The microcircuit is made in the SOP-8 package (see datasheet ), has a metal heat sink on its belly that is not connected to the contacts, which allows for more efficient heat removal. Allows you to charge the battery with current up to 1A (current depends on the current-carrying resistor).
The connection scheme requires the very minimum of mounted elements:
The scheme implements the classical process of charging – first charging with a constant current, then with a constant voltage and a falling current. All in a scientific way. If you disassemble charging steps, then we can distinguish several stages:
1. Monitoring the voltage of the connected battery (this happens all the time).
2. Precharge stage (if the battery is discharged below 2.9 V). The charge is 1/10 current from the programmed resistor R prog (100 mA at R prog = 1.2 kΩ) to the level of 2.9 V.
3. Charging with a maximum constant current (1000 mA at R prog = 1.2 kΩ);
4. When the battery reaches 4.2 V, the battery voltage is fixed at this level. Begins a smooth decrease in the charging current.
5. When the current reaches 1/10 of the programmed resistor R prog (100 mA at R prog = 1.2 kΩ), the charger turns off.
6. After charging is complete, the controller continues monitoring the battery voltage (see item 1). The current consumed by the monitoring circuit is 2-3 μA. After the voltage drops to 4.0V, charging starts up again. And so in a circle.
The charge current (in amperes) is calculated by the formula I = 1200 / R prog . The maximum allowed is 1000 mA.
The actual charging test with a 18650 battery at 3400 mAh is shown in the graph:
The advantage of the chip is that the charge current is given by only one resistor. Powerful low impedance resistors are not required. Plus there is an indicator of the process of charging, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks once every few seconds.
The supply voltage of the circuit should be within 4.5 … 8 volts. The closer to 4.5V, the better (as the chip heats up less).
The first leg is used to connect a temperature sensor built into the lithium-ion battery (usually the average cell phone battery output). If the output voltage is below 45% or above 80% of the supply voltage, the charging is suspended. If you don’t need temperature control, just put that foot on th Signet is simple, done in an hour on the knee. If time is patient, you can order ready-made modules. Some manufacturers of finished modules add protection against over-current and over-discharge ( here , for example, you can choose which board you need – with or without protection, and with which connector).
Signet is simple, done in an hour on the knee. If time is patient, you can order ready-made modules. Some manufacturers of finished modules add protection against over-current and over-discharge ( here , for example, you can choose which board you need – with or without protection, and with which connector).