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While lithium-ion batteries have traditionally served short-duration needs, recent projects are pushing beyond conventional 4-6 hour limits, with 8-10 hour lithium-ion systems now appearing in grid-scale applications, challenging established assumptions about technology constraints.
Market trends of lithium-ion batteries The market trends of lithium-ion batteries are dynamic and reflective of the evolving landscape of energy storage technologies. Lithium-ion batteries have experienced substantial growth, driven by their widespread adoption in diverse applications.
While lithium-ion batteries have dominated the energy storage landscape, there is a growing interest in exploring alternative battery technologies that offer improved performance, safety, and sustainability .
Recent advancements enable 80 % recharge in under 30 min, enhancing usability in transportation and consumer applications. The demand for lithium-ion batteries is rapidly expanding, particularly in EVs and grid energy storage. Improved recycling processes and alternative materials are critical for minimizing environmental impact.
In 2020, global sales of EVs reached 1.5 million units, with a corresponding lithium-ion battery demand of 65 GWh. Projections indicate a substantial increase to 137 GWh in 2025 and 245 GWh in 2030, emphasizing the pivotal role of lithium-ion batteries in the automotive industry.
Recent research by Li et al. explores technological innovations in lithium-ion battery design to improve sustainability. The study focuses on developing cathodes with reduced reliance on critical materials like cobalt, aiming to enhance the environmental profile of batteries.
While lithium-ion batteries have traditionally served short-duration needs, recent projects are pushing beyond conventional 4-6 hour limits, with 8-10 hour lithium-ion systems now appearing in grid-scale applications, challenging established assumptions about technology constraints.
In a significant advancement for the UK's renewable energy landscape, Statera Energy has announced plans to construct a 680-megawatt battery energy storage system (BESS) at the Trafford Low Carbon Energy Park, located eight miles southwest of Manchester.
One of UK's largest battery energy storage projects has changed hands and will come online next year as part of a low carbon energy park in Greater Manchester. UK-based developer Statera Energy has acquired a 680 MW/1360 MWh battery energy storage project in Greater Manchester from Carlton Power.
Planning permission has been granted for a £750m battery energy storage scheme (BESS) near Manchester. Carlton Power, the independent energy-infrastructure developer behind the venture, said the 1GW facility at the Trafford Low Carbon Energy Park would be the world's largest battery-storage facility.
Carlton Power secures planning permission for a 1GW battery energy storage scheme in Manchester, aiming for commercial operation in 2025. The project will strengthen regional energy security and surpass the current largest BESS in the world.
UK-based developer Statera Energy has acquired a 680 MW/1360 MWh battery energy storage project in Greater Manchester from Carlton Power. Located at Trafford Low Carbon Energy Park, Carrington Storage is expected to become one of the largest of its kind in Europe once fully energised in 2026.
Carlton Power have been given planning permission to build a £750m 1GW battery energy storage scheme (BESS) at the Trafford Low Carbon Energy Park in Greater Manchester Planning permission for the BESS was granted by Trafford Council, the local planning authority and subject to a final investment decision, construction
Failed to load Related. Planning permission for the battery-storage facility was granted by Trafford Council. The council's leader, Tom Ross, said that the battery storage and green-hydrogen schemes would put Trafford and Greater Manchester “at the forefront of the UK's energy transition”.
The Asia-Pacific region dominates the global solar photovoltaic glass market with significant manufacturing capabilities and installations across major economies. China leads the manufacturing landscape, while.
Region : Global | Format: PDF | Report ID: BRI102553 | SKU ID: 21776130 The global photovoltaic glass market size was USD 6.5 billion in 2024 & the market is expected to reach USD 26.4 billion by 2033, exhibiting a CAGR of 16.85% during the forecast period.
The photovoltaic glass market in North America is anticipated to grow at a highestCAGR in terms of value-energy utilization over the forecast period, whereas the market is anticipatedto represent an important incremental possibility over the coming years. "Key Players Focus on Partnerships to Gain a Competitive Advantage "
The solar photovoltaic glass market is consolidated in nature. The major players in this market include Xinyi Solar Holdings Limited, Flat Glass Group Co., Ltd, AGC Inc., Nippon Sheet Glass Co., Ltd, and Saint-Gobain, among others (not in a particular order). Need More Details on Market Players and Competitors?
Rising research and developmentsefforts and green building market dynamics are the main trends seen in the photovoltaic market.
The Asia-Pacific region is expected to dominate the solar photovoltaic glass market. In developing countries like China, India, and Japan, the crisis in electricity supply has resulted in increasing the scope for self-producing electricity using solar photovoltaic glass.
In addition to lowering energy costs, photovoltaic glass use has the potential to improve marketing and public relations by lowering facilities' thus promotingcarbon footprints and promoting sustainability.
