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eBike to simulate motorbike

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Easy-X
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Joined: 08 Mar 2019
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PostPosted: 10:32 - 28 May 2019    Post subject: eBike to simulate motorbike Reply with quote

So upgraded the tyres on my ebike at the weekend from E-marked 50kph tyres to 75kph as top speed now is ~30mph. And was giving it a bit of a test ride...

Then I realised a crucial difference: on a motorbike if you ease off the throttle you start to get engine braking so the throttle regulates speed in both a positive and negative manner.

For the ebike you have no such effect. It's the equivalent of getting up to 30mph, letting go of the throttle and, at the same time, grabbing the clutch and coasting. Not great! Now the thing about my latest build is that the motor has a regenerative braking feature: when you hit the brake lever [switches] the motor goes into reverse and turns into a generator.

I'm wondering how close I can get to the "motorbike experience" by having throttle zero = activate regen. Unfortunately this is binary - either the regen is on or it's not - unlike a motorbike throttle.
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thx1138
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PostPosted: 11:16 - 28 May 2019    Post subject: Reply with quote

You think that's bad, try cornering on a front wheel drive ebike.
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G
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Joined: 02 Feb 2002
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PostPosted: 11:18 - 28 May 2019    Post subject: Re: eBike to simulate motorbike Reply with quote

With a decent programmable controller you should be able to setup it to do, well, whatever you want.

I've got a decent slipper clutch on my (most-used) ICE bike to prevent too much engine braking.

Even without regen, my direct drive hub motor e-bike definitely does offer some 'engine braking' - one of the reasons I went for geared hub motors on the trailer!
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Easy-X
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PostPosted: 13:02 - 28 May 2019    Post subject: Reply with quote

thx1138 wrote:
You think that's bad, try cornering on a front wheel drive ebike.


Mmm... you don't see many front wheel drive motorbikes! My very first ebike build was front wheel drive - you can get away with it for a tiny 250W motor but even then it's not great. Everything I've built since has been rear-wheel.
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Easy-X
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PostPosted: 13:07 - 28 May 2019    Post subject: Re: eBike to simulate motorbike Reply with quote

G wrote:
With a decent programmable controller you should be able to setup it to do, well, whatever you want.

I've got a decent slipper clutch on my (most-used) ICE bike to prevent too much engine braking.

Even without regen, my direct drive hub motor e-bike definitely does offer some 'engine braking' - one of the reasons I went for geared hub motors on the trailer!


The motor I have at the moment offers almost no resistance with regen switched off and that's direct drive...

I was thinking of conjuring up a circuit that checked if the throttle output was zero volts and then flipped the brake switch but I'll have a look what the controller can do.
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Easy-X
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PostPosted: 13:03 - 29 May 2019    Post subject: Reply with quote

So looking at basic controller programming I can affect the strength of the engine braking / regen but it will only trigger on a brake signal. Other than going with custom firmware the easiest way is to link the throttle to the brake signal externally. I have an opto-isolated relay circuit kicking about that I was going to use for the brake light and it's configurable to trigger on either high or low inputs... should be pretty easy to test how "low" low is by wiring it up to the throttle and hearing when the relay clicks...

On the plus side I was thinking about this riding the 125 this morning and you only really notice engine braking completely off the throttle (at lowish speeds at least) so "zero throttle on ebike triggers regen" at least has a chance of simulating the feel of conventional engine braking.

The experiments continue...
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G
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PostPosted: 13:25 - 29 May 2019    Post subject: Reply with quote

HardlyDavidson wrote:

On the plus side I was thinking about this riding the 125 this morning and you only really notice engine braking completely off the throttle (at lowish speeds at least) so "zero throttle on ebike triggers regen" at least has a chance of simulating the feel of conventional engine braking.

And that's part of it - a 1000cc twin can have massive engine braking shutting off the throttle.
That's before dropping it down a gear.
While a 50cc 2 stroke will probably be near zero.
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Easy-X
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PostPosted: 14:48 - 29 May 2019    Post subject: Reply with quote

Experiment 1: at what point will an off the shelf circuit (like an opto-isolated relay) activate from the low signal from the throttle? (Throttle position generates a voltage from 0v to 5v.) Hopefully lower than a typical LED trigger voltage of 1.2v otherwise the bottom 24% of the throttle is dead zone Sad

Experiment 2: run a manual push button to the controller's ebrake input. Ease off the throttle and stab button. Use imagination to consider if this was the effect I was looking for.

Bonus news item: my boss is on holiday and he's left a stack of ebike connectors and wiring and things on his desk where he rigged up a relay switched 12v headlamp from his 6v Bafang lamp output Smile
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G
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PostPosted: 15:36 - 29 May 2019    Post subject: Reply with quote

Depending on how your controller works - something you could very easily setup using Arduino, but potentially also creating a variable effect using a PWM style output. (Or the PWM might blow up your controller, or make it really jerky to ride.)
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GettinBetter
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PostPosted: 14:40 - 20 Jun 2019    Post subject: Re: eBike to simulate motorbike Reply with quote

HardlyDavidson wrote:
...
For the ebike you have no such effect. It's the equivalent of getting up to 30mph, letting go of the throttle and, at the same time, grabbing the clutch and coasting. Not great! Now the thing about my latest build is that the motor has a regenerative braking feature: when you hit the brake lever [switches] the motor goes into reverse and turns into a generator..

One thing that comes to mind, is that Lithium Ion batteries have a charging limitation, so what is the estimated charge rate from the motor on a longish downhill, and could it be a problem for your battery pack? Just a thought.
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Easy-X
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PostPosted: 17:33 - 20 Jun 2019    Post subject: Reply with quote

Nobody with any sense connects lithium-ion batteries to anything directly Wink

I have a 2-wire BMS (battery management system) which handles both charging and discharging, over & under voltage, etc.

As an aside you can also get 3 or 4-wire BMS boards where the charging and discharging circuit are separate which obviously would be no use in a regen scenario.
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