120 replies to this topic

[fikus01]

the way i understood it the tesla system was an all in 1 contained charging system, invertor, power supply that monitered its self to make sure none of the lithium based cells failed and if they did it was all self contained and there was very little loss to the power genrted!

[Silicon Skum]

i've thought as lot about this i did email the people at tesla and ask how much a bettery pack cost but they never replied! they mentioned on their site they were doing them as a seperate unit!

The thing with the batteries they used is that you need special battery management and special chargers. would cost a bomb! Think they were willing to supply batteries to other car manufactuers but not to individuals.

Agreed, you would need the charging equiptment to go with the battery pack - as far as I'm aware, it is a Litium ion / polymer battery, and they DO require certain safety features in the charging system (or they will go BANG really fast!). Also to USE those batteries, you need special equiptment to monitor the state of charge (cell voltage actually) during use, because once again, if you run them down too far (below 2.0v per cell can cause damage to the battery and ar fire / explosion risk!).

Lithium chemistry batteries are VERY powerfull, but are VERY dangerous to use if you are not familiar with them.

You know, there is / was a "company" (which has since dissapeared....) that had developed the lead-acid battery to similar power density as Li-ion / poly batteries. I don't have much information about this, but from what I understand, it was to do with the lead plate construction / chemistry - used something like 70 or 80% less metallic lead as compared to a simialr "standard" flooded cell lead-acid. Basically it was super-spongey lead (more surface area exposed to the electrolite, so less weight - same power).


The "safer" battery technology for most people to use is Lead-acid or NiCd, both have high output power and relatively cheap, without the need for expensive monitoring systems for charge / discharge. NiMH is also quite safe, and offers better performance than Ni-cad - but does have it's own drawbacks too, also more costly.
Only one other storage battery tech I can think of with possibities for use in cars, is the Nickel - Hydrogen battery (Ni/H2), very high cycle life, lightweight, 10+ years life at 60% DOD etc. But you aint got a hope in hell of getting any easily, and they do run at VERY high internal pressure (about 350PSI Nom. I think). Speak to NASA if you want to get some......

Lead-acid is the way to go for DIY coversions, the batteries are readily available just about anywhere, and can give a long service life if looked after properly.

SS

[Scruffs]

Hi All,

Will try to answer most questions…

Driving it will be cool, no clutch, instantaneous acceleration! Unlike petrol engines i will have maximum motor torque at zero rpm!

Don’t know when its going to be finished, been thinking about it for ages, had the motor a year now! Maybe have a running car next summer? Really don’t know.

The motor was shipped from the US, weighs 56Kg so it cost £250 in shipping alone. The motor itself cost £600 and is used in fork lifts in the US. You might be lucky and find one in the UK, you can get a motor from a milk float or something but it wont have the same performance and will be much heavier.

I wish I could afford Ni-Cds or Lion batteries but they cost a bomb and need special chargers or they catch fire when charging!

I have bought replacement bearing for the front mini hub off ebay and have fitted them to my swing arm, also bought roller bearings for the pivot point.

Cheers

Suren

Thumbs up to you man, absolutely awesome project

I've just graduated and am getting into get into electric vehicles in a big way, would love to do something like this! Don't think I have the knowledge of power electronics yet though...Would agree that for a safe self-build electric then lead acid's got to be the way forward though! I assume the motor is brushed? How are you planning to cool itl?

If I may, could I ask about your rear radius arms you've made? I think the horizontal bending stresses in those will be huge at the roots where the tubes meet at the hub and the pivot pivot - are you planning to slap big gussets on them? Obviously you're pretty constrained for space there and proper triangulation isn't going to be possible..You say you've got roller bearings for the pivot - are you keeping the thrust washers from the mini setup? Can you tell I've thought about doing my own radius arms before?!

Anyway, best of luck, I'll be keeping an eye on this thread and soaking up the electronics knowledge...

Al

[brightsparkz]

Hi,

I dont plan on doing much of the electronics. Plan on getting one of these - http://www.cafeelectric.com/ its a 156V 1000A controller designed for electric cars with all the safety features you could ever want. Tad expencive though!

