Battery 101


4s Li-Ion 40A 14.4V - 16.8V BMS with balance

This BMS balance board is used for a lithium battery pack to equalize voltage and protect the cells. This module monitors and protects the charging & discharging of the cells, balancing of the cells and acts as a low voltage/over charge cut-off. 


  • MOSFET-based BMS modules may arrive "activated" or trigger during battery assembly. 16V across the load terminals will reset the module.
  • Suitable for lithium batteries with a nominal voltage of 3.7V and a full voltage of 4.2V (Including 18650, 26650, polymer lithium batteries, no restrictions on the size) 
  • Product size: L:60 x W:45 x D:3.4mm 
  • Nominal voltage: 14.4V
  • Fully charged voltage: 16.8V
  • Continuous discharge current (upper limit): 40A Please reduce load current if FETS get too hot. If you do plan to drive this higher than 10A, we advise you to fit a heat-sink to the FETS with heat transfer compound. Alternatively, please add additional suitable cooling for better thermal management.
  • Continuous charging current (upper limit): 20A, but make sure your cells are rated for this.
  • Charging voltage: 16.8V
  • The BMS will cut the load should one or more cells fall below ~2.9V.
  • Connect 0V, 4.2V, 8.4V, 12.6V, 16.8V strictly according to the wiring diagram. When soldering the wires, please make sure nothing metallic touch any components on the board as this will cause a short circuit and damage the module board.
  1. These BMS modules are also suitable for electric drills with starting current below 80A and power below 230W. 
  1. Successful start of electric drill requires 4 pieces 10C-20C high drain cells, or 8 pieces 5C-10C high drain cells (Recommended power battery models: SAMSUNG 25R, MOLICEL P26A, P28A, P42A, SONY VTC4, VTC4A, VTC4A, VTC6), 0V and 16.8V connecting cables, use copper wire of 3 mm square or more (no nickel strips !!).
  1. It's recommended to connect a non-polar capacitor (withstand voltage above 25V, capacity 10uF-100uF) to the motor's positive and negative terminals to prevent a reverse spike from the motor breaking the power transistors.
  1. Do not mix good and bad cells, please ensure that they are all the same quality and age, cells from the same batch are the most ideal.


This BMS will require a competent and knowledgeable person with an electronic background and skills to install and operate. As these are sensitive products, we will only accept returns if its un-opened and un-used. 

Please double check and triple check your wiring, especially the balance/sense wires are correct. Even temporary incorrect wiring may damage this device.

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