# Dual-motor Austin Mini



## major (Apr 4, 2008)

MalcolmB said:


> The question is, if I have the motors wired in series to a single controller, is the small difference in load on each motor likely to cause any problems?


Hi Malc,

I assume they are series motors, identical designs. Then when in series, they will be forced to have the same load; that is current therefore the same torque. So if you take more torque from one motor shaft for accessories than the other, one of your drive wheels will get a little less torque. I don't really have any idea if that would be noticeable to you or not 

Which Prestolite motors are those?

major


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## MalcolmB (Jun 10, 2008)

major said:


> Which Prestolite motors are those?


I've searched high and low for more information, but no luck. All I have is from the rating plate: Part no. LKAR4002, Class H, 3.6 kW, Class H windings. They have a 33 bar comm. Pretty sure they're series wound. They were Army surplus.


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## major (Apr 4, 2008)

MalcolmB said:


> I've searched high and low for more information, but no luck. All I have is from the rating plate: Part no. LKAR4002, Class H, 3.6 kW, Class H windings. They have a 33 bar comm. Pretty sure they're series wound. They were Army surplus.


My experience with Prestolite dates way back. I didn't know they did any "Army" motors and the LKAR prefix is post my time. Also, Prestolite went bankrupt and split apart, and there was also an Asian Prestolite (non-related from what I can tell) and divisions in the UK.

But if they are the 7.2 inch diameter frame with the 33 slot and bar armature (from the old design), they are very good machines. If you can post some photos of the guts, I may be able to tell you more.

major


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## MalcolmB (Jun 10, 2008)

Yes I've read some of your earlier comments about the Prestolite motors. This one is labelled Ametek-Prestolite, so it would have been after the split, but it looks to me to be similar in construction to the earlier ones I've seen. The stack is shorter though, at around 5 1/2 inches. Here are a couple of photos I posted ages ago in the fork lift motor thread.


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## major (Apr 4, 2008)

MalcolmB said:


> Yes I've read some of your earlier comments about the Prestolite motors. This one is labelled Ametek-Prestolite, so it would have been after the split, but it looks to me to be similar in construction to the earlier ones I've seen. The stack is shorter though, at around 5 1/2 inches. Here are a couple of photos I posted ages ago in the fork lift motor thread.


Kool  Ametek-Prestolite. I think they ended up with the Prestolite factories and tooling. Then it might just be MGP lamination. Likely a 5" stack. And they look like series field coils. And dual double shunt brushes. About the same brush as a Warp9 or 11  I think you have a couple of keepers


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## MalcolmB (Jun 10, 2008)

That's good to hear, especially from you Major. One thing that's been nagging me is whether I'll have enough torque for decent bottom end performance. Obviously that depends on the gear ratio, but space is so tight in a Mini that the practical upper limit is about 4.5:1 with a single-stage reduction. These motors produce 10.5 ft lbs of torque at 130A (5 hp at 2500 rpm), which doesn't seem much when you compare it with some of the brutes that others are playing with here.

Looking around at other motors of similar size and rating I've been using a guesstimated figure of 70 ft lbs from each motor at 500A. Does that sound too optimistic?


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## Huff (Apr 2, 2010)

Hi,
I saw the word Mini and had to investigate  (have owned 2 of the things!)

Why don't you remove the vacuum assisted brake servo and change it for an older type (1990 or earlier from memory) non assisted cylinder? Surely that would simplify matters.

I was looking to do a similar conversion. Perhaps with a Mini Estate/Van for more battery space.
2 (or 4!) agini motors. With one or two proving direct drive to each driveshaft. Not sure if it would fit?! Can agini motors be stacked up or 'siamised'?

N


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## MalcolmB (Jun 10, 2008)

Huff said:


> Hi, I saw the word Mini and had to investigate


Welcome Huff!
Removing the servo would make things a lot easier like you say. Unservoed brakes can be very good on a Mini, but my wife has arthritic ankles so I fitted the servo for her. She wants to drive this car as well, and she's been very tolerant of my obsession for all things electrovehicular, so I reckon it's a concession well worth making 

A Mini van or estate would make a great conversion, though it's becoming hard to find a good one. The company that made my glass fibre shell (Domino) also made a pick-up version, and I'd really like to get one of those.

I believe the Lynch motors can be stacked, not so sure about the Agni motors. The man to ask would be Jozzer (a member here). He has lots of experience with them.


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## DIYguy (Sep 18, 2008)

MalcolmB said:


> Now to the first of many daft questions: I want to keep this conversion as simple (and hopefully cheap) as possible. I've been looking at options for providing vacuum and 12V power and the simplest way I can see to do that would be to use the tail shaft on one motor to drive a mechanical vacuum pump, and use the tail shaft on the other to drive a lightweight alternator. The question is, if I have the motors wired in series to a single controller, is the small difference in load on each motor likely to cause any problems?


Hi Malcolm,... just a comment on the ideas for vacuum and 12 volt power. I don't see your method as being the simplest way. Perhaps "simple" and "cheap" are mutually exclusive...not sure...but in my little brain a vacuum pump and DC/DC (or even just a battery with enough Ah) is much simpler. Vacuum pumps can be relatively inexpensive...depends on how much noise you like to put up with. DC/DC's aren't all that much either. I would say these devices are on the lower end of the cost spectrum for what you need. Perhaps you should just let the motors drive the car....??

