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Discussion Starter #1
Hi everyone,

I found a donor car that I want and bought it the other day. Its a 25th Anniversary Mk III Mini with no working engine, no exhaust and the cabin gutted. Talk about ripe for conversion. My plan is to build a 120V system with a 100Ah battery pack. The car weighs in or arround 650kg and I want a top speed near 100kmph with 40 mile range.



I, like everyone else here, am trying to part with as little of my precious, hard earned money as possible on the build. I was thinking of a setup similar to the ADC fb1 4001 or NetGain Impulse 9 with a Curtis 1231c controller and who knows what battery pack (Hopefully LiFePO4) and whatever BMS matches. I know there are a number of ways of doing this but I was wondering if there was a kit that made this cheaper or where the cheapest supplies for this type of setup might be available. I'm living in Ireland so postage is a bit of an issue as far as I can see. There is an expensive kit on electro-vehicles.eu which seems to do all the thinking for you but reduces a) the fun and b) my bank balance. I've been looking on the usual sites (evparts.com, everything-ev.com, ev america, etc) but I'm putting it out to you guys to see if anyone got a better deal. Also trying to bring down the tax burden on imports so I think european dealers may be better.

Let me know what you think of the plan. I'm going to start next week by taking out the engine auxilaries and measuring up a base plate for the motor mount before ordering the motor so I'd love to get your thoughts.

Cheers!

Irel
 

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Based in Ireland myself just starting a bmw316 conversion. Best advice i can give you is to get as much of the shelf as possible. A forklift motor is a great start. See my posts on the forklift motor thread. I have a line on a few nice 72v traction and pump motors if your interested. A pump motor would be better for the mini i reckon due to size.

I seem to remember some minis share the engine and gearbox oil which could be a problem. Also may have a line on batteries.
 

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I would think an 8" ADC motor and 400amp (Curits 1221c) would be more than adequate for a car that size. I use those components in a car that weighs 3200lbs (post conversion)(1451kg) and get reasonable acceleration. I also have a 120 volt system and can easily get to 70mph, so you could most likely do your 100km/h easily with a 96volt system. The reason I say all this is those compenents are much cheaper than the ones you listed.

you might also look at this place for parts: http://www.kta-ev.com/index.html
 

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9 inch motor is definitely an overkill for this tiny car. It probably won't even fit in there. Go with 8 inch motor and save your cash for batteries :)

You can save on controller if you go with less than 120V system, although you need at least 96V to go 100km/h as others have said.

You could probably get away with 100ah or 120ah LiFePo4 cells to get your range and still keep the car relatively light. Say 30 cells of 100ah will give you total of 9.6 kWh or 7.7kWh at 80% DoD. Assuming about 200 Wh/mile for a small light car you get exactly 40 miles range. So 100ah is your minimum size cells at 96V. From here you can get more 100ah cells and get higher voltage and more range, or use 120Ah cells with same voltage and still get more range. Choice of motor/controller is the key to decide battery voltage, then pick cell size to get your range.

Hope this helps.
 

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Discussion Starter #6
Nice! The overwhelming advice then seems to be to go for a 96V system so I can slot a smaller motor under the hood, reduce the battery requirement (kinda) and reduce costs from both the motor and controller. This package from everything-ev seems to do most of the thinking for me:

http://www.everything-ev.com/basic-dc-series-conversion-kit-to-suit-vehicles-up-to-750-kg-p-210.html

I'm going to send an email off to them to find out what the nitty gritty of what I'd be getting. This also saves me money because I can pick it up and there won't be any import tax! :D

Have any of you had dealings with this company? Any feedback from dealing with them? I know there was mentions of a forklift motor. Is that any more difficult then doing things from a kit like this? I've read nightmare stories of trying to almost hack into the software for rescued siemens motor controllers.

Thanks,

Irel
 

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That basic DC kit doesn't even list specific part numbers for motor / controller. I wouldn't buy it until they tell you exact parts specs.

Have you considered their AC kits? This is the same AC motor / controller combo that some people here consider for smaller conversions. Its not that much more expensive, but will give you regen capability.

Also, you didn't mention if there are many hills that you need to climb during your 40 mile commute, this could be challenging with smaller motor / controller.
 

