[Andrew Burns]

Hi all, my name is Andrew Burns from Sydney, Australia and I'm considering an EV conversion to a car. The exact car and parts I don't know and I'm hoping for some comments and advice from people here! My situation is as follows:

I currently work about 16 km (10 miles) from home, I drive to and from work every day in relatively bad traffic because the public transport available is expensive, slow and convolouted. I'd really like a small (perhaps even 2 seat) electric car to take me two and from work every day, while I can keep my current car for longer trips when I need it.

Mechanical skill level: I'm a control systems engineer, I have a lot of practical experience with electronics, motors, drive systems etc but less so with car mechanics and fabrication. I do however know some people with a lot more experience and have access to various mills, lathes, welders etc

Range: At least 30 miles per charge (enough to get to work and back)

Performance: I don't want to be holding up traffic but don't care if it goes like a sports car. Maximum speed I get to on the way to work and back is 70 kph (about 45 mph) so a top speed of 50 mph would be fine.

Budget: Not sure about the money, I don't mind dropping perhaps up to 10k over time or more but I don't want to break the bank.

Parts considered: I've not really considered anything. A small car, I'd like to use lithium batteries, perhaps a brushless motor (how common are these in EV conversions?) Keep in mind it has to be available in Australia or importable.

So, as a newb, do people have any recommendations for basically any aspect? Car, motor, battery, controller etc? Anyone in Australia have any tips?

Thanks for your help!
Andrew

 

[Andrew Burns]

Salty, thanks a lot for the info, it will certainly be a big help! Luckily the father of somebody I work with has done an electric conversion and so I have some help with the regulatory side of things (a helpful automotive engineer etc).

I've spent the night reading around on power systems, motors, cheap used cars etc. I'm currently thinking that a brushless DC power system like this:

http://currentevtech.com/Drive-Syst...lers/40KW-BLDC-Motor-and-Controller-p166.html

Might be a good option. Anybody have any knowledge or opinions of them? I've emailed currentevtech to try to get more specs but I think either the 40 or 80kW peak motor will be within the power levels I'll need. The price and specs seem quite good which makes me a little nervous...

What do people usually do about taking care of all the auxiliary functions the IC engine usually runs, things like aircon, power steering, brakes, coolant flow etc?

 

[Andrew Burns]

No particular reason, I was just thinking that a brushless motor would supply better performance and efficiency and require less maintenance (plus they're what I'm used to working with).

As I said I've not really had any experience with automotive engineering, how hard is it to convert a relatively modern car (say, post 2000) as opposed to an older car? I see a lot of older car conversions, is that because they can be bought for cheap or because they're easier to work with (I'd imagine all of the technology and gadgets in a modern car could be a huge pain).

 

[Andrew Burns]

Ok narrowing down to what I want, currently thinking of a 1999 Toyota Echo as my donor vehicle. Critical stats:

- 5 speed Manual
- Kerb weight 925 kg
- Original max power 62.6 kW
- Original max torque 122 Nm
- Top gear ratio 0.86
- Final gear ratio 3.72
- Power steering

Any thoughts on this choice? It's quite a safe car for its age and still fairly cheap second hand. I have no other real knowledge of it though so I don't know if an engine transplant is viable (can't see why it wouldn't be).

It's a nice small car though, shouldn't require a huge power system to meet my specs.

 

[Andrew Burns]

Ok so I've been running some numbers through a spreadsheet and very basically it's looking like I'll need at least 6.4kWh of battery power. On my drive to work the most challenging portion is a 300m run of 8.5 degree (15% grade) incline at 70 kph though in reality traffic is so bad that the speed is usually lower. Assuming my end vehicle weighs 1000kg I'll need a power system capable of at least 40 kW for a few minutes (cruising power use should be well under 10kW at 70 kph though).

I've so far run 3 systems through my spreadsheet, the first is the brushless DC motor I had originally planned on using, the second a Netgain warp 9 and the third a Kostov K9 (both available in Australia). The required voltage of the BLDC system requires 90 lithium cells at 40Ah each (for a total pack power of 11.8kWh) while the Warp 9 and K9 motors call for 45 cells at 90Ah each (total pack power 13.4kWh). In each of these situations the power pack easily meets the range and continuous/burst current requirements. Interestingly enough the high voltage pack is about $800 AUD cheaper and about 10kg lighter but the cost advantage is cancelled out by the significantly lower price of the Kostov motor (the warp 9 is significantly more expensive).

Additionally the HV solution requires a more expensive charging system, battery management system, DC/DC converter etc. My estimated total system cost (motor, controller, BMS, charger, power steering pump, DC/DC converter + $2000 for misc items) came to:

BLDC: $14761 AUD
Warp 9: $14049 AUD
Kostov K9: $12664 AUD

Clearly the Kostov is the winner in price and the total weight is comparable to the BLDC system (everything above weighs in at under 220kg, which would make the final car only slightly over stock weight). The K9 should easily meet the cruise requirement of 10kW output and at the rated current of the controller (600A) and ~120V (allowing for sag) will far exceed the power I predict that I'll need for the climb (probably about 50kW available after system inefficiencies). What's more is that the peak output of the Kostov system is only about 13 Hp under the stock motor of the car and the torque should be about the same, so all things considered the car shouldn't be too gutless.

I'm a little surprised by how expensive the conversion is but I suppose in this case I'm taking no effort to reduce cost (all new parts, lithium battery etc) and I'm also surprised that for my range the battery size is limited by the C rating of the cells (3C continuous for the cells though I'd not want to go above 1.5C when cruising). Then again, including buying a good quality second hand car the total conversion won't be more than $20k and if there was a new electric car meeting my specs available in Australia for around that value I'd be jumping on it! (and I'm sure others would too, so where are the production electrics!!).

So there we have it, looks like I've been swung towards the series wound DC motors anyway, which is probably for the best because there's a ton more info around about them as well. As much as the tech aspect of the BLDC motor appeals to me the numbers aren't there in my case and I'm very concerned about the lack of information available about the motors and controllers (I'd hate to buy a $5k dud).

Andrew

 

[Andrew Burns]

Reverse trike? Like a trike with two wheels at the front? I would do a bike or a trike conversion except I'm too worried about being in an accident without a car around me, I know for a fact that my girlfriend wouldn't allow it for one thing