below the warning level (down to zero in some cases). Again, similar to the battery protection, it is recommended that you not rely on LVP to prevent over-discharge of batteries.
8. Sizes and Types of Li-ion Batteries.
- There are different sizes of li-ion batteries. The first two digits represent the diameter in millimeters. The next two digits represent the length in millimeters. Hence, a 10440 battery (about the size of a AAA battery) is 10mm wide by 44mm long. A 14500 battery (about the size of an AA battery) is 14mm wide by 50mm long. The last “0” at the end of the 10440 and 14500 represents the shape of the battery, i.e., circular in shape. Note: These are nominal dimensions, they'll be longer if they have a button top or use a protection circuit.
- There are a number of different types of batteries that are referred to as lithium-based batteries. It is customary to distinguish “lithium” batteries as those primary (non-rechargeable) 3.0V batteries, “LiFePO4” batteries as the rechargeable 3.2V-3.3V batteries, and “li-ion” batteries as the rechargeable 3.7V batteries. And within the set of so called “li-ion” 3.7V batteries, there are several different chemistries: LiCoO2 (ICR), LiMn2O4 (IMR), LiNiMnCoO2 (INR), hybrid of other chemistries (NCR).