Anyways, good luck!


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## MalcolmB (Jun 10, 2008)

DIYguy said:


> ...a vacuum pump and DC/DC (or even just a battery with enough Ah) is much simpler


I'm not sure – it would definitely be lighter, which is good. I guess it depends to some extent on the skills you have. I don't have a great deal of electrical experience but I worked in heavy fabrication for a few years, so it seems easier to make up some new mountings for a mechanical pump and alternator and just hook them up to the original connections.

Part of the reason I've taken so long to make a start on this build is that I'm torn between two approaches. On the one hand I want to make it as simple as possible by reusing as many original/familiar parts as possible. When people look under the bonnet (hood) I want them to understand how it works straight away. On the other hand I want to do it right 

I did buy a Saab electric vacuum pump on ebay a while back, but haven't found a vacuum switch for it yet. I've also looked around for DC converters, but I'm planning a pack voltage of around 220V and there doesn't seem to be much choice at that end. I could run a pair of isolated 110V converters but that's getting more complicated and more expensive... Any other suggestions are very welcome


> Anyways, good luck!


Thanks!


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## DIYguy (Sep 18, 2008)

MalcolmB said:


> I'm not sure – it would definitely be lighter, which is good. I guess it depends to some extent on the skills you have. I don't have a great deal of electrical experience but I worked in heavy fabrication for a few years, so it seems easier to make up some new mountings for a mechanical pump and alternator and just hook them up to the original connections.
> 
> Part of the reason I've taken so long to make a start on this build is that I'm torn between two approaches. On the one hand I want to make it as simple as possible by reusing as many original/familiar parts as possible. When people look under the bonnet (hood) I want them to understand how it works straight away. On the other hand I want to do it right
> 
> ...


Hi Malcolm,

You can likely use the Iota DLS-220-45. This is what I am using. These things work with DC input also. They tested this model for me to ensure it would work ok at my pack voltage. My charger cycles up to 250 volts and I have the DC/DC on too... no problems. You may want to confirm for your application. Mine is 192 nominal, 208 charged. http://www.iotaengineering.com/dls22045.htm
They are very helpful.

I'm more of a mechanical guy also, so...we are drawn to what we know. The DC/DC is very straight fwd. Go for it!


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## MalcolmB (Jun 10, 2008)

Thanks for the link DIYguy. I guess the Iota unit takes a DC input as well. I've just been reading through your thread, got to page 26 and I'm exhausted  You've done a really neat job so far. It's good to read all the little details like sorting out the tach input. I've got that to look forward to yet.


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## DIYguy (Sep 18, 2008)

MalcolmB said:


> Thanks for the link DIYguy. I guess the Iota unit takes a DC input as well. I've just been reading through your thread, got to page 26 and I'm exhausted  You've done a really neat job so far. It's good to read all the little details like sorting out the tach input. I've got that to look forward to yet.


Thanks Malcolm. Interestingly enough... the tach turned out to be 3 pulses/rev after all ...lol Having the Soliton1 made this a very simple adjustment. The tach output is programmable. I input 2 pulses/rev and output 3 to my tach..


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## Coley (Jul 26, 2007)

By not using a differential, I hope the steering is not to jumpy, especially when parking.


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## MalcolmB (Jun 10, 2008)

Coley said:


> By not using a differential, I hope the steering is not to jumpy.


Me too! It's a bit of a grey area so I'm looking forward to finding out. The accepted wisdom is that with motors connected in series to a single controller the car will behave as if it has a conventional diff, and if they're connected in parallel it will act as if it has a limited slip diff. I haven't found anyone who's tried both on the front wheels, apart from on radio control cars, so it'll be interesting to see how it feels.

A few people have warned that running the motors in parallel could be unsafe, with the risk of dangerous handling and damage to the controller/motors. I believe some golf carts drive both front wheels in parallel, but they have a narrow track and generally run on grass, which allows the wheels to slip relative to each other.

Wiring them in parallel would be easier in some ways as it requires a lower voltage pack, so there are fewer connections to make and parts like chargers, fuses and dc converters tend to be cheaper and more widely available.


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## MalcolmB (Jun 10, 2008)

It's been a while, but I've actually got some progress to show today, so Im celebrating with a drop of malt whisky. A belated Happy New Year to Everyone. Cheers!

Photos first:


























This was just a trial fit of one of the two motors (affectionately known as "Righty"). It went well, with no unforeseen conflicts, which is unusual for me, though I will have to rotate the motor 60 degrees to avoid fouling the subframe with one of the terminals.

I'm going with 3/8" duplex chain drive for the time being, but the plan is to switch to belt drive if everything works out well. The Gates carbon belts and sprockets are bit too pricey to experiment with.

A 75x25mm rectangular section will go across the top of the subframe to stiffen everything up and provide a fixing point for the turnbuckles that will be used to adjust chain/belt tension.

I need to get some little machining jobs done next: boring out the motor sprockets and getting keyways cut, and turning the driven shafts so that they'll fit inside the CV cups. Very tempted to buy a small lathe and do it myself, as I know it would get plenty of use in the future.


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## Woodsmith (Jun 5, 2008)

MalcolmB said:


> Very tempted to buy a small lathe and do it myself, as I know it would get plenty of use in the future.


