Electric Bike Battery Explained

E-bike batteries are rechargeable batteries that power electric bikes. They are usually made of lead-acid batteries or lithium-ion batteries.

Lead-acid batteries are the most common and cheapest type of e-bike battery. They are heavy and bulky and have limited range, but they are affordable and easy to maintain.

Lithium-ion batteries are lighter, more durable, and last longer than lead-acid batteries. However, they are also more expensive.

E-bike batteries are typically 12, 24, 36, or 48 volts. The higher the voltage, the more power the battery can provide. The capacity of an e-bike battery is typically measured in ampere-hours (Ah). The higher the capacity, the more charge the battery can store.

The expected life of an e-bike battery is 2 to 5 years, depending on the battery type and usage. The battery life can be extended by charging it regularly and avoiding extreme temperatures.

Types of E-Bike Lithium-ion batteries

Ternary lithium-ion battery (LiNio) 

This battery has high energy density and cycle life and is widely used in pure electric vehicles and plug-in hybrid vehicles. Ternary lithium electric bicycle batteries also have the following characteristics:

• Small size and lightweight
• Long driving range
• Good acceleration performance
• Good low-temperature resistance

Lithium Iron Phosphate Battery (LiFePO4) 

This battery has good safety and stability but has a lower energy density. Lithium Iron Phosphate electric bicycle batteries also have the following characteristics:

• High safety performance, not prone to explosion and combustion
• Long cycle life
• low cost

Lithium manganese oxide battery (LiMn2O4) 

This battery has higher safety, but the energy density and cycle life are relatively low. Lithium manganese oxide electric bicycle battery also has the following characteristics:

• Cheap price
• Environmentally friendly

Internal structure and working principle of lithium-ion battery pack for electric bicycles

The lithium-ion battery pack of an electric bicycle is made up of multiple cells connected in series or in parallel and is equipped with a protection circuit and management system.

Internal structure

Cell: The cell is the basic unit of a battery pack, consisting of a positive electrode, a negative electrode, an electrolyte, a separator, and a shell. The positive electrode material is usually lithium cobalt oxide, lithium manganese oxide or lithium iron phosphate, and the negative electrode material is usually graphite. The electrolyte is a lithium salt solution used to transfer lithium ions between the positive and negative electrodes. The separator is used to prevent the positive and negative electrodes from contacting and allow lithium ions to pass through. The shell is used to protect the internal components of the battery.

Protection circuit: The protection circuit is used to protect the battery from overcharge, over-discharge, over-current, short circuit, and other faults. The protection circuit usually includes components such as fuses, MOSFETs, temperature sensors, and voltage sensors.

Battery Management System: The battery management system is used to monitor the status of the battery and optimize the performance and life of the battery. The management system usually includes components such as microcontrollers, data acquisition modules, and power modules.

How it works

• Charging: During the charging process, the charger converts electrical energy into electrical energy that can be used by the lithium-ion battery. Lithium ions move between the positive and negative electrodes and store the electrical energy in the form of chemical energy.
• Discharge: During the discharge process, lithium-ion batteries convert chemical energy into electrical energy. Lithium ions move from the negative electrode to the positive electrode to power the electric bike’s motor and other electrical components.

Advantage

Electric bicycle lithium-ion battery pack has the following advantages:

• High energy density: The energy density of lithium-ion batteries is much higher than that of traditional lead-acid batteries, which means that lithium-ion batteries can store more electricity in the same volume and weight.
• Long cycle life: Lithium-ion batteries have a much longer cycle life than lead-acid batteries, which means that lithium-ion batteries can be charged and discharged repeatedly hundreds of times without performance degradation.
• Environmental protection: Lithium-ion batteries do not contain toxic substances such as lead and are more environmentally friendly.

Shortcoming

There are also some disadvantages of lithium-ion battery packs for electric bicycles:

• High cost: Lithium-ion batteries cost more than traditional lead-acid batteries.
• Safety: Lithium-ion batteries have certain safety risks. For example, overcharging or overheating can cause the battery to explode or catch fire.

