CycleAnalyst Operates w/o Battery

CycleAnalyist: StandAlone model, battery physically disconnected from the system, 9C motor.

Somewhere around 10-11 mph, the CycleAnalyst boots up and shows speed along with voltage.

At 13 mph, it's showing a voltage of 18v.

Normal operation, I'm sure... and this is purely idle curiosity... but can somebody explain?

there's enough back emf on a motor to power up the miliwatts needed to run the CA.
A visual demonstration of what cogging does.

I use my bike without batteries often enough. with the 4012 hooked up, it powers on around 6mph. might power up sooner if I disabled the backlight.
there's no regen on my old controller, but there's enough leakage in the fets to allow miliwatts through.

PeteCress said:

Normal operation, I'm sure... and this is purely idle curiosity... but can somebody explain?

Click to expand...

The 3-phase AC back-emf of your hub motor is being recitified by the mosfet body diodes in the controller and powering up the DC bus. If you stick a multimeter in the battery port of your motor controller, you'll see exactly the same voltage that the CA is displaying. Totally normal behaviour for any direct-drive permanent magnet motor.

Your controller draws about 50mA to stay powered up, so you are in this case using the hub motor as a generator and running the controller and CA from it. The act of riding with the controller plugged into the motor this way but no battery pack results in a higher drag from the hub than if you either unplug the motor from the controller, or have a battery connected to the controller but no throttle.

-Justin

Just to prove that no good deed goes unpunished: one more question.

Variable cogging: when I start out on a ride having applied no electric assist, the cogging is imperceptable to me.

Give it a few hundred watts to ease a hill climb, crest the hill, take my thumb off the throttle, and cogging kicks in big time.

Pedal unassisted for 1-2 minutes, and cogging is back to being imperceptable.

I tried starting a thread on this, but all I came away with was that it might be my imagination. Granted I'm one of those people whose car seems to run better after a wash/wax. But that notwithstanding, I'm pretty sure the variable cogging thing is really happening.

This is another totally-idle curiosity question... but can you explain what's going on?

Something to do with motor temperature?

I find cogging varies with speed. I feel very little at 5 mph, more at 10 and so on.

PeteCress said:

Variable cogging: when I start out on a ride having applied no electric assist, the cogging is imperceptable to me.
Give it a few hundred watts to ease a hill climb, crest the hill, take my thumb off the throttle, and cogging kicks in big time.
Pedal unassisted for 1-2 minutes, and cogging is back to being imperceptable.

This is another totally-idle curiosity question... but can you explain what's going on?
Something to do with motor temperature?

Click to expand...

Ha ha, no those who said it is your imagination are totally correct. It's more like ebike 'acclimatization'. You get used to having the few hundred watts on your side and start to assume that as the norm. When it's suddenly taken away then you feel like you have a few hundred watts of drag. The human body plays this kind of trick all the time in many contexts. You'll notice the same thing with the geared eZee hub which freewheels and has no cogging. It's all in your head.

-Justin

dogman said:

I find cogging varies with speed. I feel very little at 5 mph, more at 10 and so on.

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The actual cogging torque of most direct drive hubs if you care to measure it does increase with speed but not by very much (not enough for you to feel the difference, it might be 0.4 N-m at 5mph, and like 0.45 N-m at 10 Mph).

Justin

I'm with you PeteCress on this one.

The same thing happens to me. When I first get on the bike after a shift at work, I will turn the bike and lights on and start riding without any throttle. Sometimes I will look down at the speed and see that I am doing 26kmh+ without any cogging. As soon as I give it some throttle and let go the cogging will kick in at 21 kmh and I will have to add 10w with the throttle to get back up to 26 with the same amount of effort.
I dont have a lot of luck getting it back, but it does happen occasionally.

Greg

tailwind said:

As soon as I give it some throttle and let go the cogging will kick in at 21 kmh and I will have to add 10w with the throttle to get back up to 26 with the same amount of effort.
I dont have a lot of luck getting it back, but it does happen occasionally.

Greg

Click to expand...

It's all in your head too, Greg.

Justin

So, I'm a total noob to ebikes, but it makes sense as a commuter vehicle for me where I live,

Anyway - long story short - I pick up a 9C conversion kit with a 25A controller & set my bike up & have two weeks to wait until my battery arrives. Beautiful day the other day, couldn't resist riding the new rails to trails route near my house. After reading this thread I figured it was no problem to ride the bike w/o a battery hooked up - so off I went. Around the corner from my house the CA lights up, 24v -0.1A & and wrong speed (I haven't calibrated it yet of course, no battery...) 500m further down the road I'm playing with the thumb throttle (it was sticking open when I tightened it onto the bars while setting it up - wanted to see if it was still sticking) and it sticks open for a moment - then flicks closed and *wham!* someone throws on the e-brake! The wheel is cogging like crazy, can't manage to get it going faster than about 8-9kph, so I unplug the leads to the controller, and it is again fine. Limp home. Some poking around with some help from the shop and it sounds like I've somehow blown the mosfets in the controller!? No, this set-up is not rigged for regen, that lead coming from the controller is bagged, and zapstrapped to the frame...

I wonder if anyone else has ever managed to toast a controller so soon in their ebike expereince? Any thoughts how this happened?

Anyway - ye be warned!

You blew a fet. The back emf was enough to power on the controller but not enough to power everything properly. It sounds like the same thing that happens if you let the voltage drop so low that the input resistors arent allowing enough current through to the mcu to work properly and for the gate drive to operate properly under a load which shorted your mosfet. If you are lucky you only blew 2 high side mosfets on one phase (12fet controller). At the very worse you blew the gate drive also.

icecube57 said:

You blew a fet. The back emf was enough to power on the controller but not enough to power everything properly. It sounds like the same thing that happens if you let the voltage drop so low that the input resistors arent allowing enough current through to the mcu to work properly and for the gate drive to operate properly under a load which shorted your mosfet. If you are lucky you only blew 2 high side mosfets on one phase (12fet controller). At the very worse you blew the gate drive also.

Click to expand...

Can I dumb this discussion down to: "Don't ride an ebike without a battery connected." ?