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Introduction: Supercapacitor is a charge storage device which stores electrical charge via electrochemical and electrostaticprocesses. Due to their benefits as mentioned below, they have potential to replace or complement traditional batteries andcapacitors in various applications. They are being used worldwide in. Following are the benefits or advantages of Supercapacitor: ➨It offers high energy density and high power density compare to common capacitor. ➨It. Following are the drawbacks or disadvantages of Supercapacitor: ➨They have higher self discharge rate. This is considerably high compare to battery. ➨Individual cells have low voltages. Hence series connections.
Batteries have the disadvantage in this characteristic due to the chemical reactions that take place to store and release energy. Supercapacitors have faster charge and discharge rates than batteries because the chemical reactions that take place within batteries take longer to release electrons than the electrical discharge in supercapacitors.
Advantages of the battery: Disadvantages of the batteries are: Can you use a capacitor in place of a battery: In short - no. The issue is that the applications om which we use batteries rely on the battery's capacity to power the application.
Batteries will have a higher energy density meaning that they can store more energy than supercapacitors but have a latency transferring the chemical energy into electrical energy.
Supercapacitors have faster charge and discharge rates than batteries because the chemical reactions that take place within batteries take longer to release electrons than the electrical discharge in supercapacitors. Chemical reactions are the limiting factor for the lifetime of batteries.
While supercapacitors have many attractive features, they are not yet able to completely replace batteries in all applications. This is because they have a lower energy density than batteries, which means they are not able to store as much energy in a given volume or weight.
The discharge rate of supercapacitors is significantly higher than lithium-ion batteries; they can lose as much as 10-20 percent of their charge per day due to self-discharge. Gradual voltage loss. While batteries provide a near-constant voltage output until spent, the voltage output of capacitors declines linearly with their charge.
Cycle life can be negatively impacted when batteries from different manufacturers are charged in the same manner. Even the same types of batteries, such as Li-lon and NiMH, may require separate charging considerations. Inspection of the manufacturer's data sheet revealed that some types of NiMH batteries can take a. Insufficient run time is caused by undercharging the battery, which can happen by misapplying technology. For example, charging of a 4.2. By ensuring proper Li-Ion and NiCd battery charging, your result is improved time-to-market, reduced development costs, and a finely tuned battery and charger system. Avoiding all of these overarching concerns. The "one stop shop" approach to custom battery packsand chargers is extremely beneficial to the person purchasing the batteries and chargers. If the battery pack and charger are ordered.
[PDF Version]The blue wire W1 must be connected to the opposite end of the battery pack as the black wire at the top of the battery pack. When batteries are connected in parallel, only use one charger. Do not connect a charger to each battery, unless you break the electrical connection between the batteries.
To charge the battery, set the charger to the appropriate settings as indicated in the user manual. Turn on the charger and monitor for any unusual signs such as overheating or fumes. The charging time will vary based on the battery size and charger type.
Do not mix and match different battery voltages in the same battery pack. In this example the battery pack voltage is 12 volts which is exactly the same as each of the individual 12-volt batteries. The capacity of the battery pack is the sum of the capacities of the individual batteries.
Batteries connected in series strings can also be recharged by a single charger having the same nominal charging voltage output as the nominal battery pack voltage. In Figure 8, a single 24-volt charger is connected to a 24-volt battery pack. In Figure 9 we see a pair of 12-volt batteries connected in parallel.
How to use a battery charger and the battery type should be determined first—lead-acid, lithium-ion, or any other—as each requires a different charger. To ensure a smooth connection, match the charger and battery voltage and amperage specifications.
When batteries are connected in parallel, only use one charger. Do not connect a charger to each battery, unless you break the electrical connection between the batteries. The reason is that the chargers will very likely complete one or more their charging subroutines (charge modes or stages) at different times.
The full battery designation identifies not only the size, shape and terminal layout of the battery but also the chemistry (and therefore the voltage per cell) and the number of cells in the battery. For example, a CR123 battery is always LiMnO 2 ('Lithium') chemistry, in addition to its unique size. This is a list of the sizes, shapes, and general characteristics of some common primary and secondary in household, automotive and light industrial use. The complete no. Coin-shaped cells are thin compared to their diameter. is usually stamped on the metal casing. The IEC prefix "CR" denotes lithium manganese dioxide chemistry. Since LiMnO2 cells pro.