The main parameters of electric bicycle lithium-ion batteries

The main parameters of electric bicycle lithium-ion batteries include:

• Battery type: The cathode materials of lithium-ion batteries mainly include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), etc. Different types of batteries have different performances, such as energy density, cycle life, safety, etc.
• Nominal voltage: The nominal voltage refers to the voltage of the battery in a fully discharged state, usually 3.7V or 3.2V. The total voltage of the battery pack is the nominal voltage of multiple cells connected in series, and the common ones are 12V, 24V, 36V, and 48V.
• Nominal capacity: Nominal capacity refers to the amount of electricity that a battery can discharge at a rated current, measured in ampere-hours (Ah). The larger the nominal capacity of a battery, the longer the battery life it can provide.
• Energy density: Energy density refers to the amount of electricity that a battery can store per unit weight, measured in watt-hours per kilogram (Wh/kg). The higher the energy density of a battery, the smaller its size and weight, and the longer its range.
• Cycle life: Cycle life refers to the number of cycles that a battery goes through after being fully charged and discharged. The longer the cycle life of a battery, the longer its service life.
• Working temperature: Working temperature refers to the ambient temperature range in which the battery can work normally. When the battery exceeds the working temperature range, the performance will decline or even be damaged.
• Size: The size of the battery is usually expressed in diameter and height, in millimeters (mm). Common sizes include 18650, 21700, 26650, etc.

Here are the meanings of some main parameters:

• Battery type: determines the performance of the battery, such as energy density, cycle life, safety, etc.
• Nominal voltage: determines the total voltage of the battery pack and affects the power and speed of the motor.
• Nominal capacity: determines the battery life.
• Energy density: determines the volume and weight of the battery, as well as its range.
• Cycle life: determines the service life of the battery.
• Operating temperature: affects the performance and safety of the battery.
• Size: Determines whether the battery can be installed on an e-bike.

Does a higher battery voltage make sense?

1. Increase power and speed

Battery voltage is an important factor affecting motor power. According to the formula P=U×I, when the current is constant, the higher the voltage, the greater the power. The greater the motor power, the higher the acceleration and speed that the electric vehicle can provide.

2. Extended driving range

The battery’s range is directly proportional to the battery’s capacity and voltage. When the battery capacity is constant, a higher voltage means the battery can store more power, thus extending the range.

3. Reduce losses

When transmitting the same electrical power, a higher voltage can reduce the current. According to the formula P=I^2×R, the smaller the current, the smaller the loss in the wire. This can improve the efficiency of the battery and extend the battery life.

4. Simplify the circuit

With the same power, a higher voltage can reduce the current. This can simplify the circuit design, reduce the number of components in the circuit, and reduce costs.

5. Improve charging speed

The charging speed is related to the charging current. Under the condition of constant charging power, a higher voltage can make the charging current larger, thus increasing the charging speed.

Of course, higher battery voltages also have some potential disadvantages:

• Increased cost: The materials and manufacturing processes of high-voltage batteries are generally more complex, and therefore more expensive.
• Increased safety risks: High-voltage batteries have a higher energy density and are more likely to cause fire or explosion in the event of an accident.

In general, higher battery voltage can bring a series of advantages, but it also has some potential disadvantages. In practical applications, it is necessary to weigh the pros and cons according to the specific application scenario and choose the appropriate battery voltage.

Here are some common e-bike battery voltages:

• Electric vehicles: 24V, 36V, 48V, 60V, 72V

The structure and working principle of lithium-ion battery cells

Lithium-ion battery cells are the basic units of electric bicycle lithium-ion battery packs and consist of positive electrodes, negative electrodes, electrolytes, separators, and shells.

Structure of lithium-ion cells

Positive electrode: The positive electrode material is usually lithium cobalt oxide, lithium manganese oxide or lithium iron phosphate, which has redox properties and can release or absorb lithium ions during the charge and discharge process. The performance of the positive electrode material will affect the capacity, voltage, and cycle life of the battery.

Negative electrode: The negative electrode material is usually graphite, which has good conductivity and reversible intercalation, and can absorb or release lithium ions during charging and discharging. The performance of the negative electrode material will affect the capacity and cycle life of the battery.

