Learn the key feature of each Li-ion in a summary table.
The term lithium-ion points to a family of batteries that shares similarities, but the chemistries can vary greatly. Li-cobalt, Li-manganese, NMC and Li-aluminum are similar in that they deliver high capacity and are used in portable applications. Li-phosphate and Li-titanate have lower voltages and have less capacity, but are very durable. These batteries are mainly found in wheeled and stationary uses. Table 1 summarizes the characteristics of major Li-ion batteries.
Chemistry
Lithium Cobalt Oxide
Lithium Manganese Oxide
Lithium Nickel Manganese Oxide
Lithium Iron Phosphate
Lithium Nickel Cobalt Aluminum Oxide
Lithium Titanate Oxide
Short form
Li-cobalt
Li-manganese
NMC
Li-phosphate
Li-aluminum
Li-titanate
Abbreviation
LiCoO2
(LCO)
LiMn2O4
(LMO)
LiNiMnCoO2 (NMC)
LiFePO4
(LFP)
LiNiCoAlO2 (NCA)
Li2TiO3 (common)
(LTO)
Nominal voltage
3.60V
3.70V (3.80V)
3.60V (3.70V)
3.20, 3.30V
3.60V
2.40V
Full charge
4.20V
4.20V
4.20V (or higher)
3.65V
4.20V
2.85V
Full discharge
3.00V
3.00V
3.00V
2.50V
3.00V
1.80V
Minimal voltage
2.50V
2.50V
2.50V
2.00V
2.50V
1.50V (est.)
Specific Energy
150–200Wh/kg
100–150Wh/kg
150–220Wh/kg
90–120Wh/kg
200-260Wh/kg
70–80Wh/kg
Charge rate
0.7–1C (3h)
0.7–1C (3h)
0.7–1C (3h)
1C (3h)
1C
1C (5C max)
Discharge rate
1C (1h)
1C, 10C possible
1–2C
1C (25C pule)
1C
10C possible
Cycle life (ideal)
500–1000
300–700
1000–2000
1000–2000
500
3,000–7,000
Thermal runaway
150°C (higher when empty)
250°C (higher when empty)
210°C(higher when empty)
270°C (safe at full charge)
150°C (higher when empty)
One of safest
Li-ion batteries
Maintenance
Keep cool; store partially charged; prevent full charge cycles, use moderate charge and discharge currents
Packaging (typical)
18650, prismatic and pouch cell
prismatic
18650, prismatic and pouch cell
26650, prismatic
18650
prismatic
History
1991 (Sony)
1996
2008
1996
1999
2008
Applications
Mobile phones, tablets, laptops, cameras
Power tools, medical devices, powertrains
E-bikes, medical devices, EVs, industrial
Stationary with high currents and endurance
Medical, industrial,
EV (Tesla)
UPS, EV, solar street lighting
Comments
High energy, limited power. Market share has stabilized.
High power, less capacity; safer than Li-cobalt; often mixed with NMC to improve performance.
High capacity and high power. Market share is increasing. Also NCM, CMN, MNC, MCN
Flat discharge voltage, high power low capacity, very safe; elevated self-discharge.
Highest capacity with moderate power. Similar to Li-cobalt.
Long life, fast charge, wide temperature range and safe. Low capacity, expensive.
Table 1: Summary of most common lithium-ion based batteries.
https://himaxelectronics.com/wp-content/uploads/2021/05/Summary-Table-of-Lithium-based-Batteries.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-05-21 10:45:322024-04-29 01:35:34Summary Table of Lithium-based Batteries
Learn how to arrange batteries to increase voltage or gain higher capacity.
Batteries achieve the desired operating voltage by connecting several cells in series; each cell adds its voltage potential to derive at the total terminal voltage. Parallel connection attains higher capacity by adding up the total ampere-hour (Ah).
Some packs may consist of a combination of series and parallel connections. Laptop batteries commonly have four 3.6V Li-ion cells in series to achieve a nominal voltage 14.4V and two in parallel to boost the capacity from 2,400mAh to 4,800mAh. Such a configuration is called 4s2p, meaning four cells in series and two in parallel. Insulating foil between the cells prevents the conductive metallic skin from causing an electrical short.
Most battery chemistries lend themselves to series and parallel connection. It is important to use the same battery type with equal voltage and capacity (Ah) and never to mix different makes and sizes. A weaker cell would cause an imbalance. This is especially critical in a series configuration because a battery is only as strong as the weakest link in the chain. An analogy is a chain in which the links represent the cells of a battery connected in series (Figure 1).
Figure 1: Comparing a battery with a chain.
Chain links represent cells in series to increase voltage, doubling a link denotes parallel connection to boost current loading.
A weak cell may not fail immediately but will get exhausted more quickly than the strong ones when on a load. On charge, the low cell fills up before the strong ones because there is less to fill and it remains in over-charge longer than the others. On discharge, the weak cell empties first and gets hammered by the stronger brothers. Cells in multi-packs must be matched, especially when used under heavy loads. (See BU-803a: Cell Mismatch, Balancing).
Single Cell Applications
The single-cell configuration is the simplest battery pack; the cell does not need matching and the protection circuit on a small Li-ion cell can be kept simple. Typical examples are mobile phones and tablets with one 3.60V Li-ion cell. Other uses of a single cell are wall clocks, which typically use a 1.5V alkaline cell, wristwatches and memory backup, most of which are very low power applications.
The nominal cell voltage for a nickel-based battery is 1.2V, alkaline is 1.5V; silver-oxide is 1.6V and lead acid is 2.0V. Primary lithium batteries range between 3.0V and 3.9V. Li-ion is 3.6V; Li-phosphate is 3.2V and Li-titanate is 2.4V.
