Electric Race Motorbike for NZ Bucket Class

[Neeps]

Howdy,

I'm building an electric motorbike for the NZ Bucket class. I've helped on a few electric vehicle projects before (an Aprillia RS250, buses, a rubbish truck and soon a ferry) and want to go racing now.

These are bikes that go up to 125CC 2-stroke and 150CC 4-stroke from basic commuter bikes that get put into lightweight and racier frames and get hotted up to 20hp. The races are on go-kart circuits that go for around 10 minutes where you'll hit 90km/h top speed. The racing is tight and full of customization and a whole lot of fun.

For that style of racing I think I will need a motor comfortable to race with 15kW being put through it for 10 minutes pretty heavily, and about 2kWh of battery per race, of which there are 5 races per meet.

Batteries
I would like to use 30Q's from Samsung in a 20S 15P config that would give me 72V, 3.24kWh and 225A peak current. These batteries are available from a friend who is building packs so I will head to him for that. I have some buffer in that pack so I think we might get two race out of it, with charging at the track I might be able to do 3 races per meet.

Motor
I've looked at a few motors and the QS273 V3 70H looks like it would definitely be up to the task. I wanted to gauge ES for some help here though, there are a few people saying they are using motors rated for less power to get 15+kW, which if it works is fantastic. Are there other motors that would suit the context? I'm biased to a hub motor due to the simplicity of the system. Unsprung weight won't affect me on track, so I see no reason to go mid drive unless cost's can be reduced by using that style.

Controller
I need something to work with the 72V and ~220A that they battery can give, FOC preferred. I really liked the Mobipus 72200 but it seems that they are getting hard to come by.. Oh well. Are there any similar controllers to the Mobipus 72200?

I'm going to nail down the main components now and then look at charging later. But super excited about showing some petrol boys the future

Here's an example of the racing from my local track by the current president of the group

https://www.youtube.com/watch?v=uXrMhIvHUI8

 

[jonescg]

If you want bulk power as a priority and don't mind spending a bit, LiPo pouches are the best.
Those Sammy 30Qs will sag pretty badly and get hot. They would last about as long as pouches in terms of cycle life.

 

[Neeps]

Interesting, I didn't think the sag would be too bad. A few more in parallel could aid that.

If you were to do a LiPo pack, 72v, 200A capable 2kWh, what would you recommend?

 

[jonescg]

2000 Wh, at a nominal 72 V suggests 27 Ah.

A 72 V, 30 Ah pack (20s,6p) battery made from 35C cont, 60 C peak LiPo pouch cells might measure 260 mm tall, 170 mm wide and 215 mm long, and weigh about 16 kg. It will dish out almost 1000 amps if the conductors were up to it.

Look up Sketch Coleman's electric supermoto. I built the battery for his bike, but he had to split it up a bit to make it all work.
https://www.youtube.com/watch?v=85FRe7MI2os

Still goes like a shower of shit though.

 

[Dui ni shuo de dui]

LiPo would get the most performance, that's for sure. But they are a bit difficult to maintain and they also are a bit expensive.
What you need here is some cells capable of a high discharge rate without too much sagging. I know what I'm going to say might be a bit controversial but I'd recommend you to have a look at the A123 LiFePO4 cells.

Sure they are heavier and bigger than the lipos, but they are capable of very high discharge rates too and they are almost free of maintainance plus they last quite a while even under high demanding applications, they are very reliable. I have a 72V 40Ah pack on my bike, it weights 25 kilos, which is around 4 kilos heavier than what it would be with liPo if my math is correct, but it's capable of more than 600Amps of continuous discharge with reasonable sagging. It can deliver way upwards 1200 Amps peak in theory but I never had a powertrain that powerful to test it out. Also, they are pretty cheap regarding how much power they can deliver, mine cost me only 360 Usd, plus about a hundred bucks for the BMS... Not sure if you can find those at that price in New Zealand but might worth a try, saves you a ton of money to get the best possible motor, controller, etc.

The main drawbacks are weight and available space in your frame, weight can be compensated by lightening some other parts of the bike and lightening yourself And there are always some ways to make some space in a frame to put a big battery if you have some welding skills.
I think that could be a good alternative to start racing for cheap while still being competitive and, importantly, very reliable. Saves you some money for a powerful motor and controller, ride it for a while and maybe later switch to a more powerful and lighter LiPo if necessary. That's probably how I'd start racing if I had the opportunity to do so.

