Browse technical resources about solar mounting systems, tracker technology, structural design, and installation best practices.
HOME / Development Of Automcatic Switch Off Battery Charger - BeTheFuture Solar Foundation & Infrastructure
You can get 3-phase supply installed in your home by your local Distribution Network Operator (DNO). The Network Operator is the company that manages the energy supply for your area, you (or your electrician) must apply to the DNO to have the work approved. The DNO is the only entity allowed to upgrade the. If you are planning to install a 22kW charger you must first discover if your property already has a 3-phase supply in place. Here's a list of. The minimum cost charged by the UK Power Networks (the DPO responsible for East Anglia & London) for upgrading an electricity supply to Phase 3 is £1,800 inclusive of VAT. Residential properties are able to upgrade their electricity supply from single-phase to 3 phase supply. You should initially contact your local.
The constant rate of the 3 phases ensures that power transfer is constant and can handle a heavier load at a supply of around 3 times that of a single phase. If you are planning to install a 22kW charger you must first discover if your property already has a 3-phase supply in place.
You've got a powerful three-phase EV charger, and your vehicle can charge with three phases. The perfect combo. Wait, one more thing can be a limiting factor, power grid capacity. When you are at home, you only have a limited amount of energy that you can call on once at a time. If the limit is exceeded, the whole house may black out.
If you are considering the installation of a fast 22kW EV home charger you may need to upgrade your current power supply from a single phase to 3-phase supply. This guide will help you understand your current setup and the steps for upgrading your supply to 3-phase power.
And here, we come to the main distinction between the phases. 1-phase charging: Power flows through a single conductor (wire). Max charging power - 7.4 kW (In some countries, single-phase charging is only permitted or possible at lower charging power. 3-phase charging: Power flows through three conductors (wires). Max charging power - 11 or 22 kW.
Most houses in the UK have a single-phase power supply, which is sufficient to power a 7.4kW EV charger but nothing more. If you want an 11kW charger for an EV, you must upgrade to a 3-phase power supply, which requires modifications to your electrical installation. Can you go from single-phase to 3 phase? Yes!
Note: In addition to supporting 3-phase charging, a 3-phase cable can also be used for single-phase charging. Even though there are several links in the charging chain, the main factor in your decision-making should be your electric car, of course.
Yes, you can charge a battery pack while using it, but there are risks involved. Simultaneous charging and discharging can lead to overheating, which may damage the battery or the device.
Note that a 20W or higher power adapter is recommended for charging and is required for charging the iPhone at 15W when the MagSafe Battery Pack is plugged in. Charging the MagSafe Battery Pack either through the Battery Pack itself or through the iPhone requires a Lightning cable.
Charging the MagSafe Battery Pack requires a Lightning cable as does the iPhone. Having a USB-C to Lightning cable plus adapter for outlet, should be all the cables you need. It will not charge if placed on the charger alone. We have included a resource about the MagSafe Battery Pack below for more detailed specifications below.
When charging the iPhone and MagSafe Battery Pack simultaneously, the iPhone will charge to 80 percent or higher before the MagSafe Battery Pack begins to charge. Note that a 20W or higher power adapter is recommended for charging and is required for charging the iPhone at 15W when the MagSafe Battery Pack is plugged in.
The MagSafe Battery Pack has a reverse wireless charging feature. This means that if you charge your iPhone, the MagSafe Battery Pack will also charge at the same time.
There's no interference with your credit cards or key fobs either. The MagSafe Battery Pack can charge even faster when coupled with a 27W or higher charger, like those that ship with MacBook. And when you're in need of a wireless charger, just plug in a Lightning cable for up to 15W of wireless charging. Recommended:
There are built-in charge management features in the MagSafe Battery Pack that are designed to help maintain battery health in situations where the MagSafe Battery Pack is connected to power for long periods of time. Apple says that an iPhone might get warm while it charges.
Vanadium battery is a relatively mature liquid current battery with long life, high energy storage, easy maintenance, flexible design, green and other outstanding advantages, commonly used in renewable energy storage and smart grid peak shaving, with high economic value and development prospects.
Vanadium flow batteries are expected to accelerate rapidly in the coming years, especially as renewable energy generation reaches 60-70% of the power system's market share. Long-term energy storage systems will become the most cost-effective flexible solution. Renewable Energy Growth and Storage Needs
8 August 2024 – Prof. Zhang Huamin, Chief Researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, announced a significant forecast in the energy storage sector. He predicts that in the next 5 to 10 years, the installed capacity of vanadium flow batteries could exceed that of lithium-ion batteries.
Unlike lithium-ion batteries, Vanadium flow batteries store energy in a non-flammable electrolyte solution, which does not degrade with cycling, offering superior economic and safety benefits. Prof. Zhang highlighted that the practical large-scale energy storage technologies include physical and electrochemical storage.
Currently, besides the demonstration projects of the two major power grids, the National Energy Group and several provinces including Jilin, Hebei, Sichuan, Jiangsu, and Shenzhen have issued vanadium flow battery tender projects. Vanitec is the only global vanadium organisation.
