what is preferred? KT or S866 for replacement controller-display combo?

[derekderek]

we bought a 350 buck ali express bike. controller died after 2 weeks. i robbed the back wheel for another older bike that ate the gears. putting it back together after wheel repair i got 3 amazon controller-display combos. same controller all 3 times. (return-replace) all throw e07 and e10. and the 2 bikes they don't work on all run plugged into my 2 live bikes. tried to return for same one a second time and they no longer sell that one. is there a very high fail rate with these controllers? of did i just luck into a bad batch?

 

[99t4]

is there a very high fail rate with these controllers? of did i just luck into a bad batch?

Hard to say. Did they ever work? Or did they arrive DOA? Did they all exhibit the exact same failure modes?

 

[derekderek]

putting a couple of bikes together and have 1 that is alive with older analog 3 speed "display". i have had bad luck with 1 batch of S866's and just bought 1 KT for a bike that has KT display. haven't fired the KTup yet cuz it has anderson connectors on the phase lines and i don't wanna cut them off until i do jury rig to make sure controller doesn't need to go back. but i may need 2 more and wondering the consensus on the best way to go with conversion setups. 1 motor is 500 watt geared and other is 1000 watt Voilamart direct drive. and is SW900 essentially same as S866, or completely different? thanks.

 

[stancecoke]

SW900 essentially same as S866, or completely different?

This are displays with the so called "No2" UART protocol, that is used by many cheap Chinese "no name" controllers, sold as Greentime, Brainpower or other brands.
It's always a lottery, which firmware version the controller has, so the behaviour of this kind of controllers may vary.
Kuntengs have the advantage, that they always work in the same way and are configurable by the display. Therefore they are popular with DIY E-Bike tinkerers. But they are outdated.

I would recommend FOC controllers like the ones from Lishui or JYTCON, even if they are slightly more expensive....

regards
stancecoke

 

[fill]

@stancecoke what do you mean by FOC? i read this a 'free of charge/cost' ie $0 price tag, google tends to agree, offering up 'Firm Order Commitment' as an alternative.

My expertise as a limited ebike tinkerer, would suggest sourcing a controller and matched display together whenever possible to avoid throwing cash away at incompatible displays.

If replacing a display on an off the shelf ebike, the chances of the manufacturer/fabricator/'designer' opted to install branded f/w to make their bike 'stand out' is high. So a generic display matching the model number on your bike without the custom f/w wont work as expected if used to replace an original. - hence the general recommendation to replace both with a matched pair if a display on a branded bike is not available from the seller.

KT controllers/displays are popular with us ebike tinkerers for a few main reasons, - many of the niggles that hamper smooth running can be sorted within the configuration of a KT controller, and the can provide a reasonable emulation of proportional power output based on cadence sensor input. In addition the display options which are all compatible with KT controllers cover a range of aesthetic tastes.

If looking to just add displays to controllers already in your possession? what are the controllers and whats their pedigree? if ripped from an off the shelf ebike - track down the spares for that ebike to source a display, if known to be generic stock controllers buy a compatible generic display, if it came with a sw900 its not going to work with anything starting 'KTLCD'

 

[stancecoke]

@stancecoke what do you mean by FOC?

FOC stands for "Field Oriented Control". This is the state of the art to drive a BLCD motor. There are tons of literature about it.
Controllers like the Kuntengs or the Brainpowers are not able to do FOC, (even the sine-types of the Kuntengs can't do it), so they drive the motor more noisy and less efficient than a FOC controller.
Of course, the Kunteng does it's job, but if you have ever tried something better, you won't want to have it back

 

[marka-ee]

is the FOC technology, the one that can run a bit faster but consumes a somewhat more power while doing so?

 

[stancecoke]

is the FOC technology, the one that can run a bit faster but consumes a somewhat more power while doing so?

You can do the so called "field weakening". A part of the input power is used to weaken the field of the permanent magnets of the rotor. This reduces the BEMF voltage of the motor, so it can spin faster with the given voltage of the battery. Field weakening can be done very easily with FOC (just apply a negative id), but you can achieve it with simple sine commutation also, by increasing the advance angle (see the OSF for the TSDZ2 for example)

I've experimented with field weakening in the EBiCS firmware a while ago

 

[Chalo]

Controllers like the Kuntengs or the Brainpowers are not able to do FOC, (even the sine-types of the Kuntengs can't do it), so they drive the motor more noisy and less efficient than a FOC controller.
Of course, the Kunteng does it's job, but if you have ever tried something better, you won't want to have it back

Actually, I like controllers that don't have to be configured or programmed for them to work. To me, that's the measure of a good controller. If I have to do any matchmaking between controller and motor, I don't care what the subtle benefits are.

