Controller throttle response

[MalcolmB]

I recently built an electric motorbike with an Etek motor and Alltrax controller. I’m really pleased with it, but there is one area where I’m not totally satisfied. The response to the throttle is very sudden, so it can be difficult to control the bike at slow speed, and even potholes in the road can cause changes in speed due to slight movement of the throttle. I’ve tried adjusting the throttle ramp in the controller, but this doesn’t remedy the problem. The other day I found that Cedric Lynch has already described this problem on the Agni Motors website:

‘we recommend the Brusa MD95 series models, an old design but still best because they control torque directly in proportion to the throttle position and without any time delays. The difference this makes is that if you suddenly apply one-tenth throttle with the Brusa controller in a stationary vehicle you will get one-tenth of maximum acceleration with no definite speed (you will eventually reach full speed if the air resistance is low and you don’t ease off the throttle). If you do this with the other controllers you get full acceleration up to one-tenth of top speed and then the acceleration stops, constituting a substantial jerk! The makers have attempted to mitigate this effect with delay “rampsâ€Â

[EVguru]

Have you tried changing the throttle curve?

My bike was very smooth with throttle resonse as fast as possible, but with the progressive curve.

[MalcolmB]

Yes, I'm using the progressive throttle curve, but have the ramp set at 6. I don't think I'd like to ride it at the fastest ramp setting. How much does your bike weigh? Just wondering if that would explain the difference.

[electricvehicles]

Hi,
What voltage are you running at and what sort of current loadings are you putting on the controller ?

Might just have the answer

Regards
Dave

[MalcolmB]

Hi Dave,

I'm running a 60-volt system with the current limit set at 300 Amps, but obviously I don't use the maximum current very often. The controller is an Alltrax 7245.

[electricvehicles]

I do have a Curtis 48-72V 400A speed controller going spare, new I hasten to add. You are more than welcome to try it. Only requires a simple 0-5K input.
Not the most technically advanced controller on the market, but they work and work very well.
If you are interested let me know your address and I will send it off.

Regards
Dave
electricvehicles@aol.com

[MalcolmB]

Thanks Dave, I've sent you a pm

Malcolm

[EVguru]

Yes, my bike is heavy, it's carrying 80Kg of battery and only running at 48 Volt.

It's going to be a problem with nearly all controllers. There is a 72 volt version of the Brusa, but it's only available through ASMO and comes with no warantee ('race use only').

Even with the Brusa you can have problems. When trying to climb a curb, you wind the throttle on until it supplies enough current (torque), but once you're over the curb you take off like a scalded cat becuase your torque requirement had just gone right down.

The Curtis isn't going to be better than the Alltrax and it's less efficient (partly becuase it has a lower switching frequency). There's also a small risk that the Curtis will object to driving a low impeadance etek, Lemco, or Agni and fail (some do, some don't).

What you really need is a PI (proportional integral) throttle response, where the rate of change of throttle signal to the controller is based on the difference between the current throttle position and the new throttle position. I'm just having a look at building an add on circuit for the alltrax myself.

[MalcolmB]

once you're over the curb you take off like a scalded cat becuase your torque requirement had just gone right down

Thanks for pointing that out Paul, sounds like out of the frying pan into the fire

There's also a small risk that the Curtis will object to driving a low impeadance etek, Lemco, or Agni and fail (some do, some don't).

Yes, I want to check that out. I know the early versions of the Alltrax controller that I'm using now suffered from a similar problem, but Alltrax told me they fixed that problem a couple of years ago, which was one of the reasons I went with Alltrax in the first place.
An add-on circuit sounds very interesting. There's a little company in the states that is working on something similar (www.maxdon.com), but it's still at the prototype stage. Please keep me updated on how you get on.

Malcolm

[electricvehicles]

Hi Ev Guru

Beg to differ on you comments regarding the Curtis controllers not being as efficient at the alltrax. The US rate their outputs quite differently to the UK/Eu markets. Normally they as usual overate everything. Just as Alltrax do. One thing to consider is that the alltrax is NOT CE approved and as such could result in your insurance company voiding any claim should one occur.
I have been dealing with Evs for more years that I can remember and could have purchased many speed controllers from across the pond for far less but none are Ce approved other than the Curtis, Sevcon, and GE. Regarding the CE approval on Curtis controllers those with an X on the end of their part number are Ce certified any others are not.
Also I dont see the alltrax being fitted to any new vehicles, Taylor Dunn use Curtis as do: Cushman, Ezgo, Motrec, Clubcar - all US manufacturers.