Hello and my EKSR build

[magicmicros]

Hey people!

New at the group here.
I'm Jesper, a Dane now living in Thailand.

Made my first e-bike about 3 years ago with a no-name controller and a 72V 20Ah battery.
No idea about top speed, at 70km/h, I had enough.

My second, which is about 2 years old, is based on a 2016 Kawasaki KSR150, which I stripped down and rebuilt.
Controller and BMS is under the tank.
Battery is 96V, 48Ah (2 pack of 48V 48Ah).
12V battery is charged with a DC/DC from 96 to 13.8V through a no-loss "diode".
Motor is a QS138 90H V3, controller is a Fardriver NG96530 and BMS a JK Smart BMS.
Initially, I kept the original handlebars and made a 3D-printed throttle, using a slide pot and a spring.
Worked great for about 3000 km, were I replaced the handlebars and totally redid all of the bike wiring.
Motor mounting plates a laser cut from 5mm aluminum, front sprocket cover from 0.5mm stainless.
New gearing is 14 front to 56 back.

When I built it, I was excited by the potential. With the setup I would be able to push it to 30kW (for short peaks).
The original KSR had about 8 hp, 8.6 Nm, the EKSR about 45 hp, 500 Nm
Bike is a pocket rocket, it's trimmed down a bit to be manageable. I rarely use the top gear.

I calculated some performance numbers when I built it :
Top speed - 140+ km/h
0-100km/h - just under 3 seconds
Range - 95km

And, it fullfilled all expectations, except for range, that is about 80km (I might have underestimated my wind drag, or maybe I'm just a little conservative on when to charge).

The display is custom made, based on a ESP32 microcontroller the talks to the BLE on the controller.
I have posted in another thread about that with some technical details.

Questions welcome, of course.

/Jesper

My firstborn


Before


Almost naked


Old Throttle



Left


Right


Handlebars


Under the hood 1


Under the hood 2


Front sprocket cover with EKSR logo


Display (sorry for bad reflections)

 

[dominik h]

Nice build.
I´m interested in more details from the display. How fast is the refresh rate form the display over the controller BLE connection.
Which battery modules are this. They look like those used in EVs.

 

[harrisonpatm]

Very nice build!

 

[magicmicros]

Nice build.
I´m interested in more details from the display. How fast is the refresh rate form the display over the controller BLE connection.
Which battery modules are this. They look like those used in EVs.

The updates are basically instantaneous, I don't notice any lag. Only the throttle indicator (the violet bar to the right) is a bit erratic.
I just added that yesterday, so there may be a bit more to do with that. Also, the gear indicator is currently incorrect, but I know what the issue is and will correct it.
I will create a repository on GitHub with all details about the display, PCB data, schematics and code.
Will post an update here when it's done.

The batteries were bought on an online site locally, I don't know exactly where they're from, but from what I understand, they are from some kind of EV.

 

[magicmicros]

The GitHub repository for the EKSR Instrument is now up at:
EKSR Instrument at GitHub

 

[j bjork]

Those battery modules are meant to sit inside an enclosure, sealed from moisture and dirt. You probably get an isolation fault when they get wet, if it is not too bad there might not be any damage for a while. But I think it will be a problem in the long run.

 

[magicmicros]

Those battery modules are meant to sit inside an enclosure, sealed from moisture and dirt. You probably get an isolation fault when they get wet, if it is not too bad there might not be any damage for a while. But I think it will be a problem in the long run.

The isolation distances within the battery is 10-20mm between each cell (and the frame), so it's not much of a problem.
So far, 3000+ km in sometimes rainy, and ALWAYS humid Thailand.
Looks dandy inside.

 

[j bjork]

Do you mean that there is 10-20mm between the cells, and also to the cage? Sounds really strange to waste that amount of space. The modules that looks similar to yours that I have seen has prismatic cells inside, pressed tightly together with maybe 0.3mm plastic sheet between them. Between the cells and cage there is a thicker plastic sheet maybe 0.5-1mm.

Measure the voltage from the + and - to the cage around the cells when the modules are wet, I would be surprised if you dont get a reading

 

[magicmicros]

Do you mean that there is 10-20mm between the cells, and also to the cage? Sounds really strange to waste that amount of space. The modules that looks similar to yours that I have seen has prismatic cells inside, pressed tightly together with maybe 0.3mm plastic sheet between them. Between the cells and cage there is a thicker plastic sheet maybe 0.5-1mm.

Measure the voltage from the + and - to the cage around the cells when the modules are wet, I would be surprised if you dont get a reading

Sorry, I meant between the poles of each cell. The cells themselves are hermetically sealed.