In addition to Li Batts’ much higher upfront cost, many of their disadvantages are rooted in the same characteristics as their advantages.

Higher upfront cost

For assistive technology applications, Li Batts – both Li-NMC and LiFePO₄ – are typically two-three times more expensive than traditional batteries.

Depth of discharge (DoD)

Compared to traditional batteries, for optimal performance, greater care and precision must be applied to charging Li Batts. Li-NMC Batts can become dangerously unstable at the end of their useful life, if charged improperly, or if their battery management system (BMS) fails; LiFePO₄ Batts are significantly less prone to these modes of failure.

Materials – Combustibility

In Li Batts, lithium metal (cathode) and lithium salts (electrolyte) are highly flammable, and if Li Batts are compromised, the resulting electrochemical process can lead to “thermal runaway” where the battery’s internal temperature accelerates, releasing more energy, further increasing temperature, releasing more energy, etc. in a self-perpetuating uncontrolled cycle – which can lead to very intense, hard-to-extinguish fires and/or explosions. Research and experience generally show that LiFePO₄ Batts are significantly less prone to these risks.

High energy and power density

Since they can store and deliver so much energy for their weight, when the medium-to-high-capacity Li Batts used in assistive technology applications (especially Li-NMC Batts) malfunction or fail, they have a much higher potential to do so catastrophically and dangerously compared to traditional batteries.

Environmental/recycling concerns

Currently, facilities are few for recycling Li Batts at the end of their useful lives back into constituent parts than can be used to make new Li Batts as part of a circular economy sustainability and social value plan.  Specialist electrical waste management companies have to gather economically viable quantities of Li Batts and transport them to the nearest recycler – but assembling large quantities of end-of-life and/or damaged Li Batts has to be done very carefully to manage fire and explosion risks, adding significant expense and complexity to Li Batts.

Li Batts present many advantages for assistive technology, especially mobility scooters and powered wheelchairs.

Materials – Light weight

Typically, Li-NMC Batts are around 1/3 the weight of traditional batteries – and LiFePO₄ Batts only 20 percent heavier than Li-NMC Batts – which makes them easier for users and carers to move and reduces the overall weight of the device being powered.

Long life

Cared for properly, Li Batts may last significantly longer than traditional batteries – Li-NMC Batts up to two times longer and LiFePO₄ Batts up to five-seven times longer – due in part to their higher cycle life (the number of charging and discharging cycles a battery can undergo without compromising its performance).

Even discharge

Whereas traditional batteries’ voltage drops significantly throughout the charge-life (experienced as weakening power output as the charge dissipates), Li Batts’ voltage remains steady throughout the charge-life, weakening only when nearly fully discharged.

High energy density (power storage)

Compared to traditional batteries, Li Batts are capable of storing much larger amounts of energy.

High power density (power delivery)

Again, compared to traditional batteries, Li Batts are capable of delivering much larger amounts of energy relative to their weight.

Depth of discharge (DoD)

DoD is the maximum capacity of a fully charged battery that can be used prior to recharging without negatively affecting the battery’s overall lifecycle; traditional batteries have a c. 50 percent DoD whereas Li Batts have a c. 80-90 percent DoD – meaning, effectively, Li Batts can be used for longer without recharging.

Possible lower total lifetime cost

Li Batts for assistive technology applications are typically 2-3 times more expensive than traditional batteries – however, due to longer life, Li Batts (especially LiFePO₄ Batts) can, if maintained properly, reduce overall cost.

In advance of BHTA’s forthcoming guidance, companies should consider existing Li Batt Policy and End-of-Life Disposal practices. Within one’s own company and company value-chain, it is especially important to determine:

• What processes already exist for consumers to return Li Batts via UK Government-mandated take-back/recycling schemes; and
• Who – within the company value-chain – is responsible for operating this scheme.

This will require cooperation and collaboration between Manufacturers and Distributors/Retailers, as well as clear instructions to Consumers; per OPSS/DEFRA guidance:

• “The manufacturer or importer that first places batteries on the UK market – including those in products – is classed as the producer and is therefore responsible for compliance if the business has a UK presence.
• The only exception is the collection of Portable Batteries[i] – UK distributors and retailers that sell or supply more than 32 kg of batteries a year must provide a take back service [NB, batteries for mobility scooters and powered wheelchairs are Industrial Batteries, and fall outside this exception]
• The guiding principles of [UK battery waste compliance] are that all waste batteries are processed by an Approved Battery Treatment Operator (ABTO) or an Approved Battery Exporter (ABE) and that producers pay for their collection, treatment and recycling. Distributors and retailers [per specific guidance] that sell or supply more than 32 kg of batteries a year must participate in the take back scheme. This involves providing a free collection point for waste portable batteries at their premises and arranging their transport to an ABTO or ABE, usually through a Battery Compliance Scheme.”