Li-manganese and other lithium-based systems often use cell voltages of 3.7V and higher. This has less to do with chemistry than promoting a higher watt-hour (Wh), which is made possible with a higher voltage. The argument goes that a low internal cell resistance keeps the voltage high under load. For operational purposes these cells go as 3.6V candidates. (See BU-303 Confusion with Voltages)
Series Connection
Portable equipment needing higher voltages use battery packs with two or more cells connected in series. Figure 2 shows a battery pack with four 3.6V Li-ion cells in series, also known as 4S, to produce 14.4V nominal. In comparison, a six-cell lead acid string with 2V/cell will generate 12V, and four alkaline with 1.5V/cell will give 6V.
Figure 2: Series connection of four cells (4s).
Adding cells in a string increases the voltage; the capacity remains the same.
Courtesy of Cadex
If you need an odd voltage of, say, 9.50 volts, connect five lead acid, eight NiMH or NiCd, or three Li-ion in series. The end battery voltage does not need to be exact as long as it is higher than what the device specifies. A 12V supply might work in lieu of 9.50V. Most battery-operated devices can tolerate some over-voltage; the end-of-discharge voltage must be respected, however.
High voltage batteries keep the conductor size small. Cordless power tools run on 12V and 18V batteries; high-end models use 24V and 36V. Most e-bikes come with 36V Li-ion, some are 48V. The car industry wanted to increase the starter battery from 12V (14V) to 36V, better known as 42V, by placing 18 lead acid cells in series. Logistics of changing the electrical components and arcing problems on mechanical switches derailed the move.
Some mild hybrid cars run on 48V Li-ion and use DC-DC conversion to 12V for the electrical system. Starting the engine is often done by a separate 12V lead acid battery. Early hybrid cars ran on a 148V battery; electric vehicles are typically 450–500V. Such a battery needs more than 100 Li-ion cells connected in series.
High-voltage batteries require careful cell matching, especially when drawing heavy loads or when operating at cold temperatures. With multiple cells connected in a string, the possibility of one cell failing is real and this would cause a failure. To prevent this from happening, a solid state switch in some large packs bypasses the failing cell to allow continued current flow, albeit at a lower string voltage.
Cell matching is a challenge when replacing a faulty cell in an aging pack. A new cell has a higher capacity than the others, causing an imbalance. Welded construction adds to the complexity of the repair, and this is why battery packs are commonly replaced as a unit.
High-voltage batteries in electric vehicles, in which a full replacement would be prohibitive, divide the pack into modules, each consisting of a specific number of cells. If one cell fails, only the affected module is replaced. A slight imbalance might occur if the new module is fitted with new cells. (See BU-910: How to Repair a Battery Pack.)
Figure 3 illustrates a battery pack in which “cell 3” produces only 2.8V instead of the full nominal 3.6V. With depressed operating voltage, this battery reaches the end-of-discharge point sooner than a normal pack. The voltage collapses and the device turns off with a “Low Battery” message.
Figure 3: Series connection with a faulty cell.
Faulty cell 3 lowers the voltage and cuts the equipment off prematurely.
Courtesy of Cadex
Batteries in drones and remote controls for hobbyist requiring high load current often exhibit an unexpected voltage drop if one cell in a string is weak. Drawing maximum current stresses frail cells, leading to a possible crash. Reading the voltage after a charge does not identify this anomaly; examining the cell-balance or checking the capacity with a battery analyzer will.
Tapping into a Series String
There is a common practice to tap into the series string of a lead acid array to obtain a lower voltage. Heavy duty equipment running on a 24V battery bank may need a 12V supply for an auxiliary operation and this voltage is conveniently available at the half-way point.
Tapping is not recommended because it creates a cell imbalance as one side of the battery bank is loaded more than the other. Unless the disparity can be corrected by a special charger, the side effect is a shorter battery life. Here is why:
When charging an imbalanced lead acid battery bank with a regular charger, the undercharged section tends to develop sulfation as the cells never receive a full charge. The high voltage section of the battery that does not receive the extra load tends to get overcharged and this leads to corrosion and loss of water due to gassing. Please note that the charger charging the entire string looks at the average voltage and terminates the charge accordingly.
Tapping is also common on Li-ion and nickel-based batteries and the results are similar to lead acid: reduced cycle life. (See BU-803a: Cell Matching and Balancing.) Newer devices use a DC-DC converter to deliver the correct voltage. Electric and hybrid vehicles, alternatively, use a separate low-voltage battery for the auxiliary system.
Parallel Connection
If higher currents are needed and larger cells are not available or do not fit the design constraint, one or more cells can be connected in parallel. Most battery chemistries allow parallel configurations with little side effect. Figure 4 illustrates four cells connected in parallel in a P4 arrangement. The nominal voltage of the illustrated pack remains at 3.60V, but the capacity (Ah) and runtime are increased fourfold.
Figure 4: Parallel connection of four cells (4p).
With parallel cells, capacity in Ah and runtime increases while the voltage stays the same.
Courtesy of Cadex
A cell that develops high resistance or opens is less critical in a parallel circuit than in a series configuration, but a failing cell will reduce the total load capability. It’s like an engine only firing on three cylinders instead of on all four. An electrical short, on the other hand, is more serious as the faulty cell drains energy from the other cells, causing a fire hazard. Most so-called electrical shorts are mild and manifest themselves as elevated self-discharge.
A total short can occur through reverse polarization or dendrite growth. Large packs often include a fuse that disconnects the failing cell from the parallel circuit if it were to short. Figure 5 illustrates a parallel configuration with one faulty cell.
Figure 5: Parallel/connection with one faulty cell.
A weak cell will not affect the voltage but provide a low runtime due to reduced capacity. A shorted cell could cause excessive heat and become a fire hazard. On larger packs a fuse prevents high current by isolating the cell.
Courtesy of Cadex
Series/parallel Connection
The series/parallel configuration shown in Figure 6 enables design flexibility and achieves the desired voltage and current ratings with a standard cell size. The total power is the sum of voltage times current; a 3.6V (nominal) cell multiplied by 3,400mAh produces 12.24Wh. Four 18650 Energy Cells of 3,400mAh each can be connected in series and parallel as shown to get 7.2V nominal and a total of 48.96Wh. A combination with 8 cells would produce 97.92Wh, the allowable limit for carry on an aircraft or shipped without Class 9 hazardous material. (See BU-704a: Shipping Lithium-based Batteries by Air) The slim cell allows flexible pack design but a protection circuit is needed.
