2S 5A Protection Board

2S 5A Lithium Battery BMS Protection Board

Suitable for 2 pieces of 18650 battery. It does not charge batteries. It is for battery protection. It takes on the balancing task.

Suitable for 2 pieces of 18650 battery. It does not charge batteries. It is for battery protection.

     This board is a 17.5mm diameter round BMS protection board for 2 cell series (2S, 7.4V nominal, 8.4V full) lithium-ion battery packs. It is marked HX-2S-A2; it carries one protection IC and 2 pieces of 4406A MOSFET. It protects the cells against overcharge, over-discharge, overcurrent and short circuit; it is suitable for 5A continuous and 7A instantaneous peak current. Thanks to its round shape it sits directly on the end of an 18650 cell and needs no extra space in small battery packs.

     On the battery side there are 3 wide solder pads, B+, BM (the midpoint of the two cells) and B-; at the lower edge of the board there are the common through-hole P+ and P- pads for charging and load (solderable from both sides); the charger and the load are connected to the same P+ / P- terminals. The board does not charge the batteries, it only protects them; an 8.4V lithium charger is needed for charging. The board does not balance; the capacity, voltage and internal resistance of the two cells must be the same. For packs that need higher current and balancing, a 2S 20A balanced BMS board is preferred.

Key features:

     Round board that fits on an 18650: With 17.5mm diameter and 3.2mm thickness it sits on the end of an 18650 cell; it fits the battery pack of narrow devices such as flashlights and headlamps.

     Four-way protection: It cuts overcharge at 4.25V - 4.35V per cell, over-discharge at low voltage, overcurrent and short circuit.

     5A continuous, 7A peak current: Suitable for medium current loads such as small motor toys, speakers and lighting.

     Low standby current: The board itself draws less than 10µA; it does not drain the batteries while the device is not in use.

     Common charge / discharge terminal: The charger and the load connect to the same P+ / P- pads; only two wires leave the battery pack.

Features:

• Cell count: 2S (2 pieces of series 3.7V lithium-ion cells), pack 7.4V nominal
• Continuous working current: 5A
• Instantaneous peak current: 7A
• Charging voltage: 8.4V - 9V
• Overcharge detection voltage: 4.25V - 4.35V ±0.05V per cell
• Over-discharge detection voltage: approx. 2.3V - 3.0V per cell
• Protection: Overcharge, over-discharge, overcurrent, short circuit
• After a short circuit: the board restores output when a charger is connected to P+ / P-
• Standby current: less than 10µA
• Balancing: None
• Current switch: 2 pieces of 4406A N channel MOSFET
• Battery pads: B+, BM (cell midpoint), B-
• Charge / load pads: P+, P- (common charge and discharge terminal)
• Board marking: HX-2S-A2
• Operating temperature: -40°C - +50°C
• Material and colour: Blue round circuit board
• Dimensions: Diameter 17.5mm, thickness 3.2mm (17.5mm x 17.5mm x 3.2mm)
• Weight: approx. 1gr

Usage information:

• Connect the two cells in series. Solder the positive of cell 1 to the B+ pad, the junction of the two cells to the BM pad and the negative of cell 2 to the B- pad. Connect the positive of the charger and the load to P+ and the negative to P-.
• After connecting the cells, no voltage may appear at P+ / P-; in that case connect an 8.4V charger to the terminals briefly, the board activates and gives output.
• The two cells to be connected in series must have the same capacity, voltage and internal resistance; equalise their voltages around 3.7V before connecting. Charge the pack with an 8.4V 2S lithium charger.

Areas of use:

•  Rechargeable flashlight battery pack
•  Headlamps and camping lamps
•  Portable Bluetooth speakers
•  Battery powered and motorised toys
•  Small RC car and boat battery packs
•  Walkie talkie spare battery packs
•  Security and action camera battery packs
•  Portable LED lighting
•  Building a 7.4V battery pack with 2 pieces of 18650
   

Precautions:

•  The board does not charge batteries, it only protects them. Use a 2S lithium charger with 8.4V output for charging.
•  The board does not balance. If a voltage difference builds up between the cells it does not correct it; use matched cells. Use a balanced 2S BMS board for packs that need balancing.
•  The continuous current is 5A. Do not use it in high current power tools such as drills and screwdrivers; a 2S 20A BMS board is needed for higher current.
•  The BM pad must be connected to the junction point of the two cells. A wrong connection damages the board and disables the protection.
•  The board is for 3.7V lithium-ion / lithium polymer cells; since its overcharge limit is 4.25V - 4.35V it is not used with LiFePO4 (3.2V) cells.

Package contents:

•  1 Piece 2S 5A BMS Protection Board
•  Note: 18650 batteries, nickel strip and charger are not included.