BMS 4S 30A Protection Board

4S 30A Lithium Battery BMS Protection Board

Suitable for 4 series 18650 batteries. It does not charge batteries. It is for battery protection. It performs the balancing task.

     The 4S 30A BMS is a protection board for battery packs made of 4 series-connected 3.7V Li-ion / Li-Po cells (such as 18650), 14.4V - 14.8V nominal and 16.8V fully charged. The board does not charge the battery; during charging and discharging it monitors the voltage of each cell separately and cuts the pack current when any cell reaches the overcharge (4.25V) or over-discharge (2.50V) limit, on overcurrent and on short circuit. When the protection condition clears, the board returns to normal operation by itself; no activation is needed.

     The board carries an S-8254AA four-cell protection IC, 4 power MOSFETs that cut the current and 2 R010 (10 milliohm) current sense resistors. It is suitable for 10A continuous current with natural cooling and 15A with an added heat sink; it withstands 30A instantaneous current and the overcurrent protection trips in the 20A - 30A range. The narrow board, approximately 50mm x 22mm, fits easily beside or on top of the battery pack.

     Connections are made with the solder pads on the board: B+ / B- go to the battery pack terminals, P+ / P- to the load and charger, VL / VM / VH and + to the cell junctions. The board is not a cell balancing board; it works as a protection board.

Key features:

     Per-cell protection: The voltage of all four cells is monitored separately. Charging is cut when any cell exceeds 4.25V and discharging is cut when it drops below 2.50V, so a weak cell in the pack is not damaged by overcharge or deep discharge.

     10A - 15A depending on cooling, 30A peak: Delivers 10A continuous with natural cooling and 15A with a heat sink. It withstands 30A instantaneous current; the "30A" value is the peak and overcurrent limit, not the continuous current.

     Short circuit and overcurrent protection: The current is cut when the output is shorted or the current exceeds the 20A - 30A limit; short circuit protection is delayed and self-recovering.

     Automatic recovery: When the cell returns to 4.15V after overcharge or to 3.00V after over-discharge, the board conducts again by itself; no button or activation is needed.

     Narrow and thin board: With approximately 50mm x 22mm x 4mm size and approximately 10gr weight it fits beside 18650 packs; the wide solder pads suit thick wire or nickel strip soldering.

Features:

• Product type: 4 cell series (4S) lithium battery protection board (BMS)
• Model: 4S 30A BMS
• Suitable cells: 4 series 3.6V / 3.7V Li-ion or Li-Po cells (such as 18650)
• Pack voltage: 14.4V / 14.8V nominal, 16.8V fully charged
• Charging voltage: 16.8V (4S lithium charger)
• Continuous working current: 10A (natural cooling), 15A (with heat sink)
• Maximum instantaneous current: 30A
• Overcurrent protection: 20A - 30A
• Overcharge detection voltage: 4.25V ±0.025V (per cell)
• Overcharge release voltage: 4.15V ±0.05V
• Over-discharge detection voltage: 2.50V ±0.08V (per cell)
• Over-discharge recovery voltage: 3.00V ±0.1V
• Short circuit protection: yes, delayed and self-recovering
• Recovery after protection: automatic, no activation required
• Protection IC: S-8254AA; 4 power MOSFETs, 2 R010 current sense resistors
• Terminals: B+, B-, P+, P- solder pads; cell junction terminals VL, VM, VH and +
• Cell balancing: none
• Connection type: soldered connection (no cable or socket fitted)
• Operating temperature: -40°C - +50°C
• Storage temperature: -40°C - +80°C
• Color: Red PCB
• Dimensions: approximately 50mm x 22mm x 4mm
• Weight: approximately 10gr

Usage information:

• After connecting the cells in series, solder B- to the pack negative (0V), VL to the junction of cells 1 and 2 (4.2V), VM to the junction of cells 2 and 3 (8.4V), VH to the junction of cells 3 and 4 (12.6V), + and B+ to the pack positive (16.8V). Make the connections in the order shown in the diagram.
• Connect the load and the charger to P+ and P-. The board does not charge the battery; use a current-limited 4S lithium charger with 16.8V output.
• If you will draw more than 10A continuously, add a heat sink on the MOSFETs; even with a heat sink the continuous current must not exceed 15A.

Applications:

•  Building 4S 18650 Li-ion battery packs
•  Solar energy storage batteries
•  UPS (uninterruptible power) batteries for modem, router and camera
•  Portable speaker batteries
•  Camping lamp and LED lighting batteries
•  RC car and boat batteries
•  Powerbank and portable power box
•  Replacing the protection board of old Li-ion battery packs
•  Portable measuring and test devices running on 14.8V

Precautions:

•  30A is the instantaneous current value; continuous current is 10A with natural cooling and 15A with a heat sink. Do not exceed these limits in motor devices with high starting current.
•  The board has no cell balancing circuit. Use cells of the same type, capacity and voltage; equalize the cell voltages before connecting them to the pack.
•  The board is for 3.7V Li-ion / Li-Po cells (4.25V overcharge limit). It is not used with 3.2V LiFePO4 cells.
•  Connecting the cell junction terminals (VL, VM, VH) in the wrong order or to the wrong cell can damage the protection IC. Measure the voltage of each terminal before soldering.
•  The board does not charge the battery and does not limit charging current; do not connect an adapter directly, use a lithium charger.

Package contents:

•  1 pc 4S 30A BMS Protection Board
•  Note: Batteries, cables, heat sink and charger are not included in the package.