Nice work there.

If you are going to get a lathe get the biggest one you can afford and can find space for. You will always find a 'need' for a bigger lathe so start big and have fewer upgrades. My lathe can just about accomodate a 10.5" diameter and I need 11" to make my motor DE cap!
If you have never used one before then a good book and guidance from an turner will be invaluable, especially before spending money.


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## MalcolmB (Jun 10, 2008)

Thanks Woody
It's the space that's the problem when it comes to choosing a lathe. I'd love to get something like an old Harrison, but I have a typically tiny British garage measuring 2.4 x 4.8 metres, half-filled with kids bikes and my assorted junk, so I may have to compromise. This is why all my photos are wide-angle...


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## Woodsmith (Jun 5, 2008)

How about adding a 6'x4' shed out the back of the garage. All it need hold is the lathe.

I have thought about that on my front drive or at the side of the house as I wouldn't be able to get a decent sized lathe into the basement workshop. I figured I could place a lathe on the shed base and then build the shed around it. A 500w tubular heater underneath will keep it warm enough to stay dry.


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## MalcolmB (Jun 10, 2008)

Spent most of the weekend tidying up the garage as there was barely room to swing a ferret. But I did manage to fit the cross-member and tack up the mounts for one of the turnbuckles for tensioning the chain.

There was some wobble in the driven sprocket when I tried spinning it in the bearings. I'm not sure whether this comes from the taper hub mounting or whether the platewheel itself is distorted, so I've asked a mate who has access to a measuring machine to check it out. I want this to run smooth as butter!


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## MalcolmB (Jun 10, 2008)

Just a small update. I've been stripping the running gear off the Mini, cleaning it up and transferring it to the new subframe. Replaced all the steering ball joints and one CV joint. The Mini normally has one long and one short drive shaft, which is handy, as it means I can use two of the short shafts, so there's no need to make up custom shafts.

I got a local machine shop to cut keyways in the motor shafts, the drive sprockets and the stub shafts that carry the driven sprockets.

The CV cups actually sit about 20mm further forward now than they would normally. I had to do this to provide enough clearance for the driven sprockets at the back of the subframe. I was a little worried this would cause the drive shafts to foul the sides of the subframe where they pass through it, but it turns out there's just enough clearance. Phew.

Now that I've checked everything fits I can weld the CV cups to the stub shafts, then mount the motors and start running the brushes in.


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## jddcircuit (Mar 18, 2010)

Thanks for the pictures. This is a great project. I am planning a very similar dual wheel drive. My plan is for a rear wheel VW drive setup (belt or chain?). I am in the gathering parts mode. I want to try and use as many off the self parts as possible for pulleys, axles, and cv joints, since my machining abilities are limited and I may want to repeat the process. I will be using two synchronous AC motors out of a prius transaxle with two homemade controllers. This might give me the opportunity for traction control since my motor is synchronous I already know the speed of each motor. I might also be able to push the outer turning motor harder through a turn if it helps handling. However, I have to complete my single motor conversion before I start on my dual motor project or my wife will know that I am insane. Everything I am learning on my first project should apply nicely. I just finished fabricating one of my drive axles that connects the prius tripod to the inner racer of the VW CV joint and next weekend hopefully the other. Looking at your design I was also picturing the larger chain sprocket might be a nice place to put disc brakes.

Keep the pictures coming.
Good work
Jeff


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## lockduke (Dec 25, 2009)

Was reading your post on putting brake caliper on drive sprocket. One simple suggestion is to make a replaceable rotor surface, so you don't need to replace the drive sprockets when the brake wear's out the rotor surface. Unless these sprockets need to be changed on a regular basis like motor cycle sprockets from wear. Just a thought I looked into doing this on my 57 Harley for simplicity sake of a few less parts to maintain.I think you are on the right track for using belt drive a lot quieter drive system and just as strong and plenty of gear ratios to fit your drive arrangement. I am going to use a 12v DC vacuum pump for my brake's as my wife wants to drive MY 63 Falcone. Much to my displeasure since she has her own 65 Fairlane. It does require power brake's since she like your wife has problems with her ankle's. oh well just one more fabrication hurdle to overcome and the switch you are going to need is called a hobb's switch and a vacuum chamber like a metal travel canteen/bottle. Have seen it used on one of the kiwi guy's site's. the hobbs switch can be set to maintain a set vacuum for break booster and I have seen several extremely small booster's for aftermarket hot rod applications to save room for those other items we find to add as we go along our way to EV bliss.


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## MalcolmB (Jun 10, 2008)

Thanks Jeff. I've been watching your project with the Prius motors. You really have something there if you can get that motor working reliably with your controller. A pair of them driving a little VW should prove very efficient, and relatively cheap. Hope it all goes well for you.

Using the sprockets as brake discs would be an elegant solution, but I may end up enclosing the sprockets and running them in an oil bath to prevent premature wear. The mini already has outboard disc brakes, so I'll leave them there and make life easy for myself


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## MalcolmB (Jun 10, 2008)

lockduke said:


> the switch you are going to need is called a hobb's switch


Thanks for that Duke, I'd not come across that name before. It brings up a few more likely candidates. I've found a source for new ones but don't like paying retail price


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## etischer (Jun 16, 2008)

Nice clean build so far! 