Figure 6: Series/ parallel connection of four cells (2s2p).
This configuration provides maximum design flexibility. Paralleling the cells helps in voltage management.
Courtesy of Cadex
Li-ion lends itself well to series/parallel configurations but the cells need monitoring to stay within voltage and current limits. Integrated circuits (ICs) for various cell combinations are available to supervise up to 13 Li-ion cells. Larger packs need custom circuits, and this applies to e-bike batteries, hybrid cars and the Tesla Model 85 that devours over 7000 18650 cells to make up the 90kWh pack.
Terminology to describe Series and Parallel Connection
The battery industry specifies the number of cells in series first, followed by the cells placed in parallel. An example is 2s2p. With Li-ion, the parallel strings are always made first; the completed parallel units are then placed in series. Li-ion is a voltage based system that lends itself well for parallel formation. Combining several cells into a parallel and then adding the units serially reduces complexity in terms of voltages control for pack protection.
Building series strings first and then placing them in in parallel may be more common with NiCd packs to satisfy the chemical shuttle mechanism that balances charge at the top of charge. “2s2p” is common; white papers have been issued that refer to 2p2s when a serial string is paralleled.
Safety devices in Series and Parallel Connection
Positive Temperature Coefficient Switches (PTC) and Charge Interrupt Devices (CID) protect the battery from overcurrent and excessive pressure. While recommended for safety in a smaller 2- or 3-cell pack with serial and parallel configuration, these protection devices are often being omitted in larger multi-cell batteries, such as those for power tool.
The PTC and CID work as expected to switch of the cell on excessive current and internal cell pressure; however the shutdown occurs in cascade format. While some cells may go offline early, the load current causes excess current on the remaining cells. Such overload condition could lead to a thermal runaway before the remaining safety devices activate.
Some cells have built-in PCT and CID; these protection devices can also be added retroactively. The design engineer must be aware than any safety device is subject to failure. In addition, the PTC induces a small internal resistance that reduces the load current. (See also BU-304b: Making Lithium-ion Safe)
Simple Guidelines for Using Household Primary Batteries
Keep the battery contacts clean. A four-cell configuration has eight contacts and each contact adds resistance (cell to holder and holder to next cell).
Never mix batteries; replace all cells when weak. The overall performance is only as good as the weakest link in the chain.
Observe polarity. A reversed cell subtracts rather than adds to the cell voltage.
Remove batteries from the equipment when no longer in use to prevent leakage and corrosion. This is especially important with zinc-carbon primary cells.
Do not store loose cells in a metal box. Place individual cells in small plastic bags to prevent an electrical short. Do not carry loose cells in your pockets.
Keep batteries away from small children. In addition to being a choking hazard, the current-flow of the battery can ulcerate the stomach wall if swallowed. The battery can also rupture and cause poisoning. (See BU-703: Health Concerns with Batteries.)
Do not recharge non-rechargeable batteries; hydrogen buildup can lead to an explosion. Perform experimental charging only under supervision.
Simple Guidelines for Using Secondary Batteries
Observe polarity when charging a secondary cell. Reversed polarity can cause an electrical short, leading to a hazardous condition.
Remove fully charged batteries from the charger. A consumer charger may not apply the correct trickle charge when fully charged and the cell can overheat.
Charge only at room temperature.
https://himaxelectronics.com/wp-content/uploads/2021/05/1s4p-copy.jpg274320administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-05-14 02:58:132024-04-26 06:34:56Series and Parallel Battery Configurations
You walk into work one morning and find out that a battery system isn’t working. What happens? How much time will you lose trying to fix it? Getting it back online will probably cost money, but how much?
When it comes to battery malfunctions, that’s not even the worst-case scenario. What if damage to the battery system causes equipment damage further downstream or even creates a fire?
You consider eventualities like this whenever you integrate a new piece of machinery or develop a new work process, but have you gone through this process when integrating your battery system?
In this article, we’ll take a look at circuit protection and why it’s so important for industrial batteries. We’ll analyze a few of the different options you have for battery protection systems and how each system can help you to avoid battery damage and dangerous accidents.
Let’s start with the basics:
What Are Battery Protection Systems?
A battery protection system is any device that safeguards against battery malfunctions. Some are only effective against basic issues like overcharge or short circuit, while others provide complex monitoring and balancing for an entire battery system.
What Do They Protect Against?
To really understand why battery protection systems are so important, you need to know what can happen if they’re not in place:
Short Circuits
These occur when a current takes a shortcut. Electricity always wants to go back to the ground as soon as possible, but a correctly functioning circuit keeps it on the proper track. If the wiring in the circuit malfunctions, the current can escape and go back to the ground another way. That way might involve going through your equipment or one of your workers.
Overcharge
When you put too much charge into a rechargeable battery, that extra energy becomes heat. The temperature of the battery can rise beyond safe limits and reduce the battery’s lifespan.
Over Discharge
Draining too much of the charge from a battery can damage it in several ways, including decreasing the capacity of the battery, causing it to require charging more often, and causing a short circuit within the battery. If a lithium-ion battery lacks a protection system, it is highly prone to these and other malfunctions related to over-discharge.
Overcurrent
Too much current within the circuit can result from a number of malfunctions, including short circuits. If there is enough excess current, it can ignite components of the machinery and cause a fire.
Battery protection systems serve to keep the temperature and voltage balanced in your battery. Steady temperatures are critical for optimal battery life, which increases the safety of your operations and reduces your material costs.
An effective battery protection system will measure the current and temperature in your battery and adjust the circuit to provide protection if levels become unsafe. The process typically involves a thermistor, a ceramic-type semiconductor that decreases in resistance when the temperature of the battery rises. When this happens, it indicates the need for control and simultaneously acts as a battery “first aid.”
