Emmo Knight (Grom clone) salvage

[pwd]

So I just acquired an Emmo Knight Turbo:


Emmo (if you aren't familiar) are a run-of-the-mill cheap Chinese made scooter/motorcycle style ebike we have hear in Canada which are sold under different brands world wide. EDIT: I also see that this is the common Grom clone style of ebike; which is a curse (cheaply made) and a blessing (common parts from Aliexpress etc...).

This one is in rough shape electrically since the wire harness has been butchered. It smells like cigarette smoke and has bolts missing. I'm sure you know the type. The 60 pound lead acid battery pack is shot (one of the 12V packs are dead). I've tested the motor, which works.


I'm not quite sure where this build will go. I might try and flip it for some profit or build it up for myself. This is my first foray into a non-bicycle style ebike.

 

[skeetab5780]

I got one of these little bikes off the side of the road for $20 missing the battery and some plastics, its good fun for putting around town they max out at 30mph on 20s lifepo4 cheap ebay battery that was $200
https://endless-sphere.com/forums/viewtopic.php?f=49&t=113634

If you want a better top speed you can run it on 96v sla or get a 20s lithium battery for 84v fully charged

I like the bike because it handles good and is comfortable with lights horn and blinkers for commuting, but it is heavy slow up hills and made from the cheapest possible components. The hub motor is the most valuable item on the entire bike by far and its probably worth $300

I rewired my whole bike took off the entire bottom battery tray, moved the controller and bolted it under the downtube. Im going to make it look more bobber ish i guess. I am in the process of neatening the wiring up now

 

[pwd]

Ha! That looks like the same bike skeetab5780. Maybe just some different plastics etc... but the frame looks very close.

I just opened the controller and it is only a 12 mosfet but all the components seem good for up to 100V


Seems good for a bicycle but not a bike like this. I'm going to at least try to get it working. So far, it has +5V at the motor hall sensor plug and throttle - a good start.

 

[skeetab5780]

funny your is a 12fet since mine is clearly an 18fet and its still not enough power. My controller was completely filled with water, I opened it up drained the water out and let it air dry with a fan on it for a few days

plugged it in and it still works perfect!

 

[pwd]

I've got the controller powering the motor. The throttle on the bike was bad so I tested the controller with a different one. I've also got the brake cut-off pins on the controller verified but not much else.

The wiring harness is quite overwhelming. Lots of crappy looking splices everywhere.

For those who have gone down this road, do you just start from scratch to get all the lights and functions working correctly?

 

[pwd]

NONE of the lights (headlight, markers, turn indicators or brake) worked when I applied 12V directly... someone must have shorted all of them out. The ignition switch isn't working well either (intermittent contact). The horn works though!

I've decided to ditch the existing wire harness and start from scratch. Motor function first (throttle and brake cut-off), accessories later. To get this heap rolling, I might borrow a 72V pack from one of my other builds just to see how it goes.

 

[pwd]

The controller testing continues...
I've mapped out some of the following from the controller with their voltage measurements:
F2 -> GND = ? (5V)
F2 -> GND = Speed 1 (5V)
SH -> GND = ? (0V)
SL -> Ground = Low Brake (not measured)
Q -> GND = Cruise (5V)
DC -> = High Brake? (5V)
XX -> GND = ? (0V)
SD = Throttle Input Signal

I don't see where "Speed 3" for the 3 position switch would go to on the controller? I know that "Speed 2" is usually the default if nothing is hooked up. There is also an alarm plug (I think) that has a 4 pin connector with only three pins.

I got the new throttle wired up and brake cut-offs working.




The label on the controller case is worn off and I don't see any model numbers or markings on the PCB. Does anyone recognize the controller from the photos above?

 

[SlowCo]

Nice bike :thumb:
Time for a better battery pack and controller.

 

[pwd]

Thanks SlowCo, a new battery and controller will be on the list.

