Question about PAS Speeds with KT Controllers

[adcockj]

I'm considering replacing the generic square wave controller with a KT sine wave controller on my DIY rear hub ebike (Bafang G020.500 motor, generic controller, DPC18 display). I'd also get the LCD-8H display, and program the parameters as it allows.

I have a question, though, about the assisted speed for each PAS level. It appears that I can change the power levels to an extent (low, medium, high) and that the ebike will get more power at each PAS level. However, it doesn't show anywhere (that I can find) about how the assisted speed will also change as I go up in PAS levels. The current Bafang system gets speed assist up to about 50% of the maximum speed in Level 1, about 60% in Level 2, about 70% in Level 3, about 85% in Level 4, and 100% in Level 5). And each level gets a higher amount of assist power.

Does the KT controller do the same? Or does the assist stay on all the way up to the maximum speed in every level? I wouldn't want Level 1 to stay assisted all of the way up to 28 mph if that's the maximum speed I have set on the bike. If the assist does cut off at a lower speed depending on the level, is it a % of the maximum speed, or something else?

As an aside, it appears that I would get either the 20a max controller or the 25a max (and limit it to 20a) for my 500w system. Any recommendations in that regard?

 

[docw009]

I have built a few bikes with the 20A controller (6 FET) and recently upgraded one to the 25A (9 FET) controller.

KT controllers, if set in current mode (C2=0), which everyone does, will have a max current for each of the PAS levels. My LCD3 gives 5 levels. For example, the 20A unit on 36V will do about 100-120 watts in level 1, 140-150 watts in level 2, so on up to 600-700 watts in level 5. The throttle will override to max current in any level. The 25A unit will start at 140-150W in level 1. And each level has its own speed associated with the current.


I'm told weird things happen if you set C2 so it's not in current mode.

There is one setup parameter (C5) that allows you to change the current from max to about 50% in about 6 increments. It works as advertised.

If you have the room, a 500W motor is probably more fun with the 25A controller.

 

[AHicks]

Agree with the Doc. on a few things anyway.

Where I differ big time is regarding his thoughts on the C2 setting. Not everyone is crazy about using C2=0. I would set C2=1
This eliminates the relevance of the bike's speed, instead basing it solely on the amount of power going to the motor for each PAS level (which can be set to your 'druthers using C5 and C14). In PAS 1 for instance you can set the power to 50w, and no matter what your speed, it will have that same amount of power, or "assist". If you want more assist, go to a higher PAS level. This way there is no max speed for each PAS level, forcing you to increase the PAS level in order to go faster.

There's 2 types of pure cadence control. There's speed based, which the least expensive bikes use most often, and there's power based - which is light years better. At the very least, try it both ways. In my experience, you're going to like the C2=1/power based cadence much better.

As far as setting PAS speeds, as he mentions you can limit the power from the battery using C5, and then trim that setting using the high/med/low available in C14. Even the guys with the big mid drive Bafangs are using it....

I just installed a KT 20a on a new bike with 500w Bafang (bike didn't have 10 miles on it yet). I ended up setting C5 to get about 700w max. (C5=05) Motor is surprisingly "sporty". Made a really nice install. Might take a little screwing around with the settings, but I'll bet you love it in the end!

 

[adcockj]

Thanks for the replies. It looks like I'll have some experimentation to do (but that's part of the fun), but it should work. Cheers.