Do you have to do anything special for the motor which is spinning backwards?


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## MalcolmB (Jun 10, 2008)

Well, I did think of just using that for reverse, as it would reduce the parts count even further 

Seriously though, the motors were originally neutrally timed, so should work just as well in either direction at the rated voltage. I plan to run the motors at around 100V so I've advanced them by 8 degrees in their respective direction of rotation. To be honest I'm not sure advancing is really necessary, as most of the time I guess the motors will only 'see' around 60V. It's something else to test once I've got her running. I'll be putting temperature sensors close to each brush set to monitor temperatures.

The brushes on these motors are set at an angle, but according to Jim Husted this is simply to maximise brush area and doesn't affect the direction of rotation. I've measured the motor current with the motors running in both directions on the bench and couldn't see any significant difference using my rough and ready test setup.


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## lockduke (Dec 25, 2009)

Sorry Malcom: I was out working till 1:00am just got in and saw you responded. The Hobbs switches are not all that expensive and they are also adjustable for pressure or vacuum in several ranges I will check on the part number we used on our last alcohol injector it ranged from 5-20hg vacuum to inject alcohol into our fuel mix to cool under extreme turbo boost of 40-55 lbs on my four cyl 2300. that is now going in to an 80 pinto for a fun rocket ride, and fairly good fuel mileage around 40 mpg under lite load and around 25 under full boost. I guess we have to go to extreme's on our projects sometime's


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## lockduke (Dec 25, 2009)

Sorry Malcolm about the misspelling of your name just saw that I did that my apologies. the Hobbs company is now owned by Honeywell. That part number is a 5000 series, it is adjustable from 1hg vacuum to 30hg.


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## MalcolmB (Jun 10, 2008)

Many thanks Duke!


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## MalcolmB (Jun 10, 2008)

It lives! Admittedly the wheels turn in opposite directions, but that's just a minor oversight... There's a slight misalignment in one of the motor mountings, but easily remedied.

I've been working against the clock to make this presentable as there's a Maker Faire on here in Newcastle on 12/13 March and I'm planning to show my motorcycle and the completed Mini subframe.


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## Woodsmith (Jun 5, 2008)

That looks just right, set up like that. 

What size chain is that?

Interesting shade of green, trying to remember where I have have seen it used before.


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## MalcolmB (Jun 10, 2008)

It's 3/8" duplex, the largest pitch I could use and still get a reasonable reduction ratio. A side benefit of using such a small pitch (as I'm sure you know) is that it can run at higher rpm and generates less noise. I've also considered silent chain, which is expensive, although not too bad if you buy replacement chains for use in transfer cases 

The colour is Mowog green (MOrris WOlseley Garages, I think). It's a high-temp engine paint.


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## Woodsmith (Jun 5, 2008)

MalcolmB said:


> It's 3/8" duplex, the largest pitch I could use and still get a reasonable reduction ratio. A side benefit of using such a small pitch (as I'm sure you know) is that it can run at higher rpm and generates less noise. I've also considered silent chain, which is expensive, although not too bad if you buy replacement chains for use in transfer cases
> 
> The colour is Mowog green (MOrris WOlseley Garages, I think). It's a high-temp engine paint.


Ahhh, Now I recognise the paint colour.

I am planning on using 5/8" duplex on the back of the trike mainly because of the standard rear sprocket has a very large bore. I'm planning on putting two together to make a duplex to save machining one each time I change them. Back wheel will be running at 1130rpm at 80mph.


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## MalcolmB (Jun 10, 2008)

I've been playing with my motors a little today and noticed something odd. I have the motors wired in series with a 12 V battery, with both fields switched by a single reversing contactor. I found that one of the motors spins a good deal faster than the other, in either direction. When I measure the voltage across the armature I get around 7.5V across the faster motor, and around half that across the slower motor.

I expected a slight difference between the motors, but not this much. When I turn the hubs by hand the mechanical resistance feels very similar. It just occurred to me while writing this that I can easily check how similar they are by adding a torque arm to each hub and hanging a weight from it...

I'm just wondering if this difference is solely down to slight electrical and mechanical differences between the motors and drive trains, will it become less significant as I increase voltage and load?


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## Woodsmith (Jun 5, 2008)

From elementary electrics I seem to remember that if two light bulbs were wired in series then one bulb would be brighter then the other due to the voltage drops as the first bulb acted as a resistor for the second.

I guess it would be the same thing and significant al low voltages but maybe negligable at high voltages.

Would they work wired in parallel?


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## MalcolmB (Jun 10, 2008)

Woodsmith said:


> From elementary electrics I seem to remember that if two light bulbs were wired in series then one bulb would be brighter then the other due to the voltage drops as the first bulb acted as a resistor for the second.


Elementary is about my level, but for me that begs the question how do they decide which one is first? 

Yes, I plan to try parallel as well. I'm curious about the differences in steering feel. Ultimately though, series seems a little more efficient/simpler, as it means lower current and needs just one reversing contactor, I think.


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## Picasso (Sep 28, 2010)

The fab work has looked great but the green paint still puts a bigger smile on my face. It's been a long long time since I've seen that green. Mmmm Almond Green.