Batteries can be classified according to their chemistry or specific electrochemical composition, which heavily dictates the reactions that will occur within the cells to convert chemical to electrical energy. Battery chemistry tells the electrode and electrolyte materials to be used for the battery construction.
Although BCI is the most common battery group classification system in the United States, others do exist. EN and DIN are other battery group classification systems that you will sometimes see in owner's manuals or when shopping for batteries.
In this study, two types of classification settings are considered. The first setting considers y i = {0 1}, which is a binary classification task grouping batteries into {s h o r t, l o n g} lifetime.
The complete nomenclature for a battery specifies size, chemistry, terminal arrangement, and special characteristics. The same physically interchangeable cell size or battery size may have widely different characteristics; physical interchangeability is not the sole factor in substituting a battery. [ 1 ]
Considering the above, it appears timely to propose a simple and uniform classification system encompassing all battery types. Conceptually, every battery is simply made of three layers: positive electrode layer, electrolyte layer, negative electrode layer.
Primary batteries come in three major chemistries: (1) zinc–carbon and (2) alkaline zinc–manganese, and (3) lithium (or lithium-metal) battery. Zinc–carbon batteries is among the earliest commercially available primary cells. It is composed of a solid, high-purity zinc anode (99.99%).
A lead-acid battery consists of two lead plates separated by a liquid or gel containing sulfuric acid in water. The battery is rechargeable, with charging and discharging chemical reactions. When the battery is being used (discharged), electrons move from the negatively-charged lead plate to the positively-charged plate. The. When the battery is fully charged, the negative plate is lead, the electrolyte is concentrated sulfuric acid, and the positive plate is lead dioxide. If the battery is overcharged, electrolysis of water produces hydrogen gas. Calling sulfuric acid"battery acid" gives an indication of the acid concentration. There are, in fact, several different names for sulfuric acid that typically reflect its usage. 1. Concentration less than.
The battery acid is made of sulfuric acid (H2So4) diluted with purified water to get an overall concentration of around 29-32, a density of 1.25-1.28 kg/L, and a concentration of 4.2 mol/L. The pH value of electrolytes is about 0.8, so we need to take utmost care when handling battery acid. What Is Battery Acid?
Batteries contain acid because it's fundamental to the electrochemical reaction that takes place. Also referred to as battery electrolyte, battery acid is the medium that carries the electrical flow between positive and negative electrodes.
Car battery acid is around 35% sulfuric acid in water. Battery acid is a solution of sulfuric acid (H 2 SO 4) in water that serves as the conductive medium within batteries. It facilitates the exchange of ions between the battery's anode and cathode, allowing for energy storage and discharge.
Battery acid primarily refers to sulfuric acid, with the chemical formula H2SO4. Now, if we break that down, we get two hydrogen atoms, one sulfur atom, and four oxygen atoms working together in harmony to perform a critical role in the battery's operations. Think of it as the fuel that powers the entire battery system. Why Sulfuric Acid?
Battery acid (AKA sulfuric acid) is used in lead-acid batteries to help create and store electrical energy, which powers many devices and vehicles.
These batteries are highly corrosive, and react vigorously with the skin, causing burns and irritation. Battery acids have a high electrical conductivity. Usually, these acids are colorless. However, they can easily pick on impurities. The density of an acid battery is twice that of water.
The zinc–bromine (ZBRFB) is a hybrid flow battery. A solution of is stored in two tanks. When the battery is charged or discharged, the solutions (electrolytes) are pumped through a reactor stack from one tank to the other. One tank is used to store the electrolyte for positive electrode reactions, and the other stores the negative. range between 60 and 85 W·h/kg.
Zinc bromine flow batteries or Zinc bromine redux flow batteries (ZBFBs or ZBFRBs) are a type of rechargeable electrochemical energy storage system that relies on the redox reactions between zinc and bromine. Like all flow batteries, ZFBs are unique in that the electrolytes are not solid-state that store energy in metals.
Three examples of zinc–bromine flow batteries are ZBB Energy Corporation′s Zinc Energy Storage System (ZESS), RedFlow Limited′s Zinc Bromine Module (ZBM), and Premium Power′s Zinc-Flow Technology.
Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to the inherent high energy density and low cost. However, practical applications of this technology are hindered by low power density and short cycle life, mainly due to large polarization and non-uniform zinc deposition.
While zinc bromine flow batteries offer a plethora of benefits, they do come with certain challenges. These include lower energy density compared to lithium-ion batteries, lower round-trip efficiency, and the need for periodic full discharges to prevent the formation of zinc dendrites, which could puncture the separator.