My favorites so far are "three mode" controllers without a display. Just plug in and go, silently.

 

[stancecoke]

To me, that's the measure of a good controller. If I have to do any matchmaking between controller and motor,

that's a disadvatage of the Kuntengs also. They have no self learning routine. So you have to fiddle around to find the right phase- and hall-sensor combination by trial and error, even if tutorials exist, it is not convenient. The Brainpower controllers have the self learning function. So it doesn't matter, in which combination the wires are connected, the controller finds the right commutation automatically.
Of course the modern 9pin Higo motor connectors brought some kind of standard for the wire connection, but if you deal a lot with old stuff, that used japan bullets for the phase wires and JST SM connectors for the hallsensors, you will be happy about the self learning function

regards
stancecoke

 

[derekderek]

i understand the old 3 mode analogs work, but people want to see speed, volts, etc. and the 3 i bought off amazon were controller-display combos. all said E10. and the 4th was an off-shelf sub-400 buck bike. controller just died. 500 watt motor. 14 amp controller. 14x36 is only 504 watts. 4 watts wiggle room between what motor can take and what controller can give. and does FOC eliminate the 3 hall sensors?

 

[docw009]

I own the SW900, S866 and KT displays. I like the current control pedal assist used by the KT controllers. Can't stand the speed based PAS in the SW900 and S866 combos. Retired them. If you're riding Voilamarts at 18 mph and faster the pedal response may not matter. Anyway, KT is a good choice for low power ebikes. If you're pushing bigger motors at higher speeds, others are better at that, KT has a bunch of displays. I've got four bikes with LCD3's, and two with the smaller color displays, LCD9 and LCD11 with built in throttle. The latter are hard to see in daylight and text too small for my old eyes.

I've used bafang, AKM, MXUS, and ebikeling motors. They all follow the bafang color standard. I guess KT follows bafang too, because they always worked when I just matched by colors. Self learning is not important to me, but I do have the unused S866 I can use as a motor tester.

You can always add an external voltmeter to the handlebars, but I still haven't found one I can read outside. At least I can tell in the garage whether my battery is fully charged before I l;eave,

 

[stancecoke]

Self learning is not important to me

Then you were really lucky in the past, the tutorial how to find the right combination is there not just for fun
You will find much reports of users, that struggled with wrong combinations....

and does FOC eliminate the 3 hall sensors?

No. FOC has nothing to do with sensorless or not. In any case you have to know the rotor position to apply the right field angle to the coils, to make the motor turn.
With six step commutation it is quite easy to do sensorless control, as only two phase wires are powered. From the third (floating) phase you can get the rotor position by reading the BEMF.
With sinosoidal commutation, all three phases are powered all the time, so it is more difficult to do sensorless control, you have to use an "observer" that simulates the motor and calculates the rotor position out of the phase currents, the inductivity, resistance and the flux of the motor. So it is more tricky to tune the observer parameters. But it's state of the art, too.
All better controllers are able to do sensorless FOC.

 

[docw009]

Then you were really lucky in the past, the tutorial how to find the right combination is there not just for fun
You will find much reports of users, that struggled with wrong combinations....

I've been following ES since 8-2-2015, the week I did my first conversion using an ebikeling kit with standard wire colors, by the way. Sure, there are dozen of posts every year with this problem, I've stayed with the bigger sellers, like BMS battery, pswpower, topbikekit. Most motors are 9 pin modular too, which helps.

I have learned quite a bit from ES. I recall buying a sensorless controller by mistake and got help understanding it. Maybe one of these days, I'll encounter that motor with rogue wire colors.

Ha ha, Just looked at that link about the users, that struggled with wrong combinations.. I was the only responder in it! Are you implying that the poster's KT controller had the wrong colors? COuld be. Who knows.

 

[stancecoke]

Are you implying that the poster's KT controller had the wrong colors?

The colours just mean nothing, as there is no standard. I can't understand, why Kunteng doesn't add a self learning function to its firmware. It would be just a few lines of code. It seems, that Kunteng sells the same cheap stuff for almost 20 years now, without any improvement.
Of course you don't get in trouble with incompatible firmware versions of display and controller in this case, but your product can't be up to date, if you don't do any development. This gives others the chance to overtake you.