lithium 3400mah 3.7v 18650 battery.Battery technology applications for portable electronic devices

　　Applying the battery technology of portable electronic equipment is the basis for selecting lithium-ion batteries, lithium polymer batteries and their chargers. How to choose correctly must also depend on the specific requirements of portable electronic equipment.

　　1. Battery charging algorithms for trickle charging, fast charging and stable charging

　　Depending on the energy requirements of the end application, a battery pack may contain up to 4 lithium-ion or lithium-polymer cells in a variety of configurations, with a major power adapter: direct adapter, USB port or car charging device. Regardless of differences in cell count, cell configuration, or power adapter type, these battery packs have the same charging characteristics. So their charging algorithms are the same. The best charging algorithm for lithium-ion and lithium-polymer batteries can be divided into 3 stages: trickle charging, fast charging and stable charging.

　　*Triple flow charging. Used to charge deeply discharged cells. When the cell voltage is below approximately 2.8V, it is charged with a constant current of 0.1C.

　　*Fast charging. When the cell voltage exceeds the threshold of trickle charging, the charging current is increased for fast charging. Fast charging current should be lower than 1.0C.

　　*Stable voltage. During fast charging, once the cell voltage reaches 4.2V, the voltage stabilization phase begins. At this time, charging can be interrupted by the minimum charging current or timer, or a combination of the two. When the minimum current is lower than approximately 0.07C, charging can be interrupted. The timer relies on a preset timer to trigger the interrupt.

　　Advanced battery chargers often come with additional safety features. For example, if the cell temperature exceeds a given window, usually 0℃--45℃, charging will be suspended.

　　Except for some very low-end devices, the lithium-ion/lithium polymer battery charging solutions currently on the market all integrate or have external components to charge according to the charging characteristics. This is not only to achieve better charging results, but also It is also for safety.

　　*Charging application example of lithium-ion/polymer battery-dual input 1.2A lithium battery charger LTC4097

　　The LTC4097 can be used to charge single-cell Li-ion/Polymer batteries from an AC adapter or USB power source. Figure 1 is a schematic diagram of the dual-input 1.2A lithium battery charger LTC4097. It uses a constant current/constant voltage algorithm for charging. When charging from the AC adapter power supply, the programmable charging current is up to 1.2A, and when using USB power supply, it can be up to 1A, while automatically Detects the presence of voltage at each input. The device also provides USB current limiting. Applications include PDAs, MP3 players, digital cameras, lightweight portable medical and test equipment, and large color screen cell phones. Its performance features: No need for external microcontroller to terminate charging; Automatic input power detection and selection; Programmable charging current up to 1.2A via resistor from AC adapter input; Programmable USB charging current via resistor up to 1A; 100% or 20 %USB charge current setting; input power present output and NTC bias (VNTC) pin with 120mA drive capability; NTC thermistor input (NTC) pin for temperature qualified charging; preset battery float voltage with ±0.6% accuracy; thermal regulation maximizes charge rates without overheating. The LTC4097 can be used with an AC adapter or USB power source to charge single-cell Li-ion/Polymer batteries. It charges using a constant current/constant voltage algorithm, with programmable charging current up to 1.2A when charging from AC adapter power, or up to 1A when using USB power, while automatically detecting the presence of voltage at each input. The device also provides USB current limiting. Applications include PDAs, MP3 players, digital cameras, lightweight portable medical and test equipment, and large color screen cell phones.

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