Application of multifunctional lithium battery charging board

I have mail-ordered several charging boards. After power-on testing, I found that one of the charging boards using the MM1332G integrated circuit outputs a voltage of 4.15v. The charging integrated circuit is HHl332G. After checking the information, I learned that this integrated circuit is a special constant current and constant voltage lithium-ion battery charging IC produced by Japan's Misami Company. It contains battery voltage detection and full charge detection, and the accuracy of controlling the cut-off charging voltage of each cell can reach ±50mV. The charging cut-off voltage is 4.2V, and the charging voltage and current can be controlled by external resistors. The ② and ③ pins of this integrated circuit have a short-circuit protection function (also known as low voltage detection), which can detect internal or external short circuits in the battery and cut off the output. Use this charging board to charge the purchased 550mA lithium battery. The current is about 160mA. It can be fully charged in about four hours, and the charging will stop automatically.

The author mapped the charging board circuit according to the actual object as shown in the attached figure. The component parameters in the figure are marked according to the actual object. The size of the charging board is 3.5cm×2.5cm, and it has an L-shaped structure. Because it contains a rectifier part, the circuit board is easy to use, but the maximum AC input voltage should not exceed 10v, otherwise, the power tube Q1 (B1247) will be overheated and damaged due to the lack of a heat sink. After experiments, the author found that the DC voltage across the capacitor EC1 of the charging board can work normally at 5V~12V. When it is 12V, Q1 heats up seriously, so it is best to install a heat sink. The voltage difference across B1 247 should be as small as possible to avoid overheating. When the author made a charger, he used a ready-made micro-switching power supply DC5.6V/0.6A adapter. In order to utilize the remaining space and reduce the volume, the rectifier part of the charging board was cut off and installed in the adapter. After the charging end was connected with a wire, two micro metal clips were welded on, which was very convenient to use. Of course, other power adapters can also be used externally. At this time, there is no need to distinguish the positive and negative polarity of the power supply.

Connect the two ends of the EC1 capacitor to a USB cable and charge it using the USB port on a computer, or modify it with a universal charger to make it a dual-purpose charger.

It is very convenient and worth the money, which is even more important for charging "bare" lithium batteries without charge and discharge protection boards.

This board can also be changed to charge 8.4V or 12.6V lithium batteries. According to the test, when R9 (183) is changed to 2.7kΩ～7.5kΩ, the output voltage can be adjusted to 8.4V～12.6V by adjusting R8. In this way, it can be changed to charge two or three lithium batteries.

Increasing the charging current can reduce the detection resistor R6∥R7 to 0.3Ω, and the charging current can reach about 300mA (charging time = battery capacity / charging current). In addition, there is an improved model of the MM1332G integrated circuit, LM3622, produced by National Semiconductor. Its performance is superior to that of the MM1332G, and the pin distribution is slightly different. The specific use can be modified according to actual needs. The author believes that it is generally better to charge with a small current. In this way, the battery is not easy to heat up, which correspondingly extends its service life, and is relatively safe and reliable.

The author once posted an application article of this lithium battery charging board on the Internet, which aroused the interest of many DIY enthusiasts and also led to many articles on the production of various chargers that can be used with this board, such as adding a full charge indication circuit and a solar charger.