 

[Dui ni shuo de dui]

Motor
I've looked at a few motors and the QS273 V3 70H looks like it would definitely be up to the task. I wanted to gauge ES for some help here though, there are a few people saying they are using motors rated for less power to get 15+kW, which if it works is fantastic. Are there other motors that would suit the context? I'm biased to a hub motor due to the simplicity of the system. Unsprung weight won't affect me on track, so I see no reason to go mid drive unless cost's can be reduced by using that style.

I think it's a good choice, those motors can tolerate quite a lot of power. I wouldn't cheap out on the motor for track racing if I were you, spend the extra buck to get the most powerful version you can afford, you want to keep it from heating too much so a higher rated version will help with that. Some water cooled versions exist too, might worth looking into heat. For racing, power matters as much as reliability, you can't win if you don't finish the race!
I'm using a 3KW rated motor on my bike and I'm apparenttly very lucky because it doesn't heat much and still runs fine at more than 500Amps/phase after 3 years, but I can't guarantee you that this will be the case for all the 3KW motors, it's possible I've got my hands on a very good motor by pure luck.

Controller
I need something to work with the 72V and ~220A that they battery can give, FOC preferred. I really liked the Mobipus 72200 but it seems that they are getting hard to come by.. Oh well. Are there any similar controllers to the Mobipus 72200?

The Mobipus is really good but it's a pain to work with them so I can't really recommend it.
In China, most of the winning teams are using APT controllers, but same here, they don't really like to sell to individuals.
That leaves you with Kellys which are relatively affordable but a bit low tech and some other western brands which are far more expensive.
I'd recommend you to go for at least 400A battery and 600 or more phase amps, if the plan is to win races it seems to me that this would be the very minimum.

 

[Neeps]

I've been looking around and think I would prefer to go for a stronger powertrain, so have started looking for a Motoenergy ME1114 motor and a Sevcon Gen4 Size 4, these have great peak powers that would allow me to use them in a more powerful class later if the need arises (I like racing, the need will arise). EV Power from Australia sell these, I've sent them an email and I'm hoping to hear back soon.

The QS273 still interests me, but mid will look sexier too.. as for the Mobipus it seems hard to find now that Ballarat Ebikes arent really replying to people.. I emailed a while ago with no repsonse.

I know what I'm going to say might be a bit controversial but I'd recommend you to have a look at the A123 LiFePO4 cells.

Yeah, Id love to consider these, have you got a spec sheet for the ones you've chosen? Weirdly enough I might actually know a supply of these here in NZ.

A 72 V, 30 Ah pack (20s,6p) battery made from 35C cont, 60 C peak LiPo pouch cells might measure 260 mm tall, 170 mm wide and 215 mm long, and weigh about 16 kg. It will dish out almost 1000 amps if the conductors were up to it.

This sounds pretty good. Would you be able to show me where you purchase your cells from? Or even a price for how much it costs for you to build one for me?

I've also seen EV Power have some Westart 75Ah NCM cells capable of 225A Cont, so in essence they could do well. Any opinion on those? Again, waiting to hear back from them on that front first.

 

[flat tire]

Could the QS IPM 70H mid drive do that?

 

[jonescg]

This sounds pretty good. Would you be able to show me where you purchase your cells from? Or even a price for how much it costs for you to build one for me?

I'd be happy to build you one. But you won't be happy to pay for it. AUD is in the shitter right now, and the Pacific Peso is no better.

If you're keen you can source them from First Energy Power in China. Ask for the 9050135 35C/60C pouch cell, and say Chris sent you. It won't give you a discount, but they might put an effort in to shipping them properly :lol:

 

[Dui ni shuo de dui]

Yeah, Id love to consider these, have you got a spec sheet for the ones you've chosen? Weirdly enough I might actually know a supply of these here in NZ.

Here you go:
https://formula-hybrid.org/wp-content/uploads/A123_AMP20_battery_Design_guide.pdf

Also some interesting threads on the forum:
https://www.endless-sphere.com/forums/viewtopic.php?t=44494

https://endless-sphere.com/forums/viewtopic.php?t=38761

.

 

[John in CR]

There's no 18650 cells which can sufficiently power a 273 70h motor in a 15p pack. You need better more powerful batteries or much more parallel structure.

