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Lithium-ion Battery Technology

We design, manufacture, supply and support lithium-ion battery packs for industrial and material handling equipment industries.

The Technology Behind Flux Power Lithium-ion Forklift Battery Packs

Experience the new power of lithium-ion battery technology from Flux Power and learn about the science driving modern industrial solutions.

Contents

Introduction to Lithium  -  Why Flux Power Uses LiFeP04 Battery Management System

 

Introduction to Lithium-ion Batteries

Lithium-ion batteries were invented in 1980 by John Goodenough; they were commercialized in 1991 by Sony. In the past decade lithium-ion batteries have become the dominant rechargeable battery chemistry in nearly all industries. Lithium-ion, in comparison to previous popular chemistries, (Lead-acid, Nickel-Cadmium, and alkaline) are better in many ways. With the advancement in technology, a battery that is safe and powerful is in great need. Lithium is the most energy dense chemistry in use and with added features can be the safest. Lithium energy is an active area of study so new chemistries are being developed every year. Some of the most popular chemistries are:


1. Lithium Titanate (LTO)
2. Lithium Cobalt Oxide (LCO)
3. Lithium Nickel Manganese Cobalt (NMC)
4. Lithium Iron Phosphate (LFP)

While these are all lithium batteries, there are key differences between them.

LTO has a very long life and a wide temperature range. They are capable of handling large charge currents greater than 10C. They have one of the lowest energy densities (2.4V/Cell) of all lithium batteries and are one of the most expensive.

LCO became very popular because of its high energy density (3.6 V/Cell). Cobalt is a very energy dense material but is extremely volatile and expensive. It is a resource that is depleting quickly and is estimated to run out in 50 years, or due to its recent increase in consumption. LCO has many negatives, they cannot handle large charge currents, are very sensitive to temperature, and have a short cycle life.

NMC is a rapidly developing chemistry, at the time this is written. The blending of nickel, manganese, and cobalt produces a very well-rounded battery. With a high energy density (3.6V/Cell) and a decreased use in cobalt, it has become one of the most desired batteries in the industry. Due to its lower cobalt concentration, it is safer than LCO. Its life cycle is longer than LCO but shorter than LTO. It can handle charge currents up to 2C and a greater range in temperature. It is also important to know that batteries that contain cobalt require more safety features which make the batteries more expensive.

LFP is popular in industries with heavy use and rough environments. While this chemistry has a slightly lower energy density (3.2V/Cell), it can withstand a lot of abuse. It has a long-life span, it’s less costly and much safer because it does not contain cobalt and can withstand a very wide range of temperatures. It can also withstand discharge currents up to 20C. Overall this is the safest and most reliable chemistry.

  LTO LCO NMC LFP
Voltages 2.4 volts 3.60 volts 3.6 volts 3.2 volts
C-Rate 10C 1C 2C 20C
Cycle Life 3000 500 1500 2500
Thermal Runaway 280 °C 150 °C 210 °C 270 °C
Cost $1,000 per kWh $450 per kWh $700 per kWh $400 per kWh

Table 1: Comparison of LTO, LCO, NMC, LFP


In the simplest terms, a lithium-ion battery refers to a battery with a negative electrode(anode) and a positive electrode(cathode) that transfers lithium ions between the two materials. Lithium-ions move from the anode to the cathode during discharge and deposit themselves(intercalate) into the positive electrode (Figure 1.), which is composed of Lithium and other metals. During charge this process is reversed.

flow of electronsFigure 1. Electron and Li+ Ion Flow During Use


Within the cells there are many layers of anode and cathode with a separator in between. Between the two plates, there is also an electrolyte solution, typically LiPF6 mixed with a liquid solution. This combination of materials can either be stacked (prismatic cells) or wound in a spiral (cylindrical cells). Cells vary in size and shape; some are encased in plastic while others are in aluminum cases. The casing is dependent on the environment they are going into and the size is determined by the amount of capacity needed for the application.

Cylindrical, prismatic, and pouch cell typesFigure 2. Cylindrical, prismatic, and pouch cell types.