Thermistors work in conjunction with other safety mechanisms. Together, these systems provide the current and temperature control that a battery needs to stay operational. Let’s take a look at some of the most effective options:
Polymeric Positive Temperature Coefficients
The polymeric positive temperature coefficient, or PPTC, helps to balance the circuit against excess energy. Just like a standard fuse, it opens to create high resistance when there is too much current in the system. When the current decreases back to normal levels, it resets.
Unlike some types of fuses, the PPTC resets itself so that you can still use the battery after the overcurrent is corrected. It simply serves to keep the battery functional until electricity resets back to normal levels.
PPTCs are most commonly used for nickel batteries. They’re affordable, easy to install, and are compatible with most systems.
Protection Circuit Modules
Protection circuit modules, or PCMs, protect against overcharge, over-discharge, and excessively fast discharge, all of which can cause an excess of current. In lithium batteries, the PCM usually protects against these situations using a metal-oxide-semiconductor field-effect transistor, or MOSFET.
The MOSFET alters the circuit’s conduction by switching cells on if the voltage falls too quickly or off if the voltage rises to unsafe levels. It keeps the battery running while helping to avoid damage, preserving battery life in the short and long term.
Battery Management Systems
A battery management system, or BMS, is necessary when you need more precise control over multiple batteries. They provide all of the standard protection involved with simpler systems while monitoring individual cells and the system as a whole.
A BMS can do any of the following:
Preserve the life of the battery and keep it safe to use
Report the state of the battery’s charge and capacity
Indicate when the battery is in need of replacement
Warn the user when the battery needs repair or when the voltage flow is too high
The most important difference between a BMS and a simpler battery protection system is the ability of the BMS to monitor each cell as well as the full system.
Individual cell monitoring is critical for battery health because systemwide malfunctions often show themselves at the individual cell level first. By monitoring the voltage in each cell and alerting the user to voltage overages or drops, a BMS can prompt repair of issues such as corrosion or dry-out before they do extensive damage.
In addition to monitoring, a BMS provides safety protection during key processes, including charging and discharging and disconnects the battery in case of failure or safety hazard. It integrates completely with the machine’s software system, allowing the user to get battery alerts as readily as texts or emails.
The Takeaway
Battery protection systems ensure the correct flow of voltage through your batteries, protecting your machinery as well as the health and safety of your personnel.
At Himax, we understand that battery protection is an essential safety function. We offer a variety of products to meet the needs of our industrial clients, and we take pride in our ability to help you select the right product for your business.
If you’re in need of a custom battery or battery charger, contact us today to get started.
https://himaxelectronics.com/wp-content/uploads/2021/05/Battery-BMS.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-05-05 02:53:342024-04-26 03:59:22What Are the Benefits of Battery Protection Systems?
As technology advances, portable energy solutions are becoming more available and more sophisticated. Highly specialized technologies call for highly specialized batteries.
Custom OEM batteries can help your business operate more efficiently and increase your profits. Himax has many years of experience in designing batteries for Lead-acid replacement, as well as in other industrial and commercial industries. Our custom battery solutions have the power to fulfill your mission-critical requirements and advance your company’s reputation.
How Custom OEM Batteries Benefit Your Brand
Precision Safety
High-quality custom batteries are specifically designed with your product’s application in mind. For instance, your product might be designed for operation in harsh, dirty, or dangerous conditions, in which case you need custom OEM batteries that can operate in rigorous environments for long periods of time.
Whether it’s strong winds, high altitudes, varying humidity levels, extreme temperatures, or other challenging environmental conditions, you need a custom battery that will power through without failure or malfunction. An experienced company will design and develop custom batteries to suit your product and application while implementing safety features that protect your investment and your reputation.
Optimal Performance
When you use high-quality, custom OEM batteries, you enhance your product’s performance. Precisely engineered batteries not only minimize safety hazards to people and investments, but they also reduce wasted energy. This increased energy efficiency optimizes your product’s potential, which positions you ahead of the competition.
Additionally, custom OEM batteries for drones and other high-tech applications can be used as primary power sources or as backup sources for protection in the case of a combustion engine failure or other critical issues. Many custom OEM batteries can also be used in hybrid fuel or battery systems, enhancing performance while providing flexibility.
Increased Endurance
The increased energy efficiency provided by custom OEM batteries also increases your product’s endurance. Drone batteries and other technical-use batteries have come a very long way in terms of longevity, but nothing improves endurance like a custom battery solution. When your product goes farther and lasts longer than the competition’s, it increases your brand’s credibility. That translates to boosted sales.
Targeted Testing
High-quality, custom OEM batteries undergo rigorous, application-specific testing to guarantee their performance, durability, and strength when used in your product. You’ll want to know how your custom commercial or industrial battery performs while engaged in various applications and under specific conditions.
Reputable and experienced companies ensure functionality by performing both routine and additional mechanical testing for custom battery designs. Routine tests include component inspection, in-process inspection, and final testing on the completed product. Additional tests should be performed according to your application’s requirements. Reputable companies maintain complete testing data records that can be supplied upon request.
Direct Support & Transparency
Look for a portable energy solutions company that will provide direct and continual support for your custom OEM batteries. They should be well-staffed, with after-sales support to ensure that you always receive the answers you need, when you need them.
For your custom OEM battery needs, you’ll want to partner with a company that has access to an extensive, highly vetted network with a strong global presence. Experienced and reputable companies are forthcoming about their supply chains and professional network, so be sure you ask the right questions.
Additionally, any company you partner with should be transparent concerning their security protocols, especially regarding their supply chains in Asian markets. Find out how they intend to keep your sensitive IP projects secure.
Himax Delivers Safe and Professional Custom Battery Solutions
At Himax, we value innovation and integrity. We partner with you to generate, design and implement custom battery solutions and custom charging solutions for your critical operations.
For over 15 years we’ve supplied the energy, aerospace, and automation industries with high-quality, reliable, custom OEM batteries. We’ll work closely with your design team to ensure timely delivery. We’re here to provide support throughout the process and after the sale.
If you’d like to learn more about how our custom OEM batteries can benefit your product or company, please contact us today.
https://himaxelectronics.com/wp-content/uploads/2021/04/200ah-12v-Battery-Pack.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-04-30 08:10:502024-04-26 06:59:54Why Are Custom Battery Designs Essential for Your Project?
