I have a problem each time when I start my Roboclaw 2 x 60A motor controller. When I power it I always see a blinking red light and attaching the USB I see, in the Basicmicro Motion Studio, that I have an alarm which says Logic Battery Low.

Basic Motion Studio

I can solve the problem by updating the firmware, but I don't want to do this every time I turn it on. Does somebody have a solution for this?

  • 1
    \$\begingroup\$ Logic Battery Low implies you need to change (or charge) the logic battery. Does it have a logic battery? \$\endgroup\$ – Brian Drummond Feb 25 '20 at 15:57
  • \$\begingroup\$ Are your wires properly sized? Too small of wires will cause a voltage drop which can be interpreted as low battery. \$\endgroup\$ – Aaron Feb 25 '20 at 17:04
  • \$\begingroup\$ @BrianDrummond, but why is it working when I update the firmware? \$\endgroup\$ – bjornsing Feb 25 '20 at 18:57
  • \$\begingroup\$ @Aaron, right now I have been powering the battery by using the USB, but I also tried using jumper wires (Arduino style) which should work I think. \$\endgroup\$ – bjornsing Feb 25 '20 at 19:02
  • \$\begingroup\$ No idea. If the firmware update cable also provides power, that might do it. Or it might bypass the battery check until the ext reset. Or something else. \$\endgroup\$ – Brian Drummond Feb 25 '20 at 19:57

Our first solution for this problem was to apply 12V to the main power input of Roboclaw before applying any voltage to the signal input.

Roboclaw overview

To clarify this a bit: We use two separate power sources. One for 12V input and one to power the Arduino (which controls the Roboclaw motor controller). This enables us to power the signal input before powering the main input, which triggers the "Logic Battery Low"-alarm

We also found out that it is really important to apply directly 12V and not slowly adjust up from 0 to 12 V as we did. In this prototyping phase, we use an AC/DC adjustable power supply. In most cases, we used to start the power supply and, slowly, find the right voltage. This also triggers the "Logic Battery Low"-alarm.


For a more robust and sustainable solution, we asked Basicmicro about their experience with this problem.

Answer from Basicmicro:

The normal solution for a false Logic Battery under voltage is to jumper the LB IN + and - pins as you mentioned. If you are not using those pins this will not hurt the board in any way. The LB+ pin is connected through a power Schmitt trigger diode so power can only flow into the Roboclaw except for a very small amount of leakage. The false reading is happening because under some conditions the floating logic battery + pin can float higher than 3v which is the point we start checking if there is an under-voltage on that pin.

We have not verified this solution yet


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