[Update 8-25] CN3765, 1-5 string batteries can be charged at any time with equalization

Important reminder:

1: You can consider replacing the MOS with a smaller capacitance. The capacitance of the MOS in this schematic diagram is too large and may not be the best choice. 2: The balancing part has not been measured, and the 10 ohm resistor may not be suitable. 3: Do not leave the FB pin open for a long time. , it is very likely to damage the chip 4: The version of the chip you bought is inconsistent with the version in the data sheet. It is currently known that the two pins for charging instructions may be swapped. No other differences have been found yet. Please pay attention when powering on and standby. Whether the red light is on or the green light is on, the green light should prevail. If the red light is on, please swap the welding positions of the two LEDs (updated on 2020-10-7)

Design goals:

Implement a high-power fast charging circuit suitable for any battery pack within 25V

Design reference:

https://oshwhub.com/LiuComJack/LL601_BC3765LKJ_ADJ (Thanks very much for his design, which reduces a lot of obstacles) is its basis. During our testing of this module, we noticed the problem of heat generation, so we redesigned the PCB design suitable for high power and installed an external cooling fan.

Module parameters:

• Input voltage: 12-30VDC

• Output voltage: no more than 25VDC

• Output current: 4A maximum

• Output power: 25V @ 4A 100W maximum (theoretical power, currently 50W power has been measured)

• Module working mode: DC-DC step-down, external power P-MOS tube

• Two LED lights indicate charging status respectively (charging completed/charging)

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Operating characteristics:

• The external fan is of 4040 specification, which is a brushless fan with a size of 4CM and 12V power supply.

• There are various ways to control the fan. It can be controlled by a switch or an external [normally open] temperature switch can be used to customize the fan starting temperature.

• Use a short-circuiting cap to connect the pin header to quickly switch the output voltage (actually, it quickly jumps to a closer voltage), and then use the potentiometer for correction and fine-tuning.

• The short-circuit cap falls off to protect the chip from damage (FB open circuit).

• There are three ways to input the input: back pad soldering wire, DC005 socket, soldering-free wire terminal,

• The output terminal provides two methods of soldering-free wire terminals and top pads to connect the target battery (pack).

• The output is anti-backflow, and the battery (pack) will not output reversely to the power provider of the module, which improves certain safety.

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Update log:

1: [2020-6-28]: The project design has been completed and the planning is in progress. . .

2:【2020-7-03】：

It was found that the fan power switch MOS could not control the fan switch normally. The reason was that the G pole was not correctly guided to a low level by the switch (it was left floating). So let’s just not add MOS (Actually, you don’t need MOS either.), just use the switch load directly, the current is not large.

3:【2020-7-06】：

The above problems have been fixed and updated in the PCB and schematic diagram, but since the main charging circuits between the old and new PCBs are still the same, we decided to post a few test pictures. The following is a record of the charging process of 1S Power 18650.

4: [2020-7-31]: A balancing module for battery packs within 5S has been produced. The theoretical balancing current value is approximately 400MA, and there are currently no conditions for testing. Close-up of the new PCB: Since there are not enough temperature control switches here, only one temperature control switch is installed. The parameters of the switch are: 45 degrees normally open, which means that when the temperature exceeds 45 degrees, the switch is closed and the fan is powered on. heat dissipation.

Important update on 8-25:

HSU4103, it is recommended to use this PMOS tube. The capacitance is greatly reduced, which can greatly reduce heat generation. However, the schematic diagram will not be updated for the time being, mainly because I am too lazy to change it.

Module development plan:

Between our pursuit of excellence (Not) quality, we will design a battery balancing board for it, and may also arrange the balancing PCB and charging circuit on the same board (the board is equipped with an 18650 battery holder). The development of this module is not over yet, and we will try our best to out a better circuit

This project will continue to be updated. We hope that interested friends will continue to pay attention to our progress. If you feel that our production is helpful to you, you may wish to like, collect, and vote (?)! ,Many thanks!