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Electric blue2012 R53
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Discussion Starter · #1 ·
"I've had my Cooper S for about 6 months now and have had great fun in it but it was bought with a project in mind and I am nearly ready to pull it apart
so at some point I will be selling the engine (80k) with all ancillaries and the 30mm lowered springs as I'm converting it to electric
I'll be using a modified leaf inverter and motor, two sets of BMW 530e hybrid batteries each with a Simpbms battery monitoring system a Volvo charger not sure on the DC to DC converter yet a handful of custom electronics to keep the dash and warning lights and mot tester happy and almost definitely some blood sweat an tears
so I thought I'd create an account here and if you're interested you can come along for the ride"

this is the Leaf drive unit including charger as it arrived

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And this is the Leaf motor and inverter in it's current state sat on my shed floor

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Behind the motor and also up on the bench are the batteries modules each one is about 60 Volts and I have 12
this is how they come out of the BMW

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and this is the inside containing the 6 60V modules' cooling system, contactors and BMW battery management system I'm trying to use as much of the OEM systems as possible
for cost reasons also BMW have a huge budget to develop this stuff so unless there's a reason why I can't such as the BMS and contactor controller because currently the information isn't available to control them then i am

So far the Mini is intact as I've been concentrating on the electronics and can-bus systems the can bus interface between the leaf inverter and the Mini is pretty much sorted
this will basically replace the ECU sending the correct signals to the dash from the inverter and throttle, brake and start signals to the inverter from the car I've also allowed for lots of different inputs and outputs on the board because I'm 99% certain that I've forgotten about something.
The PCB itself was made on my CNC mill

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Electric blue2012 R53
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15 Posts
Discussion Starter · #9 ·
So far as budget goes for this build
Motor and inverter cost £1500
Modified Open Inverter control board for inverter cost £300
Batteries one set was £1100 the other £1000
Charger cost £300
DC to DC converter will be £300-£600 (not purchased yet)
Hardware for adapter plate, battery boxes and motor mounts etc I estimate £300-500
The components for the various electronics approx £300
Cable and connectors £500-£600
Electric water pump for cooling system was £40
Vacuum pump for brake servo was £40
That's basically it current cost approx £4400
Estimated £5700 to £6300
If I can keep it under £7000 the car was £2000 total £9000 I'll be happy
:)
 

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Electric blue2012 R53
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15 Posts
Discussion Starter · #11 · (Edited)


I’ve just finished building another control board for the conversion
This new board is to control the pre-charge relay and contactors in the battery box that will switch power to the inverter I had already built one for test purposes but there will be two sets of batteries each with their own set of relays/contactors so I have now built a new board to control both sets this board is basically just a power stage taking the load off of the control board in the inverter also allowing for a PWM drive for the negative contactor which is not supplied by the inverter control board this is used to operate the contactor at a lower power level after the contacts have closed

Ok to clear a few things up
A contactor is basically a relay designed to switch much higher voltages/current than a conventional relay sometimes the contacts themselves are sealed in a vacuum or an inert gas to control arcing
A pre-charge relay and resistor are there to protect the contactors and other components that may be damaged by the inrush of current you would get if you just connected your battery pack to your controller containing uncharged capacitors. to avoid this you usually connect your battery to the controller through a resistor via a pre-charge relay to charge the capacitors gradually before switching over to the main contactor this can be controlled by a timer or by monitoring capacitor voltage
In PWM the power is switched on and off at high speed using this method we can use digital electronics to give us what seems to be an analogue output for example if the on voltage is 10 volts and the off voltage is 0 volts and you switch it on and off so that it is on 50% and off 50% of the time the average voltage will be 5volts if it’s on 25% of the time and off 75% you would see an average of 2.5volts
**these are simplified explanations sufficient for the purposes of this post
These two boards should be sufficient for the purpose of interfacing the two systems
:)
 

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Electric blue2012 R53
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Discussion Starter · #12 ·
So I was asked the other day why I was doing this conversion "it has been done before you know and you can even just buy one"
So in answer to that.

There are two other conversions that I know of one from what I know was quite expensive and I wanted to do it on a reasonable budget the other was really cheap used a DC motor, had the back full of batteries and a dash full of warning lights don't get me wrong it did the job but wouldn't pass a uk MOT

And yes you could just go buy one for £25,000 I think it's about 200kg heavier at some point they're going to have to stop calling it a Mini and start calling it a Largie but anyway I'm retired and liked the idea of an EV conversion as I've not done one before and also happened to own the Cooper S so why not.
 

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Love it - great explanations above too in terms of how the stuff works. You obviously know what you're doing, some serious skilks keep the posts coming! Keen to see the progress.
 

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Really interested in watching this unfold!
 

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This is great stuff Andy. Thanks for posting. I love the idea of doing this, but my patience and understanding of electronics is sadly lacking.

The reality of creating an EV with a great little car you’ve already got is great. Even more so if you can keep it under £10k.

Can I ask how the classification of the EV, once finished, is handled? MOT testing, tax and emissions etc…

Will the MinEV still be regarded as a petrol 1.6 officially or a zero emission vehicle?

All the best. John.
 

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Electric blue2012 R53
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Discussion Starter · #17 ·
The tax side is the biggest problem to get it classed as a zero emissions vehicle for tax purposes is currently extremely difficult because the dvla are being D**** this doesn't apply to all vehicles
just vehicles after march 2001 but getting it inspected by a garage and lots of photo's of the work should solve all the other issues insurance and mot testing etc worst case is I have to pay full tax
:)
 

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The tax side is the biggest problem to get it classed as a zero emissions vehicle for tax purposes is currently extremely difficult because the dvla are being D**** this doesn't apply to all vehicles
just vehicles after march 2001 but getting it inspected by a garage and lots of photo's of the work should solve all the other issues insurance and mot testing etc worst case is I have to pay full tax
:)
Thanks for the reply. I’ll follow this thread closely.
 

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Electric blue2012 R53
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Discussion Starter · #19 ·
You remember when I said these two boards were all that would be required for interfacing with the mini, well I now have a third as I had to rethink my battery management system so now I have three this one will be the interface between the two battery packs and control the charger lots of software to write my back and neck hurt just thinking about it :geek:


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:)
 

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2005 R53
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Amazing how powerful those little ARM cortex-M7's are, and so many of the software tools are hald-decent too and do the annoying setup work for you with IO and basic driver stuff. Not worked with that specific NXP chip though, mostly the SAM series. Looks a really good project!
 
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