26650 lithium battery definition
26650 lithium battery is a type and specification of cylindrical lithium battery, which is suitable for special equipment, medical equipment, instrumentation, power tools, transportation and logistics, security monitoring, exploration and mapping and other fields. 26650 lithium battery size: 26mm in diameter and 65mm in length.
26650 lithium battery advantages
26650 lithium battery has energy density, low self-discharge rate, stable charge and discharge performance, no memory effect, no decomposition when heated, high safety performance, long life cycle, high voltage, can be used in series or parallel to form a 26650 lithium battery pack, environmental protection and no Pollution.
Single 26650 lithium battery
26650 lithium batteries are mainly divided into two types: ternary materials and lithium iron phosphate materials
Voltage: INR26650 lithium battery nominal voltage 3.6V, fully charged voltage 4.2V, discharge cut-off voltage: 3.0V
IFR26650 lithium battery nominal voltage 3.2V, fully charged voltage 3.65V, discharge cut-off voltage: 2.0V
Capacity: IFR26650 lithium battery capacity includes 2800mAh, 3000mAh, 3200mAh, 3400mAh, 3600mAh, 3800mAh, 4000mAh and other capacity segments.
The capacity of INR26650 lithium battery is generally 4500mAh, 5000mAh, 5500mAh, and 6000mAh.
26650 Lithium battery cathode material
The positive electrode materials of 26650 lithium battery include lithium cobalt oxide, lithium manganate, nickel-cobalt-aluminum ternary, nickel-cobalt-manganese ternary, lithium iron phosphate, etc. The material system determines the working voltage and unit capacity of the battery. Core manufacturers improve the overall battery voltage and capacity by adding special substances, coating processes, and manufacturing process improvements to the materials. Under normal circumstances, the working voltage and theoretical gram capacity of various materials are:
The theoretical capacity of lithium cobalt oxide 3.6V is: 274mAh/g
The theoretical capacity of lithium manganate 3.7V is: 148mAh/g
The theoretical capacity of ternary material 3.65V is: 278mAh/g
The theoretical capacity of lithium iron phosphate 3.2V is: 170mAh/g
Various materials themselves will determine the cycle life of the battery, and the manufacturing level of the battery manufacturer will also affect the life.
The advantages of 26650 lithium iron phosphate battery
High energy density: The theoretical specific capacity is 170mAh/g, and the actual specific capacity is ≥140 mAh/g (0.2C, 25°C);
High safety: the safest cathode material for lithium-ion batteries at present;
No pollution: does not contain any heavy metal elements that are harmful to the human body;
Long cycle life: under the condition of 100% DOD, it can be charged and discharged more than 2000 times;
Fast charging performance: Lithium batteries with lithium iron phosphate cathode materials can be charged at high rates.
18650 VS 26650 Lithium battery
Compared with the traditional 18650, the 26650 lithium battery has a larger capacity under the same material system, and the number of cells is 52% less than that of the 18650 battery. This means that the complexity of the battery management system, the number of metal structural parts, the volume occupied by the battery, and the cost and selling price of the battery system can be greatly reduced for a power battery of the same capacity.
What is the difference between 18650 lithium battery and 26650 lithium battery?
The rated capacity is different: the rated capacity of IFR26650 lithium battery is 3000-5000mAh, and the rated capacity of IFR18650 lithium battery is 2200~3200mAh.
The two batteries are not the same size: the diameter of the IFR26650 is 26mm, and the diameter of the IFR18650 is 18mm.
The reference mass is different: the production test mass of IFR26650 lithium battery is 94 grams, and the production test mass of IFR18650 lithium battery is 45 grams.
Different battery capacity: The battery capacity of 26650 is larger than that of 18650 under the same battery material. Assuming that the 26650 battery with the same ternary material is generally about 5200mAh, the capacity of 18650 battery is mostly about 2600mAh.
Different application environments: 18650 lithium batteries are used in lighting lamps batteries, industrial lithium battery packs, power tool batteries, electric bicycle batteries, power lithium battery packs, etc., while 26650 lithium batteries are used in energy storage base stations, solar energy storage batteries and more.
The battery life is different: the 26650 must have a larger volume ratio than the 18650, so it has more space to fill the material and achieve a larger capacity. At present, the capacity of the 18650 is 2200mAh, 2600mAh, 3100mAh, etc., and the capacity of the 26650 can be 4000mAh , 4200mAh, 4500mAh, the battery life will be longer.