Electrolyte: The electrolyte is a lithium salt solution used to transfer lithium ions between the positive and negative electrodes. The performance of the electrolyte affects the conductivity, operating temperature, and safety performance of the battery.

Separator: The separator is a porous film that prevents the positive electrode and the negative electrode from directly contacting each other and allows lithium ions to pass through. The performance of the separator affects the safety and cycle life of the battery.

Shell: The shell is used to protect the internal components of the battery and provide good sealing. The material and design of the shell will affect the safety and reliability of the battery.

Working principle

During the charging and discharging process, lithium ions move between the positive electrode and the negative electrode, accompanied by the mutual conversion of chemical energy and electrical energy.

• Charging: During charging, an external power source provides electrical energy to the battery, increasing the potential of the positive electrode. Lithium ions move from the negative electrode to the positive electrode under the action of the electrolyte and are embedded in the lattice structure of the positive electrode material. In this process, chemical energy is stored in the form of lithium ions combined with the positive electrode material.
• Discharge: During discharge, the battery converts chemical energy into electrical energy. Lithium ions in the positive electrode material move from the positive electrode to the negative electrode under the action of the electrolyte and are embedded in the lattice structure of the negative electrode material. In this process, electrical energy is output in the form of electron flow.

Influencing factors

Lithium-ion battery cells are affected by the following factors:

• Positive/negative electrode materials: The type, particle size and structure of positive/negative electrode materials will affect the capacity, voltage, cycle life, and safety of the battery.
• Electrolyte: The type, concentration, and solvent of the electrolyte will affect the conductivity, operating temperature, and safety performance of the battery.
• Separator: The pore size, thickness, and mechanical strength of the separator will affect the safety and cycle life of the battery.
• Housing: The material and design of the housing will affect the safety and reliability of the battery.

Specifications/Parameters of cells in lithium-ion battery packs

Size: The size of a lithium-ion battery cell is usually expressed in diameter and height in millimeters (mm). Common sizes include 18650, 21700, 26650, etc.

Capacity:  The capacity of a lithium-ion battery cell refers to the amount of electricity it can store, measured in ampere-hours (Ah). The larger the capacity of a battery, the longer it can last.

Voltage: The voltage of lithium-ion battery cells is usually 3.7V or 3.2V.

Chemical composition: The positive and negative electrode materials of lithium-ion battery cells affect their performance, including capacity, voltage, cycle life, and safety. Common chemical compositions include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), etc.

According to the above specifications, lithium-ion battery cells can be divided into the following categories:

• 18650 3.7V LCO: This battery is the most common lithium-ion battery cell, with dimensions of 18 mm in diameter and 65 mm in height. The capacity is usually between 2000mAh and 3500mAh, the voltage is 3.7V, and the positive electrode material is lithium cobalt oxide. It has a high energy density and cycle life, but relatively low safety.
• 21700 3.7V LCO: This battery has a size of 21mm diameter and 70mm height, and the capacity is usually between 4000mAh and 6000mAh. Other performance is similar to 18650 3.7V LCO.
• 26650 3.7V LCO: This battery has a size of 26mm diameter and 65mm height, and the capacity is usually between 6000mAh and 12000mAh. Other performance is similar to 18650 3.7V LCO.
• 18650 3.2V LFP: This battery has the same size as the 18650 3.7V LCO, with a capacity usually between 1500mAh and 3000mAh, a voltage of 3.2V, and a positive electrode material of lithium iron phosphate, which is safer, but has a relatively low energy density and cycle life.

When choosing a lithium-ion battery cell, you need to select the appropriate specification based on the actual application requirements. For example, if you need a longer battery life, you can choose a battery with a larger capacity; if you have higher safety requirements, you can choose a battery made of LFP material.

Here are some common lithium-ion battery cell brands:

• Samsung
• LG
• ATL
• CATL

What is the consistency of lithium-ion batteries?

lithium-ion battery cells refer to the closeness of the electrical performance indicators such as capacity, internal resistance, self-discharge rate, voltage, etc. of batteries produced in the same batch. A battery pack with good consistency can maintain consistent performance during the charge and discharge process, thereby improving the overall efficiency and service life of the battery pack.