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## spdas (Nov 28, 2009)

Seeing your build and subframes/bellhousing/torque arm, brings back fond memories of my 1960 850 mini (that i got for $40.00 in 1968) and 1969 1275 Cooper S that I paid $2000.00 in 1974. I was almost ready to chastise you for converting until I saw it had fiberglass aftermarket items and now I see the green (not BRG, but green like the original generators/starters?). Looks like a sweet job
Francis


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## DawidvC (Feb 14, 2010)

MalcolmB said:


> I've been playing with my motors a little today and noticed something odd. I have the motors wired in series with a 12 V battery, with both fields switched by a single reversing contactor. I found that one of the motors spins a good deal faster than the other, in either direction. When I measure the voltage across the armature I get around 7.5V across the faster motor, and around half that across the slower motor.
> 
> I expected a slight difference between the motors, but not this much. When I turn the hubs by hand the mechanical resistance feels very similar. It just occurred to me while writing this that I can easily check how similar they are by adding a torque arm to each hub and hanging a weight from it...
> 
> I'm just wondering if this difference is solely down to slight electrical and mechanical differences between the motors and drive trains, will it become less significant as I increase voltage and load?


It will happen while the motors and wheels are free-wheeling. The motor encountering the highest mechanical resistance will basically stall, giving most of the voltage to the other motor, which will allow it to spin faster.

The moment you drive on a road, the wheels will be connected to each other via the road, and things will even out. It is a good test to see which drive system has the highest resistance to turning, nothing else.

Regards
Dawid


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## DC Braveheart (Oct 12, 2008)

Woodsmith said:


> From elementary electrics I seem to remember that if two light bulbs were wired in series then one bulb would be brighter then the other due to the voltage drops as the first bulb acted as a resistor for the second.


I don't think that's correct. Assuming that both bulbs have the same resistance then, when you connect them in series, each will have half of the total voltage across them and the current flowing through each will be half what it would have been with just one bulb. 

Here's a good reference (see sections on "Resistances in series" and "Resistances in parallel"): http://www.wikihow.com/Analyze-Resistive-Circuits-Using-Ohm's-Law

I think the same applies when connecting multiple motors in series vs in parallel. In series each motor will see a voltage of V/n (where V is the total pack voltage and n is the number of motors - so 2 motors with a pack voltage of 144V will see 72V each). Since the speed of a series motor is directly proportional to the voltage that means that the motors will run half as fast as they would individually on the same pack. But since the same current flows through both motors you get full torque from both.

If you connect 2 motors in parallel, then both will see the full pack voltage - so they will run at full speed. But each motor only gets half the current so produces half the torque.


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## Jimdear2 (Oct 12, 2008)

I think this is just a case of the brushes needing to be re seated. He did after all, disassemble, clean, modify the motors. once the motors have been run in for a day or two, this may even out.

Jim


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## MalcolmB (Jun 10, 2008)

Picasso and spdas: Yes, I liked the colour too  I'm tempted to get the whole mini done in the same colour with a cream roof.

Dawid: Thanks, that makes good sense. I was just a little surprised at how much difference there is. In terms of watts difference, I guess it's pretty small though. I've already got temperature gauges for each motor and I want to install individual voltmeters as well, just to keep an eye on how they play together.

Jim: Good advice, the motors were actually brand new, so were already clean, but the commutators have been handled a few times during machining and the brushes are bound to need some seating in.


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## MalcolmB (Jun 10, 2008)

No updates in a while but I'm gradually making progress with the mini conversion.

Jobs done in the last few months:

Removed engine, gearbox, exhaust and gave engine bay a wash down.

Refurbished calipers and master cylinder with new seals; bought new braided hoses, front discs and pads. I've also fitted an electric vacuum pump.

Rather than waiting till I can afford a full lithium pack I've decided to get her on the road using what I've got on hand. I've robbed most of the parts from my motorcycle. So the battery pack will consist of six 42 Ah Odyssey lead acid batteries (configured for 36V 84 Ah) in series with 75 LifeBatt 10 Ah cells (configured for 48V 50 Ah).

This gives me an 84V pack with a useable capacity of around 45 Ah. I'm also using the Alltrax 7245 controller from my bike, which can operate up to 90V.
Performance and range obviously won't be great, but I just want to get her rolling. I plan to replace the lead with more lithium as soon as possible.

I also intend to use a set of contactors to switch the motors between series and parallel, which should give adequate power for takeoff combined with a decent (50 mph?) top speed.

Jobs I need to finish before reinstalling the subframe and motors in the car include making a chain guard, mounting the contactors and controller and building a battery box for the boot.

Because there's so little space in the boot I'm going to cut out a hole in the GRP boot floor and sink a battery tray into the rectangular space between the rear subframe rails. At the moment I'm thinking of making this from GRP bonded over plywood, but I'd welcome any other suggestions.


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## Anaerin (Feb 4, 2009)

MalcolmB said:


> Rather than waiting till I can afford a full lithium pack I've decided to get her on the road using what I've got on hand. I've robbed most of the parts from my motorcycle. So the battery pack will consist of six 42 Ah Odyssey lead acid batteries (configured for 36V 84 Ah) in series with 75 LifeBatt 10 Ah cells (configured for 48V 50 Ah).
> 
> This gives me an 84V pack with a useable capacity of around 45 Ah. I'm also using the Alltrax 7245 controller from my bike, which can operate up to 90V.
> Performance and range obviously won't be great, but I just want to get her rolling. I plan to replace the lead with more lithium as soon as possible.


