The myths about lithium

14th of November 2018
The myths about lithium

Battery Service Hub (BSH) is an independent provider of battery and charger solutions to a number of industrial markets. Director Andy Riddle looks at why lithium ion technology has been slow to be adopted by the cleaning sector.

While it is proving to be successful in a number of mobile applications, lithium ion has been slow to emerge into the cleaning industry. It is widely available for small equipment such as vacuum cleaners and small scrubber dryers and it is clear to see its advantages - especially for applications such as daytime cleaning even though conventional battery technology offers the advantages of cableless cleaning. It is the fast charging capability of lithium batteries and or the ability to have a “plug and play” replacement battery that are the key benefits.

Maintenance free batteries such as AGM or gel have long been the choice of cleaning equipment manufacturers, equipment suppliers and cleaning contractors although flooded or wet cell batteries are still used in a number of machines.

But why not lithium?

One reason could be the cost of a lithium battery versus its wet or sealed lead alternative. However, has the user considered the advantages of lithium over existing technology and could it reduce their costs in the long term? More recently lead crystal has also been promoted as an alternative to lithium because of a price advantage but do customers understand that technology and if it offers any benefits for their equipment, or more importantly the application it is being used for?

One key area that is always promoted as an advantage of both lead crystal and lithium is cycle life – the number of times the battery can be recharged – over and above conventional batteries. This life varies, depending on the supplier’s claims, from between 800 to as much 5,000 cycles but where do these results come from and why do they vary so much? Given the industry standard cycle life of a battery discharged to 80 per cent of its capacity is as follows: wet flat plate 500 cycles, wet tubular blocs 1,200 cycles, wet two- volt cells 1,500 cycles, sealed AGM 500 cycles, gel 700 cycles. Why is there so much disparity when it comes to lead crystal and lithium?

Firstly lead crystal technology has been proven by a number of manufacturers that have carried out “tear downs” of a battery to be no more than a sealed gel bloc that offers no real advantages over a standard sealed bloc. That is not to say the technology does not work as it can be found in many fast release applications, however, it is widely viewed that it offers no advantages over existing sealed technology in deep cycle applications such as cleaning or industrial equipment.

Perhaps understanding lithium a little closer may explain some of the disparity of claims with regards to cycle life. The two main lithium chemistries offered are lithium iron phosphate (LiFePO4) and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC).

LiFePO4 is best suited to portable and stationary equipment needing high load currents and endurance ie, starter battery. Its characteristics are viewed as one of the more stable lithium ion chemistries but not ideal for deep cycle applications such as industrial or cleaning equipment.
LiNiMnCoO2 or NMC due to its more commercial viability, stability and characteristics is fast becoming the preferred battery technology for electric vehicles and applications that require frequent cycling-charging such as AGV’s (automatically guided vehicles) electric bikes, etc so the specification of these batteries would suggest it suits cleaning equipment well.

Lithium NMC has now become the standard technology offered by BSH to new and existing customers to suit a number of industrial applications and comes in a number of configurations with programmable CAN bus communication. The blocs are paired with the correct charger with the correct lithium charging profile to ensure the battery is protected.

LiFePO4 and NMC have been used for a number of years but NMC has fast become the preferred choice of many car manufacturers and there is an emerging market from this industry and others that is offering what is termed as “secondary“ cells. The cells used to make up the battery once deemed they have reached the end of their life, possibly due to lack of performance as a battery pack, then find their way into other markets where they can be reconfigured for new applications such as renewable energy in the case for LiFePO4 as this technology is best suited for this or in the case of NMC battery packs for industrial applications.

Not recyclable

Whilst this could be seen as an advantage from an environmental view, unlike lead acid, lithium in any form is not recyclable currently and is very expensive to dispose of. This reuse of secondary lithium cells also brings us back to the cycle life claims. Lithium battery packs are generally made up of a number of cells equal to 3.6 volts per cell which are connected together to then produce the required voltage ie, 12, 24, 36, 48, 72, 80 volts and capacity. When a single cell is new the cycle life could be expected to be very much higher than that of a secondary cell, however there are a number of parameters that can determine the cycle life and these are but not limited to:

• The state and age of the cells being used
• How the cells are connected inside the battery pack
• The conditions the new battery will be used in
• The type of equipment being used
• Average discharge current
• Charge current
• Cycles per day
• Cycle per year.

Another area that should be considered when reviewing batteries that have been produced using secondary cells is to understand the underlying risks and performance issues that often arise from such battery packs.

One last vital area is that lithium batteries require a BMS (Battery Management System) to ensure the cells are being charged and discharged evenly in order not to damage the battery. Unlike conventional batteries, if a lithium battery is over discharged it is unlikely that it could be recovered. Therefore, the BMS is essential in protecting the battery and is a critical part of the battery pack configuration.

What are the advantages of using the right lithium technology?

• Fast charging
• Opportunity charging - charge in a coffee break or lunch time without damaging the lifetime of the battery
• Longer run times with less capacity
• Battery can be discharged to 100 per cent unlike lead acid where maximum recommended is 80 per cent
• A high charging efficiency means that almost all the energy that is delivered by the charger will actually be stored in the battery, which in turn should result in lower charging costs
• Light weight – 24volt 40ah battery
8.6kg compared to equivalent two x 12volt 50ah sealed blocs  with a combined weight of 30kg
• Easily interchangeable

So what should be considered when deciding if lithium will benefit your application?  Firstly we would recommend that the battery being offered is configured using NMC cell technology. Does the ability to charge the battery when not in use for short periods of time (opportunity charging*) or fully charge within one to three hours offer the operation an advantage?
*Opportunity charging (short periods of charge of both sealed and wet batteries) shortens their life leading to less runtime and early replacement.

Could using lithium, due to its ability to be recharged faster, reduce the number of machines required in a facility? Potentially reducing labour costs or allowing the rescheduling of cleaning times as conventional batteries take 10-12 hours to recharge assuming the process is not interrupted.

Lithium batteries can be retrospectively fitted into most industrial machines that exist in the market today including scrubber dryers and sweepers with very few, if any, modifications required.


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