Using the VEX EXP Robot Battery

This article describes the features and characteristics of the VEX EXP—part number 280-7126—including the Status Button, LED indicators, charge time, and the built-in energy-saving shutdown mode.

LED Status Display

The VEX EXP Robot Battery Li-ion 2,500 mAh has 4 green LEDs, which form a bar graph that displays the level of charge of the Battery. During normal operation, these LEDs are off to conserve energy. The Battery also has a Status Button. Pressing and releasing the Status Button causes the LEDs to turn on for about 4 seconds to indicate the current charge level of the Battery. View this animation to see how to check the Battery level using the Battery’s LEDs.

The following table shows the charge level thresholds and the corresponding LEDs:

Charge Level

LEDs on When Status Button Pressed




1, 2


1, 2, 3


1, 2, 3, 4


When the Battery is charging, the highest-most LED (i.e., the LED farthest from the Status Button) will blink, indicating the charge level. For example, when the charge level is between 50-74%, LEDs 1 and 2 will be solidly on, and LED 3 will be blinking (LED 4 will be off). If the charge level is between 0 and 24%, then LED 1 will be blinking, and the other LEDs will be off. View this animation to see how the Battery’s LEDs indicate the current charge level during charging.

Charge Times

Charging from 0% to 100% normally takes just over 2 hours. When a new Battery is charged for the first time, or when a Battery has been stored over long periods of time (a few months), it may take longer to charge the Battery. This is because the Battery has to pre-charge at a slower rate to protect the cells. After this initial charge, the Battery charge rate will return to normal.
For fastest charge times, using the recommended USB cable and charger is recommended. The charger needs to be able to supply at least 2.4 A of current. Chargers with a current rating of 0.5 A or more will still charge the Battery but will cause charge times to increase accordingly.

Energy-saving Shutdown Mode

If the Battery has not been used for several hours, it will go into shutdown mode to save energy. This means the Battery’s output will be disabled, and it will not supply power to the Brain. Pressing the Status Button will wake up the Battery. This means if the Battery has been inserted into the Brain and the Brain will not turn on, you must first press the Status Button on the Battery. This wakes up the Battery. Then press the power Button (Check Button) on the Brain to turn it on.

Plugging the Battery into a charger will also automatically wake up the Battery.

Technical Characteristics of the Battery


EXP Li-ion Battery
Nominal capacity 2500 mAh

Approximate charge time

2.5 hours
Max continuous current*

15 A

*Current is also temperature-limited, so max continuous current may be lower in very hot environments.

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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