What’s C-rate?
The C-rate is a unit to declare a current value which is used for estimating and/or designating the expected effective time of battery under variable charge/discharge condition. The charge and discharge current of a battery is measured in C-rate. Most of portable batteries are rated at 1C. This means that a mAh battery would provide mA for one hour if discharged at 1C rate. The same battery discharged at 0.5C would provide 500mA for two hours. At 2C, the mAh battery would deliver mA for 30 minutes. 1C is often referred to as a one-hour discharge; a 0.5C would be a two-hour, and a 0.1C a 10-hour discharge. The capacity of a battery is commonly measured with a battery analyzer. If the analyzer’s capacity readout is displayed in percentage of the nominal rating, 100% is shown if a mAh battery can provide this current for one hour. If the battery only lasts for 30 minutes before cut-off, 50% will be displayed. A new battery sometimes provides more than 100% capacity. When discharging a battery with a battery analyzer that allows the setting of different discharge C-rates, a higher capacity reading is observed if the battery is discharged at a lower C-rate and vice versa. By discharging the mAh battery at 2C, or mA, the analyzer is scaled to derive the full capacity in 30 minutes. Theoretically, the capacity reading should be the same as with a slower discharge, since the identical amount of energy is dispensed, only over a shorter time. Due to internal energy losses and a voltage drop that causes the battery to reach the low-end voltage cut-off sooner, the capacity reading may be lowered to 95%. Discharging the same battery at 0.5C, or 500mA over two hours may increase the capacity reading to about 105%. The discrepancy in capacity readings with different C-rates is related to the internal resistance of the battery.
To calculate of load current value with charge/discharge rate, it can be obtained by;
∴ C-Rate (C) = Charge or Discharge Current (A) / Rated Capacity of Battery
Also, expected available time of the battery on given discharge capacity can be obtained by;
∴ Used hour of the battery = Discharge capacity (Ah) / Discharge current (A)
[Example] In High Power products, rated capacity of SLPBH model is 4.8Ah. A Lithium-ion NMC cell.
1. What is 1C discharge current condition at this model?
∴ Charge (or discharge) Current (A) = Rated capacity of the battery * C-rate = 4.8 * 1(C) = 4.8 A
It’s means the battery is available for 1 hour by this current discharge condition.
2. The discharge current value under 20C discharge condition is 4.8(A)*20(C)=96A This battery reveals the excellent performance even if the battery discharges 20C discharge condition. The following is the available time of the battery when the capacity of battery shows 4.15Ah
∴ Used hours (h) = Discharged capacity(Ah) / Applied current(A) = 4.15(Ah) / 96(A) ≒ 0.043hours ≒ 2.6 minutes with 96A
It means the battery can be use for 2.6minute (0.043h) with load current of 96A
Learn more about lithium batteries here:
Advantages and disadvantages of lithium batteries, batteries in our lives is more common, generally in electric vehicles lithium batteries and batteries more, for batteries we may not be particularly well understood, there are numerous orders of batteries? Then is a look at what are the advantages and disadvantages of lithium batteries.
The advantages and disadvantages of lithium batteries
Lithium- ion batteries have the following advantages.
1, high voltage, the working voltage of a single cell up to 3, 6-3, 9V, Ni-Cd, Ni-H batteries 3 times 2, large specific energy, the actual specific energy can be achieved at present 100-125Wh/kg and 240-300Wh/L (2 times more than Ni-Cd, 1, 5 times more than Ni-MH,, the future with the development of technology, the specific energy can be as high as 150Wh/kg and 400Wh/L
2, long cycle life, generally can reach more than 500 times, or even more than times, for small current discharge of electrical appliances, the battery life will multiply the competitiveness of electrical appliances.
3, good safety performance, no pollution, no memory effect, as Li-ion predecessor of lithium batteries, because of the formation of lithium metal dendrites prone to short circuit, reducing its application areas: Li-ion does not contain cadmium, lead, mercury and other elements of environmental pollution: part of the process (such as sintered, Ni-Cd batteries have a major drawback for the "memory effect "This is a major drawback of some processes (e.g. sintered, Ni-Cd batteries), which severely restricts the use of batteries, but Li-ion does not have this problem at all.
4. Small self-discharge, the self-discharge rate of a fully charged Li-ion stored at room temperature for 1 month is about 10%, much lower than the 25-30% of Ni-Cd and 30-35% of Ni, MH.
5. Fast charging and discharging, 1C charging can reach more than 80% of the nominal capacity.
6.High operating temperature range, operating temperature of -25~45°C, with the electrolyte and cathode improvement, expect to be able to expand to -40~70°C.
