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Electric Mini - Early Planning Phase - Comments Welcome


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#16 MalcolmB

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Posted 29 June 2012 - 10:03 AM

Just stumbled across this thread a little late. There's a guy in Ireland doing an AC conversion that sounds similar to what you want to do. He's still in the early stages of conversion, but you might find some useful information in his thread here: http://www.diyelectr...t electric mini

I'm slowly converting a mini myself, but using twin fork lift motors with independent chain drive to the front drive shafts. It's not an approach I'd recommend to anyone else though - more of an experiment to see if it works.

Malcolm

#17 minipiglet1

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Posted 14 July 2012 - 10:40 AM

I made a electric bike a while ago and use it everyday to get to work, I found this forum which was very helpful

http://endless-spher...22325ade016c87d

There is a section on electric cars, hopefully there is some good information on there you can use, good luck with your build I will be watching for a build thread!

#18 tiger99

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Posted 04 August 2012 - 07:39 PM

I don't know why you have so many potential difficulties with the transmission, unless the speed range of an AC drive is limited. With DC drive you could just retain the Mini diff and use the standard final drive gears (in a cut-down gearbox casing) to get from motor rpm to wheel rpm, as DC drives will run right down to zero speed. I think that some AC drives will go to zero speed, after all the rail industry uses them without multiple gears or clutch, just a simple fixed ratio. A standard industrial AC induction motor might run at 1500 or 3000 rpm nominally at 50Hz, with a variable frequency drive, 1500rpm motor and max of say 150Hz (motor losses will be acceptable at that frequency) you get 4500rpm (actually a bit less) so a standard Mini diff ratio is about right.

I used to work, a long time ago, with variable frequency industrial drives. They were a novelty then, and mostly used where machines had to be started and stopped very gently due to the process involved (weaving), but are now very common.

Good luck with the project! It is extremenly interesting.

#19 docka

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Posted 29 November 2015 - 07:27 PM

Any updates on this?

 

I'm looking into it too...


Edited by docka, 29 November 2015 - 07:27 PM.


#20 schelle63

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Posted 17 November 2018 - 12:46 PM

Hello,

some of this thread's observers may still be thinking about converting the Mini into an EV (some - as can be read already did it). So this is for You:

I started my conversion some 4 years (!) ago, and it is not yet finished (however pretty close to be). The idea to do that came up many years earlier, so I had plenty of time to think about how to make it, and to find examples how most of the many tasks have already been realized.

 

Here are some details of my project:

  • take the EV drivetrain from an existing donor car (Th!nk A266), providing a complete electric and mechanical pack, proven technology and components already fitting

  • eliminate the Mini-gearbox, which is not required, and which is way too heavy and space consuming

  • buying batteries at the very end of the project (they become better, lighter and cheaper every month)

  • placing all components as deep as possible, keeping the center of gravity low provides safety and fun

  • keep the weight under 750 kg, up to now not yet confrmed, it might stay a 4-seater when ready

  • rated power 20kW, which I consider absolutely sufficient for a car of some 3/4 ton only.

  • min. range 100km, my daily ride to work and back home is 50km

I am very lucky to have a local Mini-shop in town, whose owner knows every detail of any Mini and gave me countless advices what to do and what to avoid.

In addition, there is a specialist in EVs close to the place I live, who supplied the donor car and the battery-packs, as well as unvaluable hints.

By the way, I was very surprised to find out that Caspar from Norway already finished his nearly identical project some years ago: fitting exacly the same drivetrain into his Mini Pickup. What a perfect car! And a perfect presentation on YouTube, by the way.

I want to thank at least these 3 guys for their assistance up to now!

The first 3 years were for the restoration, including little changes on the front subframe, floor panel, battery tray and back seat. I had expected that this portion would be the heaviest, this turned out to be correct. I can say now that I know every mm of my car's shell.

I kept the car's outside appearance as plain as possible. Most people won't even realize that an EV just passed.

As most of the work was done by myself, conversion cost is quite low up to now: I guess I spent some 11000,--€ on batteries, drivetrain, panels, putty and paint.

 

The Car is not on the road yet, but all I can say is: it was and still is worth to do it.

 

Have a great day!

Markus



#21 klivins

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Posted 24 November 2018 - 01:04 PM

Hi Markus

Thanks for sharing! Any pictures? Where you are to put the batteries? 

Im slowly thinking of the same thing:)



#22 schelle63

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Posted 24 November 2018 - 04:45 PM

Hi,

the battery tray in the trunk is expanded from left to right, giving space for 3 battery boxes (48V each); in addition, the crossmember square tunnel is also much bigger now (in fact it fills now the whole space under the front seats) to accomodate another 3 boxes and some relays.

I also changed the panel below the back seat (it is horizontal now) to create a parallel space for more batteries. I cut out the corresponding material from the seat's foam, so the modification is "invisible". This space is not yet filled with batteries, as I am currently fine with the expected range. It is good anyway to know that I could fit another battery pack there.

The dashboard is still a wiring mess, but the car is running already...progress is only in little steps.