Factors that affect the consistency of lithium-ion battery cells mainly include:

• Raw materials: The quality and consistency of raw materials such as the positive electrode material, negative electrode material, electrolyte, etc. of the battery will directly affect the performance of the battery.
• Manufacturing process: The manufacturing process of batteries includes coating, pressing, winding, drying, formation, etc. The process parameters and control accuracy of these links will affect the performance of the battery.
• Use environment: During use, the battery will be affected by environmental factors such as temperature, humidity, vibration, etc. These factors will affect the performance of the battery.

Lithium-ion battery cells can be improved by:

• Strictly control the quality and consistency of raw materials.
• Optimize battery manufacturing process.
• Reasonably design the battery management system.

Lithium-ion battery cells is crucial to the performance and life of the battery pack. A battery pack with good consistency can improve charging and discharging efficiency, extend service life, and reduce safety risks. Therefore, in the production and application of lithium-ion batteries, the consistency of batteries should be highly valued.

Here are some lithium-ion battery cell consistency testing methods:

• Capacity test: Measures the charge and discharge capacity of the battery.
• Internal resistance test: measure the internal resistance of the battery.
• Self-discharge rate test: measures the discharge rate of a battery when it is at rest.
• Voltage test: Measures the voltage of the battery.

Through these test methods, the consistency of the battery can be evaluated. The test results of a battery with good consistency should have a small deviation.

The structure and working principle of BMS in lithium-ion battery pack

The battery management system (BMS) is an important component of the lithium-ion battery pack, responsible for monitoring and managing the operating status of the battery pack to ensure the safety and performance of the battery. The BMS usually consists of the following parts:

• Data acquisition module: responsible for collecting data such as voltage, current, temperature, etc. of each battery cell in the battery pack.
• Control module: controls and manages the battery pack based on the collected data, including balanced charging, overcharge protection, over-discharge protection, overcurrent protection, short circuit protection, etc.
• Communication module: responsible for communicating with external devices such as battery chargers, motor controllers, etc.
• Power module: provides power for the BMS itself.

How BMS works

The working principle of BMS mainly includes the following aspects:

• Data acquisition: BMS collects data such as voltage, current, temperature, etc. of each battery cell in the battery pack through the data acquisition module. These data reflect the real-time status of the battery and are the basis for BMS control and management.
• Status monitoring: BMS monitors the operating status of the battery pack based on the collected data, including the battery’s voltage, current, temperature, capacity, health status, etc. If any abnormality is found, BMS will promptly alarm and take appropriate measures.
• Balanced charging: During the charging and discharging process of lithium-ion batteries, due to the influence of factors such as the manufacturing process and the use environment, the capacity of individual batteries may deviate greatly. If the batteries are not balanced charged, the battery pack capacity will decrease and the cycle life will be shortened. BMS uses the balanced charging function to keep the voltage of each cell in the battery pack consistent, thereby improving the overall performance and life of the battery pack.
• Protection function: BMS has multiple protection functions to prevent the battery pack from overcharging, over-discharging, over-current, short circuit, and other faults, thereby ensuring the safety and reliability of the battery.

Importance of BMS

The BMS plays a vital role in a lithium-ion battery pack by:

• Improve battery safety and reliability: BMS can prevent battery packs from overcharging, over-discharging, over-current, short circuit, and other faults, thereby ensuring battery safety and reliability.
• Extend battery life: BMS can extend the battery life through functions such as balanced charging and status monitoring.
• Improve battery performance: BMS can improve battery performance through functions such as balanced charging and status monitoring.

Range per charge of ebike batteries

The range of an electric bicycle is affected by many factors, including battery parameters, motor parameters, riding conditions, etc. The following is a method to estimate the range based on battery parameters and motor parameters :

1. Determine battery parameters

Battery parameters include battery voltage (V), battery capacity (Ah), and battery energy density (Wh/kg).

