What's the best way to limit top speed?

The Maestro

Esteemed Pedelecer
May 15, 2008
296
0
I'm planning on going to a 48V battery soon and want to limit the top speed to remain legal but also have it switchable.

I assume this invoves limiting voltage at some point? What components do I need and where should I wire them? E.g. do I put something in the wiring between the throttle and the controller or battery and controller etc?
 

The Maestro

Esteemed Pedelecer
May 15, 2008
296
0
The cycle analyst will do the job.
Regards,
Jo
Thanks for the suggestion, I know about the cycle analyst but I want something more 'lightweight'. The cycle analyst does tons of stuff I don't want and will never use and I don't want that mounted on my handlebars ready to get pinched. I also don't know how fast it can switch between speed limiter settings for 'on road/off road setting' but I doubt its as fast as a traditional physical toggle switch.
 

torrent99

Esteemed Pedelecer
Nov 14, 2008
395
36
Highgate, London
Thanks for the suggestion, I know about the cycle analyst but I want something more 'lightweight'. The cycle analyst does tons of stuff I don't want and will never use and I don't want that mounted on my handlebars ready to get pinched. I also don't know how fast it can switch between speed limiter settings for 'on road/off road setting' but I doubt its as fast as a traditional physical toggle switch.
If you want lightweight (but inaccurate), you could put a resistor in series between the 5V line going into the throttle and the throttle itself. That should lower the voltage and limit the max throttle.

Even better would be to put use a preset potentiometer to scale the output of the throttle.

Use a switch to switch this in and out of circuit.

None of this will work on the pedelec bit though.

Cheers

Steve
 

frank9755

Esteemed Pedelecer
May 19, 2007
1,228
2
London
Even simpler - but also throttle only - would be a physical restriction on how far the throttle turns round. Basically a strategically glued piece of plastic that could be "switched" out of the way when off-road
 

torrent99

Esteemed Pedelecer
Nov 14, 2008
395
36
Highgate, London
Even simpler - but also throttle only - would be a physical restriction on how far the throttle turns round. Basically a strategically glued piece of plastic that could be "switched" out of the way when off-road
Of course what you really need is some sort of lever you can pull that, when the bike exceeds the speed you'd like, slows the bike down....hold on I think that's already been done! :p ;) :D

Seriously though if you want a more sophisticated solution, you should try Endless-Sphere. There's been a thread on there recently about a similar subject but with a sophisticated current limiting circuit. Try searching for "RC Throttle" on ES.

Cheers

Steve
 

The Maestro

Esteemed Pedelecer
May 15, 2008
296
0
Thanks guys, those ideas sound good. Something on the throttle wire would suit me without having to do a lot of re-wiring.

Just out of interest, does the Cycle Analyst allow fast selection of different speed modes? I might consider getting one in the future.

I quite like the low tech option of physically stopping the throttle turning past a certain point but I think it might be a difficuly modification to make it switchable on a thumb throttle. Its also very sensitive and tiny movements on the throttle affect the speed quite a lot since the 'active' part of the throttle is only the final 30 degrees of turn (i.e. the first bit of the throttle does nothing).

I'll check out endless-sphere too.
 

The Maestro

Esteemed Pedelecer
May 15, 2008
296
0
Of course what you really need is some sort of lever you can pull that, when the bike exceeds the speed you'd like, slows the bike down....hold on I think that's already been done! :p ;) :D
Yes, its a pity that we aren't trusted to keep our speed to a sensible level whereas most cars are able to do at least twice the speed limit and trusted to keep below 70.
 

Tiberius

Esteemed Pedelecer
Nov 9, 2007
919
1
Somerset
There isn't actually a good off the shelf solution to this, unless the feature is built into the controller.

Going to 48 V and limiting the throttle to 3/4 will put you back in the same situation as having 36 V. Limiting the throttle isn't really a good solution.

The Cycle Analyst will do it, but not very well. The control loop is set up for target seeking rather than hard limiting, so it will overshoot a long way before settling. I think Justin knows this and is working on it. You can get in and hack some of the control loop parameters, but I haven't tried it. It also takes a lot of button pressing to turn the limit on and off. I've fitted a physical override switch to get round that problem but you're still left with the actual speed regulation not being good enough.

Nick
 

The Maestro

Esteemed Pedelecer
May 15, 2008
296
0
There isn't actually a good off the shelf solution to this, unless the feature is built into the controller.

Going to 48 V and limiting the throttle to 3/4 will put you back in the same situation as having 36 V. Limiting the throttle isn't really a good solution.

The Cycle Analyst will do it, but not very well. The control loop is set up for target seeking rather than hard limiting, so it will overshoot a long way before settling. I think Justin knows this and is working on it. You can get in and hack some of the control loop parameters, but I haven't tried it. It also takes a lot of button pressing to turn the limit on and off. I've fitted a physical override switch to get round that problem but you're still left with the actual speed regulation not being good enough.

Nick
I think even if its built into the controller it may not be very good. The controller that came with my original Alien kit had a limiter (variable resistor or similar) on a loop of wire that came out of the controller but if you restricted the top speed it would also limit the low end torque and acceleration by a similar amount.

I thought the cycle analyst measured the actual speed of the bike either using a magnetic pickup on the wheel or reading it from the hall effect sensors somehow, and if it went over a certain speed cuts the power. Wouldn't this be accurate and not compromise torque at lower speeds?

I'll go for a low tech solution, the 36V is fine for me in town, I'd just like to use the full 48V power in a few situations.
 

joab

Pedelecer
i have the CA on my bike. version 2 and it works very well. The speed is limited on 26km and does cut out at 27 max. My other limit is 6A to save my battery. It goes to a max of 350 watt but them very quickly drops to the max of 220 watt. To switch you just have to hold the reset switch and change the values you want. I really like the CA.
Regards, Jo