KZ440 road legal cafe racer

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Buildsix

1 mW
Joined
May 4, 2024
Messages
11
Location
Australia
Hi everyone

I just joined the forum today after checking out some other builds on here and found some really impressive stuff!

I also started building an EV conversion recently using a 1981 KZ440 LTD cafe racer donor and have made some decent progress over the last few weeks. The drive system is now together and on the bench and I’m about to start the 12v wiring and the battery box fabrication. Just wanted to share what I’ve done so far as I’ve gone through a bit of pain in some areas and it may help other builders… plus I’ll have more questions as well.

Overview for the conversion:
1981 kz440 ltd with ktm duke 390 front end
Custom adapted duke 390 brakes
17” 8kw QS hub motor driven by a Kelly Controller
24s NMC lipo pack @ 7.4kWh
Thunderstruck tsm2500 charger with dilithium MCU, BMS and SOC meter
Vicor 400W switch mode dc-dc converter
8Ah antigravity 12v battery
Motogadget mo.unit blue
Motogadget motoscope pro

EST weight ~140kg

IMG_2518.jpeg
IMG_9048.jpeg

I put some videos together for the build if anyone is interested in checking them out. I ended up doing something a bit different with the drivetrain power so it may be of interest to some. It’s a bit cringy as it’s my first attempt at doing videos so excuse the bad acting and terrible voiceover :D

KZ 440 EV Restomod - Episode 1: KTM 390 front end conversion

KZ 440 EV Restomod - Episode 2: KTM front brake and rear disc conversion

KZ 440 EV Restomod - Episode 3: Electric drivetrain build and bench test
 
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I've been looking through some of the prismatic battery build threads and noticed compression being discussed for these. Sounds like I may need to add some extra spacer plates between the levels and strap the pack?
 
harrisonpatm said:
Why both?
Click to expand...
The DC-DC converter was intended to act as a charger for the battery. The EV conversion standards here require that lights etc can still be operated for 20 min after the traction pack runs flat. I'm still in discussions with the certifying engineer about this one though because a lot of that requirement refers to things like hazard lights which are only in cars. I've not been able to get a straight answer on this so am factoring in a battery for the time being just in case.
 
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Buildsix said:
The DC-DC converter was intended to act as a charger for the battery. The EV conversion standards here require that lights etc can still be operated for 30 min after the traction pack runs flat. I'm still in discussions with the certifying engineer about this one though because a lot of that requirement refers to things like hazard lights which are only in cars. I've not been able to get a straight answer on this so am factoring in a battery for the time being just in case.
Click to expand...
Gotcha, rules and regulations.
 
Buildsix said:
The DC-DC converter was intended to act as a charger for the battery. The EV conversion standards here require that lights etc can still be operated for 30 min after the traction pack runs flat. I'm still in discussions with the certifying engineer about this one though because a lot of that requirement refers to things like hazard lights which are only in cars. I've not been able to get a straight answer on this so am factoring in a battery for the time being just in case.
Click to expand...
I'm in Australia too and am going through the same process now. I'm going with this approach to meet the NCOP requirement:
endless-sphere.com

KTM conversion ELXC

Kicking off a build thread on a 2010 KTM EXC Objective is to have a road registrable e-moto that can be used for commuting and to have fun off road. I'm based in Darwin, Northern Territory, Australia. Build List: Motor: QS 138 90h V3 mid drive with 2.35:1 reduction Controller: Votol Em260s...
endless-sphere.com endless-sphere.com
Great looking build by the way, should be a stealth rocket with the massive hub motor!
 
Buildsix said:
I've been looking through some of the prismatic battery build threads and noticed compression being discussed for these. Sounds like I may need to add some extra spacer plates between the levels and strap the pack?
Click to expand...
Yeah, that was the consensus I came to in my research, especially based of the VDA modules made from prismatic NMC cells. Looks to be even more of a requirement for the pouch cells like you have. Though I'm m being a bit more conservative with my build due to it being a dirt bike that will be dropped from time to time.
 
bunya said:
I'm in Australia too and am going through the same process now. I'm going with this approach to meet the NCOP requirement:
endless-sphere.com

KTM conversion ELXC

Kicking off a build thread on a 2010 KTM EXC Objective is to have a road registrable e-moto that can be used for commuting and to have fun off road. I'm based in Darwin, Northern Territory, Australia. Build List: Motor: QS 138 90h V3 mid drive with 2.35:1 reduction Controller: Votol Em260s...
endless-sphere.com endless-sphere.com
Great looking build by the way, should be a stealth rocket with the massive hub motor!
Click to expand...