The SEI (solid electrolyte interphase) is formed on the surface of the anode from the electrochemical reduction of the electrolyte and plays a crucial role in the long-term cyclability of a lithium-based battery.
Introduction of SEI
During the first charge and discharge of a lithium-ion battery, the electrode material reacts with the electrolyte at the solid-liquid phase interface. After the reaction, a thin film forms on the surface of the electrode material, where Li+ can be embedded and removed freely while electrons cannot. The SEI is about 100-120 nm thick, and it is mainly composed of various inorganic components, such as Lithium Carbonate (Li2CO3), Lithium Fluoride (LiF), Lithium Oxide (Li2O), Lithium Hydroxide (LiOH), as well as some organic components like Lithium Alkyl Carbonates (ROCO2Li).
Source of SEI
When a lithium-ion battery starts to charge and discharge, the lithium ions are extracted from the active material of the positive electrode. At which point, they enter the electrolyte, penetrate the separator, enter the electrolyte, and finally embed themselves into the layered gap of the negative carbon material.
Electrons then come out of the positive electrode along the outer end loop and enter the negative electrode carbon material. At this point, an oxidation-reduction reaction occurs between the electrons, the solvent in the electrolyte, and the lithium ions. As the thickness of the SEI increases to the point where electrons cannot penetrate it, a passivation layer is formed, which inhibits the continuation of the redox reaction.
SEI’s impact on batteries
The formation of the SEI film has a crucial impact on the performance of electrode materials. On one hand, in the formation of the SEI film, parts of the lithium ions are consumed, which increases the irreversible capacity of batteries and reduces the charge and discharge efficiency of the electrode material.
On the other hand, the SEI is insoluble in organic solvents and can exist in stable conditions in organic electrolyte solutions. Furthermore, solvent molecules cannot pass through it, thus effectively preventing the co-embedding of the ions and avoiding damage to the electrode material. This greatly improves the cycling performance and service life of the battery.
SEI’s affecting factors
The formation of the SEI is mainly influenced by the following aspects. First, electrolytes (Li salts, solvents, admixtures, etc.), with different compositions will result in different SEI compositions and affect the stability. Next, the formation, that is, the intensity of the first charge and discharges current. High temperature will also reduce the stability of the SEI and affect the battery cycle life. In addition, the thickness of the SEI changes based on the type of negative electrode material.
Conclusion
In-depth research on the SEI with its formation mechanism, structure and stability, and further search for effective ways to improve the performance have been hot topics of research in the electrochemical community.
https://himaxelectronics.com/wp-content/uploads/2021/04/What-Is-The-SEI.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-04-13 02:41:002024-04-28 15:42:16What Is The SEI, And What Effect Does It Have On The Battery?
The power output depends on the battery, and the battery management system (BMS) is the core of it. It is a system for monitoring and managing the battery. It controls the charge and discharge of the battery by collecting and calculating parameters such as voltage, current, temperature, and SOC. The process, the management system that realizes the protection of the battery and improves the overall performance of the battery is an important link between the battery and the battery application equipment.
BMS mainly includes three parts: hardware, bottom layer software, and application layer software.
The hardware of the battery management system (BMS)
1. Architecture
The topology of Battery Management System(BMS) hardware is divided into two types: centralized and distributed.
(1) The centralized type
The centralized type is to concentrate all the electrical components into a large board, the sampling chip channel utilization is the highest and the daisy chain communication can be adopted between the sampling chip and the main chip, the circuit design is relatively simple, the product cost is greatly reduced, but All the collection wiring harnesses will be connected to the mainboard, which poses a greater challenge to the security of the BMS, and there may also be problems in the stability of the daisy chain communication. It is more suitable for occasions where the battery pack capacity is relatively small and the module and battery pack types are relatively fixed.
(2) The Distributed type
Distributed includes a mainboard and a slave board. It is possible that a battery module is equipped with a slave board. The disadvantage of this design is that if the number of battery modules is less than 12, the sampling channel will be wasted (generally there are 12 sampling chips. Channel), or 2-3 slave boards to collect all battery modules. This structure has multiple sampling chips in one slave board. The advantages are high channel utilization, cost-saving, flexibility in system configuration, and adaptation to different capacities. Modules and battery packs of different specifications and types.
2. Function
The hardware design and specific selection should be combined with the functional requirements of the vehicle and battery system. The general functions mainly include collection functions (such as voltage, current, and temperature collection), charging port detection (CC and CC2), and charging wake-up (CP and A+) ), relay control and status diagnosis, insulation detection, high voltage interlock, collision detection, CAN communication and data storage requirements.
(1) Main controller
Process the information reported from the controller and the high-voltage controller, and at the same time judge and control the battery operating status according to the reported information, realize the BMS-related control strategy, and make the corresponding fault diagnosis and processing.
(2) High voltage controller
Collect and report the total voltage and current information of the battery in real-time, and realize timely integration through its hardware circuit, and provide accurate data for the calculation of the state of charge (SOC) and the state of health (SOH) for the motherboard. Charge detection and insulation detection function.
(3) Slave controller
Real-time collection and reporting of battery cell voltage and temperature information, feedback of the SOH and SOC of each string of cells, and a passive equalization function, effectively ensuring the consistency of cells during power use.
(4) Sampling control harness
Provide hardware support for battery information collection and information interaction between controllers, and at the same time add redundant insurance function to each voltage sampling line, effectively avoid battery short circuit caused by wiring harness or management system.
3. Communication method
There are two ways to transfer information between the sampling chip and the main chip: CAN communication and daisy chain communication. CAN communication is the most stable. However, due to the high cost of power chips and isolation circuits, daisy chain communication is actually SPI communication. The cost is very low, and the stability is relatively poor. However, as the pressure on cost control is increasing, many manufacturers are shifting to the daisy chain mode. Generally, two or more daisy chains are used to enhance communication stability.
