6 replies to this topic

[bobsbits]

This might go down like a huge red lead balloon, but one of the eight minis I have access to is becoming the donor vehicle for an electric vehicle. I'm looking to retain the original mini look, but with some distinctly modern tech added.

Lights will be LED with custom made tail lights that will be let in flush with the body. New wiring throughout using CAN and LIN bus (save weight, increases functionality). While MK 1 body, side windows will be wind-up and possibly in carbon fibre panels. Roof and floor replaced with carbon fibre (reduce weight) and, depending on what I find as I strip it down, the front wings may be CF too.

Two 10KW AC 'pankake' motors and a dual channel 15KW per channel inverter provide motivation and control as well as regenerative braking. The motors have a peak rating of 70KW each for 20 seconds, so it should clip along okay. The motors and inverters are to be gas cooled and the same system will provide climate control as well as recovery of some energy. Looking at 10-15KWH of LiFePO4 batteries and a bank of ultracapacitors for taking regen power more efficiently than the batteries can. Complete custom interior with LCD displays for instrumentation, audio and GPS (or "infotainment" as the yanks like to call it).

Looking at flexible Photo-Voltaic cells on the roof - reasonable amount of sunshine in NZ to help top up the batteries while its sitting around waiting for me to drive it. Most of the charging is by plugging into the mains using the on-board charger (effectively, it will just need an extension cord to charge - take around 7.5hrs from dead flat to fully charged.)

The estimated range should be between 150 - 200km, depending on the terrain and how hard its driven (okay, so it will probably do 150km tops then!), but that is enough for what I need and will only require me to charge it 1-2 times a week in winter (not much sun) or once a week in summer.

[holmesy]

welcome to the forum,

sounds like you have a clear idea on what you want to do with it i like it.

its good to see someone who wants to use a regenerative braking system to re-charge into the system as most people forget that its a fairly simple process to revert reverse load to the capacitors, should work quite effectively

however a few questions may i ask?
how many batteries are you planning to run and which ones?
Do you plan to supply a small load onto the motors when braking, this is how you could then use the motors to recharge the batteries as that would then turning them into generators? ( this way would take a fair bit of weight and space in inverters and other hardware)
Depending on your batteries would it be wise to keep the electronic gadgets as minimal as possible or will you be able to shut down while driving say if the batteries are running too low?

really interested in this and will be following closely :)

[chadd123]

welcome to tmf

[bobsbits]

Thank you for the welcome Chadd123 and Holmesy.

Holmesy: Happy to answer questions!

I will be using a locally produced inverter/charger/controller to drive the motors which also provides the regen functionality - this is one of the reasons for implementing the CAN bus system, as this unit has CAN built in. Because it is 'addressable' and can be configured at a system level, it gives me the opportunity to 'tweak' the level of regen applied and even set it to be variable - bit like a piano key - get a different result if you press less quickly than if given a sharp bang. In this case, a light application of the brake pedal would cause a mild regen, a hard and fast application would invoke an aggressive regen. It will do this change on the fly too, so you might start off with a light touch, but then stand on the pedal hard. Another 'cool' feature which is software programmable is anti-skid braking. The mechanical brakes are there because the law requires them to be there, regen alone wont bring the vehicle to a complete stop (actually, this isn't strictly true, as it is possible to implement 'pulsed reverse direction proportional braking' - bit of a mouthful, but means that as the generator starts to not turn sufficiently to generate a braking force, pulses of power are applied that cause the unit to switch into 'motor mode' for one or a number of cycles in the reverse direction to the movement. This would bring the vehicle to a very rapid stop and would be able to hold the vehicle on an incline, but would use quite a bit of power to do so.) and finally, because I like the idea of having a back-up stopping system

Because the setup is redundant (two of almost everything), there would have to be a catastrophic failure to cause a total failure. I'm pretty sure that one 10KW motor alone will provide reasonable performance, certainly sufficient to get home or to a safe location to fix whatever the problem is. It is possible the driver may not be aware of a problem, as the computers will compensate very effectively where possible.

The batteries I intend using are LiFePO4 - Lithium iron phosphate. They have a very good energy density at a reasonable price and each cell has its own BMU (Battery Management Unit) that reports, using CAN, back to the main processor. In effect, each cell looks after itself as far as charge rate/discharge rate is concerned. I'm using a heat recovery process to keep the cells within operational range and the recovered heat is used to generate either a small amount of charge or help with the climate control (it gets reasonably hot and humid in NZ - it also gets reasonably cold at times too and the change between these two can be really short! Aircon is a real blessing!) I'm starting with 10KW of batteries to see how that goes, but I will allow for 15-16KW if needed - I would prefer to do more with energy harvesting, from the suspension for example, than put more batteries in.

