Advantages of a Li-Ion Battery Pack
Lithium-ion batteries are used in a wide range of mobility equipment such as electric wheelchairs and scooters. They offer a number of advantages over other types of batteries.
Lithium battery packs have a plastic casing, cell(s), a protection device and internal connections (wires and tabs). They can be opportunity charged to prevent loss of capacity during storage.
Lightweight
Lithium-ion battery packs are lightweight and compact. They also offer excellent cycle life, which is important for many applications. They can be molded to fit various devices and provide an easy way to add power where needed.
A lithium-ion battery pack contains anode and cathode electrodes, a separator between them, and an electrolyte. It also has positive and negative terminals. The electrodes can be made of different materials, but the most common are lithium cobalt oxide (ICR-type) and graphite. Other types include lithium iron phosphate (used in electric cars) and lithium manganese cobalt oxide (used in laptops).
Battery cells can be assembled into large batteries. They can be flat, rectangular and thin for cell phones and portable electronics, cylindrical like 18650 (common in laptop batteries), or hump-shaped like the Energizer EZ-Go and Dometic PLB 40AH battery that provides off-grid mobile power.
Lithium-ion batteries have one of the highest energy densities of any rechargeable battery technology. They also do not have a memory effect, a detrimental process that results from scheduled Li-ion battery pack discharge/charge cycles, and do not contain toxic lead or cadmium.
High Energy Density
Li-ion batteries have one of the highest energy densities of any rechargeable battery technology. They are two to five times more energy dense than nickel-cadmium and nickel metal hydride, making them an ideal power source for smartphones, laptops, electric cars and electrical grid storage systems.
They are also less prone to performance fluctuations, losing only about 5% of their charge each month, while nickel-metal hydride loses more than 20%. They are very light, too, since they have electrodes made of lightweight carbon and lithium rather than the heavier materials used in nickel-cadmium and nickel metal hydrate batteries.
They require a non-aqueous electrolyte to keep the lithium ions safely confined, and they are sealed in air-tight containers that exclude moisture. To prevent the possible formation of metallic lithium plating during cycling, most packs have a built-in protection circuit that limits peak cell voltage during charging and prevents cell voltage from dropping too low on discharge. This is called intercalation battery chemistry because the lithium ions “intercalate” between the electrodes and are exchanged back and forth during discharging and charging.
Rechargeable
A lithium battery pack is a collection of modular lithium cells designed to meet the voltage and energy requirements of a specific application. They are the largest assembly in the hierarchy of battery systems and serve as the power source for a range of applications from portable electronic devices to electric vehicles.
Modular lithium-ion batteries are constructed using a non-aqueous electrolyte that excludes moisture and allows for safe operation in the presence of air. This is crucial because lithium reacts vigorously with water to form metallic lithium plating, which is a fire and explosion hazard. Safety circuits built into the packs prevent excessive peak cell voltage polymer lithium battery during charge and prevent a single cell from reaching a low voltage during discharge.
Like other rechargeable battery chemistries, lithium does not enjoy a deep discharge but rather prefers a partial discharge to maintain its energy capacity. However, unlike other battery chemistries, it does not suffer from the memory effect which negatively impacts battery efficiency and cycle life. At the end of their useful life, lithium-ion batteries can be recycled through a number of outlets including electronics recyclers and participating retailers in takeback programs or household hazardous waste collections.
Long Lifespan
A lithium battery’s lifespan is a key factor when selecting the right batteries for your fleet. Most vehicle manufacturers now offer eight-year or 100,000-mile warranties that cover the longevity of their EV battery packs. This warranty not only covers against premature pack failure, but also degradation of the pack’s capacity over time.
Unlike lead acid batteries, lithium-ion battery lifespans don’t depend on how long the battery sits on the charger or how often it’s used. Instead, a battery’s lifespan depends on the number of cycles it goes through.
Cycles refer to a battery’s complete charge and discharge cycle. Each cycle reduces the capacity of the battery slightly. Keeping the battery’s depth of discharge (DOD) low and topping off the charge regularly reduces capacity loss over time.
To increase the lifespan of your Li-ion batteries, store them at a moderate room temperature. Avoid exposing them to high temperatures as this will cause the cells to degrade more quickly. It’s also a good idea to keep track of the room humidity and ensure that it stays below 50%.
Safety
Lithium ion batteries are designed with safety in mind. Each battery cell has a safe operating voltage range that it can operate in (based on the specific battery chemistry) and each pack is built with safety features such as vents that allow for release of gasses, circuitry to regulate energy flow, and backup thermostats or fuses.
Because they can contain so much energy, lithium ion batteries must be carefully handled and stored to avoid a fire. They can also be damaged by excessive heat, and they can burn or explode if they overheat, even in a small amount of time. This can be prevented by keeping them away from high temperatures, never allowing them to exceed their maximum charge or discharge temperature, and regularly inspecting and following the device manufacturer’s instructions for proper battery storage, charging and disposal.
NFPA provides a lithium-ion battery pack safety resource, with photos, videos, blogs and other information. This can be used in presentations, as part of safety training for e-bikes and e-scooters, or to help spread the word about the importance of battery and battery pack safety.