I did check out your build after posting here. How will you prioritise the 12V circuit over the traction circuit when the pack is starting to get low? Do you have some kind of cutoff on the motor controller that doesn't allow it to run past a certain discharge point for the 20min requirement? Keen to understand this more.

Thanks RE the build! really hope I managed to pick and size all the electrical appropriately for it to perform. This is my first attempt at any HV stuff so I'm not sure how it will turn out just yet. Seems to work fine so far on the build table with the motor free spinning but loading it up will be the real test.
 
bunya said:
Yeah, that was the consensus I came to in my research, especially based of the VDA modules made from prismatic NMC cells. Looks to be even more of a requirement for the pouch cells like you have. Though I'm m being a bit more conservative with my build due to it being a dirt bike that will be dropped from time to time.
Click to expand...

Good to know, thanks. I've come up with a couple of options to retrofit my pack so will get that all together before starting to fab the battery enclosure for it
 
Buildsix said:
How will you prioritise the 12V circuit over the traction circuit when the pack is starting to get low? Do you have some kind of cutoff on the motor controller that doesn't allow it to run past a certain discharge point for the 20min requirement? Keen to understand this more.
Click to expand...
The DC-DC converter I'm using to supply the 12V ancillaries will be connected directly to the main pack (via a fuse). I'll keep ~10% of the battery in reserve to prolong life and this will be more than enough to run lights for 20mins when the discharge contactor is open. It is my interpretation to meet the VSB14 requirement, though it may not be successful.
 
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bunya said:
The DC-DC converter I'm using to supply the 12V ancillaries will be connected directly to the main pack (via a fuse). I'll keep ~10% of the battery in reserve to prolong life and this will be more that enough to run lights for 20mins when the discharge contactor is open. It is my interpretation to meet the VSB14 requirement, though it may not be successful.
Click to expand...
That sounds like it'll meet the requirement. How will you enforce the 10% reserve?
 
bunya said:
Undervoltage limits on controller and BMS. I think I can also set an SoC limit on the BMS if required
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ah, of course. I think you may be on the money with that setup.

EDIT: I just checked my motor controller config and it also appears to have a low voltage cutoff so I can try a similar approach. The Vicor DC-DC converter also has a type of enable pin which means it can be wired into the traction pack and be turned off when the bike is off.
 
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I had a bit of progress with the dash over the weekend. It looks like the “meter output” (apparently it relays one of the hall signals) from the Kelly motor controller is able to drive the speedometer in the Motoscope. It’ll need to be calibrated using the teach speed function but the idea is essentially proofed out. This also and means I won’t need to make a custom encoder for the front wheel sensor after the brake conversion. I’ll try to use the tach to show motor (wheel in this case) rpm if I can calibrate it as well to some degree.

IMG_4297.jpeg
 
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So calibration on the motoscope has to be done at 50kph for the "teach speed" function. The Kelly Controller speed output appears to show a single phase from a single hall sensor (I think), and so 1 wheel rotation per second reads 120 for the motor speed in monitoring mode - this equates to 60rpm. From some basic calcs using the circumference of a 130/80R17 tire (2009mm), the wheel needs to rotate at ~414 RPM, so the wheel speed measurement was held at 828 for calibration. The speedo maxes out at about 160kph with without load, which seems about right.

One thing I did notice though is that the always on power needs a 12V source to maintain the configuration, so this pretty much forces my hand on having a 12V battery.
 
Buildsix said:
One thing I did notice though is that the always on power needs a 12V source to maintain the configuration, so this pretty much forces my hand on having a 12V battery.
Click to expand...
We need one anyway yes? VSB14 requires an auxiliary ELV pack capable of operating hazard lights etc for 20 minutes..
 
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