The leading potential application is stationary energy storage, either for the grid, or for domestic or stand-alone power systems. The aqueous electrolyte makes the system less prone to overheating and fire compared with lithium-ion battery systems. Zinc–bromine batteries can be split into two groups: flow batteries and non-flow batteries.
In the early stage of zinc–bromine batteries, electrodes were immersed in a non-flowing solution of zinc–bromide that was developed as a flowing electrolyte over time. Both the zinc–bromine static (non-flow) system and the flow system share the same electrochemistry, albeit with different features and limitations.
There are several options that can be used in to help mitigate the risk presented by lithium-ion battery charging, they include:Place the battery in an appropriately located fire compartment with access for maintenance and repair. Environmentally controlled environments, to prevent overheating of the space. Provide battery thermal management devices that automatically cut charging if issues detected.
Over the past four years, insurance companies have changed the status of Lithium-ion batteries and the devices which contain them, from being an emerging fire risk to a recognised risk, therefore those responsible for fire safety in workplaces and public spaces need a much better understanding of this risk, and how best to mitigate it.
There are several options that can be used in to help mitigate the risk presented by lithium-ion battery charging, they include: Place the battery in an appropriately located fire compartment with access for maintenance and repair. Environmentally controlled environments, to prevent overheating of the space. Fire Detection. Fire Suppression.
With the advantages of high energy density, short response time and low economic cost, utility-scale lithium-ion battery energy storage systems are built and installed around the world. However, due to the thermal runaway characteristics of lithium-ion batteries, much more attention is attracted to the fire safety of battery energy storage systems.
A survey of more than 500 organisations carried out between September 2023 and February 2024 revealed that 71 per cent of respondents had not updated their fire risk assessments to cover the risk of Lithium-ion battery fires, with just 15 per cent having done so and a further 14 per cent unsure.
This guide focusses on fire hazards and good-practice risk control measures for the charging of EVs using lithium-ion batteries, driven on highways, (i.e. cars, motorcycles, bicycles, lorries, coaches/buses, etc.) Lithium-ion batteries are the predominant type of rechargeable battery used in EVs.
Specific risk control measures should be determined through site, task and activity risk assessments, with the handling of and work on batteries clearly changing the risk profile. Considerations include: Segregation of charging and any areas where work on or handling of lithium-ion batteries is undertaken.
For the purposes of this document, the following terms and definitions apply; Power Generating Modules are categorised in EREC G99 as Power Park Modules (PPM) or Synchronous Power Generating Modules (SPGM). Both contain one or more. When you are ready to submit a formal application for connection, we will require information from you to enable us to make a reasonable assessment of the works required to facilitate the. Discussing your plans with us at an early stage can help to provide a better insight to any potential network reinforcement and complexity issues that. If you are not ready to enter into a formal agreement for connection works, or you do not yet have full details of the specific conditions required, you.
Learn how raw materials like lead, sulfuric acid, and water come together to form these essential energy storage devices. From grid casting to battery formation, we explain each step in detail.
This document provides an overview of the lead acid battery manufacturing process. It discusses the key steps which include alloy production, grid casting, paste mixing and pasting, plate curing, and assembly. The alloy production process involves preparing mother alloy and KL-alloy from reclaimed lead using furnaces.
The lead battery is manufactured by using lead alloy ingots and lead oxide It comprises two chemically dissimilar leads based plates immersed in sulphuric acid solution. The positive plate is made up of lead dioxide PbO2 and the negative plate with pure lead.
A typical lead–acid battery contains a mixture with varying concentrations of water and acid. Sulfuric acid has a higher density than water, which causes the acid formed at the plates during charging to flow downward and collect at the bottom of the battery.
During the charging process, the cycle is reversed, that is, lead sulphate and water are converted to lead, lead oxide and electrolyte of sulphuric acid by an external charging source. This process is reversible, which means lead acid battery can be discharged or recharged many times.
The positive plate is made up of lead dioxide PbO2 and the negative plate with pure lead. The nominal electric potential between these two plates is 2 volts when these plates are immersed in dilute sulfuric acid. This potential is universal for all lead acid batteries.
In applications, a nominal 12V lead-acid battery is frequently created by connecting six single-cell lead-acid batteries in series. Additionally, it can be incorporated into 24V, 36V, and 48V batteries. Further, the lead acid manufacturing process has been discussed in detail. Lead Acid Battery Manufacturing Equipment Process 1.
