Expandable 4S BMS Support Series and Parallel Connection CAN RS485 Bluetooth for

Product Specification

Expandable 4S BMS Support Series and Parallel Connection CAN RS485 Bluetooth for Battery Banks

A Protection Board That You Can Configure
Most BMS units come with fixed protection limits that cannot be changed. The YKN BMS4S takes a different approach. Using the upper computer software connected via RS485 or CAN you can adjust overvoltage thresholds undervoltage limits overcurrent values temperature cutoffs and balancing parameters. This means the same hardware can be tuned for high energy cells high power cells or cold climate operation without replacing the board.

Balancing That Works Your Way
Passive balancing is included but you decide when it runs. Set the voltage at which balancing starts and the voltage difference between cells that triggers balancing. Then choose between charge balancing which only evens cells while charging or static balancing which works even when the battery sits idle. Every 8 channels can activate one balancing channel at a time preventing excessive heat buildup.

Sleep Mode Saves Battery During Storage
When your battery pack is not in use the BMS detects inactivity and automatically enters sleep mode. Power draw drops from 25 milliamps down to just 300 microamps. This feature is critical for seasonal equipment like RVs boats or solar street lights that sit unused for months. The battery stays healthy and the BMS wakes instantly when a load or charger is connected.

Products	Technical parameters
YKN-BMS4S(Bluetooth)	Basic parameters
	Cell specifications	4 series of lithium iron phosphate cells
	Interface type	Charge and discharge are both at the same port
	Charging Voltage	14.6V
	Cell voltage range	9.6~15V
	Continuous charging current	≤150A
	Continuous discharge current	≤150A
	Consumption of running	≤25mA
	Consumption of sleep	≤300uA
	Operating temperature	-30℃~75℃
	Size (L*W*H)	160mm*95mm*25mm

Built for Extreme Temperatures
The YKN BMS4S operates from -30°C to 75°C ambient. This wide range allows installation in uninsulated sheds engine compartments or outdoor enclosures. The five temperature sensor inputs four for cells and one for the BMS itself let the system cut off charging when cells are too cold and cut off discharge when anything overheats.

Expand Your Battery System Easily
Unlike many BMS units that cannot work together the YKN BMS4S supports both series and parallel connections. Connect two 4S packs in series to create a 24V battery with each pack protected by its own BMS. Connect packs in parallel to increase capacity while maintaining 12V. The BMS units communicate and coordinate protection so one failing pack does not bring down the whole bank.

Same Port Simplicity
Charge and discharge share the same positive and negative terminals. This reduces wiring errors simplifies installation and works with standard single port chargers and loads. The single pair of heavy gauge wires handles up to 150A continuously both ways.

Heating and Buzzer for Advanced Applications
Two reserved functions add value for demanding users. The heating output can drive an external resistive heater pad to warm LiFePO4 cells before charging below 0°C. The buzzer output can connect to an audible alarm that sounds when the BMS triggers a protection event such as overvoltage undervoltage or over temperature. Both are optional but available when needed.

Monitoring From Anywhere
Bluetooth gives you real time data on your phone. Check each cell voltage pack current temperature readings and protection status without opening the battery box. For industrial installations RS485 and CAN provide wired connectivity to remote displays PLCs or energy management systems. All three communication methods are supported simultaneously on the same board.

Built for Real World Use
Dimensions are 160 by 95 by 25 millimeters making the board compact enough to fit inside most battery enclosures. The power MOSFETs are sized for 150A continuous current with adequate copper area and thermal vias. Operating consumption is low enough that the BMS itself does not need active cooling in most installations.

Typical Projects That Use This BMS
DIY builders use it to assemble 12V 200Ah to 300Ah LiFePO4 batteries for solar storage. Small manufacturers integrate it into pre built 12V lithium batteries sold for marine and RV markets. Off grid homeowners use it to protect battery banks powering lights phones and small refrigerators. EV converters use it for 12V auxiliary batteries in electric vehicles.