For wind and solar power generation, the main electrochemical storage technologies encompass lithium-ion, flow, lead-carbon, and sodium-ion batteries. Vanadium flow batteries are expected to accelerate rapidly in the coming years, especially as renewable energy generation reaches 60-70% of the power system's market share.
As an important branch of RFBs, all-vanadium RFBs (VRFBs) have become the most commercialized and technologically mature batteries among current RFBs due to their intrinsic safety, no pollution, high energy efficiency, excellent charge and discharge performance, long cycle life, and excellent capacity-power decoupling .
The performance and capacity of lithium-ion batteries increased as development progressed. • 1991: and started commercial sale of the first rechargeable lithium-ion battery. The Japanese team that successfully commercialized the technology was led by Yoshio Nishi. 1991 ushered the Second Period (commercialization) in the history of lithium-ion batteries, which is reflected as points in the plots "The log number of publications about electrochemica.
1991 ushered the Second Period (commercialization) in the history of lithium-ion batteries, which is reflected as inflection points in the plots "The log number of publications about electrochemical powersources by year" and "The number of non-patent publications about lithium-ion batteries" shown on this page.
Precisely because lithium-ion batteries have high volume-specific and mass-specific energy, are rechargeable and non-polluting, and have the three major characteristics of the current development of the battery industry, they are growing rapidly in developed countries.
In 1999, eight Japanese companies led by Panasonic launched their first polylithium products. It is called the first year of polymer lithium-ion batteries by the Japanese. In 1999, South Korea entered the lithium-ion battery market, and LG Chem completed South Korea's first battery product. In 2000, BYD won an order from Moto.
The performance and capacity of lithium-ion batteries increased as development progressed. 1991: Sony and Asahi Kasei started commercial sale of the first rechargeable lithium-ion battery. The Japanese team that successfully commercialized the technology was led by Yoshio Nishi.
As the world shifts towards renewable energy sources, lithium-ion batteries are playing a crucial role in energy storage. Future developments will focus on integrating lithium-ion batteries with renewable energy systems to provide reliable and efficient energy storage solutions.
Polymer lithium-ion batteries are known as the “batteries of the 21st century”. They will open up a new era of batteries with very optimistic development prospects. Part 9. FAQs Are lithium batteries environmentally friendly?
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.
Below is a detailed explanation of the primary technical parameters of lithium batteries, along with additional related knowledge, to assist you in better applying and managing energy storage systems.
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.
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.
Specific capacity, energy density, power density, efficiency, and charge/discharge times are determined, with specific C-rates correlating to the inspection time. The test scheme must specify the working voltage window, C-rate, weight, and thickness of electrodes to accurately determine the lifespan of the LIBs. 3.4.2.
Energy density is often a more relevant indicator than capacity in practical applications. Current lithium-ion battery technology achieves energy densities of approximately 100 to 200 Wh/kg. This level is relatively low and poses challenges in various applications, particularly in electric vehicles where both weight and volume are restricted.
LIBs are prominent energy storage devices to meet the growing energy demands of the modern era. They offer high specific capacity, energy density, thermal stability, and long calendar life compared to other types of batteries. LIBs are used in a diverse range of applications, from powering household appliances to supporting electric vehicles.
Battery storage is a technology that enables power system operators and utilities to store energy for later use.
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.
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%).
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.
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.
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.
These advanced materials include mica, intumescent materials, and ablative coatings. Each material offers unique properties and benefits suitable for different aspects of battery protection.
Foams also act as thermal and electrical conductors, depending on their material and the compression amount within the battery. An extra layer can be added to the foam to make it more suitable for EMI shielding. Battery components need protection from electromagnetic waves due to their high frequencies and small size.
Regarding EV battery production, foam ensures optimal performance and longevity. Foam is widely used as an insulation material within battery packs, protecting the cells from extreme temperatures and vibrations. This insulation not only enhances safety but also helps maximise energy efficiency.
One plug-in hybrid EV built in China is already using a thermoplastic polypropylene compound instead of aluminium for its battery case cover, providing savings in weight. Other EVs now in production around world are using several thermoplastic materials for components such as cell carriers and housings, battery modules and battery enclosures.
Polyurethane foam, silicone foam, and Ethylene-Vinyl Acetate (EVA) foam are commonly used foams in EV battery manufacturing. Each type serves specific purposes, such as thermal, electrical, and shock absorption. What are some advancements in foam technology for EV batteries?
Additionally, polyurethane foam provides structural support, reducing the risk of damage due to shocks or vibrations. Silicone foam, another popular choice, excels in maintaining electrical insulation. Creating a barrier against moisture and dust ingress ensures the battery pack's long-term reliability.
These foams are built with fire-resistant materials, ensuring if something such as thermal runaway occurs in the battery, the foam will be an essential factor in reducing the chances of spreading. Dielectric foams and insulation are critical components to protecting the battery cells as they expand and contract while in use.