Generally, large-scale battery systems such as those used in electric vehicles consist of around 200 to more than 1,000 individual cells. These are mostly connected to form modules containing around 10 to 16 cells and are installed in a battery housing. These systems' sealing components are housing gaskets, gaskets for. Usually, it has to be possible to open and close the battery housing to easily repair minor defects such as loose electrical contacts or leaking coolant lines. Depending on the housing's position in the vehicle, stability, tightness,. Automotive battery systems are subjected to pressure changes, which are inherent to such systems. They are mainly effected by atmospheric conditions, heating-up and cooling-down processes, uphill and downhill roads, entrance. The sealings to connect power electronics are usually integrated directly into the plug. Silicon rubber-based components are used for this application in most cases. They have increased. Large-scale battery systems require intelligent temperature management, which has two tasks: First, it dissipates heat from the cells and therefore protects them from overheating.
[PDF Version]Learn about the key technical parameters of lithium batteries, including capacity, voltage, discharge rate, and safety, to optimize performance and enhance the reliability of energy storage systems. Lithium batteries play a crucial role in energy storage systems, providing stable and reliable energy for the entire system.
The sealing components used also have to be chemically stable toward organic electrolytes. In addition, during the battery's entire service life, the sealing material must not leach out contaminating substances into the battery electrolyte as this could have a long-term negative influence on the cells' electrochemistry.
The adhesion of the lithium second battery can be improved by using a binder that has better adhesion performance than PVDF (poly vinylidene fluoride) or by increasing the material density of an electrode. There are a number of works regarding the binding and adhesion mechanisms and properties for use in LSB,, .
The elongation imbalance of the electrode also causes the electrode deformation during the pressing process. Such deformation subsequently induces imbalance in the electrode surface, which eventually decreases the capacity of the lithium secondary battery, , , , , .
Lithium batteries play a crucial role in energy storage systems, providing stable and reliable energy for the entire system. Understanding the key technical parameters of lithium batteries not only helps us grasp their performance characteristics but also enhances the overall efficiency of energy storage systems.
Kritzer P, Clemens M, Heldmann R (2011) Innovative seals: a robust and reliable seal design can provide efficient battery cooling cycles for electric vehicles and hybrid electric vehicles. Engine Technology International, June 2011, p. 64
Sealed lead acid batteries may be charged by using any of the following charging techniques: 1. Constant Voltage 2. Constant Current 3. Taper Current 4. Two Step Constant Voltage To obtain maximum battery ser. During constant voltage or taper charging, the battery's current acceptance decreases as voltage and state of charge increase. The battery is fully charged once the current stabilize. Selecting the appropriate charging method for your sealed lead acid battery depends on the intended u. Constant voltage charging is the best method to charge sealed lead acid batteries. Depending on the application, batteries may be charged either on a continuous or no. Constant current charging is suited for applications where discharged ampere-hours of the preceding discharge cycle are known. Charge time and charge quantity can easily be cal.
The lead-acid battery mainly uses two types of charging methods namely the constant voltage charging and constant current charging. It is the most common method of charging the lead acid battery. It reduces the charging time and increases the capacity up to 20%. But this method reduces the efficiency by approximately 10%.
Just multiply the voltages by 2 for 24V or 4 for 48V batteries. The only way to get an accurate reading of a lead acid battery's state of charge from voltage is to measure its open circuit voltage. This means the battery must be disconnected from all loads and chargers and allowed to rest for several hours until its voltage stabilizes.
The optimal charging voltage for 48V flooded lead acid batteries is typically around 58V to 62V at the start of charging. Sealed batteries may need slightly higher voltages. Refer to the battery specifications. How Can I Revive a Dead Lead Acid Battery?
Customers often ask us about the ideal charging current for recharging our AGM sealed lead acid batteries. We have the answer: 25% of the battery capacity. The battery capacity is indicated by Ah (Ampere Hour). For example: In a 12V 45Ah Sealed Lead Acid Battery, the capacity is 45 Ah.
For example: In a 12V 45Ah Sealed Lead Acid Battery, the capacity is 45 Ah. So, the charging current should be no more than 11.25 Amps (to prevent thermal runaway and battery expiration). Importantly, if you have other equipment connected to the battery during chargning, it also needs to be powered, so you need to add that to your calculations.
