Help! Controller - speed or current? Carrera Kraken conversion?

[Slightlypedantic]

I have a Lishui speed controller. As I understand it, it gives maximum torque (current) until it reaches a limiting speed according to the "power" level selected, when the current is tailed off by the controller. Hence "speed" controller.

I believe a "current" controller limits the current to the motor according to the "power" level selected. This results in lower torque for lower "power" settings and higher torque for higher "power" settings. All "power" levels top out at the 25kph legal limit. I believe Lishui also make this type, as do other manufacturers.

I have read on some forum threads that current control is much more intuitive and natural than speed control. For a future project (Carrera Kraken hardtail mtb conversion) I would like to use an existing rear hub motor and battery but combine these with a current controller.

Does anyone have any thoughts on whether this is likely to give a good result?

Can the controller be a straight swap? Wouldn't it be nice if the plugs/sockets and pin-outs all matched .... or am I being over-optimistic?!

How do I ensure compatibility and reliability?

Thanks in advance!

NB The battery and rear hub motor were previously associated with a Lishui controller YCSH-D, 36V, 15A. It's built in to the battery base, which looks like a re-badged HL. The battery terminals are five round brass sockets. The two outer ones are larger, presumably for current. The three in the middle are smaller and arranged in a triangle, presumably for communication between BMS and controller.

 

[Nealh]

It is doubtful whether you will find a LSW current controller so your best option is to buy a kt along with the necessary peripherals, then the only wiring needed is maybe the battery connections.

 

[Slightlypedantic]

Thanks Nealh. I'll look into that, sounds relatively straightforward.

Would a KT controller work with and (perhaps?) plug straight into a C500 display? Or should I consider a better display?

Motor is an Aikema 95RX (rear hub). Do you think a current controller would make this a nice mtb conversion?

Having tried speed controllers I've been a bit underwhelmed. I seemed to work either bloody hard or hardly at all! Battery life didn't seem all that good. Doesn't feel as though speed control would translate well to the single tracks at Bedgbury Pinetum (Kent). I mainly need a bit of extra oompf on the steeper bits (old age creeping on, sadly) and don't want it to suddenly die on me because it's hit a power level speed limit. Perhaps a current controller would improve things all round?

Current controllers sound like a much better place to be but, having been able read only a little about what they are like to actually use, I'd be glad to hear other opinions before dipping my toe in the water.

 

[saneagle]

Thanks Nealh. I'll look into that, sounds relatively straightforward.

Would a KT controller work with and (perhaps?) plug straight into a C500 display? Or should I consider a better display?

Motor is an Aikema 95RX (rear hub). Do you think a current controller would make this a nice mtb conversion?

Having tried speed controllers I've been a bit underwhelmed. I seemed to work either bloody hard or hardly at all! Battery life didn't seem all that good. Doesn't feel as though speed control would translate well to the single tracks at Bedgbury Pinetum (Kent). I mainly need a bit of extra oompf on the steeper bits (old age creeping on, sadly) and don't want it to suddenly die on me because it's hit a power level speed limit. Perhaps a current controller would improve things all round?

Current controllers sound like a much better place to be but, having been able read only a little about what they are like to actually use, I'd be glad to hear other opinions before dipping my toe in the water.

You'll be very happy with a KT controller.

 

[Nealh]

You will have to buy a KT LCD of which there are a dozen or more to choose from, the C500 will switch on but will have limited use .

Speed control generally is poor for battery range/life as they give mostly max current all the time , with a KT you choose the current amount to use 13, 20, 33, 50 or 100% of available power. They are though preset %'s and one can't physically change the %'s but can change the current draw in the settings by approx. 50% is need be.

 

[Nealh]

I use my KT's in PAS 1 99.99% of the time, I find the 13% current draw of a 22a controller more then enough for my needs . If need be one can easily opt for more current as and when needed , not something the LSW's can do .

Woosh programme theirs's a little higher with PAS1 at approx. 40% which for me would be way to high.

Even with the KT PAS 2 is very noticable in power increase over PAS 1.

 

[Nealh]

For kt everything is plug and play whether you opt for W/P or the user freindly SM block connection sytsem, just buy everything from the same buyer.
You need a controller, a lcd, a wheel speed sensor (if you don't have internal hub speed sensor), a PAS unit and throttle (if needed).
Motor cable connecton should work colour to colour , the akm 95 should be 9 pin so a wheel speed sensor shouldn't be needed.

 

[Woosh]

Woosh programme theirs's a little higher with PAS1 at approx. 40% which for me would be way to high.

it's not a limitation by Lishui. They supply the code to suit OEMs. Their default code is practical for most users. It's not an on/off switch based on speed, it's a step change in effort based on the selected assist level. The main difference in the Lishui's 'speed control' - for lack of a better descriptive word, and current control is the starting current. In current control mode, starting current = sustain current. The acceleration is uniform with current control, you don't have the strong push when you start or when you change assist level. With 'speed control', the current is shaped, start and sustain, some people dislike that. You get a strong starting push for about 2-3 seconds then the push reduces to cruising push. In both profiles, your speed is controlled by the speed of your pedalling, the assist level controls the effort of your pedalling. You never quite ghost pedal. As for percentages, it depends on the LCD. The KD58C I use with the Lishui lets you choose number of assist levels and percentage of each level, it's called 'power sets', the KM529 doesn't have power sets.
All the 2023 bikes have current control code.

 

[Slightlypedantic]

Wow! That's really helpful, thanks everybody. Lots to think about.

From what Woosh says there are aspects of speed control that are more sophisticated than current control. It would be very interesting to see graphs of current/torque against speed for each assist level, and for each type of control.

Is it possible that speed control may be better suited to more casual/less fit cyclists (including some with health issues) who don't have strong legs or stamina, and current control may be better suited to stronger/more experienced cyclists who just want a bit of help with hills and headwinds and need longer range?

Does current control always need to be a straight line, i.e. constant current/torque regardless of speed? Could lower assist settings not have a torque "hump" at lower speeds to help get you rolling? Soft start too? "Humpiness" could be reduced progressively in higher settings, obviously to zero at full power. Degree of "humpiness" could be a setting (e.g. "start assist" or "boost" - off, mild, strong) to suit a cyclist's particular preference?

 

[Woosh]

Does current control always need to be a straight line, i.e. constant current/torque regardless of speed?

The fundamental of PAS programming is still the same, the controller keeps you pedalling regardless of 'speed control' or current control. Basically, if you put zero effort into moving the pedals, the current will be reduced to near zero and the bike will slow down to a crawl. The key difference is the controller does not give the response curve a 'hump' in current control.

Degree of "humpiness" could be a setting (e.g. "start assist" or "boost" - off, mild, strong) to suit a cyclist's particular preference?

albeit it's easy to program, you would need bluetooth and an app for that.

Pedal assist on the Woosh Camino (the Woosh bikes have same assist setup)