Each lithium-ion cell has a safe voltage range that it can be operated in. This range is dependent on the chemistry used in the battery. For example, an LFP battery at 0% State of Charge (SOC) is 2.8V and at 100% SOC is 3.6V. This is considered the safe operating range of this battery. Going below the stated 0% SOC can cause degradation of the electrodes. This is considered an over-discharge. If a cell is repeatedly over-discharged it can cause many issues that permanently damage the battery. The same is true for an over-charge, going above the stated 100% SOC. These two failures have led battery manufacturers to develop safety devices and features.

A battery is typically comprised of many cells working in conjunction with one another. Let’s consider an LFP cell with a nominal voltage of 3.2V and a capacity of 100 Ah. Most applications require a higher voltage and capacity, how would this be done? In order to increase the voltage of a battery multiple cells must be connected in series. To increase the capacity, cells must be connected in parallel. For example, let say we want a 12V battery with a capacity of 300 Ah. With the given LFP cell we would need 4 cells in series with 3 modules in parallel. This would produce a system that is 12.8V with a capacity of 300 Ah.

Cell System Diagram
Figure 3. Cell System Diagram

The four main components of a cell are the anode, cathode, separator and electrolyte solution.

Anode

The anode is the negative electrode in the cell. It is very common, in lithium-ion batteries, for it to be composed of lithium and carbon, usually a graphite powder. The current can be collected due to the copper film that is combined with the electrode. The purity, particle size, and uniformity of the anode all contribute to the aging behavior and capacity.


Cathode

The cathode is the positive electrode. This is where all the different chemistries come into play. The cathode is what determines the overall lithium chemistry. Like the anode, a current collector is combined with the material so the flow of electrons can occur. The cathode is typically combined with an aluminum film. As shown above there are many different chemistries. The key differences between them is temperature at which they react with the electrolyte (thermal runaway) and the voltages they produce.


Electrolyte

The electrolyte allows the transfer of the lithium-ions between the plates. Typically, it is composed of different organic carbonates, such as ethylene, carbonate, and diethyl carbonate. The different mixtures and ratios vary depending on the application of the cell. For example, for a low temperature application the electrolyte solution will have a lower viscosity compared to one made for a room temperature environment. Lithium salts are essential in the mixture of the electrolyte, the salt determines the conductivity of the solution as well as aids in the formation of the solid electrolyte interface (SEI). In lithium batteries lithium hexafluorophosphate (LiPF6) is the most common lithium salt. LiPF6 can produce hydrofluoric acid (HF) when mixed with water. The SEI is a chemical reaction between the lithium metal and electrolyte. Under normal conditions the cell manufacturer typically slow charges the cell to form an even SEI on the carbon anode.


Separator

Lithium-ion cell separators are porous plastic films that prevent direct contact of the anode and cathode. The films are usually 20 μm thick and have small pours that allow lithium ions to pass through during the charge and discharge process. A “shutdown” separator is the most common. This separator will close the pours to prevent lithium ions to pass through, once the cell is out of the temperature range or a short occurs. Separators continue to be developed today to improve safety, while also increasing the capacity of the cells.

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Why Flux Power Uses LiFeP04

 

Five_year_savingsWe at Flux Power pride ourselves in being experts in energy storage solutions. This is why we chose a superior battery chemistry that has been proven through decades of research and deployment in multiple applications. In addition our energy storage solutions have numerous advantages over current lead-acid technology. For further details on the differences between lithium-ion and lead-acid, review this article, "Are Lithium-ion Batteries Better than Lead-Acid for Forklifts."

Capacity & Cycle Life

One of the most important benefits of Flux Power’s choice of lithium is the dramatic increase in energy density over current lead-acid battery solutions.  Flux Power uses Lithium-Iron-Phosphate (LiFePO4) which has a specific energy of ~110 watt-hours per kilogram, compared to lead-acids ~40 watt-hours per kilogram.  What does this mean?  Our batteries can be ~1/3 the weight for similar amp-hour ratings.

Not only does Flux Power lithium store more energy, but the cycle-lifetime far exceeds that of lead-acid and many other lithium chemistries.

In our article, "5 Steps To Maximize Lithium-ion Battery Life," you'll find additional tips that will help you get the most out of your battery.

