Intro

Most of JBD BMS have onboard active balancer. If you don't need actual BMS, but just balancer they made standalone device that looks identical to the active balancer unit and still support BLE app.

Aliexpress

	JIKONG 2A 4S-8S Smart Active Balancer 4S 5S 6S 8S Lifepo4 / Lipo/ LTO Battery Equalization With APP
	JIKONG Active Balancer Bluetooth 4S 8S 16S 20S 24S Li-ion/ LiFeP04/ LT0 Batteries 2A 4A Efficient Automatically Active Balance

Teardown

Photos

Metal case looks like custom solution made with metal sheets bend. Model: JK B2A8S

It's double side board:

Board covered by conformal coating:

Cable has transparent sealing for contacts:

Components Identification

	MCU CH32F103C8T6 (clone of STM22) 72MHz 2.7-5.5V 12-bit ADC 12-bit DAC
	Logic Shifter SM74HC595 Used for many switch controlling using SPI
	N-CH MOSFET AP4013S 40V; 10A; 22mOhm@10V SOP-8 Used in all bidirectional switches
	Half-bridge Driver EG393 2-36V
	Low-side Dual Driver TPM2752 (M524 marking) 4.5-23V 5A
	N-CH MOSFET NCE3080K 30V; 80A; 6.5mOhm@10V TO-252
	N-CH MOSFET HYG013N03LS1C2 30V; 150A; 1.3mOhm@10V PDFN5X6-8L
	Schottky Diode SB1045L 45V; 10A TO-277B
	Supercapacitors KAMCAP 30F 2.7V Two in series for 5.4V and 15F
	BLE Module BK3432 Looks like simplest transparent UART (similar to JDY-x)
	EEPROM 24C16 16kBit SOP-8

Topology

It has big supercapacitors 30F 2.7V (connect in series to get 5.4V for Li-ion 4.2V) and many bidirectional switches so it's Flying Single Switched Capacitor Balancing Circuit (FSSC).

*bidirectional switch = N-CH MOSFETs 2x

The principle of work is connecting to the cell with higher voltage -> charging capacitors -> connection to the cell with lower voltage -> discharged stored energy in capacitor.

Here is simplified but clear to understand simulation using a switches instead of MOSFET switches:

	Cell 1 (most bottom) is selected
	Cell 2 is selected
	Cell 3 is selected
	Cell 4 (most top) is selected

Since it's able to multiplexing between all cells it also can measure voltage just with one ADC inputs and based on this measurements perform smart balancing, bot just switching for all cells.

Conclusions