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Electric Mini - Early Planning Phase - Comments Welcome


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#1 aboveliquidice

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Posted 28 May 2012 - 12:59 AM

Hello All,

I have searched and searched for the right kind of electric conversion project, and am seriously considering the classic Mini.

As many of you know, this is not an easy pursuit. There are many technical issues that must be resolved first before this Mini conversion can get off the ground. These Are, in order of most complicated/difficult:

1 - Mating of an electric motor to the transmission / differential
1.a - Should the stock mini transmission / differential be used. From what I've read, no. Insight would be welcome.
1.b - If a swap is possible to a more completely engineered swap (such as a vw beetle, geo metro, suzuki swift, etc.), which one?
2. Modifications of Subframe to allow EV motor, transmission, differential, controller, and connections to reside in front engine bay
3. Battery locations fore and aft. I am planning on Lithium Iron Phosphate. Goal range is 50 miles with a top speed of 70 mph (these are lofty I know).

The other technical considerations, which there are many, are more personal choices then true technical hurdles. I have already read up multiple EV conversions, and am leaning towards the following design choices.

1. AC based system. There have been numerous discussions concerning which is better and for which application. In this case, for me, AC is the way to go. I am looking at a AC50 or AC70 motor, with a curtis controller. BMS and charger have not been researched enough to make a competent decision.
2. Adjustable shocks and upgrade to discs (if not already completed on the donor). The cones are more than adequate, but do not allow for adjustments for weight distribution. The discs are self explanatory (at least in the front).

Budget:

Extremely lose at the moment. I have no shortage of funds for this project. I would like to keep it at or below 20k, but that may not be possible considering the specs I desire. I have a lose timeline of 2.5 years to complete the project, as that is the time I am scheduled to cycle home (America) and would need the vehicle finished.
That is all I can think of right now. I welcome any and all comments. Seriously. I am considering all ideas at this point. That said, please use tact when sharing ideas.

Looking forward to learning, sharing, and hopefully building.

#2 aboveliquidice

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Posted 28 May 2012 - 01:03 AM

One more thing to add. While I am following multiple EV Mini builds, This one http://elkoja.blogspot.de/ by Lars and ? (David I think) is really what I would like to emulate. Warning, website requires Swedish translation. They are really doing a great job, and I plan on borrowing some of the learned knowledge.

#3 batespeed

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Posted 28 May 2012 - 07:19 AM

electric conversions arent my field of expertese, but good luck with it anyway.
there are no incentives to build/run an electric car in the uk, apart from avoiding the congestion charges in central london.
i live out in the sticks so a 50 mile range would be completly useless (im not keen on the 70 mph top speed either )

are you an electronics engineer ? i'm not being cheeky, i'm interested what your motives are for contemplating this conversion

like i say, good luck.......... i was reading a car mag recently which featured an electric mgf, sorry i cant remember which mag it was but an internet search might find it, if i can find the magazine i will post a link

#4 aboveliquidice

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Posted 28 May 2012 - 08:40 AM

electric conversions arent my field of expertese, but good luck with it anyway.
there are no incentives to build/run an electric car in the uk, apart from avoiding the congestion charges in central london.
i live out in the sticks so a 50 mile range would be completly useless (im not keen on the 70 mph top speed either )

are you an electronics engineer ? i'm not being cheeky, i'm interested what your motives are for contemplating this conversion

like i say, good luck.......... i was reading a car mag recently which featured an electric mgf, sorry i cant remember which mag it was but an internet search might find it, if i can find the magazine i will post a link


Not an engineer, although the choice to go medical vs engineer was a close one in school. I am a Soldier and Pharmacist by trade. Working on cars is a hobby. I am actually located in Germany, but this is by far the biggest mini community. So here I am.

The comment you hear most about converting a Mini is "Why? The petrol engine is so efficient!" Which is absolutely true. I suppose it is simply an interest in making an electric car I would like to drive. I have also been toying with an Electric Porche 911, Karmann Ghia, or simply a vw beetle. I really am open to all suggestions. This is simply the planning phase.

#5 Yoda

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Posted 28 May 2012 - 04:12 PM

I am also considering a similar project but not for road use, just to see if i can do it. my plans are top secret and will not give any details until i have tried it ;D Might just turn up at a show with it on a trailer one day because i know what i have planned will actually work. Might not have a lot of range, but hey, as long as it works.

#6 evansisgreat

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Posted 29 May 2012 - 05:25 PM

I also read the magazine with the electric mgf. I think he quoted paying aound £12,000. He used a 75kW motor that was originally made for electric ford 4x4s. I think it was an explorer? He only had enough batteries to make it run at 55kW though and I think it cost him in the region of £12,000 to build. Also you can't get the motors anymore.

#7 charie t

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Posted 29 May 2012 - 06:43 PM

this lives near me, electrice lotus elise
http://www.evalbum.com/1454

And here is the ranger too
http://www.evalbum.com/4301

Edited by charie t, 29 May 2012 - 06:45 PM.


#8 mk3 Cooper S

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Posted 29 May 2012 - 10:40 PM

I have loads of experience in this field and have developed many electric vehicles. Even production vehicles.
I may be able to supply drivetrains and components too.

