2S 13A Battery Management Systems (BMS)

BMS For Two Battery Strings And 13A Max Current

BMS often ship in locked state: no output voltage is available at the output pins. Locked state is also entered whenever over-current protection was triggered. To unlock the BMS, connect it to a charger. If you did not add a dedicated charger board, apply the appropriate charging voltage to its output terminal.

When connecting batteries to your BMS, make sure to use wires with sufficient diameter for the anticipated high currents.

When designing battery packs, use batteries of same type and same state of charge only. It is recommended you fully charge all batteries before connecting. All batteries must have the same voltage (voltage difference less than 0.05V). Do not mix batteries from different vendors, types, capacity, or age.


LiIon LiPo

For currents up to 13A, this balancing BMS can be used:

All connections are available from both sides and are clearly marked:


Connect the batteries like this:

  • First battery string to B- (-) and BM (+)
  • Second battery string to BM (-) and B+ (+)

The output voltage is available at P+ and P-.

This board often has the model specification HX-2S-D20 printed on the back side.


Protection Threshold
Over-Charge >4.3V
Over-Discharge <2.5-3.0V
Over-Current 20A
Short Circuit yes, resettable
Continuous Current 13A
Size 46.0x20.0x3.6mm


When charging batteries through this BMS, the charging voltage needs to be 8.4V-9.0V. The BMS limits the charging current to 10A.

A heat sink may be required with currents exceeding 8A.


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(content created Mar 28, 2024)