Turns out not even the wire cannot be trusted on this bike. My eBrake cable I rigged up was no good because the copper wire was burnt up, which I didn't notice until I pulled back some insulation. I also discovered that one of the brake cut off switches isn't working. The lead acid packs were removed from the very rusty battery tray; man those things are heavy. 4 are still good; so I'm hoping to recoup some cash on them.

I did get the bike out for it's first test ride on an old 14S5P Samsung 30Q pack I have. It feels like a slow, heavy boat (my estimate for top speed was probably 35km/h on 14S) but the brakes work quite well. I'm not used to a full twist throttle; I feel like I'm going to accidently take off accelerating. I may end up using a half twist like I do on my other bikes.

Next up: I'm going to try my 21S3P P42A pack on it just to see how it feels on 21S. I want to see if I like the bike before I sink money into a new controller and battery pack etc...

 

[pwd]

I just got back from a ride on my 21S3P P42 pack and it was was definitely better but not a rocket like my 2WD. According to the BMS, it pulled 32A peak from the pack. This bike consumes a lot of juice being so heavy etc... I can see that I'd need a pack with at least 1800wh if I were to acquire one.

Although the speed was faster... I estimate I only hit around 50-55 km/h on 21S; not quite the speed of traffic around town. Perhaps the motor controller is still in "Speed 2" since I haven't found the "Speed 3" signal yet. Maybe the motor is a low rpm/volt winding?

The bike rides fairly well and feels like large cruiser motorcycle compared to my 2WD Rocky Mountain e-bicycle. It's a totally different ride; much more relaxed and definitely not used to it yet.

I'm looking into a new controller and am leaning toward a Fardriver due to it being FOC and programmable. Just uneasy about spending $400+ on a controller for a bike I'm not sure about yet.

 

[pwd]

While inspecting some of the lights etc... I notice that the headset was loose and had sand/grease around the headtube.



I removed the front fork assembly and have cleaned up the bearings etc... and will repack with fresh grease. I'm glad I noticed that before doing another ride.

I've finally decided on a new battery pack:
Samsung 47ah module


I will be using two of those in series for a 24S 47ah pack - on their side; they have almost the exact dimensions of the existing battery box! I expect I'll still have to modify the box a bit; but it doesn't get much closer than that. I was looking a building a 21700 pack but didn't want to go through the build process for a much larger pack than I've done before. I'm hoping these modules perform as advertised. I'm looking forward to using these since I'm only used to dealing with cylindrical cell packs. I'll be using another ANT bms which I've used in the the past but going with the 450A version to have lots of headroom.

 

[pwd]

I gave the front fork etc.. a much needed bath and got the steering bearings re-greased.


I had to tighten the steering stem nut and one of those cheap bicycle bottom bracket lock ring tools worked great:


I also notice that both the front and rear brake calipers have a bit of play (can rotate a couple mm on the vertical axis), is that normal?

 

[skeetab5780]

Looking good! Keep up posted on updates! These bikes can be pretty fun and quick little rockets if you throw enough money/power into them.

I have too many projects to put this one on my list, so I just keep it as a spare bike for people to play around on

 

[pwd]

The battery packs have arrived from BatteryHookup. They look pretty cool (nice aluminum frame) and the dimensions are as advertised. One module measured 8.8 mOhm @42V and the other 8.0 mOhms @42V - this will do nicely. I've very exited to see how these perform on the road.



Next step will be getting them to fit in the battery tray of the bike and seeing how I can attach the balance leads ...

 

[pwd]

More parts and equipment have arrived today:
Fardriver ND84530 controller


TEMCo Hydraulic Lug Crimper (Dieless)



The controller is a beast; at least compared to the smaller controllers I'm used to working with. I was originally going to use the stock controller box; but due do the new controller's weight; I will likely modify the mounting box.

I'm still figuring out the battery pack orientation:

There it is with 1 of 2 packs on its side. My concern is having the positive and negative terminals facing each other separated only by 4mm of rubber or facing the terminals to the metal box; also separated by only 4mm of rubber.

