NO_BAT - Display V1/V1.1

The "NO_BAT" error on a Stromer S-Pedelec V1 or V1.1 is a generic error message that indicates that the display is not working properly. does not receive 36V from the motor (or the battery system). This can have various causes:

1. problem with the battery or the battery management system (BMS):

• Deep discharged battery: If the battery is completely empty, the BMS can decouple the cells so that there is no voltage at the output. Even if the light is still on, the power output may not be sufficient for the motor.
• Defective battery cell: A single defective cell in the battery pack (e.g. 0.0V, while other cells are normal) can result in the BMS not releasing the battery.
• BMS error: The battery management system itself may have a fault that blocks the voltage output.
• Contact problems on the battery: Loose or dirty contacts between the battery and the battery compartment can interrupt the power supply.

2. problem with the wiring or plug connections:

• Interrupted 36V line to the display: The display receives the 36V from the motor via a blue wire in the 5-pin sensor cable. If this wire is interrupted (e.g. due to a cable break), the display shows "NO_BAT".
• Defective "Wicked cable": This is the extension cable that leads from the motor to the display. A defect in this cable may be the cause.
• Loose or damaged D-SUB connection: The high-current plug connection (D-SUB) between the battery and motor may be loose or damaged.
• Cable break on the motor: Cables on the motor may be damaged by rotating parts (e.g. brake disks).
• TMM sensorA possible source of error is also the TMM sensor or its connection to the engine. If it supplies implausible values to the engine controller, NO_BAT may be the result.

3. defect in the motor or controller:

• Error in the motor control (controller): The controller integrated in the motor (on the V1/V1.1 models, the power electronics are still in the motor) may be defective and not properly transmit the 36V to the display. This was a known problem with older Stromer models (V1 / V1.1 / ST1), as the power electronics tended to die of heat.
• Short circuit in the motor: A short circuit in the motor (e.g. due to defective MOSFET transistors) can also result in no voltage being output and the motor even offering resistance when being pushed.

4. defective display:

• Although less common, a defect in the display itself can also cause it to show "NO_BAT" even though the 36V is present. This can be a blown NPN transistor in the display, for example.

What to do with "NO_BAT"?

1. Check the battery:
   • Make sure that the battery is fully charged.
   • Remove the battery and reinsert it to check the contacts. Clean the contacts if necessary.
   • If possible, test the bike with another battery that is known to work (if available).
2. Check wiring:
   • Check all visible cables and plug connections for damage, crushing or loose connections, especially the cable from the motor to the display and the D-SUB connection.
   • Try to connect the display directly to the motor if there is a corresponding connection option to prevent a cable break in the frame.
3. Resistance of the motor:
   • If the bike has an unusually strong resistance when pushing (as in recuperation mode), this strongly indicates a short circuit in the motor.
4. Contact specialist dealer:
   • As these are often more complex electrical or electronic problems, it is advisable in most cases to visit an authorized Stromer dealer. They have the necessary diagnostic tools and expertise to determine the exact cause of the fault and rectify it. Defects in the motor/controller are not uncommon, especially with older V1/V1.1 models.