• Battery voltage (V): Usually 12V, 24V, 36V or 48V.
• Battery capacity (Ah): Indicates the amount of electricity that a battery can store.
• Battery energy density (Wh/kg): indicates the amount of electricity that can be stored per unit weight of the battery.

2. Determine the motor parameters

Motor parameters include motor power (W) and motor efficiency (η).

• Motor power (W): Indicates the maximum power that the motor can provide.
• Motor efficiency (η): It indicates the efficiency of the motor in converting electrical energy into mechanical energy.

3. Calculate driving range

The range of an electric bicycle can be estimated using the following formula :

Cruising range (km) = (battery energy density × battery capacity) / (motor power × (1 – motor efficiency))

Example

Assume that the battery parameters of an electric bicycle are as follows:

• Battery voltage: 36V
• Battery capacity: 12Ah
• Battery energy density: 250Wh/kg

The motor parameters are as follows:

• Motor power: 350W
• Motor efficiency: 80%

range of the electric bicycle is approximately:

Endurance = ( 250Wh /kg × 12Ah) / (350W × (1 – 0.8)) ≈ 35km

It should be noted that the above estimation method is for reference only, and the actual mileage may vary because the actual riding process will be affected by factors such as road conditions, slope, wind resistance, and rider weight.

Here are some tips for extending the range of your electric bike :

• Choose a battery with higher energy density.
• Choose a more efficient motor.
• Ride on a flat surface.
• Avoid frequent acceleration and braking.
• Maintain a moderate riding speed.
• Check and maintain the battery and motor regularly.

The difference between lithium-ion cells and battery packs

Lithium-ion cells and battery packs are two closely related concepts, but there are some key differences between them.

Lithium-ion battery refers to a battery cell composed of a positive electrode, a negative electrode, an electrolyte, a separator, and a shell. It is the smallest component unit of a battery and also the core component of a battery. The performance of the battery cell directly determines the performance of the battery.

A lithium-ion battery pack is a battery system consisting of multiple lithium-ion cells connected in series or parallel. It can provide power for electric bicycles, electric vehicles, energy storage systems, and other equipment. The performance of a battery pack depends not only on the performance of the cells but also on the performance of the battery management system.

The following table summarizes the main differences between lithium-ion cells and battery packs:

Simply put, lithium-ion cells are like the “bricks” of the battery, and lithium-ion battery packs are the “walls” made of these “bricks”. The performance of the cells determines the quality of the “bricks”, while the performance of the battery management system determines the structure and stability of the “wall”.

Precautions for daily use of lithium-ion batteries for e-bikes

The daily use of electric bicycle lithium-ion batteries should pay attention to the following aspects:

Charging:

• Use the original or qualified charger to charge.
• Do not overcharge or overcharge the battery. Generally, start charging when the battery has 20%-30% remaining, and unplug the charger immediately after it is fully charged.
• Avoid charging in high or low-temperature environments. The charging environment temperature should be kept between 0℃ and 40℃.
• Do not place the battery in direct sunlight or in a humid place while charging.
• When the electric bicycle is not used for a long time, the battery should be charged every two or three months to maintain the battery power.

Usage:

• Avoid using the battery in extremely high or low-temperature environments. The operating temperature of the battery should be kept between -20℃ and 60℃.
• Avoid high-current charging and discharging.
• Protect the battery from impact or crushing.
• When the battery shows abnormal conditions such as swelling, leakage, etc., stop using it immediately and contact a professional for treatment.

Maintenance:

• Check the battery connection regularly to see if it is loose or damaged, and repair or replace it promptly.
• Clean the battery surface dust and dirt regularly.
• Perform maintenance and inspection on the battery regularly to ensure that it is in good condition.

Here are some additional suggestions:

• Try to avoid starting and stopping your electric bicycle frequently.
• When riding uphill or downhill, try to use human power to reduce the burden on the battery.
• Check your e-bike’s motor and controller regularly to make sure they are in good working condition.

What are overcharge and overcharge?

Overcharging means that the charging voltage or charging time of the battery exceeds the specified limit of the battery, causing irreversible chemical reactions inside the battery, thereby reducing the performance and life of the battery, and even causing safety accidents.