[i] Defined as “a battery or battery pack [that]:

• Is sealed
• Is not an Automotive or Industrial Battery
• Can be hand-carried by an average natural person without difficulty”

Encourage consumers to ask questions about the policies and practices your company has in place to ensure the safe handling, storage, and disposal of Li Batts by you as a retailer and your staff. Be prepared to explain how you approach:

• Lithium Battery Safety Training
• Battery Inspection and Testing
• Appropriate Battery Chargers for Private Use
• Safe Charging Stations for Public Use (if applicable)
• Battery Capacity Disclosure at Point of Sale
• Battery Disposal and Recycling
• Transportation Guidelines – no Li Batt of any capacity over 100Wh/4Ah should be transported as anything other than Dangerous Goods; other traditional batteries – e.g. spillable, sealed lead acid (SLA), absorbent glass matt (AGM), or gel – may be shipped as non-Dangerous Goods provided they are undamaged, clean, and have their terminals protected; always check with the battery manufacturer for recommended transport modes
• Storage and Shelf Life
• Battery Safety Information
• Recall Management – Product Registrations and Staying Informed
• Incident Reporting and Investigation

Li Batts come in several different types, or chemistries. This guidance does not seek to describe all Li Batt types, and any Li Batts of any chemistry should be treated with special care due to unique safety factors that make them different from other, more traditional battery technologies (see Sections 7-8 for more detail). Between two of the most commonly-used Li Batt chemistries in health and social care (H&SC) devices (e.g. mobility scooters, powered wheelchairs, stairlifts), it is important to note several distinctions.

Lithium nickel / manganese / cobalt oxides (Li-NMC)

Li-NMC Batts are mixed-metal oxides of lithium, nickel, manganese and cobalt, commonly used in lithium-ion batteries (as cathode material) for mobile devices and electric vehicles (aluminum is also sometimes found in Li Batts of this type). Li-NMC Batts are among the lightest, most efficient, and most energy-dense chemistries, and their use is widespread.

Key Li-NMC Batt components (nickel, manganese, and cobalt), however, are expensive, supply-constrained, and subject to both human-rights and environmental concerns. Moreover, when Li-NMC Batts are damaged – due to improper charging, short-circuit, impact damage, or crush damage – they can produce very dangerous conditions including:

• Release of toxic gases
• Extremely energetic and hard-to-extinguish fires (see Section 8 for a more detailed description of materials combustibility, including “thermal runaway”)
• Explosions

Lithium ferro-phosphate, sometimes aka lithium iron phosphate (LiFePO₄)

A LiFePO₄ Batt is a type of lithium-ion battery using lithium iron phosphate as the cathode material, and a graphitic carbon electrode with a metallic backing as the anode. Compared to Li-NMC, LiFePO₄ chemistry yields a battery that is 20 percent heavier, less energy-dense, and sometimes more expensive (due in part to it being less widely used currently).

Unlike Li-NMC, however, LiFePO₄’s non-lithium components (iron and phosphate) are much more common in the Earth’s crust – and they last longer (c. 1,000 – 2,500 cycles) than Li-NMC (c. 650 – 1,000 cycles); see Section 7 for a more detailed description of cycle life.  Most importantly, compared to other Li Batt chemistries[i], LiFePO₄ Batts have significant safety advantages:

• Much greater thermal and chemical stability – in part due to the absence of flammable electrolyte in LiFePO₄ Batts – which reduces significantly the risk of “thermal runaway”
• Greater physical and structural stability, which reduces the risk of impact damage or crush damage
• Greater chemical durability and resilience, which reduces the risk of fire/explosion in the event of mishandling (due to physical damage or improper charge damage) and increases battery stability across a greater range of atmospheric temperatures

[i] For more detail, please see the ‘Comparison to other battery types’ section of the Lithium iron phosphate battery Wikipedia page [accessed 13-Oct-23].

Like all batteries, a Li Batt stores chemical energy and converts it to electrical energy to provide power. Specifically, a Li Batt is a type of rechargeable battery that uses the reversible reduction of lithium ions to store energy: the anode (-) carries positively charged particles via an electrolyte (a liquid or gel) through a separator (inside the battery) to the cathode (+); the movement of these particles creates energy (electrical current) in the anode (-), which flows through the device being powered, and back into the cathode (+), beginning the cycle again.

Unlike previous generations of “traditional” batteries[i] – whose anodes/cathodes used combinations of metals including lead (anodes/cathodes) and acid (electrolyte) to move particles (electrons) – Li Batts typically use graphite/copper (anode), a metallic lithium oxide (cathode), and a lithium-salt-&-solvent solution (electrolyte) to move particles (lithium ions).

[i] E.g. Sealed Lead-Acid (SLA) batteries, Absorbent Glass Mat (AGM) batteries, Gel batteries.