Author Topic: When the battery dies  (Read 627 times)

quixoticgeek

  • Mostly Harmless
When the battery dies
« on: December 10, 2019, 06:09:04 pm »


Took one of the work pedal assist cargo bikes out today, was great, nice and easy to ride, until the battery died with 3km to go, then it suddenly turned to treacle.

I was under the impression that the motor would not be coupled when not assisting, and so it should be much the same to ride when flat, as when charged or off. Or have I misunderstood what happens when a battery dies on a pedal assist e-bike?

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Kim

  • Timelord
Re: When the battery dies
« Reply #1 on: December 10, 2019, 06:20:01 pm »
I was under the impression that the motor would not be coupled when not assisting, and so it should be much the same to ride when flat, as when charged or off. Or have I misunderstood what happens when a battery dies on a pedal assist e-bike?

Depends entirely on the mechanics of the motor.  I expect everything from freewheeling to locking solid[1] is a possibility.  What sort of system is is?

As with any other motorised vehicle, the correct solution is not to run out of power.


[1] The Falco system has a security setting that causes the gearless hub motor to resist any effort to turn, which you can only disable from the (removable) console.
Careful, Kim. Your sarcasm's showing...

quixoticgeek

  • Mostly Harmless
Re: When the battery dies
« Reply #2 on: December 10, 2019, 06:26:27 pm »
I was under the impression that the motor would not be coupled when not assisting, and so it should be much the same to ride when flat, as when charged or off. Or have I misunderstood what happens when a battery dies on a pedal assist e-bike?

Depends entirely on the mechanics of the motor.  I expect everything from freewheeling to locking solid[1] is a possibility.  What sort of system is is?

As with any other motorised vehicle, the correct solution is not to run out of power.

I think it's a bosch bottom bracket mid drive.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: When the battery dies
« Reply #3 on: December 11, 2019, 12:13:42 pm »
Most ebikes are rideable when it if power. With some you would hardly know the difference, others there is noticeable but not enormous resistance.
the bosch mid drive should be in the first category. Sounds like a fault.

quixoticgeek

  • Mostly Harmless
Re: When the battery dies
« Reply #4 on: December 11, 2019, 12:16:31 pm »
Most ebikes are rideable when it if power. With some you would hardly know the difference, others there is noticeable but not enormous resistance.
the bosch mid drive should be in the first category. Sounds like a fault.

That's what I thought. I reported it as a fault when I got to the depot. Hopefully they will fix it today.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: When the battery dies
« Reply #5 on: December 11, 2019, 12:42:06 pm »
Most ebikes are rideable when it if power. With some you would hardly know the difference, others there is noticeable but not enormous resistance.
the bosch mid drive should be in the first category. Sounds like a fault.

Due to the internal gearing of the hub, which uses a modified power steering or other automotive motor, the Bosch mid-mounted motors have quite a lot of resistance when not powered and are in the second category. I believe it is mechanical / friction resistance rather than electrickery / magnetic fields. 

Re: When the battery dies
« Reply #6 on: December 11, 2019, 01:07:49 pm »
This teardown says there's a freewheel mechanism between the motor and the pedal shaft, so you shouldn't be having to spin the motor while pedalling, at least on that model.