PM me your requirements

#9 surfblue63

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Posted 30 May 2012 - 12:04 AM

There's a few electric Minis on here

http://www.evalbum.com/type/AUST

and here

http://www.evalbum.com/type/MORS

#10 James_1

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Posted 30 May 2012 - 07:25 PM

Sounds like an interesting project.

Have you considered a true hybrid where an efficient I/C engine is used as a generator and all drive (and some of the braking) is done by an electric motor? Personally I feel this is more practical because you don't have any of the issues with range and overnight recharging, the batteries can be smaller and lighter, and capacitors can be used as well, and the batteries will last longer. http://www.lincvolt.com/

With regards to gearboxes I would strongly advise against a standard mini gearbox. It is a terribly inefficent design and saps an awful lot of power. Linking the electric motor to the Mini 'box won't be simple either. I know that Suzuki Swift gearboxes have been used for electric conversions with Mini's in the past, Any small gearbox should be fine so long as it can take the torque. You will need modified drive shafts to match the Mini hubs to the gearbox pot joints but this isn't much of an issue as almost every engine conversion needs it. I would imagine some custom flanges will be needed to mate the motor to the clutch assembly.

The subframe shouldn't need much changing. Bracketry will almost certainly be needed to mount everything but the frame shouldn't need cutting. None of the components will be big enough to necessitate this. The other option would be to use something along the lines of the R1 bike conversions with a chain drive inside the standard subframe. It may make packaging simpler. http://www.google.co...OOeKy0QX28pzXBQ


Good luck!

James

#11 fuzzy-hair-man

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Posted 31 May 2012 - 12:13 AM

I was planning an electric mini at one stage, I wasn't all that far into it and it was probably never going to see the light of day but....

I liked the Solectra AC24LS motor and controller etc which gave about as much power as the original Mini Cooper S, the batteries I was looking at would have given about a 200km range and be a ~ 300V system.

Solectra has thier own single speed gear box that they can provide if you want to go without gears. The cost at the time would probably have been over 20,000 Australian but I suspect prices would have come down since then as batteries and EV components should be getting cheaper for the same performance.

I agree with your decision to go AC drive, they are much better IMO, the Siemens AC motors at the time had something like a 10 year warranty, that's ten years in which the most you might have to do is change the coolant other than that it's 10 years maintenance free! as electric motors only have one moving part they are much more reliable than an combustion engine.

The other fact strongly in favour of electric engines is thier overall efficientcy, a well to wheel efficientcy for petrol is something like 25% that is of the energy in petrol 25% is actually put towards making the car move, the rest is involved in refining, transport, heat, and other losses. Electric cars by contrast (depending on how the electricity is generated) are about 70% efficient, so that includes charging and discharging batteries, transmission of power over the grid, the motor controller and the motor it'self. (it was a fair few years I looked into this so I may be a bit out on some of the figures) Keep in mind this is a "well to wheel" efficientcy comparison too so may differ from some figures that you have see on the combustion engine.

That said I'm doing a Micra conversion because I do a lot of driving trips of greater than 300km (in Australia that's easy), range is the one big issue left for electric cars I think, the cost of batteries is coming down and will come down further with more production, I think electric is much more promising than the hydrogen fuel cells, which are electric anyway just they convert via hydrogen so you can fill up, I think fuel cells well something like 50% efficient well to wheel.

#12 James_1

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Posted 31 May 2012 - 01:31 AM

I've just remembered to mention that you really need to look into cooling. This is just as important as with an I/C powered car. The cooler the motor and circuits are the more efficient it is. Seconded about the AC.

The well to wheel figures you've given look suprisingly favourable compared to my understanding, I was under the impression that only 30% of the petrol that goes into the tank actually gets turned into useful kinetic energy. Maybe the transportation etc is far more efficient that I imagine.

Going back to the hybrid these figures can be improved upon because it opens up more options for fuels and engines. A diesel or biofuel engine very carefully tuned to run at a set speed can be far more efficient than a normal car engine because the compromises that mean that there is a nice steady powerband can be forgotten and all of the power can come in a single 'burst'. Pulse tuning really come into play and the engine will be in its element. This can get the the efficiency up to 50% and over. When using a setup like this to keep the batteries topped up when needed you'll only really need an engine able to give the power consumed at constant highway speeds to stop the batteries going flat. For a Mini at 60mph that's around 16hp so a well tuned 250cc engine would suffice.

Sorry for going on about this if it doesn't interest you!! Do say and I'll shut up about it :-)

#13 fuzzy-hair-man

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Posted 31 May 2012 - 05:03 AM

Not the paper I was remembering but something similar:
http://www.stanford....eslaReading.pdf

#14 aboveliquidice

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Posted 08 June 2012 - 09:40 PM

I appreciate all of the insight, gents. James, I will definitely look into cooling the battery boxes / motor. It will likely be fan based, which I have seen developed before. Both the Geo metro and the suzuki swift are target donor cars for the transmission / differential. Hopefully, I can locate a local donor without a high cost.

I may have just found my donor Mini, as one has just shown up on the local scene with a dead engine = PERFECT!!! There isn't much else to add to this. Ironing out the mating will be easier with a vehicle in the driveway. Wish me luck.

#15 deebo

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Posted 08 June 2012 - 09:59 PM

reading through this it made alot more sense than i thought it would lol i have never been a fan of electric cars but the idea of an electric mini is awsome.

good luck on the project buddy, hope it all goes well.

dom.




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