A quick comparison of the strengths of different types of lithium batteries
Many floor care OEMs are starting on design projects to implement lithium battery packs in their floor care machines. The transition is often from sealed lead-acid (AGM or Gel) to lithium – so many floor care machines already have advanced, robust, sealed, and lower-maintenance energy storage solutions. While the acquisition cost differences between sealed lead-acid and typical lithium solutions will be smaller than if the transition was from flooded lead-acid, the Total Cost of Ownership comparison will most likely favor lithium. Maintenance costs, life cycle, and the ability to opportunity charge with less detrimental effects all favor lithium storage.
If the decision has been made to offer a lithium battery-powered floor care machine, the first question might be which type of lithium cell to use.
Lithium batteries are widely used today in a variety of applications. The main difference in design and construction between the six widely commercialized types is in the type of cathode material used within the batteries. The six common cell types are:
- Lithium Cobalt Oxide (LiCoO2)
- Lithium Manganese Oxide (LiMn2O4)
- Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2)
- Lithium Iron Phosphate (LiFePO4)
- Lithium Cobalt Aluminum Oxide (LiNiCoAlO2)
- Lithium Titanate (Li4Ti5O12)
In order, we abbreviate them LCO, LMO, NMC, LFP, NCA, and LTO.
Factors to Evaluate
Designers need to understand the trade-offs between these batteries on a range of factors: Energy (Capacity), Power (kW output), Life Span, Cost, and Safety. Some cell types are not a fit for floor care due to life span, cost, or safety concerns. LCO cells have high capacity but are the least safe lithium type—they are often used in mobile phones, laptops, and tablets. LMO cells perform well on most evaluation metrics but have relatively short life span—they are commonly used in power tools and medical devices. LTO cells are among the safest but their energy capacity is low, and their cost is high—they are typically used in UPSs and street lighting.
NMC, LFP and NCA are the most widely used lithium cell types in motive power applications due to their performance on three of the most important factors: Power, Life Span and Cost. While there are slight differences in their rankings on those factors, designers should evaluate their performance on the other factors more completely.
- LFP is perhaps the most prevalent lithium cell type deployed in floor care today, with a combination of High Power Output, High Life Span and High Safety—offset by relatively Low Energy Density.
- NMC cells are very balanced in their performance on all five evaluation factors, offering Mid Power Output, Mid/High Life Span and Mid Safety—delivering Middle-range Energy Density.
- NCA cells are quite similar to NMC, offering slightly less Life Span but increased Energy Density.
Within each cell type, there can be a range of specific commodities included that will lead to slightly different performance on the five evaluation factors. Depending on the combination of various elements (the amount of nickel, cobalt and aluminum) in each cell type, the energy density and cost may vary. When analyzing battery options for a floor machine, these more specific differences should be considered before a final selection is made.
Floor care machine designers should evaluate the design requirements of their machines and assess each lithium cell type’s strengths against those specific requirements. The energy requirements of one machine may help define the storage capacity that is required and point to one cell type. Life span concerns on another machine may suggest a different cell type. Finally, extreme safety requirements may lead to the selection of another type.
Understanding the trade-offs between popular cell types will help designers make the right lithium choice.