66 | Battery - Battery is low

Written by Alex Kovell

Last published at: September 9th, 2025

Description

When the battery is nearly empty and the system detects low capacity for more than 10 seconds, it will trigger error code 66. If you continue using the bike in this state, it may stop working properly, such as losing riding assistance. It’s strongly recommended to find a charging station and recharge the battery as soon as possible to ensure the bike continues to function normally.

⚠️Triggers of Error Code

The following are possible causes of error code 66:

  • The battery capacity is nearly empty (reached 4%)

⚠️Warning

If the battery is not charged as soon as possible and continues to be used until it approaches empty, the system will report error code 67

1 Charge the Battery

Charge the e-bike until the battery reaches over 10%, making sure the charger indicator turns red and the battery level increases. Then, reboot the e-bike to check if the error code still exists. If charging fails or the charger indicator displays an abnormal status, proceed to the next step.

 
 

2 Replace the charger if it doesn't work properly

Replace the charger with a new spare and charge the e-bike until the battery reaches over 10%. Then, reboot the e-bike to check if the error code still exists. If charging fails or the error persists, proceed to the next step.

 
 

3 Check the Charging Port

If the e-bike's battery is charged through a charging port on the frame rather than directly plugging the charger into the battery, replace the charging socket with a new spare, then reboot the e-bike to check if the error code still exists. If this doesn't fix the issue, proceed to the next step.
(The reason for needing to reboot the e-bike is that the system will detect whether the error code still exists during the reboot.
This allows us to determine whether the troubleshooting mentioned above has successfully resolved the issue.)

 
 

4 Connect the bike to DST and update Battery Firmware

Connect the e-bike to the Trek Dealer Service Tool and update the [Battery] firmware to the latest version. Then, reboot the e-bike to check if the error code still exists. If charging fails or the error persists, proceed to the next step.

 
 

5 Replace the Battery

Replace the [Battery] with a new spare, then reboot the e-bike to check if the error code still exists. If this doesn't fix the issue, proceed to the next step.

 
 

6 Reach out to the Service Team if you need additional support!

Contact Customer Care or the Hyena Service Center for further technical assistance.

 
 

 


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