4. Structure
BMS(Battery Management System) hardware includes power supply IC, CPU, sampling IC, high-drive IC, other IC components, isolation transformer, RTC, EEPROM, CAN module, etc. The CPU is the core component, and the functions of different models are different, and the configuration of the AUTOSAR architecture is also different. Sampling IC manufacturers mainly include Linear Technology, Maxim, Texas Instruments, etc., including collecting cell voltage, module temperature, and peripheral configuration equalization circuits.
Bottom layer software
According to the AUTOSAR architecture, it is divided into many general functional modules, which reduces the dependence on hardware, and can realize the configuration of different hardware, while the application layer software changes little. The application layer and the bottom layer need to determine the RTE interface, and consider the flexibility of DEM (fault diagnosis event management), DCM (fault diagnosis communication management), FIM (function information management), and CAN communication reserved interfaces, which are configured by the application layer.
Application layer software of the BMS
The software architecture mainly includes high and low voltage management, charging management, state estimation, balance control, and fault management, etc.
1. High and low voltage management
Generally, when the power is on normally, the VCU will wake up the BMS through the hardwire or 12V of the CAN signal. After the BMS completes the self-check and enters the standby mode, the VCU sends the high-voltage command, and the BMS controls the closed relay to complete the high-voltage. When the power is off, the VCU sends a high-voltage command and then disconnects and wakes up 12V. It can be awakened by CP or A+ signal when the gun is plugged in in the power-off state.
2. Charging management
(1) Slow charge
Slow charging uses an AC charging station (or 220V power supply) to convert AC to DC to charge the battery through an on-board charger. The charging station specifications are generally 16A, 32A, and 64A, and it can also be charged through a household power supply. The BMS can be awakened by CC or CP signal, but it should be ensured that it can sleep normally after charging. The AC charging process is relatively simple, and it can be developed in accordance with the detailed regulations of the national standard.
(2) Fast charge
Fast charging is to charge the battery with DC output from the DC charging pile, which can achieve 1C or even higher rate charging. Generally, 80% of the power can be charged in 45 minutes. Wake up by the auxiliary power A+ signal of the charging pile, the fast charging process in the national standard is more complicated, and there are two versions of 2011 and 2015 at the same time, and the different understanding of the technical details of the charging pile manufacturer’s unclear technical details of the national standard process also causes the vehicle charging adaptability A great challenge, so fast charging adaptability is a key indicator to measure the performance of BMS products.
3. Estimation function
(1) the State Of Power
SOP (State Of Power) mainly obtains the available charge and discharge power of the current battery through the temperature and SOC lookup table. The VCU determines how the current vehicle is used according to the transmitted power value. It is necessary to consider both the ability to release the battery and the protection of the battery performance, such as a partial power limit before reaching the cut-off voltage. Of course, this will have a certain impact on the driving experience of the whole vehicle.
(2) state of health
SOH (state of health) mainly characterizes the current state of health of the battery, which is a value between 0-100%. It is generally believed that the battery can no longer be used after it is lower than 80%. It can be expressed by the change of battery capacity or internal resistance. When using the capacity, the actual capacity of the current battery is estimated through the battery operating process data, and the ratio of the rated capacity to the rated capacity is the SOH. Accurate SOH will improve the estimation accuracy of other modules when the battery decays.
(3) the State Of Charge
SOC (State Of Charge) belongs to the BMS core control algorithm, which characterizes the current remaining capacity state, mainly through the ampere-hour integration method and EKF (Extended Kalman Filter) algorithm, combined with correction strategies (such as open-circuit voltage correction, full charge correction, charging End correction, capacity correction under different temperatures and SOH, etc.). The ampere-hour integration method is relatively reliable under the condition of ensuring the accuracy of current acquisition, but the robustness is not strong. Because of the error accumulation, it must be combined with a correction strategy. The EKF has strong robustness, but the algorithm is more complex and difficult to implement. Domestic mainstream manufacturers generally can achieve accuracy within 6% at room temperature, and it is difficult to estimate high and low temperatures and battery attenuation.
(4) the State Of Energy
SOE (State Of Energy) algorithm manufacturers do not develop much now or use a simpler algorithm, look up the table to get the ratio of the remaining energy to the maximum available energy in the current state. This function is mainly used to estimate the remaining cruising range.
4. Fault diagnosis
According to the different performance of the battery, it is divided into different fault levels, and in the case of different fault levels, the BMS and VCU will take different treatment measures, warning, limiting power, or directly cutting off the high voltage. Failures include data collection and rationality failures, electrical failures (sensors and actuators), communication failures, and battery status failures.
5. Balance control
The equalization function is to eliminate the inconsistency of the battery cells generated during battery use. According to the shortboard effect of the barrel, the cells with the worst performance during charging and discharging first reach the cut-off condition, and the other cells have some capabilities. It is not released, causing battery waste.
Equalization includes active equalization and passive equalization. Active equalization is the transfer of energy from more monomers to fewer monomers, which will not cause energy loss, but the structure is complex, the cost is high, and the requirements for electrical components are relatively high. Relatively passive The balance structure is simple and the cost is much lower, but the energy will be dissipated and wasted in the form of heat. Generally, the maximum balance current is about 100mA. Now many manufacturers can achieve better balance effects using passive balance.
The BMS(Battery Management System) control method, as the central control idea of the battery, directly affects the service life of the battery, the safe operation of the electric vehicle, and the performance of the entire vehicle. It has a significant impact on battery life and determines the future of new energy vehicles. A good battery management system will greatly promote the development of new energy vehicles.
https://himaxelectronics.com/wp-content/uploads/2021/03/Battery-Bms.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-03-16 03:48:572024-04-29 01:27:58What is a Battery Management System (BMS)?
Lithium-ion polymer batteries are widely used due to their long life and high capacity. However, there are some issues that can arise, such as swelling, unsatisfactory safety performance, and accelerated cycle attenuation.
This article will primarily focus on battery swelling and its causes, which can be divided into two categories: the first is a result of a change in thickness of the electrode, and the other is a result of the gas produced by the oxidation and decomposition of electrolytes.