Overdischarge means that the discharge depth of the battery exceeds the specified limit of the battery, resulting in irreversible chemical reactions inside the battery, thereby reducing the performance and life of the battery, or even damaging the battery.

The hazards of overcharging and over-discharging

Overcharging can cause the following hazards:

• Increased internal pressure in the battery may cause battery bulging, leakage, or even explosion.
• The battery-positive electrode material decomposes, resulting in a decrease in battery capacity.
• Lithium deposition at the negative electrode of the battery causes an increase in the internal resistance of the battery.

Overdischarge can cause the following hazards:

• Increased internal pressure in the battery may cause battery bulging, leakage, or even explosion.
• The battery’s positive electrode material dissolves, causing the battery’s capacity to drop.
• Lithium deposition at the negative electrode of the battery causes an increase in the internal resistance of the battery.

How to avoid overcharging and over-discharging

Avoid overcharging

• Use the original or qualified charger to charge.
• Do not overcharge the battery. Generally, start charging when the battery has 20%-30% remaining, and unplug the charger when it is fully charged.
• Avoid charging in high or low-temperature environments. The charging environment temperature should be kept between 0℃ and 40℃.
• Do not place the battery in direct sunlight or in a humid place while charging.

Avoid over-discharge

• Avoid using the battery in extremely high or low-temperature environments. The operating temperature of the battery should be kept between -20℃ and 60℃.
• Avoid high-current charging and discharging.
• Protect the battery from impact or crushing.
• When the battery is low, it should be charged in time.

Cost per charge of a lithium-ion battery pack

To calculate the cost per charge of a 48V lithium-ion battery pack, we need to consider the following factors:

The energy capacity of a battery pack: measured in ampere-hours (Ah). Common capacities for 48V lithium-ion battery packs are 10Ah, 12Ah, 15Ah, and 20Ah.

Local electricity price: measured in US dollars per kilowatt hour ($/kWh). Assume your electricity price is 0.12/kWh.

Charging efficiency: refers to the ratio of the electric energy absorbed by the battery during charging to the electric energy provided by the battery during charging. Usually around 80 %.

Here are the steps to calculate the cost per charge of a 48V lithium-ion battery pack:

1. Convert battery pack capacity units to kilowatt-hours (kWh): Energy capacity (kWh) = battery pack voltage (V) × battery pack capacity (Ah) / 1000 For example, for a 10Ah 48V battery pack: Energy capacity (kWh) = 48V × 10Ah / 1000 = 0.48kWh
2. Calculate charging cost: Charging cost = (battery pack capacity (kWh) × electricity price (/kWh)) / charging efficiency

For example, for a 10Ah 48V battery pack:

Charging cost = (0.48 kWh × $0.12/kWh) / 0.85 = $0.66

So, in this example, it would cost 0.66 to fully charge a 10Ah 48V Li-ion battery pack. Here are some factors that can reduce the cost of charging a 48V Li-ion battery pack:

Use higher capacity battery packs: Higher capacity battery packs mean more energy can be stored per charge, thus reducing the cost per charge.

Generate electricity using renewable energy sources: for example, solar or wind power.

Charge when electricity prices are lower: Many power companies offer time-of-day rates, and charging during off-peak hours can save money.

Improving charging efficiency: Using more advanced chargers or optimizing charging strategies can improve charging efficiency.

As lithium-ion battery technology advances and renewable energy becomes more widespread, the cost of charging lithium-ion battery packs will continue to drop, making them more attractive for applications such as electric bicycles and power tools. Here are some common 48V lithium-ion battery packs on the market and their single-charge costs:

Table of single charge cost of 48V lithium-ion battery pack

Please note that these costs are for reference only and actual costs may vary depending on your specific circumstances.

How to Calculate Charging Time for E-Bike Lithium-Ion Batteries

The charging time of an e-bike lithium-ion battery depends on several factors:

• Battery Capacity: Measured in ampere hours (Ah). The larger the battery capacity, the longer it takes to charge.
• Charging Current: Measured in Amperes (A). The higher the charging current, the shorter the charging time.
• Charging efficiency: refers to the ratio of the electric energy absorbed by the battery during charging to the electric energy provided by the battery during charging. Usually between 80% and 90%.

