Handbook about the safety of projectors containing lithium batteries

Introduction

With lighting devices becoming more portable, lightweight and powerful, they require batteries that offer long hours of battery life before recharging. Lithium batteries are becoming common place also in the professional lighting industry.

The typical life cycle of these lighting devices ranges even for 5 years or more in some cases, and batteries contained even if handled properly will feature a much shorter life cycle.

Overheating of the internal battery pack can cause lithium battery to cause explosion or fire, representing a danger for people and objects.

The type of problem will be based on multiple factors such as how it is charged, how it is used and handled, and other environmental factors.

This article contains few general suggestions to handle battery operated lighting devices more safely, but it is always recommended to read the safety instruction contained in the product user manual. 

General safety instructions for lighting devices containing lithium batteries is available on the www.prolights.it website and here: LINK

How many cycles can you get out of a lithium-ion battery?

According to Battery University  Lithium-Ion battery’s average life span is 2 years or 300 charge cycles, whichever comes first whereas the device is operated correctly. As we put it, a charging cycle is a duration of utilization when the battery is fully charged, drained, recharged.

For battery packs that don’t go through complete charge cycles, we can assume a 2 years average lifespan.

Rechargeable Lithium-Ion batteries have a limited lifespan and will slowly lose their ability to retain a charge. This capacity reduction (aging) is permanent. The battery’s capacity reduces with time, reducing the duration it can power the product (run time).

When not under use or stored, lithium-ion batteries go on to deplete (self-discharge) slowly. Make sure you check and confirm your battery’s charge status regularly. 

Five Signs that your batteries need to be replaced

In addition to the typical average life span of lithium batteries, these are the most common signs that indicates a battery need to be immediately inspected and replaced before using.

Age: The standard lifespan of a battery is 2 years or 300 charge cycles, whichever comes. If your batteries overcome this time range, it is time to factor replacement.

Overheating: The device becomes hotter when using or during charge (10°C or 18° above ambient measured on the battery pack) or comparing to other devices in good working order.

Performance: if you observe that performance and runtime of the battery considerably deteriorate it’s a sign that battery need to be replaced. 

Swelling: Chemical reactions create gasses that expand and push on the outer shell of the battery.

Other Visual evidences: typical visual indicators that tell you a battery need to be inspected and replaced are:  

• Pools of vented gasses that condensate on top of the battery can dry into a white dust. At times, this dust can be from a neighboring battery so routine preventative maintenance is key.
• Cracks or openings on the outer shell of the battery are a serious matter. If cracks or openings exist, seek immediate assistance from a specialized service technician.

How storage affects your battery life span

This is a very important topic to take into consideration for the Event industry, which is characterized by a certain seasonality. Battery-powered projectors may therefore be subject to periods of intense use alternating with periods of low use. 

Proper storage of these products helps to preserve the lifespan of the battery pack and decrease the risk of overheating and resulting failures.

To avoid compromising battery life, always avoid storing devices fully charged or completely discharged.

Before a period of non-use, make sure it has some charge, ideally 50 to 60 percent, before storing it. If you store the battery with some charge, it will last longer before self-discharge gets the voltage near the danger point.

It’s recommended to conduct long-term storage as near to room temperature as practicable. As a result, stay away from extremely cold rooms or placing the device near heat sources, keep it in a cool and dry environment. Moreover, if you’re keeping batteries for more than a few weeks, make sure all cables are disconnected.

If the storage period is extended, periodically inspect the state of charge of the fixtures and make sure that the state of the battery is not extremely low, restoring a charge level of 50/60%.

Why overheating batteries can catch fire?

Quality fixtures powered by lithium-ion batteries are safe if used as intended, however a high number of heat and fire failures had been reported in generic electronic products and there have been cases of failures also in the events and entertainment industry. Failures typically happen for incorrect or incautious uses.

Excessive heat it’s the real enemy for any battery, hot temperatures will break down the internal components on both physical and chemical levels.

Heat combined with a full charge is said to induce more stress to Li-ion than regular cycling, and battery packs which ended their life cycles are exposed to heat and fire failures. 

Li-ion batteries that have finished their lifespan and/or that have been exposed to stresses may function normally but they become more sensitive to overheating and mechanical abuse.

Keep the battery and a device away from heat sources and direct sun exposure.

Charging in extreme cold or high heat reduces charge acceptance, as well as exceeding the recommended charge also harms Li-ion, causing overheating and fire. Batteries that have reached the end of their lifespan or exposed to stresses, are even more sensible to the above indications.