Specific Steps for Regular MaintenanceRegular Monitoring of Battery Status: Use specialized equipment to measure the battery's voltage, internal resistance, capacity, and temperature. Inspect Cables and Connectors:. Maintain the Thermal Management System:.
Establishing an adequate battery maintenance procedure is essential for ensuring a productive & safe work environment. Charts and maintenance plans are a fantastic approach to ensuring that batteries are properly maintained. Battery maintenance is essential for ensuring their best performance and longevity.
Different types of batteries, such as lead-acid and lithium-ion, require specific maintenance techniques to ensure their longevity and performance. Knowing the type of battery you are working with is essential to guarantee the correct charging and maintenance techniques are employed.
Specific maintenance requirements will vary depending on the type of battery; however, the following are general step-by-step procedure that apply to many different types of batteries, including lead-acid batteries typically used in cars and uninterruptible power supply (UPS) systems. Step-2: Do Not Top Off Before Charging
From visual inspections & cleanliness to evaluating electrolyte levels (if appropriate), charging system tests, and load testing, this complete approach covers essential procedures for maintaining several battery types, including lead-acid & lithium-ion.
It is still important to check their state of charge regularly using a monitoring tool that interacts with the integrated battery management system. Proper charging practices, such as quick charging of the battery after each period of use, will also help maintain their performance.
Construction equipment batteries, including deep cycle batteries, may require additional maintenance due to harsh operating conditions. Ensuring proper maintenance for all batteries used for construction equipment can help prevent costly downtime and keep your equipment running smoothly.
The CEIV Li-batt certification assesses your organization based on the guidelines for the Dangerous Goods Regulations (DGR) andLithium Battery Shipping Regulations (LBSR), and covers the following critical areas of lithium battery handling and carriage operations: 1. Quality and safety management - Including organization. The IATA Certification process is designed to guide and support you to success. We give you the understanding, tools and expert advice you need to achieve your organization's certification. The process is as follows: 1. Training - At.
Transport Document: For lithium battery shipments, this specifies the UN number, shipping name, hazard class, packing group, and total quantity. Pilot Notification: For shipping lithium batteries by air, pilots must receive written information on the presence and location of lithium batteries.
In addition, lithium-ion cells and batteries shipped by themselves must be shipped at a state of charge not exceeding 30% of their rated capacity. Lithium batteries are dangerous goods, and all of the regulatory requirements must be complied with, as set out in the Lithium Battery Shipping Regulations.
That's why the International Air Transport Association (IATA) is promoting the increased viability of air transport for lithium-ion batteries through a four-part approach: Promote the development of outcome-based, harmonized safety-related screening standards and processes for lithium batteries.
As far as transport is concerned, lithium batteries, if properly certified and specially packaged, can be shipped by road, sea, rail or air. However, medium and large batteries are among the goods not accepted by airlines, which disallow their transportation on cargo flights.
A table in the Lithium Battery Shipping Regulations manual gives the precise weight of batteries per package on both cargo and passenger aircraft. All marks and labels must be clearly visible on the exterior of all packages and overpacks. Proper marking and labeling is required when shipping lithium batteries by air.
NOTE: “Section II” Lithium Battery shipments that are compliant for Air transport (i.e. as per section II of the relevant Packing Instructions from the IATA DGR) also comply with all requirements of ADR/IMDG Special Provision 188 and can therefore be transported by Road in ADR affiliated countries and globally by Sea. 4.
Marketing Battery StoresMake Your Business Stand Out Making your battery stores business stand out from the competition is essential for success. Take Advantage of Digital Platforms. Revolutionizing the Battery Store Business.
The marketing strategies you employ should highlight the unique aspects of your business, like your commitment to sustainable battery production and advanced technology. Here are essential strategies to consider: Identify Your Unique Value Proposition: Clearly articulate what sets your battery manufacturing company apart.
Here are 8 tips on how to market for the Battery Stores business: Develop an effective pricing and promotion strategy that will keep customers coming back. Make sure to advertise in the right channels and target the right audience. Create an attractive and engaging website that is user friendly.
Success in the battery stores business requires a comprehensive approach to marketing. You need to reach, engage and convert customers with an effective sales pitch and attractive visuals. To grow your business, you can use creative campaigns, such as e-mail blasts, social media posts, press releases and targeted ads.
Explore various funding options available for starting a battery manufacturing business, including government grants, private investors, and loans. Prepare to present your business plan to potential funders. Ensure compliance by registering your ev battery business and obtaining all necessary permits and licenses required in your area.
Sourcing materials that are eco-friendly and implementing responsible manufacturing practices are crucial for long-term success. A comprehensive business plan for your ev battery company should outline your production method, financial projections, and market analysis.
To successfully launch your ev battery manufacturing business, forming strategic partnerships with suppliers and distributors is essential. These relationships can provide you with the necessary resources and market access to operate efficiently and effectively.
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.