Sorry to burst your bubble like this, but mixing sizes and chemistries like this is a recipe for disaster. You may get 50Ah out of it (as that will be the limit that the LifeBatt cells can provide, taking any more out of them won't be possible, but it will be impossible to isolate or route around them as they're connected in series), and the difference in internal resistance will cause "issues" - melty, explodey issues.


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## Jozzer (Mar 29, 2009)

Aye, it's not a great setup Malcom, you'll have to keep well within the limits on both packs, cell voltage reversal would be easy and nasty. I'd rather lend you all the spare Lifebatts I have here than see you get smoked out in that little car! (seriously, I do have a fair few here..)

Car's looking great! It's going to be a fun ride..

Steve


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## MalcolmB (Jun 10, 2008)

Thanks for your concerns guys, but I'm not planning on running this pack entirely bareback. The lithium cells will be protected by a pair of Cell-Log monitors connected through optoisolators to the half-speed input on the Alltrax controller, to give a low-voltage cutoff warning for each cell group. I also intend to set the pack low-voltage cutoff on the Alltrax to a conservative level.

The lead acid batteries are second-hand and are likely to give out before the lithium does. I'll probably connect a voltmeter across them so I can monitor their state of charge separately. These will be charged with a 36V 30A Curtis charger.

The lithium pack will be charged independently with a second 36V Curtis charger used as a bulk charger. This will feed 15 micro DC/DC converters connected to each parallel group of cells. The converters take 36–72V input and have a CV output that is adjustable from 3.3 to 3.63V. I've trimmed them to 3.50 volts each and they seem to behave very nicely, though they will need some good heat sinking and probably a cooling fan. The Curtis charger cuts off automatically when its output drops to a few amps.

I think that's everything covered, but please yell if there's any risk I've overlooked. Safety is obviously important, not just to protect the battery pack, but also because a GRP mini is not very fire-resistant.

Like I said, this is just intended to get the Mini on the road so I can test the drive train, and to give me some added motivation. I've been thinking and talking about this project for so long now that I need to make some real progress. I'm not planning on testing the maximum range.

Many thanks for your kind offer Steve. I'll give you a call soon to find out what spare cells you have.

Nearly forgot: I'll also be using a Drain Brain (old version of Cycle Analyst) to monitor pack voltage, current and Ah.

Malcolm


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## Jozzer (Mar 29, 2009)

Sounds like you know what your doing and have all the bases covered.

I've got 40+ new LifeBatt (the newer Headway type, not the older PSI studded type) should you want them..

Steve


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## MalcolmB (Jun 10, 2008)

Can anyone tell me if this will work?

I've just bought a bunch more Lifebatt 10 Ah cells (Steve: they're the ones you sold to Darren), so I've now got enough for a very small lithium pack, around 6kWh.

I'm planning to charge parallel strings of 6 cells with Vicor micro DC/DC converters. Been racking my brains the last few days trying to decide how to mount the DC converters so that they'll stay reasonably cool. In the back of my mind I've also been wondering how to keep the cells warm during the British winter.

It hit me this morning that I might be able to kill two birds with one stone, by mounting the DC converters directly on the copper busbars. Each converter puts out 25W of waste heat at maximum load (20A). If I mount a couple of decent fans in the parcel shelf above the battery pack I'm hoping it will be enough to keep the busbar temperature down to 30C and circulate the heat around the cells. The photo below is just a test pack I quickly put together. In the final version the cells will actually be supported by two sheets of acetal and spaced about 6 mm apart.


The bit I'm not sure about is how the DC converters will behave with the baseplate connected directly to the busbars. The Vicor design guide says this:



> GROUNDING OF BASEPLATE AND REFERENCING OF INPUT AND OUTPUT TERMINALS
> The baseplate of the converter should always be connected to earth ground. If for any reason this is not possible in your application please consult with Vicor Applications Engineering for acceptable alternatives for your application.
> The input and output leads of the converter should be referenced to the baseplate at some point to avoid stray voltages. For offline applications the input leads are often referenced to earth ground at the AC source ahead of the bridge rectifier. Either + or –Output terminal may be referenced to earth ground and the baseplate. “Floating” inputs or outputs should at a minimum have a high- resistance divider to bleed off stray charges to avoid damage to the insulation system.


So my question is: can the busbar be regarded as earth ground? Or should I mount the converters on electrically insulating thermal pads?


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## steven4601 (Nov 11, 2010)

The Vicor output is isolated from the input? Connecting a baseplate to each cell doesn't provide a legal earth reference. Your battery box & vehicle chassis will need to be earthed to meet legal requirements if the Vicor is ran directly from rectified mains. 
Also note that connecting the vicors directly to rectified mains without power-factor correction will fail all EMC requirements for electric appliances and including vehicles.

Cooling the dc/dc converter through the busbars causing the warming up the electrolyte sounds like a very energy efficient way to keep the batteries warm in the winter but have chance of inflicting damage in the summer. The thermal shut-down temperature is likely to be near 90C where the electrolyte starts to break-down at 50C. Also the isolator sheets inside the battery may be designed to close its pores above 50C....



What model of Vicor are you using?