I should probably mention that I am currently a bit of a CAD jockey - though exactly which bit is up for debate! My ex-wife would be able to accurately pin-point which bit I'm sure I also am an electronics engineer by training, though this may be more of a hindrance than a help My business provides Additive Fabrication services (Rapid Prototyping) in plastics and metal, so making parts isn't a big issue (paying for them is though!). We have a 3D scanner in-house, so I will - at some stage - use that to generate some CAD files for comparison to how a Mini should look/sit on the road so I get the balance right. I noticed there are some discussions on CAD files going on and I have asked for a copy of the file from one of the users, which will make things a LOT quicker and simpler - and will verify the data that I get as well as improve the data set that is out there.

I'm very happy to provide information to anyone who is interested. We have a very active EV group in NZ, including a national association - APEV (http://www.apev.org.nz/), of which I'm a member.

My goal with this project is to produce a vehicle that appeals to the old school car enthusiasts - there are a LOT of them in NZ as we have a LOT of old cars here, but appeal to the more modern vehicle enthusiast as well. I want this car to look at least as 'fresh' as when it came out of the factory, with a modern car convenience make-over and be really 'green' (a very large portion of our electricity is from hydro, geothermal or wind - so the 'carbon' value is very low) and one other thing... it needs to blow the doors of the 'smart-arse' Tessla roadster one of the members has! Notice it is the car that is the 'smart-arse' not the owner! It just sits there exuding superiority in an Anglo-American way that is difficult to quantify and equally difficult to take.

[leefleming]

Seems like an interesting project to be honest.
Keep us all informed and up to date!

[holmesy]

I have got a lot of cad software from one of the guys on here including the shell and suspension but is currently on my dead laptops which I will have to bring back to life when I need it next and will be able to send to you if you wish.

3d scanner hmmmm

sounds like you have some nice kit, fancy making some nice 7 port heads for us?

[bobsbits]

Hello Holmesy,

Ah, laptops! Wonderful things when they work well - I have a collection of dead laptops - I keep them in the hope they will either be able to be bought back to life or they will donate parts to bring one back to life. From 9, this has happened twice! I've only ever had two that became obsolete before they died, a grateful school kid had one and an old lady I know whose desktop machine bit the dust and she couldn't afford to get a replacement had the other - so I guess I'm a bit of an expert on dead laptops and getting data off them! When you do get that one going, I'd love a copy of the data please.

I'm not exactly sure what a 7 port head is, tho I expect Rex, my retired mechanic mate, who is busier now than he was when he was working, will probably know. If you have the CAD file for it, send it to a company in Germany called Voxeljet (http://www.voxeljet....r/login_en.html) The part you want needs to be in .stl file format and there is a registration section to fill out that reverts to German in places, but they will provide you with an on-line quote to produce a part made from either hard or soft plastic. Soft plastic can be packed in sand and used as the 'lost' part in investment casting, hard plastic is great for producing forms from to create multiple copies of 'lost' parts in wax or for mounting on parting boards to make forms. You will need to find yourself someone to cast it for you - Voxeljet might be able to give you some names, but you'd be better building a relationship with a local foundry to work closely with - anyone in TMF a foundryman?

We use these guys from time to time, they are generally very good and very helpful - cost is high for us - but there is a lot of extra cost in shipping to us on the other side of the world! Out of interest, have a look at this: http://www.voxeljet....s-bond-skyfall/ It's the sort of thing we can do here, but I haven't too many clients with pockets deep enough to do much of this sort of thing! Weta Workshops (Part of Peter Jackson's Weta Movies) get a bit done with us, but they tend to do a lot of this sort of work in-house with their own model makers - we've done some 'hero parts' for them in direct metal laser sintering for items used in the Lord of the Rings films and King Kong. If anyone wants to commission us to do a 1/4 or 1/3 scale model of their Mini...

We have done some experimental heads for a racing engine and helped the local University out with their SME race car a couple of years ago. Mostly our automotive work is re-creating parts that can't be found any more or improving the design of parts with an inherent design fault - mildly interesting, but not exciting! How about building the Yamaha 5 valve per cylinder head design into a head to fit the A series block? That would be interesting! We have a local machine that produces titanium parts, so the valves could be Ti - if someone had the funds, the whole thing could be Ti! - just changing the valves to Ti provides quite a bit more available power from reducing the reciprocating mass losses.

by the way, there are a number of outfits in the UK who do 3D printing of parts suitable to use for casting or pattern making - not sure if any of them have a big enough machine to do a full head. The head can be made in several parts and joined together before being used to cast, but that's a bit of fiddling around.