vetoMOTO – nee ZXR250

This is the story of how a 1992 Kawasaki ZXR250 got a second lease on life.

In 2018 I decided I wanted to learn more about batteries and motors etc., so I set about electrifying something. A car would have been too costly and I didn’t have a garage. A bike seemed a bit simple; I needed a bigger challenge. So I settled on somewhere in between; a motorbike.

In September 2018 I found a donor bike which had a bung engine and no viable solution in sight, so I bought it for pretty cheap. After stripping off all of the combustion-related parts, then it was time to build it back up again.

Most of the parts came from the US and Australia (motor, controller, DC converter, contactor, EV management system (EVMS) and BMS), while the lithium ion batteries came from Hong Kong. A lot of the knowledge required came from Google and Youtube, but also a couple books (“DIY Lithium Batteries” by Micah Toll was fantastic). Having no prior experience in the world of batteries and electronics, there was a pretty steep learning curve! But that’s alright, I get off on that sort of thing.

With a plan and all of the parts in place, it was mostly a matter of fitting everything together to make the most efficient use of space. The biggest challenge however was building the battery pack; this motorbike didn’t have a lot of space available and 480 lithium ion cells (18650’s) take up a fair bit of room. Designing and building the battery actually took just as long as the rest of the conversion combined. But after countless hours of research and head scratching it eventually came together.

Finally in February 2019 the bike was ready for certification (in New Zealand, converted vehicles have to be certified according to the Low Volume Vehicle Technical Association (LVVTA)). They have a standard to follow and a list of certifiers (there aren’t many!); just follow these links for that info. It took quite a while to get through the certification process, mostly just because the certifier was too busy, but it wasn’t too painful or expensive (about $800 for this project).

The certification must have been finalised around April/May 2019, at which point the bike was finally legal! Happy days! It was immediately put to use as a commuter and the odd fun ride, until in September 2023 when I decided to finally give it the make-over it deserved. And boy did it get an overhaul! All of the fairings were repaired/reinforced/patched and painted, the EVMS screen was moved in place of the tachometer and oil pressure gauges, any and all rusty parts were repaired and re-painted, built and installed several new carbon fibre covers, protective cover on the front of the battery box, and installed a switch for going between difference acceleration profiles. Here she is after a big makeover.

Not wanting to bore you with too much detail early on, here’s some of the specifics:

General Info

  • Donor bike: 1992 Kawasaki ZXR250
  • Bike had engine issues, would idle but had no power
  • All ICE parts were removed on September 8th 2018

Motor

  • Motenergy ME1003 Brushed Permanent Magnet DC motor
  • 72V DC
  • Mass: 17.7kg
  • Power rating: 11.5kW max continuous, 23kW max peak
  • Mounting: 3mm steel plate bolted to OEM engine mounts
  • Motor is held in place by a tight fit within the hole cut in the mounting plate and secured using 4 x 3/8″ bolts.
  • Max loaded motor speed rated at 2800 RPM.

Chain and Rear Sprocket

  • 15 tooth front sprocket with boss and 4.8mm keyway machined by EB Engineering.
  • 48 teeth rear sprocket
  • 520 chain with 120 links.
  • Rear sprocket and chain fitted by MotoXtreme on February 11th 2019.
  • Gear ratio of 3.2:1 selected to achieve the best acceleration possible with a top speed of 110-120kph.

Motor Controller

  • Alltrax SR72400 72V controller rated at maximum 400A output.
  • Mounted to frame with 3 galvanised brackets using rubber washers for vibration dampening.
  • Brackets fitted to frame using M8 bolts in tapped threads.
  • The motor controller “enable” circuit powers the main contactor coil when successfully pre-charged.

Battery

  • Custom built lithium ion battery pack using a total of 480 Panasonic NCR18650BD cells, each 3.6v nominal and an average of 3.15Ah.
  • 20S24P configuration, 72V nominal, equates to 75Ah.
  • Spot welded connections (3 welds per terminal) using 1 layer of 0.15 x 8mm nickel first for parallel connections.
  • Series connections also using 0.15 x 8mm nickel strip, 2 layers, 3 welds per terminal per layer.
  • Built in two halves, 36V each, positive and negative terminals for each pair made up of two layers copper bus bar 9 x 3mm with nickel strip from cell terminals sandwiched between and held in place using 3/16” bolts.
  • Connections between positive and negative terminals (between the two battery halves, and each final battery terminal) are 19 x 3mm copper bus bar.
  • Terminal connections are M8 stainless steel bolts.

BMS

  • 2 x ZEVA (Zero Emission Vehicles Australia) BMS12V3 modules used for maintaining balance of parallel cells; utilises dynamic balancing.
  • BMS connections to parallel groups are with 10A wiring (32 x 0.2mm strands), soldered on to series connections and the positive and negative ends of each battery half using eye terminals.
  • BMS modules communicate with each other and the EVMS via CAN bus.
  • Thermistor connected to one of the BMS modules and situated in the centre of the front half of the battery.