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## MalcolmB (Jun 10, 2008)

Hi Steven. The Vicor model number is V48C3V3C75A2 http://cdn.vicorpower.com/documents/datasheets/ds_48vin-micro-family.pdf They have isolated input/output. I'm actually using two Curtis 36V 30A lead acid chargers to supply the converters – one supplying the DC converters for one half of the pack, and the other supplying the other half. The chargers are fully isolated as well. They can be configured for several different charge profiles, including one that cuts off when the current drops to a few amps.

The Vicor design guide also recommends fitting bypassing capacitors across the input and output, and between the inputs/outputs and the baseplate. My electronics knowledge is sketchy, as you can gather, and I'm never sure what exactly is meant by "ground". Is it just a stable reference voltage?

Yes, I'll definitely have to watch the temperatures carefully in the summer. If it turns out that the busbars get hotter than 40C then I'll have to find a less elegant solution.


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## steven4601 (Nov 11, 2010)

I do not see why the base-plate cannot be used to cool it. Quite elegant in the winter as I said, quite trouble some in the summer i'm afraid. The e-Mini will mostly be driven in?

No additional electrical insulation is required as long you stay below at or below 100VDC base plate bias voltage and keep the DC input within a potential of 250V referenced from the base-plate. 

Their die-electric test voltage between DC IN and baseplate is 1500V and 500V from out to base. Vicor might have concluded higher voltage may not be nessary for its expected use, or its not within used component specs. In short detail, when a manufacturer claims a certain die-electric withstanding voltage, its wise not to operate anywhere near that voltage. 1/5th usually is safe, always refer to the spec.
Might be a good idea to add a (non-user-serviceable) fuse to both output leads just in case the isolation fails or the output stage of the converter creates a short.


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## MalcolmB (Jun 10, 2008)

Thanks Steven, I really appreciate the advice!

Yes, I planned to fuse both outputs at the connections to the busbars.

The mini will be used all year round. Temperatures here rarely climb above 25C in summer. I'll attach a couple of temperature sensors to the busbars that are likely to get hottest and see how things go. With this setup it would also make sense to use a timer to charge the pack early in the morning, when it's cooler, so that the batteries are warm when they most need it.

It may seem an unnecessary risk doing things this way, but space is so limited in a mini that I need to use it as efficiently as possible.


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## steven4601 (Nov 11, 2010)

Ingenuity has to be used to make small car's work as ev's.
It's all about the challenge. Dual motored e-mini does sound like a pocket rocket. When is your plan to be finished and have it licensed?


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## MalcolmB (Jun 10, 2008)

Finished? What a strange concept 

I should get the battery pack built over winter, and be ready to install everything early next spring. It's got the potential to be a pocket rocket, but in the 1st iteration it will just have an Alltrax controller and 84V pack, so will just be a fast neighbourhood vehicle. The advantage of using the DC converters is that I can easily increase the voltage when I have the spare cash for a higher voltage controller and more cells.

The more I work on this, the more I realise how much better it could be if I didn't have to make so many compromises to fit everything into an existing ICE vehicle.


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## Jimdear2 (Oct 12, 2008)

Howdy,

Just a comment that might save you a bit of grief.

We built up a battery pack/charging system very similar to the one you are planing and found it to work quite well, except for one problem.

The DC to DC board we used (a SYN QOR) was/is VERY sensitive to moisture. Be sure that the unit you have chosen is able to withstand the kind of condensation/moisture you will get in a vehicle e.g. Foggy day, cool spring mornings after a rain etc.

You might look into the setup we built, check some of th ealier pages, there are some pictures of our layout.

http://www.diyelectriccar.com/forum...w-headway-battery-big-13-tractor-53522p9.html

Also check out the similar battery RWaudio is building (much bigger then ours). I believe there are a couple more people building similar packs.

Looking at the Life Batt cells you are showing, they sure look like re badged Headway cells


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## MalcolmB (Jun 10, 2008)

Hi Jim

I've been watching your build and RWaudio's to see how you got on with this approach. Thanks for the heads up about the moisture issue. The little Vicor converters I'm using are sealed units, and judging by the feel of them they're fully potted, so hopefully that won't be a problem for me.

I don't know if the Lifebatt cells are rebadged Headway or not, but the quality of construction is a lot better than I would expect of Headway, just going by the various reports on here. I've not seen any defects at all in my 200 or so cells. The only weak point is the positive screw terminal, which is made of aluminium and is hollow, so you have to be very careful when torquing it up.


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## Jozzer (Mar 29, 2009)

These cells were made by PSI. Clearly different, since Headway have tapped holes not studs..
There was a period that LifeBatt had Headway making some cells with LifeBatt's chemistry iirc but these DID look like Headway's.
Though mechanically not as sound, the PSI's do perform much better than either headway OR the Lifebatt/Headway version.


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## efan (Aug 27, 2009)

everyone...sorry for going off topic here, but I waned to ask Jozzer if he has a thread with photos and videos of his mazda mx-5???


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## MalcolmB (Jun 10, 2008)

it's not off-topic as far as I'm concerned. How's your MX-5 beast coming on Steve?


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## Jozzer (Mar 29, 2009)

Yeah, sorry guys, I've been meaning to start a thread for a while, but its taken all i've got to find time to work on the car.

