Is it safe to ride without battery installed

[Jbwiden]

There are certain instances where it could make sense for me to ride the bike with a Pie hub motor, but not have the battery installed. Is there any detrimental effects to the system (motor, controller, ...)?

[Bikemad]

I would say that it is perfectly safe to ride without a battery as long your speed remains below 30mph (48km/h) for a 26" wheel or below 23mph (37km/h) for a 20" wheel.

Apart from the residual drag of the motor, I would not want to ride at high speed without a battery connected, as the motor can generate quite a high voltage which can exceed the voltage rating of the controller's capacitors if a battery is not able to absorb this generated current.
This is unlikely to cause a problem on a level road as the drag from the motor would prevent excessive speed, but an excessively high voltage could easily be generated on a very steep downhill run if you were not braking.

When the brakes are applied while descending a steep hill at high speed, the controller appears to automatically limit the maximum voltage to ~60V without a battery! But when the brakes are not operated, the voltage appears to keep increasing with the motor rpm.

I have ridden bikes equipped with both Smart Pies and Magic Pies without batteries when I have been leisurely cycling with my wife on relatively flat routes as we rarely exceed 15~20mph. However, I would not risk riding in excess of 30mph downhill without a battery unless I also had a brake lever pulled sufficiently to activate the brake switch.

Alan
 

[Adamsavage79]

You can, but I can promice you it's not fun to do. The bike is heavy, and the motor will give you a bunch of drag. It will be much more senstive to wind and road conditions as well, so you are not likely going to reach very high speeds. More than likely you would stay under the legal speed limit, by a fair margin. It sucks even more, when the battery dies and you have to pedal with all that extra weight.

[Jbwiden]

My plan is actually to get the edge, so maybe a little less bad in terms of weight and drag.

I also think I saw a slightly lower max speed for the edge so I assume this also maps to the max safe without battery being something like 28mph with 26inch wheel.


Do depleted batteries still accept current? If not I presume the same maximum speed for safety of the Caps exists as well even if battery is installed?


As an aside, I also wonder how much current would need to be sunk to ensure voltage does not exceed 60v, could be a simple diode circuit to ensure this.