Three-string lithium battery pack fast charging adapter cable (furry fan fast charging adapter cable)

Design intention: When I went to a small gathering with friends before, I encountered a situation. My friend's fan ran out of power when he was furrying, but it was difficult to find a suitable power supply to charge the fursuit fan outdoors, because such power supply is generally not available outside, and the charger he brought with him needs to be plugged into 220V. Later, when I helped another friend repair the fursuit fan, I found that the mainstream fan charging part in the circle now has no protection circuit (not referring to the battery pack protection board). There is no charging management, and it is charged with a 12V power adapter. The voltage of the small voltmeter behind the fan can only be used to see if it is fully charged. If someone with a little basic knowledge of electronics will know how to look at the voltage to determine whether the battery pack is full, but if someone has no knowledge of this aspect, it is difficult to judge. Based on these problems, this fursuit fan fast charging adapter cable was made. The device is also compatible with other three-string lithium battery packs composed of 4.2V lithium batteries, such as 12V hand drill battery packs, 12V rechargeable angle grinder battery packs, etc.
 
 
This charger is suitable for outdoor occasions without conventional power supply, and is suitable for ternary lithium battery three-string battery pack (single battery minimum voltage 3.7V maximum voltage 4.2V, 3-string battery pack voltage 12.6V)
Equipment parameters:
Input (rated maximum): 5V~20V 5A
Output (rated maximum): 12.6V 3A
Fast charging protocol: Support PD3.0, PD2.0, QC3.0, QC2.0, AFC protocol 
Design maximum output power (fast charging protocol state) 36W, (non-fast charging protocol state) 25W
Protection: overcharge protection, charging overcurrent protection, disconnection protection, overheating protection.
 
Working principle:
 
When the input voltage is less than 15V, DC-DC enable is turned on, and the input voltage is boosted to 20V and output to SLM6900. When the input voltage is greater than 15V, DC-DC enable is turned off, and the input voltage is directly output to SLM6900.
In order to improve the efficiency of the equipment, it is recommended to give priority to devices that support fast charging, such as fast charging chargers that support QC and PD protocols, and power banks that support QC and PD protocols, which will help improve the charging efficiency.
 
 
Working status and mode explanation:
 
non-fast charging state (in some fast charging states, the fast charging indicator light will not light up if the input does not reach 15V)
 
non-fast charging, fully charged (in some fast charging states, the fast charging indicator light will not light up if the input does not reach 15V)
 
 
fast charging state fully charged
 
 
test: output voltage (output voltage jumps under no-load state)
 
physical picture:
simulation picture:
 
precautions for use: This product is only suitable for 4.2V three-string lithium battery packs. Do not charge lithium battery packs of other voltages. This product does not have a voltage equalization function. Please use it with the lithium battery pack protection board when using it. This product will heat up when it is working normally, which is a normal phenomenon. When using it, the charger should be connected to the power supply first, and then the charger should be connected to the battery pack. If used in reverse, the charger may not be able to output the highest power (cannot output the highest voltage fast charge). When the charger is plugged in and not connected to the battery pack, the blue indicator light is always on and the red indicator light flashes. Indicates that the charger and battery pack are disconnected. After the connection is successful, if the battery pack is fully charged, the blue indicator light is always on and the red indicator light does not flash. If the battery pack is not fully charged, the red indicator light is always on, indicating that it is charging. After it is fully charged, the red indicator light goes out and the blue indicator light is always on. If the power supply supports the fast charging protocol and the output is the highest power, the green indicator light is always on. (In some cases, the fast charging (green) indicator light is not on, but the device is still in the fast charging state. This is because the maximum output voltage supported by the power supply does not exceed 15V.)
The author is not responsible for any adverse consequences caused by improper use of this product.
If you use this product, please strictly follow the open source agreement: CC-BY-NC-SA 3.0. Any form of commercial behavior is prohibited.