What are the common types of power batteries
Generally speaking, the power battery mainly refers to the use of batteries for electric vehicles, electric vehicles, aircraft models and other equipment that require relatively high power. The power battery has high requirements for current, relatively large capacity, and the lighter the weight, the better, especially For power batteries used in aviation models, the focus on weight is to the gram.
Common types of power batteries:
Lead-acid batteries: They are generally maintenance-free now. They are more common in electric tricycles, starting batteries for cars, etc. The rated voltage is generally a multiple of 12. The main characteristics of lead-acid batteries are that the capacity is relatively large, and the instantaneous discharge current can be large. However, the continuous high-current discharge capacity is weak; the weight is heavy, that is, the energy density is not high, and it is generally used for electric three-wheeled, old-age scooters, electric bicycles, etc., which do not require high weight, and the key is relatively cheap. Lead-acid batteries are slow to charge and cannot be charged quickly, and the charging current generally does not exceed 10 amps.
Lithium iron phosphate battery: The charge and discharge performance is much better than that of lead-acid batteries, and the energy density is also much higher. The rated voltage is 3.2, and now there are 3.7. The most common ones are 18650 and 26650 for strong light flashlights. Tesla released 21700 These are small cylindrical cells with a capacity of several thousand mA. Now there are also large square cells with a capacity of 20 amps for electric vehicles. Lithium iron phosphate has relatively high energy density and good safety performance. It is mostly used in electric vehicles. For example, Tesla's battery is composed of more than 7,000 small batteries connected in series and parallel. Of course, this requires a powerful battery management system.
Ternary lithium battery: generally has higher energy density than lithium iron phosphate battery, that is, a smaller weight can store more power. Model aircraft power batteries use this type of battery, and electric vehicles are also used. It is generally believed that the safety is lower than that of phosphoric acid. Lithium iron, generally soft pack, single voltage 4.2v, and high voltage version is 4.35v.
Several key parameters of the power battery:
Capacity and voltage: These two are easy to understand, so I won't explain more. power batteries
Energy density: It is the amount of electricity stored per unit weight, and the unit is wh/kg. In simple terms, it can be understood that the more electricity stored at the same weight, the better, and the lighter the battery with the same amount of electricity, the better.
Charge and discharge rate: It is often called c number, which represents the charge and discharge capacity of the battery. This has a lot to do with the process and quality of the battery cell. The larger the c number, the more current it can be charged. A battery with a capacity of 100Ah, if it is 0.2c, can only be charged at 20A, and if it is 1c, it can be charged at 100A. Therefore, the battery of the same capacity, the higher the c number, the more expensive the price, especially the battery of the model aircraft.
Charging: Power battery charging is not that simple, it needs a corresponding special charger, and the control technology is relatively complex. It is not simple to charge with the same voltage. Generally, a constant current is required in the initial stage of charging, that is, the voltage is slowly increased to ensure the current. Certainly, constant voltage is required in the final stage, that is, the rated voltage is reached, and the current is gradually reduced. Generally, people who play aircraft models have expensive smart chargers, and the chargers are worth more than 1000, such as
Balance: Because a large number of power batteries are connected in series and parallel to achieve the required voltage and capacity, and a bad one of them may cause the entire battery pack to fail, so charge and discharge management is very important. Taking the smallest one as the criterion, the charging can only be based on the most saturated one. In order to solve this problem, on the one hand, the consistency of the cells is required to be very high, and on the other hand, it needs to be solved by balancing. When discharging, let the saturated ones discharge more. , let the low voltage charge more when charging. That's why the battery management system is so complicated.
Notes for self-assembled batteries:
1. Cell procurement: It is best to buy cells that have been divided, that is, a batch of cells to ensure consistency as much as possible. Generally, don’t believe how good the consistency of dismantled cells is.
2. Do a good job of insulation protection: the parts that are easy to touch during the welding process must be covered with insulation first, and the cells may be damaged if touched.
3. The power of the soldering iron is higher: short-term welding to prevent the electrode from overheating and damaging the cell.
4. Pay attention to the matching output line: not too small, the line is overheated, it is best to choose a soft silicone line.
5. Packaging: highland barley paper, cloth tape, heat shrinkable film, hot melt adhesive.