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9 inch motor is definitely an overkill for this tiny car. It probably won't even fit in there. Go with 8 inch motor and save your cash for batteries :)

You can save on controller if you go with less than 120V system, although you need at least 96V to go 100km/h as others have said.

You could probably get away with 100ah or 120ah LiFePo4 cells to get your range and still keep the car relatively light. Say 30 cells of 100ah will give you total of 9.6 kWh or 7.7kWh at 80% DoD. Assuming about 200 Wh/mile for a small light car you get exactly 40 miles range. So 100ah is your minimum size cells at 96V. From here you can get more 100ah cells and get higher voltage and more range, or use 120Ah cells with same voltage and still get more range. Choice of motor/controller is the key to decide battery voltage, then pick cell size to get your range.

Hope this helps.
That is a good example of how to work out battery pack requirements and solves a lot of rethinking. Thanks for posting that.

Now just need a way to determine the Wh/mile for a vehicle at the design stage.
 

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Discussion Starter #9 (Edited)
Might have a look at the AC option alright. I'm going to have a look around about the literature on AC first before I bombard everyone with questions. I have emailled to find out about the contents of the kit. There are some hills but I don't normally commute 40miles in a day. So i factored in the hills into the range estimation. I'd like 40 miles on flat but will expect in the region of 30 with small hills. Is this appropriate?

Woodsmith: Someone reported that for the mini it worked out at 250Wh/mile. I can't remember where I saw this tho!
 

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This AC combo is nice since motor and controller come from same vendor and all matched up. Technically there is nothing special about AC kit compared to DC kit since AC is just 3 wires between controller and the motor, everything between the battery and the controller is the same for both DC and AC with exception of regen. You need to focus on regen capability of the controller and make sure it matches up with your pack voltage levels, etc. I don't have first hand experience with regen, just theory. However, one of regular members here JRP3 is planning Fiero conversion using same AC kit, I think.... Hopefully he will chime in this thread with his thoughts.

If I was doing a small car under 2000lb I would definitely look into these new AC kits, they seem to be a good competition to low end DC kits.

Keep us informed as you go, this will be a lot of fun, post lots of pictures please :)
 

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Discussion Starter #11
I'm wondering about regen. If its a front wheel drive then will that not apply a breaking moment to the front wheels which will give me understeer, potential skidding and create a moment which will want to flip the car?

How is the regen breaking actuated? Is it just that when you ease up on the accelerator that the regen naturally kicks in or is that something that you have to control by actually putting the foot on the break pedal? Maybe someone with some regen experience might be able to help me out with. Also does this rule out the need for a clutch if you can effectively control this from the accelerator pedal?

If I have regen does this mean that I still need a DC:DC voltage converter for the 12v system or can I somehow cut that out?

On a related note: I have a 4 forward speed manual gearbox in the car. Can i still use these gears. From what I read you don't really need 1st gear and then the rest just help to increase the range. Is this true?

You are all amazing at answering these endless list of questions.
 

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Regen is usually initiated by light touch on the brake pedal, just enough to activate the switch, but not enough to apply actual brakes. Regen does not brake hard, so no issues with losing control of the car :D

Regen can be set to activate on high gas pedal instead of brake, but that would mean no coasting, its really up to you how to implement it, controller just has a regen on/off signal input, no matter how its done.

Regen has no bearing on clutch/clutchless design, this is strictly a decision based on how fast/easy you want your tranny to shift gears vs. complexity of motor/tranny coupling.

You still need DC-DC for 12v stuff, this is not related to regen.

You will mostly use 2nd and 3rd gears, but 1st is sometimes useful, especially in slow stop/go and starting up hill. You will very unlikely to ever use 4th gear.

Hope this helps.
 

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Seems like a lot of people are considering a mini conversion lately, which is great – the more people I can 'borrow' ideas from the better :D

Thanks to linz for that link to the carrot blog – some great information there.

One thing I'd recommend before you start buying parts is to work out exactly how (or if) you are going to provide gearing. There's so little space in a mini engine bay that this can be a major hurdle. Variants I've seen so far are:

Mounting a motor on the existing block and driving the gears by chain or belt.

Mating the motor with a small transverse gearbox such as a Suzuki Swift unit.