Every battery cell chemistry is affected by the depth of discharge, and the deeper the discharge, the shorter the lifespan.  Flux Power lithium can be discharged a remarkable 80% while still maintaining long cycle lifetimes (>2000 cycles).  Lead-acid batteries experience drastic reductions in cycle life.  In fact, at an 80% depth of discharge, lead-acid batteries only last 400-500 cycles, meaning our batteries last 5x longer.

State-of-ChargeSpeed & Efficiency

Flux Power lithium-ion batteries are fast. They can be fast charged completely, and can handle ultra-fast charging up to 1C (a full charge in 1 hour). Lead-acid can only be fast-charged up to 80% after which charging current drops dramatically. In addition Flux Power batteries maintain excellent performance under discharge rates as high as 3C continuous (full discharge in 1/3 an hour) or 5C pulsed. Lead-acid experiences dramatic voltage sag and capacity reduction by comparison. In fact, the discharge profile of a Flux Power lithium-ion battery shows how voltage and power remain almost constant throughout its discharge, unlike lead-acid. This means that even when the battery runs low, performance stays high.

There are also no memory issues, discharge and charge the battery at any point without consequence.  With lead-acid, failure to fully charge leads to sulfation which damages the batteries.  This also occurs when storing lead-acid while not fully charged.  With Flux Power lithium-ion, store the battery at any state of charge except near zero.

Finally, Flux Power lithium-ion is ~95% energy efficient, compared to the ~80% efficiency for lead acid batteries.  This is particularly important for solar energy storage solutions, where every bit counts.

Do you need to charge your batteries on the go?  Our batteries perform better when charging during breaks in the day.  Running Flux Power lithium-ion batteries using ‘opportunity charging’ can actually increase cycle lifetime and decrease the battery size.

Safety & Reliability

There are a wide variety of chemistries to choose from when looking at advanced lithium batteries. We chose lithium-Iron-Phosphate (LiFePO4) because it has three advantages that make it the obvious choice for tough jobs.

  1. It is thermally stable up to very high temperatures, meaning no thermal runaway.  The batteries can be used safely in ambient temperatures up to 55°C (131°F).  Operating lead-acid batteries at this temperature reduces their cycle life by a whopping 80%!
  2. Flux Power lithium-ion provides remarkably long cycle lifetimes, with competing chemistries being either too expensive (lithium Titanate), or too unstable (Lithium Nickel Cobalt Aluminum Oxide).
  3. LiFePO4 provides more power and more energy density than lead-acid and many other lithium chemistries, so it’s perfect for demanding jobs, and efficient energy storage solutions.

Not all lithium batteries are created equal. There are several factors that go into creating a battery that is high-performing, long-lasting and most importantly, safe. One major factor to consider is UL certification, or at a minimum making sure the battery is designed to UL standards. For a more in-depth look at UL Certification, review our article, "Why UL Certification Is Important For A Lithium-ion Battery Pack."

Did we mention Flux Power lithium-ion is maintenance free?  No electrolyte must be added and there is no danger of acid spills or dangerous vapors.  In our case studies, fewer batteries were needed when compared to lead-acid, so even less storage room may be required. View our article on, "The Top 5 Ways a Lithium-ion Battery Makes Your Forklift Safer," for a more detailed outline on why lithium-ion is a safer alternative.

lithium-ion free-quote

 

Battery Management System

 

All of our energy storage solutions use our patented Battery Management System (BMS) which monitors the battery life and provides valuable information to the end user. The system uses a Battery Management System Module (BMSM) to monitor up to 4 individual LiFePO4 cells. The BMSMs then report to the Battery Control Module (BCM), which can manage up to 28 BMSMs. This means Flux Power lithium-ion is a scalable solution for almost any application.

A state of charge LED indicator tells the end user how much energy is left in the pack, and can display a number of diagnostic codes for monitoring battery and system health. It will also notify the user if recommended operating temperature is exceeded, or if battery servicing is required. In addition a warning buzzer sounds when the battery is close to empty, so you’ll know when to plug it in.