Battery Charger

  • Grin Technologies Cycle Satiator 5A 360W charger mounted on the rear left behind the seat.
  • The charger is fully programmable to allow the user to adjust charge parameters and enhance battery cycle life.
  • Charging is slow at a maximum of 5A, but it’s typically left overnight to slowly top up. Technically a complete charge would take 75Ah / 5A = 15 hours, however it’s nearly impossible to discharge 75Ah and 60Ah might be more realistic. 60Ah / 5A = 12 hours for a full charge.
  • Two separate relays allow the EVMS to sense when the charger is plugged in (by connecting the EVMS charge sense output to ground when the charger is plugged in) and enable/disable the charger (by connecting the EVMS charge enable output to ground across the relay’s coil).
  • The two aforementioned relays are housed within a plastic enclosure secured in the storage compartment beneath the pillion seat.

Throttle

  • Magura 0-5k Ohm twist grip throttle wired directly to the motor controller.

‘Balance of System’ Board

The following items are all mounted on a 6mm Perspex sheet fitted beneath the petrol tank (hollowed out), which is secured in place to the OEM regulator/rectifier mounts.

EVMS

  • ZEVA EVMSV3 connected to BMS modules, hall effect current sensor, and EVMS monitor V3 now mounted with the instrument cluster.
  • Permanent 12V connection exists between the battery positive and EVMS.
  • EVMS monitors the voltage of all parallel groups as well as instantaneous current. It is able to cut off power in the event of under/over voltage as well as excessive current draw.
  • The EVMS unit itself is mounted high up on the board in an attempt to keep it further “out of the elements” and to make it easier to run cables in and around it. All auxiliary wiring was completed using 10A cable, stranding = 32 x 0.2mm.
  • The Key Switch Input (KSI) terminal on the EVMS receives +12V when the key is on via a cable which originally gave +12V to the IC Ignitor. This switches the EVMS from “Idle” to “Running”.
  • The same +12V connection activates a relay, the terminals of which are wired in series with the motor controller “enable” circuit so the main contactor can not be closed without the key.
  • The EVMS main contactor output is wired to the coil of a normally open relay, the terminals of which are also wired in series with the motor controller “enable” circuit so the EVMS can disable the traction circuit in the event of excess current drawn, low battery voltage etc.
  • Both of the above mentioned relays are located in a plastic enclosure mounted on top of the DC-DC converter.

Main Contactor

  • The main contactor is an Albright SW180 contactor rated at 200A continuous duty. The coil is activated by 72V from the motor controller.
  • A 1 k Ohm resistor bridges the main contactor to pre-charge the motor controller after the manual battery isolation switch is closed. This takes at least 5-6 seconds.
  • A coil spike suppression diode is connected across the main contactor coil.

DC-DC Converter

  • Sevcon isolated DC-DC converter steps the traction battery pack (72V nominal) down to 13.5V to power the 12V onboard system directly (the 12V lead acid battery has been removed).
  • Rated at 500W at 13.5V
  • Enable function is permanently on via a 10A cable from the “Enable” to the +Vin.
  • Fully encapsulated IP67

Main Fuse

  • ANN400/CNN400 very fast-acting limiter fuse rated at 400A.

Current Sensor

  • Hall effect current sensor by ZEVA is positioned between the traction battery positive terminal and the main fuse.
  • Connection via CAN bus with the EVMS and monitor enables monitoring of battery voltage, instantaneous current, cell balance, temperature etc.

Safety Features

  • The charge sense and charge enable functions of the EVMS mean the traction circuit can not be closed while the charger is plugged in, hence no driving off while still plugged in.
  • The EVMS can cut power to the contactor coil in low voltage or excessive current situations to protect the battery from over discharge etc.
  • Temperature sensors and ability of the EVMS to cut off the traction circuit mean the battery pack is protected from excessive temperatures and resultant thermal runaway.
  • The motor controller “enable” circuit hosts numerous safety features through activation of the main contactor. In order to close the main contactor, the EVMS must be powered on (main contactor enable output), the key switch must be on, the manual switch mounted on the instrument cluster must be on, and finally the motor controller must be successfully pre-charged. A 20A fuse is also wired in series in this circuit.
  • A manual battery isolation switch is wired between the traction battery negative and the motor controller B- input. This is rated at 500A continuous at 48V.

OEM 12V System

  • The original 12V system has been maintained as original wherever possible.
  • The Key Switch Input (KSI) connection to the EVMS is via the original +12V lead which went to the IC ignitor.
  • Power to the headlights is now via the ex-radiator fan cable and is fused in the junction box by the original 10A fan fuse (the original headlight fuse was also 10A).