Lithium-Ion Battery Safety

By Jean Rydberg
Photo: Stephen Frink

Lithium-ion (Li-ion) batteries have become prevalent in consumer electronics and are found in everything from portable gaming systems and power tools to fancy sports cars. The Pew Research Center estimates that more than 5 billion people in the world carry a mobile device with these batteries. Your dive kit probably includes several items powered by one: dive computers with transmitters, perhaps a flashlight or video light and possibly a camera.

SAFETY FEATURES
In most circumstances the use of Li-ion batteries is extremely safe, but some risks are involved. It’s important to exercise proper care and use procedures that minimise risk and maximise performance of the battery pack.

To reduce the chances of catastrophic failure, manufacturers of products containing Li-ion batteries build in redundant safety features such as vents to release built-up gases, a circuit board to regulate energy flow, and often a backup thermostat or fuse. Either the device or charger should have built-in protection that strictly governs whether a charge is applied to the battery pack when plugged in.

Disaster strikes when the battery shorts out and one or more of these safety features fails. The battery pack can heat up very quickly in a reaction called thermal runaway, which can lead to fire or explosion.

SHORTING
Did you ever put the end of a 9-volt battery pack against your tongue and feel a mild tingling sensation? You are creating a short across the negative and positive terminals of the battery. Shorting a battery pack causes it to expend its energy and generate heat.

To prevent shorting, keep the battery pack away from metal objects in your bag. Install covers on the terminals to protect them when the battery is not in use, or use separate bags or pouches for each spare battery. A product called a LiPo bag can minimise the risk of shorting and reduce the severity of fire in the event of a short.

Water can create a short in the pack, so never use a battery that has been wet. Due to the increased risk of shorting, it is also recommended to not ship or travel with a battery pack that has been wet.

IMPACT AND ENVIRONMENT
It’s important to protect Li-ion batteries (and devices containing them) from impact. Li-ion batteries have a positive cathode and negative anode inside with only a thin separator in between. A heavy blow to the product may damage the inner separator and short out the battery pack. Even if you are extremely careful with your equipment, others may not be as careful when they drop their cameras on top of yours in the rinse tank. I’ve seen systems flying around (and off) the camera table on boats in rough waters, and none of us can control what might happen to our gear during a security inspection in transit.

Heat and humidity are enemies of Li-ion cells. Stress and permanent damage may result from exposing the batteries to heat for prolonged periods. Based on studies of customer usage trends, people who live in tropical or desert conditions (especially those without air conditioning) and those who travel regularly on liveaboard boats statistically experience a significant reduction in the overall lifetime of Li-ion battery packs.

Follow your battery manufacturer’s recommendations for everything related to the product, including safe operating temperatures during use and long-term storage. Store Li-ion batteries in cool, dry environments at around 50 percent capacity.

CHARGING
We might not often think about charging, yet it is perhaps the most important stage of a battery’s life cycle. Li-ion batteries should not be overcharged. Unlike some other battery types, they do not get a trickle or maintenance charge — they are either charging or not. The charger or device must be carefully calibrated to cut off charging after the battery pack reaches an established peak voltage.

The circuitry that controls this process works well but can be sensitive to fluctuations in power supply such as asudden power surge, an overloaded power circuit or a boat’s generator switching over. Check that you have a universal input charger that accepts variable input voltage, and connect the charger to a surge protector. Don’t charge too many devices at the same time on the same circuit. Watch for signs that the circuit is overloaded, including flickering or dimming lights, a buzzing sound or warm wall plates.

TRAVEL
Every Li-ion battery pack should clearly reference its chemistry and watt-hour rating on the
outside of the battery casing. This information is generally required in any airline inspection of your equipment. Security personnel may confiscate the products if that information is not available or if your batteries do not fall within the approved limits. It’s also advisable to travel with a Product Safety Data Sheet (PSDS), which you can request from the manufacturer.
The PSDS contains important information such as what to do in the event of a fire.

END OF LIFE
Most Li-ion battery packs will last a maximum of three to five years. They lose a certain percentage of their capacity each year whether or not they are used. Some estimates
suggest this loss can be as high as 20 percent. For safety reasons, Li-ion batteries are not allowed to fall below a certain voltage, which may be higher than the minimum voltage required to operate your device. At some point your Li-ion battery pack will suddenly go from working fine to not working at all. Never expose a battery pack — even a dead one — to a fire. It’s not environmentally responsible to throw away your dead batteries with the household garbage. When your batteries die, dispose of them at a battery-recycling facility.

CONCLUSION
Li-ion batteries are very safe, and accidents are rare. The best approach is twofold: Try to
prevent problems from happening, and know how to respond to problems if they occur. Follow
the product manufacturer’s recommendations for safe handling to avoid issues, enhance
performance and extend the lifetime of your battery pack.

SAFETY TIPS FOR RECHARGEABLE BATTERIES
The following tips apply to all types of rechargeable batteries, including lithium-ion
(Li-ion) and nickel metal hydride (NiMH) cells.

1.  Secure your equipment on a boat, and keep it out of the hot sun. Never leave equipment in the camera rinse tank.
2.  Always use the charger srecommended by the manufacturer.
3.  Never charge or use a battery pack that has been wet.
4. Charge your battery in a room with working fire alarms and fire-extinguishing materials on hand. Know what type of fire-extinguishing method is required for your batteries.
5.  Charge your battery on a solid, nonflammable surface such as steel shelving.
6. Connect your charger to a surge protector.
7. Don’t sleep with your cellphone on or under your pillow. Never charge any battery on your bed.
8. Always be present when charging your device, and disconnect your charger when it’s done. Avoid charging overnight; set an alarm to disconnect your chargers if necessary
9.  Occasionally feel your battery pack and charger while charging. Discontinue charging if the battery or charger gets abnormally warm.

Jean Rydberg is president and CEO of Ikelite.