Have a great day!

Markus

 

 

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#23 brightsparkz

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Posted 25 November 2018 - 09:43 PM

Hi, are those Tesla battery packs?

#24 MalcolmB

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Posted 25 November 2018 - 10:42 PM

Hi Markus. Nice project. Your fabrication work looks well thought out. The original Think specs show 34 kW (45 hp) peak for that motor at a gear ratio of 10:1, so it should be quite nippy up to 60 mph or so.

Did you build the modules yourself from 18650 cells? Have you decided on a battery management system yet? I look forward to following your progress.

#25 schelle63

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Posted 26 November 2018 - 06:19 PM

Hi,

these are not Tesla-packs, but the same cells as built in the Tesla: 18650. These were supplied from the EV specialist mentioned above, he also welded them together according to specification.

There were two types of Thinks, the earlier is the A266 with rated 20kW, the later one (A306) had more power. I chose the A266 simply because it was available and i have understood that the Siemens-drivetrain ist very robust and reliable.

And I happen to have the hard- and software to change any settings of the controller, so the 20kW may be theoretical only...we will see.

Have a great day!

Markus



#26 schelle63

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Posted 26 November 2018 - 07:51 PM

Hi again,

I forgot to write something about the BMS which is not yet existing. My provider tells me that these 18650 cells are not drifting. He installed thousands of them in many applications, including airplanes (!), without experiencing any problem. We will consequently install only some very simple monitor system where only 24V-clusters will be controlled, and there will be no cell balancing in the first step. I hope he is right and we can keep the BMS that simple, otherwise we will need to add a cell balancing.

Another issue is the making of a CAN-bus-control system, which will bring together the BMS and the charger and the DC/DC-converter (corresponds to the alternator in "normal" cars) and informations on the dashboard. There is a good friend who is really good in such things (I am not...), and he is very interested to realize such a task. I am a lucky guy.

 

Cheers,

Markus



#27 MalcolmB

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Posted 26 November 2018 - 10:12 PM

Ok, I didn't realise there were two different motor ratings. It would be a nice bonus if you could just change a few settings in the inverter to get more power.

The need for a battery management system depends to some extent on the chemistry of the cells used, as you probably know. LiFePO4 cells tend to be the safest, but are also relatively heavy. All the major plugin carmakers fit a BMS. I understand your reluctance to add more complexity and cost, as I've been in the same situation, but after hearing of several fires in DIY conversions I now see a BMS as essential safety equipment.

Edited by MalcolmB, 26 November 2018 - 10:28 PM.


#28 schelle63

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Posted 27 November 2018 - 07:50 PM

I agree with you: safety first!

There will be a (minimized) BMS from the very beginning, although it might be rather a BatteryMonitoringSystem, as I had mentioned. So when any cell is fading away, I will notice this immediately. The problem is of course that there are 18 cells parallel, which makes it a tricky job to find the damaged one. My supplier says that once a cell behaves in a irregular way, cell balancing does not really help, so it needs to be replaced early, instead of trying to compensate the weak point with cell balancing.

From that point of view, going ahead in this way may make my battery even safer.

 

The cells are US18650NC1 from Sony, not LiFePo4 but LiNiCoAlO2, voltage is 3,6V. I also have understood that LiFePo4 is regarded as the safest chemistry, but I trust on my suppllier who assures that these LiNiCoAlO2 are safe also.

Again, I hope he is right.

 

As both motor and controller are water-cooled, I see no issue with giving them some additional power. It is my understanding that for short time (1...2 minutes) you can take out 3 times the rated power, which would mean that there would be 60 (!) kW available. It will be interesting to learn if the batteries can provide te necessary current for that. With the 144V this would equal to 417A. The installed fuses do 500A.

Pretty big figures. I will approach to this in very very little steps....once the car is on the road.

 

Have a nice evening,

Markus

 

 



#29 MalcolmB

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Posted 27 November 2018 - 09:32 PM

It sounds like you and your battery supplier have a good grip on things. Those Sony cells do look good. I'm still at the stage of restoring my mini, which will take some time, so I'm looking forward to starting work on the conversion itself. Please keep us updated on your progress!

#30 schelle63

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Posted 28 November 2018 - 09:24 PM

Hi Malcolm, it is good to see that there are more people with the same idea.

I found that it was good to do things in parallel; body restoration will be affected depending on how the drivetrain will finally be. The Mini is such a good base, you can finish the entire front subframe including motor, differential, driveshaft, hubs and wheels, and install the whole assembly into the shell, then you can imediately see what needs to be modified to make all fit together. At that stage you can also easily add brackets for all the secondary components. Don't forget the many big holes for the large cables!

I will add pictures when something important happens. Currently there is not too much visible progress, i am tidying up the dashboard. Funny thing: some months ago I was so proud of having all the wires there to make the car drive, now I'm happy for every cable that is disapearing.

If You or anyone from the forum need information or detaliled pictures, just let me know.

And of course: suggestions welcome!

 

Have a great day,

Markus






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