The Government of Burkina Faso has signed a Public-Private Partnership (PPP) agreement with a local developer and a Dutch clean energy investment firm to develop a major solar and battery storage system.
At Intersolar Europe 2025, Huawei Digital Power's Intelligent PV Business Unit today launched a groundbreaking full-scenario grid-forming energy storage platform and a next-gen residential energy management system, setting new benchmarks for safety, scalability, and smart grid integration in the renewable energy sector.
Huawei inverters are becoming a benchmark for solar energy in residential and commercial applications. Huawei is a well-known brand in the solar energy sector.
On April 8, 2025, Huawei hosted a FusionSolar Industrial and Commercial Flagship Summit in Frankfurt, Germany. The theme was Future Energy Goals. Tong Jinly, the President of Huawei Digital Energy Global Industrial and Commercial Sales and Services, unveiled a new smart Hybrid cooling energy storage solution in Europe.
Huawei FusionSolar will showcase its latest smart PV and energy storage products, along with the upgraded all-scenario grid-forming solutions at SNEC PV+ 2025. The event will be held in Hall 6.1 at the National Exhibition and Convention Center in Shanghai from June 11 to 13, 2025.
Thanks to the integrated 800V high-voltage battery connection, the inverter can be extended with the HUAWEI Battery. The optional HUAWEI Smart Meter is connected via the integrated RS485 interface and provides information about house consumption and grid feed-in.
At Intersolar Europe 2025, Huawei Digital Power's Intelligent PV Business Unit today launched a groundbreaking full-scenario grid-forming energy storage platform and a next-gen residential energy management system, setting new benchmarks for safety, scalability, and smart grid integration in the renewable energy sector.
Join Huawei from June 11 to 13, 2025, in Hall 6.1 at the National Exhibition and Convention Center in Shanghai, China, as we unveil our next-generation PV+ESS products and cutting-edge all-scenario grid-forming solutions.
In 2025, the cost per kWh is between $200 and $400. The price changes based on the technology and where you live. Lithium-ion batteries, like LFP and NMC, are the most common.
In 2025, you're looking at an average cost of about $152 per kilowatt-hour (kWh) for lithium-ion battery packs, which represents a 7% increase since 2021. Energy storage systems (ESS) for four-hour durations exceed $300/kWh, marking the first price hike since 2017, largely driven by escalating raw material costs and supply chain disruptions.
As we look ahead to 2024, energy storage system (ESS) costs are expected to undergo significant changes. Currently, the average cost remains above $300/kWh for four-hour duration systems, primarily due to rising raw material prices since 2017.
We expect to see battery storage prices continue to decline in 2025, even as raw material prices rise, due to the oversupply of battery production. The rapid growth of battery manufacturing, particularly in China and Europe, has outpaced demand, which is exerting downward pressure on pricing.
Energy storage system costs for four-hour duration systems exceed $300/kWh for the first time since 2017. Rising raw material prices, particularly for lithium and nickel, contribute to increased energy storage costs. Fixed operation and maintenance costs for battery systems are estimated at 2.5% of capital costs.
Energy storage systems (ESS) for four-hour durations exceed $300/kWh, marking the first price hike since 2017, largely driven by escalating raw material costs and supply chain disruptions. Geopolitical issues have intensified these trends, especially concerning lithium and nickel.
In 2025, lithium-ion battery pack prices averaged $152/kWh, reflecting ongoing challenges, including rising raw material costs and geopolitical tensions, particularly due to Russia's war in Ukraine. These factors have led to high prices for essential metals like lithium and nickel, impacting the production of energy storage technologies.
The liquid-filled lead acid batteries used in automobiles and a range of other products have many great qualities, but are also known to “go bad” with little warning. Fortunately, you can easily do a basic health checkup on any.
Lead acid batteries recharge in various manners based on their function and manner of installation. For a lead acid vehicle battery, drive the vehicle around for at least 20 minutes. For a lead acid battery connected to solar panels, let the battery charge fully on a sunny day.
Fortunately, you can easily do a basic health checkup on any type of lead acid battery by hooking it up to a simple-to-use digital voltmeter. If you have an open-cell battery that lets you access the liquid inside, you can do a more rigorous checkup with a battery hydrometer. Charge the battery fully, then let it rest for 4 hours.
The liquid-filled lead acid batteries used in automobiles and a range of other products have many great qualities, but are also known to “go bad” with little warning. Fortunately, you can easily do a basic health checkup on any type of lead acid battery by hooking it up to a simple-to-use digital voltmeter.
Lead-acid batteries are a type of rechargeable battery that uses lead and lead oxide electrodes submerged in an electrolyte solution of sulfuric acid and water. They are commonly used in vehicles, backup power supplies, and other applications that require a reliable and long-lasting source of energy.
