- Electrification in motorsport is certainly something that's becoming far more widespread
and as the technology catches up it's also becoming much more applicable to more
and more people.
I've got Hamish here from University of Canterbury Motorsport who's going to
tell us a little bit about why they've gone electric in their Formula Student car and
how all that works.
So Hamish, we had a look at your electric car before, can you tell us a little bit about why
that thing's electric in the first place?
I know you've built both combustion and electric cars in the first place, what are
some of the advantages with going with an electric powertrain?
- Sure yeah so I was involved in the first electric powertrain that UCM built and
there's two main drivers, I think one is just the general move toward electrification in
transport because of the emissions stuff.
And the second is the performance aspect which is particularly relevant to our competition.
An electric car can deliver its maximum torque anywhere from 0 RPM pretty much all the way
to top speed and that presents some real advantages when you're dealing with a lower
speed track where you need that power right off the line to lower your lap time.
- So what is the general layout of the type of competition you guys do?
You mentioned quite low speeds, so are we talking quite tight and twisty,
stuff like that?
- We are yeah , it's not a lot of room to accelerate for too long, mainly for the
safety reasons with student drivers and what not.
So yeah it is tight, it is twisty, a lot of navigating around cones largely so the ability
to get from one corner to the next quickly is really beneficial.
- What's the general layout of the type of electric cars you guys are building, the sort
of components that are involved, the number of motors, stuff like that?
- Sure yeah I mean at the heart of any electric car is the energy storage system.
Predominantly batteries, there are some other technologies that are possibly coming up like
super capacitors but these ones all use batteries.
The batteries are then connected via high voltage DC to motor controllers or inverters as they're
sometimes called.
They invert the power to AC which drives the electric motors.
You can really choose between 2WD and 4WD.
Electric motors make 4WD quite easy because they're much easier to package than a
driveshaft running up the length of the car type thing.
- And what sort of current and voltage ranges are you guys running these cars in?
- Sure yeah so Formula Student cars are limited by rules up to 600V.
And currents generally run at 100A, peaking up to 200 type thing.
Mostly people would aim to get your voltage as high as you can by design.
That just reduces your current for the same power and reduces weight of cables and
temperature problems, things like that.
- Yeah and when it comes to temperature problems, from what I understand, that's quite a big challenge
in any sort of high performance electric vehicle.
What are the cooling circuits in the car, what parts are individually cooled and how do you go about
designing something like that?
- Sure yeah battery temperature is a big problem.
Mostly I've seen it be air cooled in Formula Student cars and that's probably the biggest
challenge and an area that I think there's probably room for improvement.
Other more commercial high performance vehicles use different kinds of liquid cooling
and that does help.
It's a bit of a challenge in Formula Student where you're only allowed to use water and
maybe oil as a cooling fluid.
Inverters and motors also present some cooling challenges.
They're perhaps a bit more easily cooled, they don't usually have as much thermal mass and
the like to deal with.
- When you said the batteries tend to be air cooled, is that a case of forcing air in there
or it's passively with air, just being in that part of the battery compartment or how
does that work?
- Yeah I guess it could be done either way, typically we've adopted kind of forcing air
through a side pod duct, pushing it through the battery and then pulling out if necessary
with a fan on the other side.
That presents some challenges because the batteries are often really tightly packed
together so there may not be a lot of room for air flow.
But yeah that's basically it.
- And does that mean that that battery is all in one big lump, there's not way to
actually force air through those individual cells?
Or is it an option to actually get air through the battery pack itself?
- It is an option, it really depends how you lay it out from a mechanical and packaging
perspective.
The batteries themselves, you can kind of choose pouch cells which are the size of a small ruler
really, a bit thicker, almost like an iPhone size type thing.
Or you choose cylindrical cells which tend to be a little bigger than a AA battery.
So you have a lot of flexibility as to how you lay those things out but obviously creating
more room for airflow means a bigger overall volume of your battery pack.
- Got you and coming back to the motor controllers and the motors themselves,
how are they cooled?
Is that something where you're cooling with fluid and you're running through a heat
exchanger, one or multiple heat exchangers in the car?
- Yeah so the motor controllers are typically bonded to a aluminium heat sink.
And water gets run through that so it's liquid cooled via a heat sink there.
And the motors themselves, we've adopted a process whereby we use a 3D printed nylon
cooling jacket around the outside of the motor and water is pumped through that in kind of a
helical fashion around the cylindrical motor.
- And what sort of volume of water would you be running in the system?
Is this adding quite a lot of weight to the car?
- No I wouldn't say, I don't know the number off the top of my head but I wouldn't say the
volume is adding a lot of weight, maybe a few kilograms.
- Look that's been a really interesting insight into these cars Hamish, really appreciate
the talk.
- No worries, thanks Tim.
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