When the battery charges, the BMS performs an auto-balancing of the cells near the top of charge, and notifies the end user when finished.  This auto-balancing feature is a vital component, and enables the end user to get the longest cycle lifetime and best performance out of our batteries.  At times balancing may be required.  In these cases, the LED indicator notifies the end user and the system should be fully charged until all cells are balanced.  Finally, if for any reason you need to interface with the BMS, it uses the robust automotive standard CAN protocol.

Design

Each Flux Power lithium-ion battery also includes an onboard charger and enough storage room for a 25 ft. charging cable.  The battery can be charged anywhere and anytime, perfect for opportunity charging.  The cases are made from 10 gauge powder coated A36 steel and our LiFT pack is designed to be pressure washed daily.  In case of power surges a breaker for shorts and over-currents is installed to protect the battery’s vitals.  Finally because Flux Power lithium-ion is so much lighter than lead-acid, we can adjust the weight of Flux Power lithium-ion to meet your needs.

Environment

The health of the environment and one’s employees is important, which is why it’s great Flux Power lithium-ion batteries use no toxic chemicals, acids, or heavy metals.  The materials are harmless and can be disposed of in landfills.  This is not necessary of course, as recycling methods are currently being developed, with reports of 60% recyclability.  Lithium-ion batteries are the future of energy storage, and recycling efficiencies are predicted to climb to 90% as the markets scale and additional recycling methods are developed.

Lead-acid batteries have a very mature recycling industry with ~96% of the battery being recycled. However they don’t last nearly as long, so during the lifetime of one Flux Power lithium-ion battery, five lead-acid batteries have been made and recycled, equating to 20% of a single lead-acid battery being wasted, not to mention the carbon footprint from the production and recycling of all five lead-acid batteries.

Carbon footprints are important, and procuring raw materials can be damaging to the environment.  Lithium-ion is obtained almost exclusively from brine pools.  It’s cheap, safe, and far less damaging to local ecosystems than other forms of mining.  So no matter what your business is, or what your needs are, Flux Power lithium-ion batteries are the best solution for staying green and competitive in today’s world.

Lithium-Ion Battery Chemistry

As we have mentioned earlier, there are several chemistries that comprise a lithium-ion battery. 

Lithium-iron phosphate is more compact and energy dense than many other chemistries. This can provide many benefits for industry, including:

  • A longer battery life cycle
  • Enhanced thermal stability
  • Improved safety
  • Higher performance and lower resistance
  • Better tolerance when fully charged (doesn’t experience as much stress as other chemistries with prolonged high voltages)
  • Zero toxic elements

In the case of lithium-iron phosphate chemistry, the anode of the battery is typically made from carbon, whereas the phosphate serves as the cathode material

Lithium-Ion Battery Uses

Lithium-ion batteries are used across multiple sectors, from industry to medical, automotive and electronics. 

There are at least a dozen different chemistries that comprise lithium-ion batteries. Because of its high energy density, however, lithium-ion batteries that feature a lithium-iron phosphate chemistry are most often used in material handling operations. 

Equipment powered by this type of lithium-ion battery include:

  • Electric forklifts
  • Narrow aisle forklifts
  • Walkie stackers and pallet jacks
  • End and center riders

Lithium-ion batteries with lithium-iron phosphate chemistry also play an important role in ensuring airport operations run smoothly and efficiently. While this leading-edge technology reduces long-term costs and improves workflow, lithium-ion batteries also provide a cleaner, green technology that many airports are seeking today.

Electric ground support equipment powered by lithium-ion batteries include:

  • Pushbacks
  • Belt loaders
  • Container loaders
  • Luggage tugs 
  • Baggage carts

Lithium batteries featuring a chemistry of lithium-nickel manganese cobalt oxide (NCO) also are found in some equipment fleets, though this type of battery is a more popular choice in electric vehicles such as:

  • E-bikes 
  • Buses 
  • Other electric powertrains 

The future of electric powered products is already here. The advantages of switching from conventionally power sources are too good to ignore. As more and more industries and businesses become aware of the benefits of lithium-ion technology, the business decision to switch over is becoming a much easier one to make.

lithium-ion forklift battery