Yeah, the motor is brushed, no cooling necessary as it will be used in its designed power range. If i did push the motor it will probably drain the batteries too fast anyway. I recon i can get ~100hp out of the motor if i pushed it, and thats not rpm power like on IC engines, its dirty wheel shredding torque!

bending stresses.... i remember that stuff from uni, i did mechanical engineering! I think you mean the vertical bending moments where the tube meets the hub. You have to remember that the hub has the coilover attached to it, the weight from the rear of the car goes from the back wheels to the hubs and directly up through the coilovers to the car body. The welded points will not take too much load.

Also when the car is moving forward, the hub will be pushing forward into the weld, creating compression in the tubes. I doubt the welds will fail under compression. But being a paranoid person, i will be welding ribs anyway. The rear swing arm is well over engineered anyway. Its much stronger then it needs to be.... i hope!

I'm tring to get the mechanical stuff done right now, as i'm a while away from doing the electrics!

[Scruffs]

That's pricey! But I guess doing something away from the norm is always going to cost...

I was talking about horizontal loads from cornering? You are right about the vertical loads being borne in the spring not the arm definitely, but if you corner hard it will be putting a lot of sideways force into the end of the arm (bending it in towards the car), and also a torque about the arm, trying to add +ve camber to the wheel. There will be alot of stress at the root of the tubes where they meet the pivot (hmm...maybe not so much at the hub). But if you're gonna be gusseting it anyway I'm sure it will be fine!

[brightsparkz]

That's pricey! But I guess doing something away from the norm is always going to cost...

I was talking about horizontal loads from cornering? You are right about the vertical loads being borne in the spring not the arm definitely, but if you corner hard it will be putting a lot of sideways force into the end of the arm (bending it in towards the car), and also a torque about the arm, trying to add +ve camber to the wheel. There will be alot of stress at the root of the tubes where they meet the pivot (hmm...maybe not so much at the hub). But if you're gonna be gusseting it anyway I'm sure it will be fine!

Hi, I hadnt thought about cornering! I had simpily thought about vertical loads. I think i will add bracing as you suggest. This guy has done somthing similar for his autocross mini...

http://www.spagweb.c...an/pierear2.htm

if what he has done works,. i see no reason why mine shouldnt! (i hope)

[brightsparkz]

Some pics of last weekends work!

Thats a sierra diff, i have cut the driveshafts from both the mini and the sierra.









anyone know how to get a CV joint back together? I took the balls out of one and cant get it back together. There must be instructions somewhere!

[chairchild]

A quick idea for you - but instead of chopping around driveshafts to make one that fits (never been a fan of them, as they WILL be weaker than a standard driveshaft) why not simply use two of the shorter mini driveshafts, and simply weld the mini's pot joint cups onto the Ford diff? This is what I'll be doing, as it means if I do manage to break any parts, I know that it's available at an almost dirt-cheap price, and I know which suppliers are decent - unlike the ford parts, as I have NO experience with them whatsoever!

also, what ratio is the FD in the sierra diff?

[ludsonline]

Have a look here, Maybe useful.

http://cgi.ebay.co.u...1QQcmdZViewItem

A used Mini Clubman fibreglass special. A unique vehicle (hydrolastic suspension), electrically powered by a 72 volt motor ( possibly from a milk float ) mounted onto a Mini gearbox. It used 6 x 12 volt batteries as its power source ( just plug into mains to re-charge ). Sitting / bonded to what looks like a home made chassis using all Mini components I.E. front and rear subframes etc. The bonnet and boot are also fibreglass, but the doors are steel. The windscreen is laminated. This shell is ideal for using as a basis for competition purposes / a non-mini engined project / fitting to a spaceframe/chassis / bike engined car or anything that has a floor/chassis. Much more to tell about it. Serious bidders please email for more information.









Good old ebay

Edited by ludsonline, 08 September 2007 - 04:08 AM.

[chairchild]

for some reason, I couldn't get your link to work - this one does mind you

http://cgi.ebay.co.u...e...00756&fvi=1

[Silicon Skum]

So what exactly are the rules regarding electric conversions on cars? I mean do I need to have the vehicle SVAed, or is it just seen as an "engine transplant"??

