BMS 1S 3A Protection Board

1S 3A Lithium Battery BMS Protection Board

Suitable for 3.7V 18650 batteries. It does not charge the battery. It is for battery protection. It undertakes the balancing task.

     The 1S 3A BMS Protection Board protects a single 3.7V Li-ion or lithium polymer (LiPo) cell against overcharge, over-discharge, overcurrent and short circuit. It stops charging when the cell voltage rises to 4.25V and cuts the current to the load when it falls to 2.54V; when the load current reaches 3A or the output is short-circuited, it disconnects the cell. Continuous charge and discharge current is up to 2A.

     The board measures 40mm x 4mm x 3mm; its very thin and long shape fits beside an 18650 cell or inside a battery box or device housing. The B+ and B- metal plates that connect to the cell are at the two ends of the board; the P+ and P- pads for the load and charger are on the bottom side next to these plates (per the silkscreen, P+ at the B+ end and P- at the B- end). The metal plates make the connection to the cell easier.

     This board does not charge the battery, it only protects it. A separate lithium charger circuit (e.g. TP4056 charger board) is needed for charging. The 1S board is for a single cell; it does not balance several cells in series.

Key features:

     Overcharge protection: Cuts the charging current when the cell voltage reaches 4.25V and reconnects below 4.23V; the cell is protected from overcharging.

     Over-discharge protection: Disconnects the load when the cell voltage drops to 2.54V; the cell is protected from deep discharge and lasts longer.

     Overcurrent and short circuit protection: The cell is disconnected when the load current reaches 3A or the output is short-circuited.

     Very thin board: At 40mm x 4mm x 3mm it fits beside an 18650 cell or in a narrow battery holder; it does not make the device bigger.

     Simple wiring: The cell connects to B+ and B-, the load and charger to P+ and P-; a plain four-terminal layout.

Features:

• Product type: Single cell (1S) lithium battery protection board (BMS / PCM)
• Model: 1S 3A BMS
• Suitable cell: 1 x 3.7V Li-ion (18650 etc.) or LiPo cell
• Overcharge detection voltage: 4.25V ± 0.05V
• Overcharge release voltage: 4.23V ± 0.05V
• Over-discharge detection voltage: 2.54V ± 0.1V
• Continuous charge current: Up to 2A
• Continuous discharge current: Up to 2A
• Overcurrent protection: 3A
• Short circuit protection: Yes (cut-off on output short circuit)
• Overcurrent detection: Three stage (overcurrent 1, overcurrent 2, load short circuit)
• Charging function: None (does not charge, only protects)
• Balancing: None (for a single cell)
• Construction: Protection IC and 8-pin dual MOSFET
• Terminals: B+, B- (cell), P+, P- (load and charger)
• Colour: Green
• Dimensions: 40mm x 4mm x 3mm

Usage information:

• Connect the + of the cell to B+ and the - to B-. Connect the load and the charger output to P+ and P-; the cell is then charged and discharged only through these terminals.
• To charge the cell, connect a lithium charger circuit with 4.2V output to P+ and P-. The board does not set the charge current; the charger sets it and it must not exceed 2A.
• When protection trips and cuts the output (e.g. after a short circuit or over-discharge), the output turns back on when the load is removed or charging voltage is applied to P+ and P-.
• Do not heat the cell for long while soldering wires to it; if possible use spot-welded nickel strip or a cell with ready tabs.

Applications:

•  Single cell 18650 battery packs
•  Powerbank building
•  Flashlight and headlamp
•  Rechargeable toys
•  Bluetooth speaker
•  Headphones and small portable devices
•  Rechargeable desk lamp and LED lamp
•  Small LiPo powered model and robot projects
•  Adding protection to unprotected lithium cells

Precautions:

•  The 3A value is the protection (cut-off) threshold, not the continuous operating current. Keep continuous charge and discharge current below 2A.
•  The board does not charge the cell. Use a separate lithium charger circuit; do not connect the board directly to a 5V adapter.
•  The board is for a single cell (1S, 3.7V). It is not used in packs with 2 or more cells in series (7.4V, 11.1V).
•  Do not mix up the B and P terminals; do not connect the cell in reverse. Reverse connection can damage the board and the cell.
•  Not suitable for LiFePO4 (3.2V) cells; the overcharge threshold is set for 3.7V lithium cells.

Package contents:

•  1 x 1S 3A BMS Protection Board
•  Note: Cell, charger circuit and cable are not included in the package.