Li-Ion BMS

Home resources tips current_splitter

Current splitter

A trick to increase the current handling of a sensor

Problem: you need to sense 2000 A, but you can only get a 400 A, cable mounted current sensor.

Solution: run just 1/5 of the current through the sensor, and let the other 4/5 bypass the sensor.

one wire through the sensor, 4 bypassing it
  1. Cut 5 identical wires, each of which can handle 1/5 of the continuous current
    • For example, if the continuous current is 670 A, each wire can be 4 AWG
  2. Strip the ends of the wires as required for the intended terminal
  3. Run one of the wires through the current sensor
  4. Join the 5 ends of the 5 wires at one end, and crimp them to a terminal
  5. Join the other 5 ends of the 5 wires at the other end, and crimp them to a terminal
  6. Program the device to which the sensor sends its signal (e.g.: BMS controller) to scale the reported current up by 5 times

Of course, this trick will work to get any integer-fraction increase in current sensing, by running some wires inside and some outside

  • With 2 wires: x 2
  • With 3 wires: x 3 or x 3/2
  • With 4 wires: x 4, x 2, or x 4/3
  • With 5 wires: x 5, x 5/2 x 5/3, or x 5/4
  • With 6 wires: x 6, x 3 x 2, 3/2 or x 6/5
  • Etc.

© 2008~2017 Davide Andrea. All rights reserved, except where noted by CC mark. Page published on Mar 16 2011. Graphic design by morninglori