Here is the formula for calculating the charging time of an e-bike lithium-ion battery:

Charging time = (battery capacity × 100%) / (charging current × charging efficiency)

For example, for a 48V 10Ah Li-ion battery pack, using a 2A charger to charge, the charging efficiency is 85%:

Charging time = (10Ah × 100%) / (2A × 0.85) = 5.88 hours

So, in this example, it would take 5.88 hours to fully charge this battery pack.

Here are some ways you can reduce the charging time of your electric bike lithium-ion battery:

• Use a higher charging current: However, it should be noted that excessive charging current may damage the battery.
• Improving charging efficiency: Using more advanced chargers or optimizing charging strategies can improve charging efficiency.
• Use fast charging technology: Some electric bikes support fast charging, which can fully charge in a shorter time.

Some common e-bike lithium-ion battery charging times:

Here are some things to keep in mind when charging your e-bike lithium-ion battery:

• Use an original or qualified charger: poor quality chargers may cause battery damage or even explosion.
• Charge in a well-ventilated place: The battery will generate heat during charging, so it needs to be charged in a well-ventilated place.
• Avoid charging in extremely high or low-temperature environments: High or low temperatures will reduce the charging efficiency of the battery and may damage the battery.
• Charge the battery promptly when it is low: Over-discharging will damage the battery.
• Do not overcharge: Overcharging will shorten the life of the battery.

Fast charging technology for lithium-ion batteries for bikes

At present, there are mainly the following types of fast charging technologies for lithium-ion batteries for electric bicycles:

• Increase the charging voltage: The charging voltage of traditional electric vehicle lithium-ion batteries is generally 48V, while fast charging technology can increase the charging voltage to 54V, 60V, or even higher. A higher charging voltage can make the charging current larger, thereby shortening the charging time.
• Increase charging current: The charging current of traditional electric vehicle lithium-ion batteries is generally 2A or 3A, while fast charging technology can increase the charging current to 5A, 8A or even higher. A larger charging current can fully charge the battery in a shorter time.
• Changing the battery’s charge and discharge characteristics: Traditional electric vehicle lithium-ion batteries follow a constant current-constant voltage charging strategy during the charge and discharge process. Fast charging technology can improve charging efficiency by changing the charging strategy, such as using pulse charging, segmented constant current charging, etc.
• Use new battery materials: Traditional electric vehicle lithium-ion batteries usually use materials such as lithium iron phosphate (LFP) or ternary lithium (NCM). Fast charging technology can use new battery materials, such as silicon-carbon negative electrode, high-nickel ternary lithium, etc. These materials have higher energy density and faster charging and discharging speeds.

The following are some common electric bicycle lithium-ion battery fast charging technologies and their characteristics:

The application of lithium-ion battery fast charging technology for electric bicycles has the following advantages:

• Shorten charging time: Fast charging technology can significantly shorten the charging time of electric bicycle lithium-ion batteries, making it more convenient and faster for riders.
• Improved cruising range: Fast charging technology allows the lithium-ion battery of an electric bicycle to be fully charged in a shorter time, thereby increasing the cruising range of the electric bicycle.
• Improve user experience: Fast charging technology can provide e-bike users with a more convenient charging experience and improve user satisfaction.

Of course, there are also some challenges in fast charging technology for electric bicycle lithium-ion batteries:

• Higher cost: Fast charging technology usually requires the use of more expensive materials and devices, so the cost is higher.
• Safety risks: Fast charging technology may increase battery safety risks, so safety management needs to be strengthened.
• Battery life: Excessively frequent fast charging may shorten the battery life, so fast charging technology needs to be used reasonably.

Why does fast charging shorten the life of lithium-ion batteries?

Lithium-ion batteries are chemical batteries that store and release electrical energy through the insertion and extraction of lithium ions. Fast charging technology can shorten the charging time by increasing the charging current or charging voltage, but this may also have the following effects on the battery life:

Accelerate battery polarization: During fast charging, lithium ions need to be quickly embedded into the negative electrode material in a short period. This will increase the surface area of the negative electrode material, thereby accelerating battery polarization. Battery polarization will reduce the capacity and efficiency of the battery and shorten the battery life.