Dispensing with the gearbox and having a single ratio drive by chain or belt to a sealed diff (such as a Quaife unit):

Mounting the motor longitudinally underneath the rear seats and connecting it directly to a diff for rear wheel drive.

And my own version, still untested and progressing veeery slowly. Two motors, with each one driving a front wheel independently.
 

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Discussion Starter #14
hey malcolm

Yeah, it doesn't appear to be the easiest of conversion jobs by a long long way. Its nearly putting me off doing the conversion. There is an ICE in this car but it doesn't work. Its due to arrive next weeks so I'll have to look at it properly then.
 

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Not trying to put you off at all, just giving a reality check. I reckon the mini will make a superb EV if you can just sort out the minor engineering obstacles. I love my car as it is, but it will be so nice to get rid of that stinkin, noisy, leaky, bone-shaking, heavy, unreliable and thirsty collection of metal under the bonnet.
 

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I'm wondering about regen. If its a front wheel drive then will that not apply a breaking moment to the front wheels which will give me understeer, potential skidding and create a moment which will want to flip the car?
Actually, braking will transfer weight towards the front, causing oversteer. As for flipping the car, you've got no chance of doing that! I did once see a Mini that had been so severely lightened at the rear that it did go onto two wheels when braking. That was due to sticky tyres and getting as much weight to the front as possible. It was used in Gymkhanas, where front grip is king in a FWD car.

As an aside, I also have a Mini project on the go. I'm still working on the 'shell at the moment but I'm hoping to use lots of small (~6KW) motors to power the car. I've been thinking of mounting the diff in a custom case and arranging the motors in a star around it. I should mention that I stole the idea from Jeremy on the BVS forums. Still, it's early days yet...
 

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it doesn't appear to be the easiest of conversion jobs by a long long way.
The classic Mini was my first choice, too. But the price here in Norway is way over my budget. Besides, the engine/transmission/differential unit seems to be the one that lasts the longest.

I think the Mini is an easy conversion and it has been converted from the very beginning. Video: http://www.britishpathe.com/images//preview/00000000/00089000/00089642.WMV

An EV does not need a multi speed transmission because the electric motor has lots of torque at low (even 0!) RPM. All factory made EVs use a single speed transmission, even the Tesla.

Depending on what top speed you want look into complete electric drive units (motor/transmission/differential) from either the G-Wiz (DC or AC) http://www.goingreen.co.uk/store or Buddy (DC). http://www.elbilnorge.no/english They are both available in the UK and should be able to supply what you need.
 

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Using the drive unit from a G-wiz or Buddy is a good idea. I know someone who got one by buying the G-wiz that was crashed on Top Gear.

I'd love to see that clip you posted Tom, but the link doesn't work. I've tried searching the Pathe site, but not had any luck.

Just a note on the need for a multi-speed gearbox. I agree it's not essential, but it can extend the useful speed range of a vehicle. The better-performing factory EVs use AC motors, which can rev to much higher speeds than a DC motor, so extending the speed range. In general, you need a bigger motor to achieve a given speed range without a gearbox than you do with a gearbox.
 

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Anyone who gives an advice that street car DC conversion does not need the transmission has oviously never driven a DC conversion EV. Comparing home EV conversion with Tesla is comparing apples to oranges ( or pears as someone here says :) ).

Air cooled DC motors have too narrow RPM range where they operate with thermal efficiency and not kill the battery in the process. You absolutely must have 2-3 gears if you want decent acceleration and top speed and range in the same EV. Without gears pick 2 out of 3 :)

Even the only affordable AC kit that I mentioned earlier has too low RPM and needs a transmission. AC kits with 12,000 RPM don't need gears, but still need proper gear reduction and cost way too much for everage home conversion.
 

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Anyone who gives an advice that street car DC conversion does not need the transmission has obviously never driven a DC conversion EV.
You are right, Dimitri, I have never driven a conversion - AC or DC. I have driven a few factory DC EVs though. They all had single speed transmissions with a total ratio between 7:1 and 9:1.

I'm not saying that connecting an electric motor directly to the differential (usually between 2.5:1 and 4:1 ratio) will work satisfactorily.

I was suggesting to use a motor/differential unit from a factory EV instead of keeping the heavy original Mini 4 speed transmission/differential unit. I will use the motor/differential unit from a 2001 Th!nk City to convert a 1973 Ginetta G15.
 
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