The change in thickness of the electrode pole piece
When a lithium battery is used, the thickness of the electrode pole pieces, especially the graphite negative electrodes, will change to a certain extent.
Lithium batteries are prone to swelling after high-temperature storage and circulation, and the thickness growth rate is about 6% to 20%. Of this, the expansion rate of the positive electrode is only 4%, the negative electrodes is more than 20%.
The fundamental reason for the increase in the thickness of the lithium battery pole piece is due to the nature of graphite. The negative electrode graphite forms LiCx (LiC24, LiC12, LiC6, etc.) when lithium is inserted, and the lattice spacing changes, resulting in microscopic internal stress and an expansion of the negative electrode.
The figure is the schematic diagram of the structure change of the graphite anode plate in the process of placement, charge, and discharge.
The expansion of graphite negative electrodes is mainly caused by irreversible expansion after lithium insertion. This part of the expansion is mainly related to the particle size, the adhesive, and the structure of the pole piece. The expansion of the negative electrode causes the core to deform, which in turn causes the following: a cavity between the electrode and the diaphragm, micro-cracks in the negative electrode particles, breaking and reorganizing of the solid electrolyte interface (SEI) membrane, the consummation of electrolytes, and deterioration of the cycle performance.
There are many factors that affect the thickness of the negative pole piece although the properties of the adhesive and the structural parameters of the pole piece are the two most important reasons.
The commonly used bonding agent for graphite negative electrodes is SBR. Different bonding agents have different elastic modulus and mechanical strength and have different effects on the thickness of the pole piece. The rolling force after the pole piece is coated also affects the thickness of the negative pole piece in battery use.
When the amount of SBR added is inconsistent, the pressure on the pole piece during rolling will be different. Different pressures will cause a certain difference in the residual stress generated by the pole piece. The higher the pressure, the greater the residual stress, which leads to physical storage expansion, a full electric state, and an increase in the expansion rate of the empty electric state.
The expansion of the anode leads to the deformation of the coil core, which affects the lithium intercalation degree and Li + diffusion rate of the negative electrode, thus seriously affecting the cycle performance of the battery.
Bloating caused by lithium battery gas production
The gas produced in the battery is another important cause of battery swelling. Dependent on whether the battery is in a normal temperature cycle, high-temperature cycle, or high-temperature shelving, it will produce different degrees of swelling and gas production.
According to the current research results, cell bloating is essentially caused by the decomposition of electrolytes. There are two cases of electrolyte decomposition: one is that there are impurities in the electrolyte, such as moisture and metal impurities, which cause the electrolyte to decompose and produce gas. The other is that the electrochemical window of the electrolyte is too low, which causes decomposition during the charging process.
After a lithium battery is assembled, a small amount of gas is generated during the pre-formation process. These gases are inevitable and are also the source of irreversible capacity loss of the battery.
During the first charging and discharging process, the electrons from the external circuit to the negative electrode react with the electrolyte on the surface of the negative electrode to generate the gas. During this process, the SEI is formed on the surface of the graphite negative electrode. As the thickness of the SEI increases, electrons cannot penetrate and inhibit the continuous oxidation and decomposition of the electrolyte.
When a battery is used, the internal gas production gradually increases due to the presence of impurities in the electrolyte or excessive moisture in the battery. These impurities in the electrolytes need to be carefully removed. Inadequate moisture control may be caused by the electrolyte itself, improper battery packaging, moisture, or damage to the corners. Any overcharge and over-discharge, abuse, and internal short-circuiting will also accelerate the gas production rate of the battery and cause battery failure.
In different systems, the degree of battery swelling is different.
For instance, in the graphite anode system battery, the main causes of gas swelling are the SEI film formation, excessive moisture in the cell, abnormal chemical conversion process, poor packaging, etc.
In the lithium titanate anode system, battery swelling is more serious. In addition to the impurities and moisture in the electrolyte, lithium titanate cannot form an SEI film on its surface like a graphite-anode system battery to inhibit its reaction to the electrolyte.
https://himaxelectronics.com/wp-content/uploads/2021/01/Causes-of-Lithium-Battery-Swelling.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2021-01-22 02:18:142024-04-29 01:23:06What Causes Lithium Batteries To Swell?
This week, we discuss the differences you experience when using lithium compared to lead-acid batteries. We compare everything from installation to weight and speed. Watch the full video to learn more about the benefits of switching to lithium.
Transcript:
Let’s start with installation. Lithium batteries are half the weight of the same capacity lead-acid batteries making them much easier to lift and install into your vehicle or equipment. A 100 Amp-hour lithium batteries weighs less than 30 lbs.!
The first thing people notice with lithium batteries when they operate their equipment, whether it’s a boat, golf cart or any other type of vehicle, is the feel. The reduced weight and higher power provided by lithium batteries, results in a noticeably faster and smoother ride.
The higher voltage of a lithium battery provides more power, which increases the ability to accelerate. You can reach top speed faster and more often. When maneuvering up a hill, or with a heavier load, or against the current, with lead-acid batteries, you just can’t reach full speed but with lithium batteries you can and do!
When lithium batteries are used for house power in an RV, people often use the benefit of less weight and more power, to add more of the items they really want in their RV.
You will experience full power throughout use. It is not uncommon to run accessories off your battery bank in a vehicle. With lead-acid batteries this can be problematic. For example, while powering a boat with lead-acid batteries, at some point the voltage will drop too low to allow the accessories to operate. With lithium you won’t lose power to those accessories as the voltage remains high until the batteries are fully depleted.
Another notable experience with lithium batteries is how long they last. You won’t be replacing your batteries every 1-5 years, depending on your particular application.
Equally important to what you experience is what you don’t experience. Let me explain.
You won’t experience a loss of valuable time. This point is two-fold in charging AND maintenance. First, lithium charges four to six times faster than lead acid. So there’s less time (and electricity) to recharge. Second, with lead-acid batteries you can’t avoid spending time cleaning acidic messes on the top of the batteries, in the battery compartment and on the floor. If you let it go too long, you may have to change battery cables due to corrosive build-up. With lithium there is no mess to clean up ever!