Leading to lithium dendrite precipitation: During fast charging, lithium ions may not have enough time to embed into the negative electrode material and precipitate on the battery surface to form lithium dendrites. Lithium dendrites can pierce the battery separator, causing a short circuit in the battery and even causing a safety accident.

Increased battery internal resistance: The heat generated during fast charging will accelerate the chemical reaction inside the battery, causing the battery’s internal resistance to increase. The increase in battery internal resistance will reduce battery efficiency and shorten the battery life.

Reduce battery cycle life: Fast charging will cause a greater impact on the positive and negative electrode materials of the battery, causing the active substances of the battery to fall off, thereby reducing the cycle life of the battery.

Charge cut-off voltage, discharge cut-off voltage, and platform voltage of lithium-ion battery pack

The voltage of lithium-ion battery packs will change during the charging and discharging process. To protect the battery and avoid damage, it is necessary to set the charging cut-off voltage and the discharging cut-off voltage. The platform voltage is a relatively stable voltage area that appears during the battery discharge process.

1. Charge cut-off voltage

The charging cut-off voltage refers to the maximum allowable voltage value reached by the lithium-ion battery during the charging process. If charging continues, the battery may be overcharged, causing the following problems:

• The pressure inside the battery increases, causing the battery to swell or even rupture.
• The battery electrolyte decomposes, generating harmful gases that corrode the internal structure of the battery.
• Battery active materials decompose, reducing battery capacity and life.

To avoid the above problems, lithium-ion battery packs usually set a charging cut-off voltage. This voltage value is usually slightly lower than the maximum allowable voltage of the battery to provide a certain safety margin. Common lithium-ion battery pack charging cut-off voltages are:

• Lithium iron phosphate battery: 3.7 V/cell
• Ternary lithium-ion battery: 4.2 V/cell

2. Discharge cut-off voltage

Discharge cut-off voltage refers to the lowest allowable voltage value reached by the lithium-ion battery during the discharge process. If the discharge continues, the battery may be over-discharged, causing the following problems:

• The internal pressure of the battery decreases, causing the battery to deform or even be damaged.
• The battery electrolyte decomposes, generating harmful gases that corrode the internal structure of the battery.
• The battery’s active materials are irreversibly deactivated, resulting in a permanent reduction in battery capacity.

To avoid the above problems, lithium-ion battery packs usually set a discharge cut-off voltage. This voltage value is usually slightly higher than the minimum allowable voltage of the battery to provide a certain safety margin. Common lithium-ion battery pack discharge cut-off voltages are:

• Lithium iron phosphate battery: 2.8 V/cell
• Ternary lithium-ion battery: 3.0 V/cell

3. Platform voltage

Platform voltage refers to a relatively stable voltage region that occurs during the discharge process of a lithium-ion battery. In this region, the battery voltage changes little and the discharge current remains relatively stable. The platform voltage occurs because different active substances undergo redox reactions in sequence during the discharge process of the battery. The redox reaction of each active substance corresponds to a specific voltage platform.

The platform voltage is of great significance for the application of lithium-ion batteries. It can be used as an indicator of the remaining battery power and to estimate the discharge time of the battery. In addition, the platform voltage can also be used as an indicator for evaluating the battery status. For example, if the platform voltage of the battery drops significantly, it may indicate that the active material of the battery has partially decomposed and the battery performance has declined.

Here are some factors that affect the platform voltage of a lithium-ion battery:

• Battery materials: Different battery materials have different redox potentials and therefore different plateau voltages.
• Charge and discharge rate: The faster the charge and discharge rate, the lower the platform voltage of the battery.
• Temperature: The higher the temperature, the higher the battery’s platform voltage.

henry

Marketing and Sales Manager at Jieli Electric | Website | + posts

Sales Manager at Jieli Electric Bikes.
Near 10 years experience in electric bike industry, researching/marketing/promoting e-bike is my daily life.

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