Safety recommendations during the recharging phase

It is known that most failures and ignition of fires or explosions occur during the recharging phase of the batteries, as the lithium batteries are exposed to greater stresses and possible overheating. During the recharging operations, it is strongly recommended to observe some general rules to reduce the risk of accidents and damages. 

Batteries powered fixtures should always stay supervised on charge, and never charged unattended. Choose a cool (never below 5°C, or above 35°C) and dry location for charge, away from any source of heating and away from any flammable object. 

Discontinue the use of a fixture or disconnect the charger if the temperature rises more than 10ºC (18ºF) above ambient under a normal charge. Li ion cannot absorb over-charge and does not receive trickle charge when full.

Li-ion has minimal losses during charge and when charged in a cool environment, the battery charges to 70 percent state-of-charge (SoC) in a very short charging time; the extra time is devoted to the saturation charge. Li-ion does not require the saturation charge as lead acid does; in fact it is better not to fully charge Li-ion, the batteries will last longer but the runtime will be a little less.

Batteries operate over a wide temperature range, but this does not give permission to also charge them at these conditions. The charging process is more delicate than discharging and special care must be taken. Extreme cold and high heat reduce charge acceptance and the battery should be brought to a moderate temperature before charging.

Battery operated lighting fixtures can be charged from 5°C to 35°C (41 to 95°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. The internal resistance of all batteries rises when cold, prolonging charge times noticeably. This also affects discharge performance noticeably with Li-ion.

To make a recap: 

• Never leave the fixtures in re-charge unattended.
• Do not charge if the lighting fixtures has any visible damage, malfunction, tampering or signs of moisture inside
• Always charge with its packing/flight-case open
• Charging a battery is most effective when its state-of-charge (SoC) is low. Charge acceptance decreases when the battery reaches a SoC of 70% and higher. A fully charged battery can no longer convert electric energy into chemical energy and charge must be terminated.
• Filling a battery beyond full state-of-charge turns excess energy into heat and gas. With Li-ion, this can result in a deposit of unwanted materials. Prolonged over-charge causes permanent damage.
• Use the original charger provided by the manufacturer for the intended battery specification. Do not charge if different.
• Check the temperature of the device when charging. Temperature should not rise more than 10ºC (18ºF) above ambient when reaching full charge.
• Remove battery when warm.
• Charge at room temperature, in a dry environment and away from heat sources. Do not charge below freezing.

What to Do When a Battery Overheats or Catches Fire

If a battery overheats, hisses or bulges, immediately move the device away from flammable materials and place it on a non-combustible surface. If at all possible, remove the battery and put it outdoors to burn out. Simply disconnecting the battery from charge may not stop its destructive path.

A small Li-ion fire can be handled like any other combustible fire. For best result use a foam extinguisher, CO₂, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate). 

Water-based products are not recommended because of the lithium metal that can reacts with water, however it can be used in case of emergency to prevent the the fire from spreading to other inflammable materials.

During a thermal runaway, the high heat of the failing cell inside a battery pack may propagate to the next cells or adjacent battery pack, causing them to become thermally unstable also. A chain reaction can occur in which each cell disintegrates on its own timetable. A pack can thus be destroyed in a few seconds or over several hours as each cell is being consumed.

A recap about how to operates in case of fire: 

• A failing Li-ion begins to hiss, bulge and leak electrolyte.
• The electrolyte consists of lithium salt in an organic solvent (lithium hexafluorophosphate) and is highly flammable. Burning electrolyte can ignite combustible material in close proximity.
• Dowse Li-ion fire with a regular fire extinguisher. Only use a Class D fire extinguisher for lithium-metal fires because of the reaction of water with lithium. (Li-ion contains little lithium metal reacting with water.)
• If a Class D extinguisher is not available, douse a lithium-metal fire with water to prevent the fire from spreading.
• For best results dowsing a Li-ion fire, use a foam extinguisher, CO₂, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate) as you would extinguish other combustible fires. Reserve the Class D extinguishers for lithium-metal fires only.
• If the fire of a burning lithium-ion battery cannot be extinguished, allow the pack to burn in a controlled and safe way.
• Be aware of cell propagation as each cell might be consumed on its own time table when hot. Place a seemingly burned-out pack outside for a time.

We thank you for reading and as always, appreciate your support. For additional questions regarding safety in lighting fixtures containing lithium batteries, please feel free to contact us.