amp limiting with CA - stuttering

[izeman]

i may have overheated my old controller during a steep long climb some time ago, and now thought about limiting the current to reduce stress during those extreme situations.

it was an eb209 feeding some 30a @48v to a mac 10t.

so i opened the ca's setup menu and set the amp limit to eg 10a. this would be enough to help a bit on those extreme climbs, but without harming the motor/controller.

the problem was that there was no smooth reduction of the power but a lot of stuttering. on - off - on - off all the time. i don't think that this is good for the gears and it's not comfortable to ride.

did i do anything wrong? if not: is there a better way to reduce amps? i can't reprogram the controller during the ride

thanks

[Philistine]

Unfortunately that is a nature of using the amp limiting through the CA. I tend to find that the more I reduce the amps from the programmed level, the more it does that kind of jerking you are talking about. I actually find for example that on my BMCV3 I can use the CA to limit amps from a programmed 40amps to 25amps, and there is no jerking or noticable bad effect, but I did try dropping it to 10a out of interest and then it was a shuddering wreck. As far as I am aware that is just how the CA is, because it is basically just cutting amps as soon as they hit the threshold, so that is what is causing the sudden shudder. As I said, I think you would find if you reduced the programmed amps to make the difference less, you would get a better result. As I said, I regularly limit my 40amp set controller to 25amps when I need bigger range, and I get no shuddering effect at all.

Cheers, Phil.

[neptronix]

3 problems:

1) 10A is starving the 10T of power on a hill. You are way better off reprogramming the controller for a lower speed.
2) The current limit on the cycle analyst is not smooth. Especially on a poor controller for the application.
3) The EB2 infineons are just plain awful on the BMC and MAC motors. Mine stuttered at anything other than 100% throttle, the throttle acted pretty much like an on-off switch, and engaging the throttle from a stall, or after letting go resulted in a jolt of torque, resulting in an audible 'clack' from the clutch. cell_man EB3 solves this. The new Lyen EB3 may solve it as well, but cell_man's EB3's have some modifications according to him that make things better for the BMC/MAC motors.

Put these 3 things together and you got a recipe for an awful experience.

If you can't afford a new controller right now, i recommend getting an EB2 programming cable from either lyen or cell_man and cutting the amps down to 25A and see how it goes.. if not, do 20A..

[izeman]

1) programming for a lower SPEED? would that help? if i use the 3 way switch to limit speed, then current stays almost the same. it's just not going that fast.
2) why poor?
3) i already ordered a 309 from cellman of course. and i ordered a second one from germany because shipping from china takes a long time sometimes.

i know that the 209 are not that good. do you think that current limiting will work better with the 309?
i want those 35a max if i can make use of it (almost always. no problem to run that on all streets uphill). but there are some very steep tracks in the woods that don't allow to do more than 5mi/km per hour. i thought that limiting current would help. of course the motor would never run freely.

[neptronix]

A lower speed might help, but the EB2 does a poor job of speed limiting on the MAC/BMC. The amp limit is in effect a speed limiter. The CA modulates the throttle signal to accomplish this. You will most likely experience the same problem.

I can't make promises about the current limiting on the eb3xx. The CA is not smooth in it's amp limiting. The situation should be improved though. You should notice it immediately in just the throttle response alone.

1) programming for a lower SPEED? would that help? if i use the 3 way switch to limit speed, then current stays almost the same. it's just not going that fast.
2) why poor?
3) i already ordered a 309 from cellman of course. and i ordered a second one from germany because shipping from china takes a long time sometimes.

i know that the 209 are not that good. do you think that current limiting will work better with the 309?
i want those 35a max if i can make use of it (almost always. no problem to run that on all streets uphill). but there are some very steep tracks in the woods that don't allow to do more than 5mi/km per hour. i thought that limiting current would help. of course the motor would never run freely.

[izeman]

ok. thanks. that's no really good news. i know how speed/amp limiting works, but i was hoping it being smoother. we'll see with the eb309.
209 was really far from perfect. no steady speed. maybe that's why i always rode wot *ggg*
i'll post my findings.

[John in CR]

Limiting current is done via PWM just like lower throttle. It lowers the duty cycle increasing phase currents and making life harder for the controller, so it can make life much harder for the controller. Pulsing like was happening with the CA, is the worst case scenario, essentially repeatedly accelerating going up a hill.

I've danced with the limits of controllers and motors many times on hills. What I've found is that you need to gain an understanding of the minimum speed you need to maintain on hills, and blast wide open at WOT. If it won't do it, then the hill is too steep. Putting a small blower in the controller to keep it ventilated works wonders for a controller and enables significantly higher power through it. A better location with more air flow over the case is another good way to help a hot controller.