Share the basics of various rechargeable batteries and common chargers
Before sharing the basic knowledge of various rechargeable batteries and common chargers, Shenzhen Weidayuan adapter manufacturer will tell you about the development of chargers, especially the detailed introduction of electronic products. So far, portable electronic products have increasingly demanded performances such as the capacity and cycle life of rechargeable batteries. There are currently four major categories, including: 1. Nickel-cadmium batteries; 2. Lead-acid maintenance-free batteries; 3. Ni-MH batteries; 4. Lithium-ion batteries.
At the same time, the two types of nickel-cadmium batteries and lead-acid maintenance-free batteries (referred to as SLA) have been generally promoted in the 1960s.The two major categories of nickel-metal hydride batteries and lithium-ion batteries (including lithium polymer batteries) have been in the last ten years. A large number of commercial use. These four major types of batteries have their own strengths, the following table gives a basic reference, the specific values of different battery manufacturers may have large differences, consult the manufacturer when using, the data in the table is for comparison only Reference use (C in the table is the nominal capacity of the battery, the unit is AH (Ah), A represents the constant current of charging.) Of course, people hope that the charger can be completed in a short time, but due to the large current and difficult to control, This has a certain degree of cost in terms of cost and technology. If the conditions of use allow, choosing a slow charging charger at night after charging for about 10 to 14 hours will have the advantages of low price and small size.
For the SLA battery used in parallel and online, it is recommended to use 2.27V / unit (corresponding to 12V battery is 13.7V) constant voltage charging. This solution will not overcharge the battery and will also help stabilize the device voltage. For the occasions where SLA batteries are frequently charged and discharged offline, 0.2C constant current, then 2.45V / unit constant voltage should be used. After the battery is charged, it immediately enters the "three-stage" charging method of 2.27V / unit constant voltage. The whole The charging time is about 8 to 10 hours. NICD batteries allow overcharging with a certain current, so it is economical to choose a simple constant current source charger with a current of 0.1C.
NIMH batteries are more sensitive to overcharging, that is, using a current of 0.1C. If the battery is charged for more than 14 hours or the battery is charged for several hours, the battery life will be greatly damaged. When the battery is fully charged, it is very important to turn off the current or reduce the charging current to below 0.02C, even for 0.1C night-time slow-charge NIMH chargers. There have been many successful cases of intelligent fast chargers with a maximum charging current of about 2C. Generally, such chargers must monitor the battery voltage, temperature and other parameters at all stages of the charging process. When the battery is about to be fully charged, the charging current is automatically reduced. Ratio, which can minimize the risk of over-temperature and over-voltage caused by battery overcharging.
The charging characteristics of the two types of NICD and NIMH batteries are very similar, except that during the charging process, the NIMH batteries generate more heat and the peak voltage is less obvious. Both types of batteries use one of the following conditions as the conditions for the termination of fast charging during fast charging: including voltage rise slope (dV / dt), negative voltage increase (-dV), and battery temperature rise slope (dT / dt) . Three other conditions are set to operate under abnormal protection conditions: maximum battery temperature, maximum battery voltage and charger built-in timer. To achieve these monitoring and intelligent switching actions, it will definitely bring up the cost of the charger, but without these measures, the battery will face safety hazards such as reduced capacity, reduced cycle life, and even liquid explosion. The charging methods of LI-ION and SLA batteries are similar. Both require constant current and then constant voltage. The difference is that lithium-ion batteries have higher voltage accuracy requirements (<1%) during the constant voltage stage of charging. Since the safety of lithium batteries is a deadly hazard, special care is required in the control and protection of end-of-charge. For different applications, the lithium-ion battery pack will have a built-in charge and discharge protection circuit to protect the battery from accidents more safely!
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