Woosh power control

[Stradageek]

Just fitted a Woosh FWD kit to my wife's Kettwiesel and she's loving it but we're a little confused.

It has a simple pedelc sensor and the motor kicks into life nicely as you start off. However when riding together with her power set at 2/5 (my Kett is unassisted) we find that she gets much more assistance on the hills than on the flat.

I'm a good hill climber and she stays with me on the climbs but on the flat, at speeds well below the 15mph maximum she lags behind.

Can anyone explain?

[Jdsk]

What does the sensor sense?

Jonathan

[Stradageek]

It's a simple hall sensor, just crank rotation. The wheel motor does have an independent speed/rotation sensor

I'm guessing that the power probably tapers off with speed, otherwise there would be an abrupt cut-off at 15mph which might be a bit disconcerting

[stodd]

I'd contact Woosh and ask them what you would expect. We've got a Woosh front (XF07) on the tandem and usually ride at 2/5. A bit underpowered for a tandem but gives us the extra 'push' we need (we were warned but nothing else suitable around at the time)

I'm pretty sure it and other Woosh kits with rotation/cadence sensors have current controllers (where the setting controls the current provided to the motor). If it were a speed controller that would explain your fall off well below 15mps on setting 2/5.

[hemo]

When hill climbing often the speed is lower, the lower the speed the more the current is delivered & this current equates to more torque. On level terrain as you go faster and nearer the cut off speed torque and current backs off, it is complicated but the motor will be operating at it's optimal voltage and back EMF comes in to play meaning less current and torque is supplied.

[philg]

What you are describing suggests you have a speed controller, not current control - I believe Whoosh supply Lishui controllers which AFAIK only use speed control.

This means that when you think you have set a 'power' level at 2 (of 5) you have actually set a speed, which based on my Lishui controllers is probably around 10mph, though that will depend on the motor RPM supplied and whether Whoosh have reprogrammed the firmware.

The controller will supply maximum current at speeds far below the set speed then taper off to zero assist once the set speed is reached.
You can easily check if this is the case by raising the motor wheel off the ground, turn the pedals and record the speed displayed for each of the 5 levels. They should be something like 8,10,12,14 and 15.5mph

Set at L5 the controller will behave exactly like a current controller set to L5 and cut off at 25kph (assuming legally set up)

[Stradageek]

When hill climbing often the speed is lower, the lower the speed the more the current is delivered & this current equates to more torque. On level terrain as you go faster and nearer the cut off speed torque and current backs off, it is complicated but the motor will be operating at it's optimal voltage and back EMF comes in to play meaning less current and torque is supplied.

It's becoming a bit clearer, data obtained from Woosh says that the taper changes with power level:

level 1: taper off quickly after 10mph
level 2: taper off quickly after 12mph
level 3: taper off quickly after 14mph
level 4 and 5: no taper.

However, I think I also need more detail on your considerations to explain why I can keep up with my wife on moderate hills (all be it at a hefty heart rate!) but lose her wheel on very steep hills. It feels as if the motor either delivers intrinsically more power at lower speeds or that I'm seeing an early programmed taper.

Can you expand?

[hemo]

I forgot about the Woosh Lishui Speed controllers, the speed controllers are different to my current control ones. The speed controllers are programmed to give max current at any given set speed as also programmed in each PAS assist level.

They use more battery per charge then current control controllers, current control reduces current as the speed nears the terminal cut off.

[Stradageek]

That all pretty much adds up, if the following is true:

At each power level there is a target speed after which power/drive current rapidly declines (as confirmed by Woosh)

At each power level there is also a maximum power/drive current which is pretty much instantaneously applied when pedal rotation is sensed

So at my wife's preferred power level she will top out at 12mph on the flat but climb hills at less than 12mph dependent upon the steepness of the hills

What still puzzles me a little is why I can stay with her on an incline that slows her to 9mph while on a steep incline with her at 7mph I lose the wheel. Surely if my maximum output can sustain 9mph to match the motor on a moderate hill why can't I match the motor on a steeper hill?

Is this because the motor is at maximum current at 7mph but tapered slightly at 9mph - i.e. there is some more progressive tapering?

[philg]

...... The speed controllers are programmed to give max current at any given set speed as also programmed in each PAS assist level.

They use more battery per charge then current control controllers, current control reduces current as the speed nears the terminal cut off.

That is incorrect, at least in regard to the Lishui and Swytch controllers I have.

Certainly at speeds much lower than the set level, the controller will provide maximum current as you would expect, but as the speed approaches the set level the current is gradually and progressively reduced in a similar way to a current controller.

I have bikes with KT current control, Lishui and Swytch speed control and find the speed controllers much preferable, especially the Swytch which gives you freedom to increase the number of PAS levels and to fully program each level to suit. I tend to set the level at the start of the ride and rarely need to change it, unlike current control where for around here it is constant button pushing to cope with the hilly terrain.

To say speed control is more wasteful of battery is simply not true; like so much of e-bikery there are too many variables to justify such a blanket assumption. If it were as bad as you believe it seems odd that Whoosh and Swytch have both chosen to use it, and Yosepower have recently changed from KT (current) to Lishui.

What I would say is that Lishui's preset levels are sub-optimal with the UK's 25kph maximum, as shown by Whoosh's figures above - out of 5 theoretical levels you only get 3 practically - hence my preference for Swytch.
KT's implementation of current control is also (IMO) sub-optimal - the jump between L4 (50%) and L5 (100%) is not ideal.

HTH

[Stradageek]

Thanks to all who have contributed to this discussion, We now understand the kit much better and can easily tailor it to suit our joint rides. We also remain very happy with the Woosh kit.

I've had excellent support from Andy at Woosh throughout (fitting the standard FWD bicycle kit to a recumbent trike, with Schlumpf drive, provided MANY challenges) and the battery range definitely exceeds expectations.

And no. I'm not on a commission

[hemo]

Every one will find personnel preference varies, my first ever kit was a Woosh kit with Lishui tbh I never ventured out of PAS 1 as I could hit 19mph all the time and found the torque/acceleration just too abrupt.
For my next kit I use them again with the BBS01, I found it more to my liking but preferred the hub drive.
Eventually after much reading and chatting I opted for the KT which I now have used for the last 5 years, the 50% PAS4 and 100% PAS5 I find are good but I seldom ever need them. For most of my riding PAS1 is all I use I can reach max cut off speed I desire with frugal battery use for longer rides, the current in PAS1 is approx 13% and ideal for my needs as I want more control over acceleration and torque and just select extra power/torque if ever needed, often I don't even adjust PAS level and just briefly blip the thumb throttle which is a pedal first option.