Unexpected Speed Warning

[Mono]

I was trolleying my V8 and started running (was in a hurry). Surprisingly the V8 started to beep, I believe like when speeding. Surprising? No, not because I couldn't run so fast  but because the wheel was off at the time. The observation is reproducible: only when off the wheel starts to beep when pushed quickly via the trolley. Has somebody else observed this and what's it for?

[Maximus]

Once I realized trolleying was so much easier with it on, I've stopped doing it when it's off.  Either way, I've never gone very fast while trolleying, sorry...maybe the beeps had something to with the battery being charged, unexpectedly?

[Mono]

3 hours ago, Maximus said:

Once I realized trolleying was so much easier with it on, I've stopped doing it when it's off.

Yeah, it takes a little more practice to trolley comfortably without turning it on. While off needs more work than on, I can easier pass over curbs and stairs only by lifting by the trolley handle.

[steve454]

5 hours ago, Mono said:

I was trolleying my V8 and started running (was in a hurry). Surprisingly the V8 started to beep, I believe like when speeding. Surprising? No, not because I couldn't run so fast  but because the wheel was off at the time. The observation is reproducible: only when off the wheel starts to beep when pushed quickly via the trolley. Has somebody else observed this and what's it for?

Running with the wheel off while trolleying?  Will try that this saturday when I ride my Ninebot.  Seems like an antitheft feature?

[meepmeepmayer]

Maybe a battery overcharge warning? You're charging when rotating the tire when the wheel is off, instead of the wheel using a little bit of power when on. Were your batteries full?

[Carlos E Rodriguez]

Well the computer is off. Spinning the wheel becomes a generator. Without knowing how the AC voltages on phase A B C feed through back through 6 MOEFETS that are not energized is known. And considering is beeping looks to me the circuit is not well designed. 

I would walk it with the power on. With the computer on, the circuits should be in the correct state. 

[esaj]

 

17 hours ago, Carlos E Rodriguez said:

Without knowing how the AC voltages on phase A B C feed through back through 6 MOEFETS that are not energized is known.

The mosfets contain body-diodes that will allow reverse current flow with some voltage drop, so if the sine-wave from the phase gets the source voltage high enough vs. the drain (high-side, from motor phase to battery +), the diode will conduct:

Same for the low-side, but as the source there is connected to common ground, it only conducts when the phase on the drain-side goes far enough below the common ground voltage.

Consider the following simplified example:

The motor produces a sine-wave, in this example I used 1KHz wave with 0V offset and 30V amplitude (so +-30V at peaks), marked as "Motor_Phase". The other side of the signal source actually goes to ground through another phase, but it isn't shown here, otherwise there wouldn't be a closed loop for the current to flow.

The high side mosfet (U1) has it's drain connected to the main voltage line (from the battery/mainboard), marked as "To_Mainboard". Of course the gates of the mosfets aren't really floating, but in this simulation it makes no difference. I've added a small capacitor and a resistor to the line to show the effect... basically when the voltage from the "Motor_Phase" - body diode voltage drop goes above the voltage of "To_Mainboard", the diode will start to conduct.

Voltages from the Motor_Phase and To_Mainboard over 10ms simulation period:

There's small ripple on the V(to_mainboard), as the capacitor is being discharged through the resistor to ground when the diode is not conducting, with a larger capacitor and/or resistor, it would be more steady, with lower values you'd see more fluctuation, as the capacitor would discharge more faster.

Current through the high-side mosfet source to drain (so in reverse) vs. the voltages:

The green is the motor phase, red is the "to_mainboard" -voltage, as you can see, there's current flowing through the mosfet in reverse each time the phase-voltage goes above the "to_mainboard"-voltage + diode-drop. There's a large spike at start, because the capacitor isn't charged yet and the voltage of the "to_mainboard" starts at 0V. In real-life, the currents wouldn't be this large, as I haven't entered any ESR -values for the cap, and the phase voltage would actually drop fast once the magnetic field starts to collapse... But this is just to show the basic idea, not to simulate it totally faithfully vs. the real world

 

 

 

 

 

[Maximus]

I was just about the say the same thing that @esaj just wrote, darn it 

[Mono]

19 hours ago, meepmeepmayer said:

Were your batteries full?

No, below 85%.