Battery 101


17s Li-Ion 45A 61.2V - 71.4V BMS with balance function

This BMS is built with Integrated Management solution with 45A continuous discharge current for a 17s Li-Ion nominal 61V configurations. It can detect each cell voltage during the discharging and charge phase, but at the same time will optimise & maximise the longevity of your battery pack. Fully charge voltage is 71.4V and has a maximum charge Current of 15A with a very low stand by power consumption.

This BMS unit has a cell level cut-off voltage of 2.8V, which makes it suitable for cylindrical type 18650, 21700, 20700 & 26650 type cells with a 3.6-3.7V rated nominal voltage.

  • Model number: BMS17S45A61#1
  • Chemistry: Li-Ion
  • Configuration: 17s
  • Max Voltage: 71.4V
  • Nominal Voltage: 61.2V
  • Continuous discharge Current: 45A
  • Max Charging Current: 15A
  • Overcharge protection: 4.25V per cell
  • Over discharge protection: 2.8V per cell
  • Balancing Current: 42mA
  • 12 x Power FETs
  • Load Short circuit protection
  • Charging port: Common port
  • Dimension: L120 x W60 x H9mm

 Balance wires included.


Technical parameters:

Discharge current: 45A

Charging current (same port): ≤15A

Main circuit conduction internal resistance: ≤15mΩ

Discharge overcurrent protection: 150±30A


Overcharge protection

Detection voltage: 4.25 ±0.025V

Detection delay: 100 ±50mS

Release voltage: 4.15 ±0.05V


Over discharge voltage protection

Detection voltage: 2.8 ±0.1V

Detection delay: 100 ±50mS

Release voltage: 3.0 ±0.1V


Balanced voltage

Detection voltage: 4.2 ±0.025V

Detection delay: 100 ±50VmS

Balance current: 42 ±5mA


Discharge overcurrent protection

Detection voltage: 150mV

Detection delay: 100 ±50mS

Current protection: 150 ±30A


Short circuit protection

Trigger condition: short circuit of external load

Detection delay: 300uS

Release condition: disconnect load/charge activation



Working power consumption: ≤35uA

Sleep over-discharge power consumption: ≤10uA

Operating temperature range: -10/+80°C




Ensure that you connect the balance loom to the battery's cell terminals in the correct voltage sequence. Check that the voltage increases in the expected order on the JST female connector (Black + first Red, + second Red, etc.) BEFORE plugging it into the male connector on the BMS board.

When connecting to your battery, the B- line should be connected first and then the voltage monitoring Balance loom. The very last step is to connect charge/discharge lines. If you want to uninstall the BMS, the order should be reversed. BMS connection order is important, or it will irreparably damage the BMS.  If you have no voltage at the BMS load terminals, then check your wiring and check again.  If the wiring is not the issue, then it's likely that you've tripped under-voltage detection; connect a charger of the correct voltage to the BMS. If there is still no voltage from the BMS and you're sure your wiring and battery are ok, then the BMS is damaged.

Furthermore, if you see the BMS cutting the load or charge before expected (i.e. before the battery has fallen or risen to overall cut-off voltage for discharge or charge) then your first step is to look for a cell or parallel group of cells exhibiting a divergent voltage.  Trying to spot the defective cell(s) is difficult because as soon as the load is cut or the charger removed, cell voltage rises or falls instantly.  It requires real-time monitoring to diagnose cell defects.


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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