Battery 101


5s Li-Ion 50A 18V - 21V BMS with balance

This 5s 21V 50A protection board has built in, over-current protection, over discharge protection, overcharge protection, disconnection protection with balanced charging and discharging. It will also turn off the charging to the batteries when at least one cell reaches its maximum voltage.  It can be used for Lithium Polymer and Lithium Ion cells only, it cannot be used for Lithium Iron Phosphate batteries.

Please ensure that the cells are identical, preferably from the same batch and have the same state of charge.



  • Chemistry: Li-Ion, LiPo
  • Strings: 5S
  • Max voltage: 21V
  • Nominal voltage: 18V
  • Cell over-charge protect voltage: 4.25V 
  • Cell over-charge protect recover voltage: 4.15V 
  • Cell over-discharge protect voltage: 2.8V  
  • Cell over-discharge protect recover voltage: 3V
  • Over-charge protect delay: 1.5-2.5S 
  • Over-charge protective current:100A
  • Over-discharge protective current:100A
  • Over-discharge protect delay: 0.5-1.5S 
  • Disconnect protect: Yes 
  • Short circuit protect: Yes 
  • Short circuit delay: 100-600 uS 
  • Short circuit protect recover mode: Off load release.
  • Discharge current: 50A (If you do plan to drive this higher than 15A, we advise you to fit a heat-sink to the FETS with heat transfer compound. Additional cooling required for optimal performance.
  • Charging current:60A (Please make sure your cells are rated for this)
  • Balance function: Yes
  • Ampere Balance (Current): 60mA 
  • Voltage Balance accuracy: 4.14-4.24V
  • Dimensions: L:61 x W42: x H:3.8mm



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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