Controller battery low indicator using VEXOS

The firmware for the controller under VEXOs sets the red battery low indicator on batteries that the old firmware says are OK. I tried several batteries that showed OK on the old firmware. About half showed low battery on the new firmware. I reinstalled the old firmware on the controller and all batteries showed OK.
Is that an intended feature?

Hi rwood359,

There were no changes made to the Controller LED behavior between firmware v1.16 and VEXos 2.0.1. If the Power/Link LED is showing red, this means that the Controller Battery charge level is low and needs to be recharged. To recharge, please connect the Controller to a source of USB power (such as a computer or a USB cell phone charger) and let the Controller recharge the battery.

If the Charge LED is showing red, this means that the battery is currently charging via either the USB Cable or the Tether Cable.

More information about the Controller LED colors can be found in the VEX IQ Control System User Guide.

If you have any additional questions or concerns, VEX Technical Support can be reached at or by calling +1-903-453-0802 to provide additional assistance.


  • Art

I understand what the Power/Link LED means. I was reporting that without changing the battery with the old firmware loaded, the LED showed green, loading the new firmware changed the LED to show red, and restoring the firmware to the old firmware showed green. More than one battery exhibited this behavior.
Perhaps it is the controller. I will not be at school for three weeks. When I return, I will try additional controllers.

What I have seen is that a controller battery charged in a controller with 1.x firmware will usually show the Red LED when installed in a controller with 2.x firmware. Batteries charged in a 2.x controller can be interchanged without getting the Red LED.