The hubs present in the Mindstorms Robot Inventor or SPIKE Prime sets have 2100mAh lithium-ion batteries which can be charged with the accompanied cable with a micro USB connector on one end and a regular USB connector on the other end. You need to provide your own USB charger and a high performant one such as the ones used with an Apple or Samsung device is recommended.

My question is, during an exposition, e.g. when the hub is used in a GBC module, can you leave the cable connected so it will function as a continuous power supply? Or is this not recommended because it could mess up the charging cycles of the rechargeable batteries? Would the performance of the models stay constant?

1 Answer 1


This is what the 45678 user guide says:


Important information: Only use a high-quality Power Adaptor, PC or Laptop for charging the rechargeable battery. Output 5V DC, 500-1500mA. Use the supplied LEGO® USB cable. How to charge the battery: Charge the battery fully the first time it is used. The battery can be charged when inserted in the TECHNIC Large Hub. Connect the LEGO USB cable to a power source. The Charging Light will turn red when the power source is connected. The Charging Light will turn green when the battery is fully charged. Charging time for the battery is up to six hours. The TECHNIC Large Hub can be used during charging but this will increase the charging time. If the battery is fully discharged and the TECHNIC Large Hub cannot be turned on when the power source is connected, the battery will need up to one hour charging time before the TECHNIC Large Hub can be turned on. Warning! Do not dispose your battery by incineration. Dispose the battery in accordance with the current legislation in your country. Do not short-circuit the battery. Do not damage the battery. Do not dispose in fire. Never use a damaged battery.

There is no information on how long the SPIKE hub can be connected and operating from an external DC power source.

For your purpose it may work or it may shutdown. It depends on if the GBC module draws more current than the USB power source can supply.

  • 1
    One would assume it will last forever as long as enough current is drawn from the charger to avoid discharging the battery.
    – user253751
    Jul 21, 2021 at 15:32
  • @user253751, Only The Lego Group could provide a definitive answer to this question. Based on my experience designing consumer devices like the SPIKE hub that can be charged from a USB host or power brick it is impossible to say how such a device will behave. For example when the USB power source cannot support the load the battery will be discharged until the device shuts down. What the hub will do cannot be determined from the information in the OPs question.
    – Dan1138
    Jul 21, 2021 at 19:58
  • Considering LEGO explicitely supports this - emphasis on "The TECHNIC Large Hub can be used during charging but this will increase the charging time. ", I don't see why there would be any issues at all or why it would stop working. I usually keep it connected when using a static robot (like the rubik's cube solver) as it seems to provide more current for the motors; never had any problem.
    – Joubarc
    Jan 31 at 8:37

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