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0 pointsMisterTea4y ago0 comments

> For example, an audible tone the moment it shuts off the motor while underway.

If it has the ability to monitor battery life then it can certainly do stuff like emit an impeding dead battery warning tone and then gently decelerate to a stop.

Though I bet its an issue where the battery level is simply monitored via voltage. So lets say a 15% charged battery has enough current to push the rider along on level ground, BUT, the moment the rider hits an uphill, the current increases beyond what the now weaker battery can provide, the voltage drops below the battery threshold and the battery protection circuit shuts down. Very unsafe design.

A proper design would allow the battery and motor drive to cooperate so when the motor current demand rises to maintain velocity, the battery pack can tell the motor, sorry, I cant give you anymore and the motor drive can then decelerate or simply refuse to continue accelerating.

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miskin4y ago

The main problem is that to push you back, the motor actually has to go faster to get in front of your center of gravity and this is exactly what is hard when the battery is getting weak. That's why nosedives often happen when users want to go too fast, ignoring the pushback from the wheel and actually "rinding the pushback". At some point, the motor does not have enough torque to counter the push down on the front and give up. This causes the front side to collapse and we can all imagine possible results when feet "want" to stop and the head is going 20mph+. It's not that battery management will simply turn the device off (although it may also be an issue in some cases). Usually motor just becomes too weak to counter rider push for a short moment and the front part of the board hits the ground.

I do not have experience with Onewheel XR, but pushback on the Pint series is rather noticeable and hard to ignore when you hit set speed limit. Onewheel XR is said to have weaker pushback.

bredren4y ago

> A proper design would allow the battery and motor drive to cooperate so when the motor current demand rises to maintain velocity, the battery pack can tell the motor, sorry, I cant give you anymore and the motor drive can then decelerate or simply refuse to continue accelerating.

These are good thoughts though even in your solution I suspect it points toward the idea that the design is fundamentally unsafe.

The reason is if the motor decelerates you still must be prepared for your weight to shift, even gradually.

shkkmo4y ago

On a self balacing PEV, if the motor decelerates on it's own (without a weight shift from the rider), the resulting weight shift will not be gradual. You might tip forward slightly slower in comparison but the nose dive would still happen pretty much immediately. This is because in order to maintain speed, the CoM must be in front of the balance point.

The design of self-balancing PEVs isn't fundentally unsafe, but it (like most sports and means of transportation) does carry risks that you should be aware of and compensate for.

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