Finally, lead-acid batteries are easy to damage. Even with the best intentions, at some point, we will most likely not add water when needed, or not fully charge our batteries or leave them discharged for an extended period of time, resulting in permanent damage, shortening life. None of this impact’s lithium batteries. Lithium batteries truly provide peace of mind.
In fact, lithium batteries are so reliable and maintenance-free, you might even forget you have them!
https://himaxelectronics.com/wp-content/uploads/2020/12/Lithium-Vs.-Lead-Acid.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-12-29 06:05:142024-04-26 03:55:47The Experience Using Lithium Vs. Lead-Acid
In today’s mobile world, standard lithium-ion batteries are used in a myriad of situations, and battery life comes to be precious. It can be especially annoying when a mobile device has to be charged in a public place with only one available outlet.
There are many reports on how to save battery power, but what can we do to extend battery life? Here are a few ways that Himax has you covered.
Keep the battery at room temperature
Store the battery between 20 to 25℃. During the charging process, the temperature of the battery will increase due to the electric current. Therefore, do not leave your battery in the car or charge it if the temperature inside the car is too high. Heat is the biggest factor in shortening the life of a lithium battery.
Consider purchasing a high-capacity rectangle lithium battery
Standard rectangular rechargeable batteries will degrade over time regardless of whether they are used or not. As a result, spare batteries will not last longer than batteries in use. When purchasing a battery, be sure to ask about the latest manufacturing date of the product.
Avoid completely discharging the lithium battery
If the discharge voltage of each cell of astandard lithium-ion battery falls below 2.5V, the safety circuit built into the battery will break, and the battery will appear to be depleted. For safety reasons, do not charge an over-discharged lithium-ion battery if it has been stored under these conditions.
If you are storing the lithium batteries for an extended period of time, store them at a storage charge in a cool place. Only by storing the battery properly can excessive power consumption be minimized and the life of the battery extended.
Stay tuned for more battery technology or visit Grepow’s Website now: https://www.grepow.com/
https://himaxelectronics.com/wp-content/uploads/2020/04/solar-street-battery.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-12-01 04:04:462024-04-26 03:55:27How to Extend the Life Of Standard Lithium-ion Battery?
Lithium-ion (Li-ion) batteries are inarguably the most popular type of rechargeable battery for consumer electronics. They can be used for a variety of products from mobile phones to cars, and their qualities are superior compared to other rechargeable batteries.
At NightSearcher we use high-quality lithium-ion (Li-ion) batteries for all but a few of our rechargeable flashlights, searchlights, head torches, and floodlights, as they allow us to provide the high-performance, durable products our customers are used to.
Below we’ve listed the biggest advantages of lithium-ion batteries from the customers’ point of view and delved into the science behind each characteristic.
Eco-friendly:
Lithium-ion batteries contain relatively low levels of toxic heavy metals found in other types of batteries, such as lead-acid and nickel-cadmium (NiCd) batteries. Cadmium, lead, and mercury have been battery stalwarts for years, but prolonged exposure to, and inadequate disposal of these metals is harmful to humans, animals, and plants. Although Li-ion batteries are safer than many other types of batteries they still require proper recycling, so never put your used batteries in with your regular rubbish.
Lightweight and compact:
Electrodes commonly used in lithium-ion batteries, lithium and carbon, are lightweight on their own, making for much smaller and lighter batteries than their older counterparts such as lead-acid batteries. For comparison’s sake, a typical 51Ah (= ampere-hour) lithium-ion battery weighs about the same as a 24Ah lead-acid battery (about 6-7kg), but provides over twice the capacity.
This particular characteristic of lithium-ion batteries is especially convenient in head torches, as we can increase the light output and runtime significantly without adding bulk and weight to the battery pack (and on your head!).
High energy density = A bigger punch:
Lithium is a highly reactive element with the ability to release and store large amounts of energy, allowing li-ion batteries to pack a high energy capacity in a small size. This translates to lithium-ion batteries lasting much longer between charges than other rechargeable batteries, while still maintaining their high level of performance.
A typical lithium-ion cell (= battery) has an average cell voltage of 3.6V, whereas a nickel-metal hydride (NiMH) cell averages at 1.2V, meaning three Ni-MH batteries are required to match the output of a single lithium-ion battery.
Low maintenance:
Older types of rechargeable batteries, such as nickel-cadmium or nickel-metal hydride batteries had a so-called “memory effect”, or “lazy battery effect”: If they were repeatedly partially discharged before being recharged, ultimately the battery would only deliver the amount of energy that was used during the partial discharges before its voltage would drop. To avoid this, NiCd and NiMH batteries would need to be regularly maintained by completely discharging and recharging them.
Lithium-ion batteries don’t suffer from the memory effect, which means they always give up their last bit of power, and you can recharge them whether you’ve used 100% or 25% of their capacity with no pesky maintenance needed!
More charge cycles:
Quality lithium-ion batteries last about a 1000 full charge cycles. A full charge cycle is when the battery is discharged to flat and then recharged to full, so using your battery until it’s at 75% capacity and then plugging it into recharge doesn’t constitute a full charge cycle. When your battery has recharged back to full, you can still use the 75% of the capacity that you were left with before you recharged your battery; only then has your battery gone through a full charge cycle.
Low self-discharge rate
Lithium-ion batteries also have a relatively low self-discharge rate. Self-discharge is a natural, irreversible phenomenon for batteries, where chemical reactions inside the batteries reduce their capacity even when the battery is not being used. The self-discharge rate of lithium-ion batteries peaks at about 5% within the first 24 hours after charging the battery, and then tapers off to 1-2% per month. In comparison, nickel-based rechargeable batteries lose about 10-15% of their capacity after charge and another 10-15% per month.
https://himaxelectronics.com/wp-content/uploads/2019/12/Recycle-Lithium-Batteries.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-11-24 03:36:012024-04-26 07:54:13Advantages of Lithium-ion Batteries