In this method the charging current is high in the beginning when a battery is in discharged condition, and it gradually drops off as the battery picks up charge resulting in increased back emf. Charging at constant voltage may be carried out only when the batteries have the same voltage, for example, 6 or 12 or 24 V.
Float voltage measured at the battery terminals General appearance and cleanliness of the whole installation Charger output current and voltage Float voltage measured at the battery terminals General appearance and cleanliness of the whole installation Crack in cells (evidence of electrolyte leakage) Evidence of corrosion at terminals, connectors, racks or cabinets I N I I N Ambient temperature and ventilation.
The complete battery modules are assembled in a housing and tested for leak rates within the range of 10-3 scc/s. Helium vacuum test or electrolyte tracing for individual battery cells Helium leak detection or decay/ flow test on battery packs components (e.g. on cooling tubes & hoses).
With HEV/EV technology comes new leak test requirements for the automotive industry: each single battery cell must be protected, reliably, against any penetration of humidity and air. The MARPOSS helium vacuum test detects leakage rate of 10-3 to 10-6 scc/s.
Leak rates within the range of 10-3 scc/s are used when cooling with a water glycol mixture and 10-5 scc/s when cooling with gas. The complete battery modules are assembled in a housing and tested for leak rates within the range of 10-3 scc/s.
Leak test on larger battery modules, packs and housing (including power electronics) after final assembly by means of the pressure decay/ flow test or with tracer gas. 10-10 10-10 10-9 10-9
Electrically propelled road vehicles – Safety specifications – Part 1: On-board rechargeable energy storage system (RESS). Standard - Lithium-based Rechargeable Cells. Electric and Hybrid Vehicle Propulsion Battery System Safety Standard - Lithium-based Rechargeable Cells. Vibration Alternative 1. Complete battery system vibration test
Even though battery leak rate standards have yet to be established, HMSLD is the preferred choice as the leak rate required to ensure battery tightness is in the 10–6 to 10–10 atm-cc/s range or lower.
This article will provide an in-depth look at the best practices for extinguishing a lithium battery fire, including the types of extinguishers to use, safety precautions, and post-fire procedures.
The following fire extinguishers are specifically designed for use on lithium-ion battery fires which are not the same as standard lithium batteries (use a Class D L2 Powder Extinguisher on standard lithium battery fires).
Our lithium battery fire extinguishers are specially designed to put out such fires. Lith-ex fire extinguishers use a non-toxic and revolutionary extinguishing agent called AVD or Aqueous Vermiculite Dispersion, which is deployed as a mist to create a film over surfaces.
Application: Aim the extinguisher at the base of the fire, and apply the powder evenly to cover the burning material. Lithium-ion battery fires can be effectively managed with standard dry chemical or ABC fire extinguishers. These extinguishers use a dry chemical agent to interrupt the chemical reaction of the fire. Key Points:
Proper use of a lithium-ion fire extinguisher, following the manufacturer's instructions and ensuring it is rated specifically for lithium-ion battery fires, is essential for effectively managing these dangerous fires. Why Should You Also Have a Lithium-Ion Fire Blanket?
While CO2 extinguishers are effective for many types of fires, they are not suitable for lithium battery fires. They do not cool the battery sufficiently, and the fire may re-ignite once the CO2 dissipates. If it is safe to do so, disconnect the battery or power source to cut off the supply of electricity.
Foam extinguishers are also ineffective and unsafe for lithium battery fires. While CO2 extinguishers are effective for many types of fires, they are not suitable for lithium battery fires. They do not cool the battery sufficiently, and the fire may re-ignite once the CO2 dissipates.
The Tesla Megapack is a large-scale stationary product, intended for use at, manufactured by, the energy subsidiary of Launched in 2019, a Megapack can store up to 3.9 megawatt-hours (MWh) of electricity. Each Megapack is a container of similar size to an. They are designed to be depl.
Capacity, Specs & More A Tesla battery pack varies in size depending on the model. The Model S and Model X use a small pack measuring 68.5 x 30 x 75 cm. In contrast, the Model 3 features a large pack measuring 185.4 x 29.2 x 9 cm. Understanding these measurements helps when choosing the right pack for your needs.
The Model Y Battery Pack shares the architecture with the Model 3. Its approximate dimensions are 60 x 50 x 8 inches. It has similar variants in capacity ranging from 50 kWh to 75 kWh, designed for efficiency and range, catering to compact SUV markets.