I'm in the process of building an electric go-kart (just for laughs - I had enough bits knocking around, so....), and this has got me thinking about doing a car conversion. I don't plan on using a mini (for now at least), but I'm thinking of doing a budget build = £100 (or less) small car from the auctions that is still structurally safe, and some sort of traction motor + controller - prolly get something from a milk float or comercial vehicle (possibly second hand / recon etc.) and lead acid fork lift batteries (will be new - not worth using old ones). Motor would just be mounted directly to the gear box - though I *might* actually keep the clutch and use slightly less complex control gear. Depends on whatever is easier / cheaper.

I plan to do this mega-cheap, so if it's a flop, I won't lose out on much - and can prolly sell on the motor and control gear. Would be tested with cheap car batteries to start with, before spending on proper batteries. I figure I could possibly do this for about £500 to start with, though the new deep cycle batteries will be a killer!

I would say the car batteries would allow a few months of testing (at VERY low milage) before they give out. Plenty of time to work out if it's worth completing the project or not.

So,... anyone know the answers to the questions?

SS

[gizmo]

just look on the internet. theres lots of info on electric cars. lots of projects to tickle your fancy.

[koss]

So what exactly are the rules regarding electric conversions on cars? I mean do I need to have the vehicle SVAed, or is it just seen as an "engine transplant"??

I'm in the process of building an electric go-kart (just for laughs - I had enough bits knocking around, so....), and this has got me thinking about doing a car conversion. I don't plan on using a mini (for now at least), but I'm thinking of doing a budget build = £100 (or less) small car from the auctions that is still structurally safe, and some sort of traction motor + controller - prolly get something from a milk float or comercial vehicle (possibly second hand / recon etc.) and lead acid fork lift batteries (will be new - not worth using old ones). Motor would just be mounted directly to the gear box - though I *might* actually keep the clutch and use slightly less complex control gear. Depends on whatever is easier / cheaper.

I plan to do this mega-cheap, so if it's a flop, I won't lose out on much - and can prolly sell on the motor and control gear. Would be tested with cheap car batteries to start with, before spending on proper batteries. I figure I could possibly do this for about £500 to start with, though the new deep cycle batteries will be a killer!

I would say the car batteries would allow a few months of testing (at VERY low milage) before they give out. Plenty of time to work out if it's worth completing the project or not.

So,... anyone know the answers to the questions?

SS

I don't think it needs a sva test as the car will of already been compliant within the eec when it was registered. However it may get a vehicle inspection when you change the taxation class. I cannot find a sva test sheet at the moment, but every thing listed will already of passed on a mass produced car. It will definitely pas the noise and emissions.
Mot wise I would think a rotary type vac pump driven from a smaller motor will be good for the servo.

Good luck finding a motor

[Silicon Skum]

I don't think it needs a sva test as the car will of already been compliant within the eec when it was registered. However it may get a vehicle inspection when you change the taxation class. I cannot find a sva test sheet at the moment, but every thing listed will already of passed on a mass produced car. It will definitely pas the noise and emissions.
Mot wise I would think a rotary type vac pump driven from a smaller motor will be good for the servo.

Good luck finding a motor

Hmmmm, good point - I hadn't thought about the servo! Not too sure about using a secondary motor, might look into running a pump + tank, from the main motor instead. Secondary motors will just add to the battery drain. And that brings up another point to look out for - power steering! Normally the pump is driven off the engine, that would not work out so good in this case. Could use the electric pump from a Bini.....but those things draw one HELL of a load from the battery when they fire up (engine running at 1500 RPM and the headlights STILL dim when the power steering pump kicks !). So will have to find a car without power steering - or at least a steering rack that is light enough to use with out the pump assisting. Need to have a think about those two things!

I tried to read up on this a little while ago, and just found a LOAD of contradicting information - and 90% of all info I found was USA based......

Finding a Motor is the easy part, a quick call to SEV, which is not too far away, should help source a motor and control gear - though I doubt they'll be all that cheap. Still they are local, and it's handy if anything goes wrong / parts blow up. If only I had thought about this a last year - they moved the factory location.....and there was a LOT of old stuff left outside the old place - batteries and MOTORS included! DOH!!

SS

[v8mini]

looks like Electric Mini has already been done
leccy mini estate