To get a more accurate reading of a lead-acid battery's health, you can use a hydrometer. This tool measures the specific gravity of the electrolyte solution within the battery, which can give you a better idea of its state of charge and overall condition. Before using a hydrometer, it's important to make sure the battery is fully charged.
Checking an open-cell lead acid battery—that is, a lead acid battery with caps that can be opened to access the liquid inside—with a battery hydrometer is most accurate when the battery is fully charged. Closed-cell lead acid batteries without the access caps cannot be tested this way.
The basic concept is that when connecting in parallel, you add the amp hour ratings of the batteries together, but the voltage remains the same. For example: 1. two 6 volt 4.5 Ah batteries wired in parallel are capable of providing 6 volt 9 amp hours (4.5 Ah + 4.5 Ah). 2. four 1.2 volt 2,000 mAh wired in parallel can provide 1.2. This is the big “no go area”. The battery with the higher voltage will attempt to charge the battery with the lower voltage to create a balance in the circuit. 1. primary (disposable). This is possible and won't cause any major issues, but it is important to note some potential issues: 1. Check your battery chemistries – Sealed Lead Acid batteries for example.
To properly wire a battery pack in series follow the illustration below. Some electric scooter, bike, and go kart batteries are wired in series and parallel to create a battery pack with a Voltage that is half the sum of all of the batteries in the pack combined.
A battery parallel assembly comprises multiple battery cells connected electrically in parallel under a specific topological configuration or geometrical arrangement. In this example, you create a parallel assembly of four cylindrical cells stacked in a square topology over four rows.
Flow batteries and other chemistries. These are commonly available in 48V. Multiple batteries can connect in parallel without any issues. Each battery has its own battery management system. Together they will generate a total state of charge value for the whole battery bank. A GX monitoring device is needed in the system.
When batteries are connected in series, the voltage increases. When batteries are connected in parallel, the capacity increases. When batteries are connected in series/parallel, both the voltage and the capacity increase. Single battery. Two batteries in series. Two batteries in parallel. Four batteries in series/parallel. Four batteries in series.
The basic concept is that when connecting in parallel, you add the amp hour ratings of the batteries together, but the voltage remains the same. For example: two 6 volt 4.5 Ah batteries wired in parallel are capable of providing 6 volt 9 amp hours (4.5 Ah + 4.5 Ah).
To wire multiple batteries in parallel, connect the negative terminal (-) of one battery to the negative terminal (-) of another, and do the same to the positive terminals (+). For example, you can connect four Renogy 12V 200Ah Core Series LiFePO4 Batteries in parallel. In this system, the system voltage and current are calculated as follows:
In this project, we will build an IoT based Battery Monitoring System using ESP8266 where you can monitor the battery charging/discharging status along with Battery Voltage & Percentage. As we know, the battery is the most important component for any device as it powers the entire system. So, it is important to monitor. You will need the following components for the IoT Based Battery Monitoring System Project. You can purchase all the components online from. A lithium-ion battery or Li-ion battery is a type of rechargeable battery. Lithium-ion batteries are commonly used for portable electronics and electric vehicles. In this battery, lithium ions move. In order to Monitor the Battery Data on ThingSpeak Server, you first need to Setup the Thingspeak. To set up the ThingSpeak Server, visit. We will design a system to monitor this battery voltage along with charging and discharging status. For the microcontroller, we use WeMos D1 Mini which has an ESP8266 wifi-enabled.
[PDF Version]In this IoT-based Battery Monitoring System, we will use the NodeMCU ESP8266 board to send the battery status data to the Arduino IoT cloud. The IoT Cloud Dashboard will display the battery voltage along with the battery percentage in both the charging and discharging conditions.
The proposed battery voltage status monitor circuit using 4 LEDs makes use of comparators in the form of opamps from the IC LM324. This IC is much versatile than the other opamp counterparts due to its higher voltage tolerance level and due to the quad opamps in one package.
How to Set up the above explained battery status indicator Circuit. It's pretty simple. Apply the full-charge voltage level across the point indicated "to battery positive" and ground. Now adjust the preset such that the last LED just illuminates at that voltage level. Done! Your circuit is all set now.
This allows users to monitor the battery status remotely from anywhere in the world via their smartphones or computer dashboards. The server displays the battery voltage, load voltage, current, and power, providing a comprehensive overview of the battery's condition in both charging and discharging states.
Battery is the most important component for any device as it powers the whole system. And it is important to monitor the voltage level of the battery as improper charging and discharging of a lithium battery may lead to a big safety issue.
In this IoT-based Battery Monitoring System, we will use Wemos D1 Mini with ESP8266 Chip to send the battery status data to ThingSpeak cloud. The Thingspeak will display the battery voltage along with the battery percentage in both the charging and discharging cases.
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.
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.
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.
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 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.
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.