Lithium-ion batteries also have certain disadvantages
Lithium-ion batteries also have certain disadvantages
1. the battery cost is higher. This is mainly due to the high price of the cathode material LiCoO2 (less resources for Co) and the difficulty of purifying the electrolyte system.
2. Cannot be discharged at high currents. Due to the organic electrolyte system and other reasons, the internal resistance of the battery is relatively large compared to other types of batteries. Therefore, require a small discharge current density, general discharge current in 0, 5C below, only suitable for small and medium current appliances.
If you want to learn more, please visit our website JOINSUN.
3. need to protect the line control.
A, overcharge protection: overcharge of the battery will destroy the positive structure and affect the performance and life; at the same time, overcharge makes the electrolyte decomposition, the internal pressure is too high and leads to leakage and other problems; therefore, it must be charged at a constant voltage of 4,1V-4,2V.
B. Over-discharge protection: over-discharge will lead to difficulties in the recovery of the active material, so it also needs to be controlled by a protective circuit.
4、Definition of rechargeable battery
Rechargeable batteries are also known as: storage batteries, secondary batteries, is the battery can be repeatedly charged and used. Commonly used are: lead-acid batteries (used in cars, commonly known as "battery", cadmium-nickel batteries, hydrogen-nickel batteries, lithium-ion batteries.
5、The rated capacity of the battery
The rated capacity of the battery refers to the power released when the battery is discharged to the cut-off voltage under certain discharge conditions, and the IEC standard stipulates that the power released by NiCd and NiMH batteries is the rated capacity of the battery when they are charged with 0,1C for 16 hours and discharged with 0,2C to 1,0V at 20±5℃. The units are Ah, mAh
Advantages and disadvantages of lithium batteries
I. Advantages
1, low carbon environmental protection, whether manufactured, applied or destroyed, they do not contain or will not contain all harmful heavy metal elements and lead, mercury, cadmium and other chemicals.
2, lithium ion has a long service life. Batteries using positive grade lithium iron phosphate have been in use for over six years. Rechargeable batteries with positive electrodes are charged and discharged using 1 disc with application records.
3, lithium high-voltage service platform: the average voltage of a single rechargeable battery is equal to or equal to the voltage of three NiCd or NiMH rechargeable batteries in series.
4, pure electric vehicle with lithium phosphate battery charging capacity of c, conducive to high toughness starting and acceleration.
5, lithium has a high specific energy. The relative density of high energy storage technology is 460 to 600 wh/kg, which is 6 to 7 times that of lead-acid batteries.
6, the net weight of lithium-ion batteries is lighter than that of lead-acid batteries, and the net weight of lithium-ion batteries is about 1/5 or 6 of the same volume.
7, lithium battery life is low, no recall effect;
8, lithium battery has strong adaptability to high temperature and ultra-low temperature. It can be applied to -c natural environment, and after processing, it can be applied to -45c natural environment.
Second, the disadvantages
1, lithium cobalt data can not be charged and discharged under high current, the safety factor is poor.
2、Lithium-ion batteries have a poor safety factor and there is a risk of explosion.
3, high production and manufacturing regulations and increased costs.
4, All lithium-ion appliances must maintain power circuits to prevent overcharging and discharging.
Advantages and disadvantages of lithium batteries
The advantages and disadvantages of lithium batteries are actually two places, one is light weight, under normal circumstances, an electric car and bicycle 48V12A lithium battery is actually compared with lead-acid batteries, it is much lighter, even a difference of more than ten kilograms, which is not the usual data ah, then a group of 60V20A battery difference may be in about 20 kg, then it is obvious that the weight of the audience has been The second advantage is its longevity.
The second advantage is its life, its life is still relatively long ', compared with lead-acid batteries, in fact, the life of lead-acid batteries is relatively short, almost in a year and a half or so, but the life of lithium batteries can be about 3 years, and the warranty period of lithium batteries is also longer than lead-acid batteries!
After saying the advantages, let's talk about its disadvantages, in fact, a thing can not be perfect, it has advantages will have disadvantages, its disadvantage is an easy spontaneous combustion, especially high-powered lithium batteries, its safety risks are actually very high, and another is the time of failure, its protection plate can not protect everything to!
The second is that the price is higher, it may be two to four times that of lead-acid batteries, after all, it is much better than lead-acid batteries, so of course the price is much higher, but this price is also acceptable to many people, so many people do not care about this problem, the third point is that it can not be traded in.
For more information, please visit high c rate lithium battery.