Energy Requirements: Energy requirements directly impact the size of a Tesla battery pack. Larger battery packs provide more energy, allowing for longer driving ranges. For example, the Tesla Model S with a 100 kWh battery pack can travel approximately 370 miles on a single charge. Vehicle Type: The type of vehicle also influences battery size.
The entire pack weighs around 450kg, making it one of the most giant battery packs in any production car today. Despite its size, the Roadster's battery pack is quite efficient, powering the car for over 400 km on a single charge. See Also: Can An Electric Car Charge While Driving? What Batteries Does Tesla Use?
The battery pack dimensions approximately measure 72 x 36 x 7 inches. The pack is capable of delivering up to 100 kWh, providing a long range and exceptional performance. Tesla's advancements in battery technology allow for faster charging times. The Model 3 Battery Pack also utilizes the 2170 cell format.
The Model X Battery Pack has similar dimensions to the Model S but is uniquely designed to accommodate the vehicle's weight and size. Its dimensions are around 72 x 36 x 7 inches, with a capacity of up to 100 kWh. The pack's robust design supports the SUV's performance and safety features.
When considering basic materials, a customer needs to determine the type of battery chemistrythat will be used. All batteries will have components such as anodes, cathodes, and electrolytes, yet these components will be made of specific materials based on whether a customer selects a lithium-based battery, alkaline. Electronics and software are becoming standard components found in battery packs today. These components may consist of: 1. Protection. When deciding on the battery enclosure, it will be dependent on how the pack fits into application. For batteries that will be completely inserted into. Battery cell chemistries, configurations, materials, and components will have certain materials more available than others. The types of standard materials that are available will be. Battery cells can experience expansion and swelling due to thermal temperatures and a buildup of gases. This problem is common with lithium-based battery chemistries, as the cells can swell up to 10% during the lifetime of.
[PDF Version]Throughout the battery from a single cell to a complete pack there are many different materials. Aluminium, copper, nickel plating etc
Battery packs are constructed from two or more individual cells or batteries. There are two basic types of battery packs: primary and secondary or rechargeable. Primary batteries are disposable, non-rechargeable devices. They must be replaced once their energy supply is depleted.
Electronics and software are becoming standard components found in battery packs today. These components may consist of: Inside of custom battery pack showing electronics, components, and materials. Many of these components will be a part of the battery management system (BMS).
If the batteries will be mounted into the device, such as on the handle or in a separate housing that will need to be accessible, injection molded plastic is commonly used. In some circumstances, metal casings will be required for the battery pack. This option is suitable for battery packs that will be used for traction applications.
There are a lot of different kinds of packs. The battery pack is composed by single cell through series or parallel. Parallel increase capacity, voltage constant. Series increase voltage, capacity constant. For example, 72V 45Ah can be assembled by 3.6V 2500mah cylindrical battery cell in the mode of 18 parallel and 20 series.
All batteries will have components such as anodes, cathodes, and electrolytes, yet these components will be made of specific materials based on whether a customer selects a lithium-based battery, alkaline battery, or nickel-based battery.
In this article, we will examine a circuit that allows charging Li-ion cells connected in series while also balancing them during the charging process.
The following graph suggests the ideal charging procedure of a standard 3.7 V Li-Ion Cell, rated with 4.2 V as the full charge level. Stage#1: At the initial stage#1 we see that the battery voltage rises from 0.25 V to 4.0 V level in around one hour at 1 amp constant current charging rate. This is indicated by the BLUE line.
If the cells are protected and one cell charges faster than the other it's protection will cut it off and current will not flow the other battery in series. That is the function of battery management circuits. Lithium ion batteries are fully charged at 4.2V, and discharged at about 3 V.
Although Li-Ion batteries are vulnerable devices, these can be charged through simpler circuits if the charging rate does not cause significant warming of the battery., and if the user does not mind a slight delay in the charging period of the cell.
It is possible to charge the cells individually, but limit the current and don't exceed 4.2V, and monitor the battery temperature. Many lithium batteries have built in protection for overdischarge.
The charging also different than the lead-acid batteries. The 3.9v Lithium-ion batteries need 4.2 v of charging voltage and 1A charging current. The charging time is about 2-3 hours. if the optimized charging is not done, the battery will be damaged or reduces the battery capacity.
You can also view the Lithium battery Charger PCB, how it will look after fabrication using the Photo View button in EasyEDA: After completing the design of this Lithium battery Charger PCB, you can order the PCB through JLCPCB.com. To order the PCB from JLCPCB, you need Gerber File.