If the tracks are pretty smooth and speeds fairly limited a big hubmotor like that may work ok for racing, though at a significant weight penalty, and all that unsprung weight will be problematic on bumpy surfaces. Unless you run it at pretty modest power levels, you'll want to modify the motor for cooling with that kind of use due to the high phase current demands of such repetitious acceleration and deceleration, which causes heat issues with all hubmotors.

 

[tylerwatts]

FYI QS Motor sells the APT controllers so would sell a kit with motor and APT controller.

Cheers
Tyler

 

[Neeps]

My tact has changed a bit dramatically the last few month but I'm happier with the new component direction

- Motenergy ME114 motor
- Sevcon Gen4 Size 4 controller
- 18x Westart 75Ah NCM modules

The motor and controller are coming from EV Power in Australia (when I finally pay the full amount). I've put a deposit on their EV PowerDrive kit (https://www.ev-power.com.au/product/ev-kit-size-4-80v-350a-dual-stator-air-cooled/). It comes with a throttle, Sevcon Clearview screen, DC contactor, full LV wiring harness, bench-tested setup that will be able to push the 15kW minimum I want really easily, so I cant wait for that to arrive. Plus it has reverse which will be cool as hell on a bike.

The cells are from Westart, EV Power sell these too but it was a little harder to get them from Aus to here so I want to go to the factory and get them instead. Westart mentioned 4C (300A) continuous and 8C (600A) peak in their data sheets so these cells will deliver an appropriate current in a 1P arrangement which is perfect because I wanted minimal battery connections aka a simple pack. Attached is the datasheet Westart sent me for the cells.

I want to create a 18S pack, so thats 67V nominal and 300A continuous delivering a comfy 20kW of power, which should equate to 15kW at the rear wheel easily.

Things in the powertrain I'm still thinking about though

- Should I bump up the controller to a size 6? The dasheets for a size 4 say it can deliver 350A for 2 min periods. I wana run for 10mins max per race. The Size 6 will do up to 550 A for 2 min periods so surely 300-350A would be an easy task for 10mins. Has anyone got some thoughts on the Sevcon size 4 controllers and how they perform?

- Should I run BMS.. I know, sounds a little strange. In order to have simplicity on the bike I would like to avoid having extra wiring and weight (I.e a 12V system, PCB's, wiring). Given the bike is only going for 10mins at a time I think I could make sure the batteries are all balanced prior to each race and when the day is done and the pack is off the bike do some manual checks and truly check the pack when the bike is back at the house. I don't need to charge in a hurry, so why not charge each cell individually to that 85% mark and monitor them thoroughly in my down time then when the pack is together and on the bike it can be all go. This one I've kinda locked in already, but I wanted to throw it out there to see what you guys think about it.

I'm also thinking of a custom tube frame to house everything too. Lots of work but could be cool as hell and seeing as this is what I want to do in the future why not get stuck in now. I've bought a KR-1S frame with some BIG brakes at the front, an R6 rear shock, GSXR400 rear wheel and some sweet machined pieces on it. Yet to decide whether the KR-1S frame will do or whether the tube frame is a better choice. That's in another part of the country at the moment so as soon as I have the ability to travel and go pick it up I will get it back and start the initial Cardboard Aided Design

 

[tylerwatts]

Hi Neeps
Looks like good setup for your use but I'd check if you can fit ml those cells into the frame comfortably, keeping it now for fast and tight lean angles. If you can stack them all flat vertically up between the frame spars into the tank area that's ideal and hopefully it'll give you room for the motor too.
I've used the gen4 before but only in a ev scooter at half current. It was a brilliant bit of kit though. I'd say it will be fine with 10min racing as you will be on full throttle for short bursts only rather than at cruising at top speed for 2 mins drawing constant 350A as I'm sure they are specified for. Plus those OEM brand controllers are over engineered for their ratings anyway and can do a lot more. Some guys hack them and run higher voltages at max amps and do better than equivalent say Kelly controllers.
I'd recommend using the KR1s donor as it's known so the race officials will be happier, competitors will be more comfortable and it'll make your life much easier. Plus Kawasaki spent some $$$ developing it and I believe they did a fantastic job so do you think you can do better?
I look forward to seeing it come together.
Good luck.

Cheers
Tyler