Safety performance test of 26650 lithium battery
- Overcharge performance
After the standard charging of the battery, measure the initial state of the battery. When the battery is in a normal state, charge it to 10.0V with a 3C current, and then transfer it to a constant voltage and charge it to a cut-off current of 0.01C. Observe the change in appearance of the battery. Result: No fire, no explosion
- Over discharge performance
After the standard charging of the battery, measure the initial state of the battery. When the battery is in normal state, discharge it to 0V at 0.5C. Observe the changes in the appearance of the battery. Result: No fire, no explosion
- External short circuit
After the standard charging of the battery, measure the initial state of the battery, and place it in an explosion-proof cover to directly short-circuit its positive and negative electrodes (the total circuit resistance is not greater than 50mΩ), and the test ends when the battery temperature drops to about 10°C lower than the peak temperature. Observe the temperature and appearance changes of the battery. Result: No fire, no explosion
- Hot box test
Measure the initial state of the battery. After the battery is standard charged, it is placed in an oven, and the temperature is raised to 130±2°C at a rate of (5±2°C)/min and kept for 30min. Observe the changes in the appearance of the battery. Result: No fire, no explosion
Test the initial capacity of the battery. After standard charging, measure the initial state of the battery, and drop the test battery from the height (the lowest point height) of 1m to the concrete floor freely in the vertical and horizontal directions, and it is required to drop twice. Result: No fire, no explosion
- Heavy impact
A steel rod with a diameter of 15.8mm was placed in the middle of a fully charged battery; then a hammer weighing 10Kg was free-falled from a height of 1.0m to the upper part of the battery. Result: No fire, no explosion
- Extrusion test
The cell is placed between the two extrusion surfaces of the extrusion equipment, the cylindrical cell axis is parallel to the extrusion surface, the pressure is gradually increased to 13kN, and the pressure is maintained for 1min. Result: No fire, no explosion
26650 lithium battery charging
26650 lithium battery charging precautions
The basic requirements for charging the 26650 lithium battery are the specific charging voltage and charging current at each stage, and some other auxiliary functions are added to improve the battery life.
In order to ensure the stable and reliable operation of the battery and prevent the interference of transient voltage changes, a delay circuit with overcharge, overdischarge and overcurrent protection should be designed inside to prevent instability caused by transient interference.
The factors that affect the safe and effective charging of 26650 lithium batteries are voltage, current and temperature. Therefore, these three factors should be carefully controlled in the charger design.
Can a 18650 battery charger charge a 26650 battery?
You can use the 18650 lithium battery charger to charge the 26650 lithium battery, but do not use it for a long time. Because the voltage platform of the 18650 lithium battery charger is relatively high, the 18650 lithium battery voltage platform is 3.6V and 4.2V, and the 26650 lithium battery voltage platform for 3.2v and 3.6V. Therefore, long-term use will cause damage to the 26650 lithium battery.
How to choose 26650 lithium battery?
26650 lithium batteries are widely used in power tools, lighting, wind and solar energy storage, electric vehicles, toys, instrumentation, ups backup power, communication equipment, medical equipment and lamps. What should we pay attention to when purchasing 26650 lithium batteries?
- Appearance and production process
Looking at the appearance refers to looking at the appearance, workmanship, size and craftsmanship of the 26650 lithium battery. The advanced technology is very comfortable to touch. After grinding, the rubber oil polishing material not only feels good, but also has strong insulation performance.
- Capacity identification
A 26650 lithium battery without a clearly marked capacity is likely to be a garbage battery reassembled with inferior battery cells or recycled battery cells. There are many cheap 26650 lithium batteries on the market. They are made of recycled battery cells or disassembled battery cells. Although the price is cheap, the lifespan is short and the quality is unstable. Careless use may damage the device or even explode.
- With or without protective plate
The characteristics of the 26650 lithium battery determine that the 26650 lithium battery must be equipped with a protective plate to prevent the occurrence of overcharge, overdischarge and short circuit of the 26650 lithium battery. Danger. Under the fierce price competition, various battery packaging factories seek lower-priced protection circuits, or omit this device at all, making the market full of explosive 26650 lithium batteries.
- Flat and pointed
The 26650 lithium battery has a flat head and a pointed head. The difference between the two is that one has a protective plate and the other does not.
Flat head 26650 lithium battery: without protective plate.
Pointed 26650 lithium battery: with a protective plate, because the top of the protective plate protrudes, the protruding part is the protective plate.
In general, I recommend buying pointed batteries to ensure compatibility with more devices and uses. Usually, the positive and negative poles of electrical appliances are designed with springs, which can be stretched and retracted, and can be used whether it is a pointed or flat battery.