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Knowledge Base

Battery current vs motor phase current

Sebastian "Seba" Łastowski
·
May 15, 2021

Users of Gotway, Begode, and Veteran wheels have probably noticed that the current and power readings displayed in various applications are significantly higher than is the case with wheels from other manufacturers. Especially people who previously used King Song, Inmotion or Ninebot unicycles weresurprised to see that their new MSP or Sherman seems to draw thousands of watts during a relatively smooth ride. And yet it would seem that nothing should change. After all, for the same person and with the same riding style and speed, the battery load should be similar.

The reason for such discrepancies is the specific design of motherboards in Gotway, Begode and Veteran unicycles. Motherboards from manufacturers such as King Song, Inmotion and Ninebot measure the current as well as the voltage in the motherboard power circuit, which is basically a battery circuit With these two pieces of information, the power drawn from the battery, and therefore the engine load, can be accurately determined at any time. However, Gotway, Begode and Veteran motherboards do not measure the current flowing in the battery circuit, but instead measure the current flowing through the motor windings. This is called the motor phase current and this value is passed over Bluetooth data link to the application.

Motor phase current doesn’t directly relate to battery current and is mainly used by the motor control rolutines as a feedback signal. Since the motor phase current is also much larger than the battery current, the power calculated in this way will not only be greatly overestimated, but more importantly will not represent the actual load on the motor. However, for historical reasons, all applications display this current and wattage derived from it just like with any other wheel. Experienced users can interpret this in their own way, but novice users may get confused.

Changes in EUC World 2.6

While developing EUC World, I had been wondering for a long time if something could be done to improve the reliability of the current and power readout. Thanks to user support, it was possible to purchase a special logging device to record the current flow in the monocycle’s battery circuit while riding. Thanks to test rides and mathematical analysis of collected data, including correlations between speed, battery current and motor phase current, I was able to develop a formula that can be used to approximate the current in the battery circuit.

Therefore, starting from version 2.6, the current displayed in the EUC World application will be a value much closer to reality than before. This will not only allow a more accurate assessment of the performance of the unicycle, but also will allow an approximate measurement of energy consumption while riding. The current value displayed so far will be presented as a separate parameter: motor phase current.

This is, of course, just the beginning. As new data will be acquired, the algorithm will be improved. But already now this change should make it easier for you to use EUC World application by providing more reliable information about battery current and engine load in Gotway, Begode and Veteran wheels

Important note

This change affects the operation of current alarms in EUC World application. If you are a Gotway, Begode or Veteran wheel owner, check the current alarm settings for your wheel in EUC World app. The previous settings may be too high and cause the alarm not to be triggered. A safe setting for a unicycle equipped with a 100.8 volt battery is 25 amps, for an 84 volt battery it will be 35 amps. Of course, fine tune these values so they will work best in your case.

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