Examples:

 

[pwd]

I fab'ed up a controller bracket to bolt onto the bike using a scrap bed frame:


I removed the balance board from the packs to gain better clearance for balance wires etc... I would have loved to use the board but wanted to run the balance leads out one end and didn't have the special Samsung connector:


BMS mocked up (about three times the footprint of the last ANT BMS I used):


balance wires and temp sensors completed (shown only attached to one sub pack):


My next trick will involve joining the two sub packs together while keeping the terminals from shorting out on each other. I've been making some modifications to the battery box to accommodate the two packs.

 

[pwd]

I'm slowing chipping away at getting the battery pack finished.

Tight bend with the series connection:



First test fit on the bike:



I am going to use some aluminum round tubing as spacers to keep the packs from contacting each other:


The packs will then be secured with threaded rod; which I will slide in via some holes I drilled into the sides of the battery box.

My charger has also arrived today. I immediately opened it up and turned to voltage down to ~98.4V for a max of 4.1V per cell.

 

[skeetab5780]

That thing is going to be a rocket! What is up with those odd pedals are you keeping those on there?

 

[j bjork]

It is interesting to see how this turns out

What is the size of these modules, and what battery are they from?

 

[amberwolf]

What is up with those odd pedals are you keeping those on there?

Might just be me, but all I can see are "standard" footpegs?

 

[skeetab5780]

What is up with those odd pedals are you keeping those on there?

Might just be me, but all I can see are "standard" footpegs?

look harder, does this thing have a legal bicycle pedal kit on it?

 

[pwd]

look harder, does this thing have a legal bicycle pedal kit on it?

Yep, those are bicycle pedals. Since the bike was sold in Canada; it had to have pedals on it to be classified as an ebike. Pretty much useless though since the crank arms are so short and the gearing is bad. I'm probably going to keep the pedals on there; just to make it look less illegal.

It is interesting to see how this turns out

What is the size of these modules, and what battery are they from?

Thanks, I'm very much looking forward to getting this thing rolling. The battery modules are Samsung 47ah 12S packs from batteryhookup.com
https://batteryhookup.com/products/samsung-ev-lithium-ion-12s-44-4v-47ah-2-07kwh-module

If not sure if I got lucky but I didn't have to pay any tax or duty on them

What is up with those odd pedals are you keeping those on there?

Might just be me, but all I can see are "standard" footpegs?

It will have the standard footpegs + the the goofy pedals

 

[pwd]

I've finally got the battery pack secured to the bike. After much grinding out holes that didn't line up and a quick coat of paint:

You can see the aluminum spacers I used to keep the packs separated.

A package from QS motor has arrived:

That is a QS 260 50H on a 12 x 3.5 inch rim

I thought that the motor would fit in perfectly but apparently I forgot to check the axle diameter before ordering... the frame was built for 12mm axle flats on an M16 spindle and the new motor is 14mm axle flats on an M18 spindle.

Let the filing begin...


This will mean I'll also have to ream out the brake plate that slides over the motor axle


A bit is 20mm and the rest is 18mm between the axle shoulders and the frame dropouts on the brake side


I had a idea to use my rotary tool+ carbide bit and depth stopper (which I've never used before)... came out pretty well

That should work out OK, I may have to shim the brake caliper with washers when I do my first fit of the rotor etc...

The motor axle is a bit short for the frame... I guess I missed that measurement too. I'm hoping two torque plates sandwiching the dropouts will suffice



I still have to acquire some washers/spacers for the phase cable side but I think I can accomplish that with some flat washers.

 

[skeetab5780]

Damn! Didn't expect you to put a new motor on this thing, you just trying to spend money? Or was the old one faulty?

The QS will take a ton more power but this caught me off guard! Thing is going to be a sleeper!

 

[pwd]

in for a penny, in for a pound

The old motor was working fine but I figured I'd want to go straight for more copper. Definitely cost a pretty penny for the motor at around $940 CAD after shipping etc... I'm hoping to recoup a couple hundred for the old motor + tire.

That's kind of what I'm after, a sleeper. I'm planning on leaving all the stock "Emmo" stickers on it to perhaps blend in with the normal ones we have in town. Very excited to get this thing rolling but it is taking lots of fine adjustments.