After a few months of inactivity I decided it was time to finish it before it ended up decorating my workshop wall forever..
It's now a runner, road legal and taxed, fitted with 150v 80AH of Turnigy Lipo packs (about half the planned pack for the moment, though I've easily got room for 3 of these packs on the car..so may step up to 33KW/H ultimatly).
It goes like stink already, and I'm looking forward to doubling the power when the voltage gets doubled..BUT, I found out last week that the Soliton I've got was one of a few units with a problem hall sensor measuring currnet...it's only outputting 600A at full bore!
EvNetics are delivering a new one express to me right now, I expect to exchange them on Tuesday (can't rate them highly enough, they are shipping it at thier own expense and risk...since I still have the old one here!!) 

All in all, absolutely fantastic drive, plenty of power, very smooth and quiet, and plenty more to come!

Anyway, this page is about Mini's not mazda's! I'll get around to a dedicated thread when I can, meantime I did make a "Garage" entry..



Oh, best economy so far is 200wh/m, average more like 250. Not too shabby huh?

I've got an A123 pack to test for a customer over the next few months (thermal testing), I'm going to add that in series for a while (being very careful, with seperate charger and LVC circuits fitted to all cells) so I can have a taste at 250V..

Steve


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## MalcolmB (Jun 10, 2008)

If it performs this well on half voltage and with the current limited the MX-5 going to be a real rubber burner. Look forward to seeing more photos and hearing performance details. 

Does your insurance company know that it goes a little faster than your average milk float?


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## Jozzer (Mar 29, 2009)

Hehe, I have a traders policy, but even if I didn't I would be showing them the figures for Continuous power not 10s peak


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## MalcolmB (Jun 10, 2008)

OK, winter’s gone and I’ve still not finished the battery pack, but at least I’ve made a start. The problem has been trying to work out how to stuff almost 200 cylindrical cells into a Mini boot. The 10Ah LifeBatt cells I’m using are fairly old tech by now and they take up a lot of space. After lots of measuring and scratching my head I finally made another compromise, and decided to install the pack in place of the rear seats. I just wasn’t happy with the idea of having expensive and fairly volatile lithium cells installed in what little crumple zone the Mini has. Besides, this is just a proof of concept, so details like this can be fixed in the next version.

I also gave up on the idea of mounting the individual cell chargers on the busbars. It seemed a neat idea at the time, but I’ve now got a better appreciation of how much waste heat these little DC converters put out – way too much. The next idea was to mount the converters on a fan-cooled aluminium plate above the cells. The plan is to build five of these 5p 8s modules, so just over 24V and 50 Ah per module. The DC converters are fed from a 40V supply, and are current limiting. The real issue with these that they have an efficiency of just over 80%, and when they’re hooked up to a parallel string of five empty cells they put out about 25A and get very hot very quickly. I keep them cool with a 12V automotive AC blower, but this just doesn’t seem the ideal solution for mounting inside a plastic car…

So the latest plan – liable to change tomorrow – is to go the conventional route and buy a decent charger, probably an Elcon. The Vicor DC converters won’t go to waste though, as I’ll use them for occasional cell balancing. The pack will be protected by Cell-logs and relays on each module that will short the throttle and switch off the charger when HVC or LVC are reached. 

By the way, if anyone has any spare unused or little used LifeBatt or PSI 10Ah cells lying around in Europe, I’m interested in buying them. I need another couple of dozen to finish off my pack.


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## Jaesin (Mar 6, 2011)

I was wondering how things were coming along. 

This is an ambitious battery pack. You make all of us prismatic cell guys look pretty lazy. hahaha.

I can't wait to see a video of this thing zoomin' around town so be sure to upload to youtube when you get it going.

- Jaesin


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## MalcolmB (Jun 10, 2008)

I'm on holiday for the next couple of weeks, so just put in a 12-hour day on the mini. Having fun is hard work...

Too tired tonight, but I'll definitely post some photos tomorrow.

Cheers, Malcolm


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## Ace_bridger (Nov 22, 2011)

Malc,

i just wanted to say a big "wow"!!. I've not seen your build thread before and bow to your obvious supreme engineering skills. Well done, very cool!!!

I'm hoping to be on the road this summer with my Golf and there is rumour of a trip to Santa Pod for the AER weekend next year for the UK EVers on here!!!

Well done and keep it up,

Adam


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## MalcolmB (Jun 10, 2008)

An update as promised:

My first attempt at making the stub drive shafts wasn't good enough, so I bought a small lathe and made up some new ones. Also made a chainguard.


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## MalcolmB (Jun 10, 2008)

Stripped away all the DC converter gubbins from the battery modules. 5p8s LifeBatt 10 Ah cells. Just need to add the Cell-log and relay unit. I plan to use just three of these to start with, to stay comfortably within the 90V limit of the Alltrax. I have enough cells to make five modules, and I'm still looking for more PSI cells if anyone has any spare.

Fitted a proximity sensor to the motors – the same one Tesseract recommends for the Soliton. And I found a nice rpm switch from Intellitronix in the US. The rpm limit can be set using dip switches, and it works perfectly with the proximity sensor. The switch is connected to a relay that shorts the throttle input.


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## MalcolmB (Jun 10, 2008)

Made another chainguard for the top of the subframe. The welding isn't great, but I always seem to be in a hurry. Fitted a pair of Albright 182B reversing contactors, one for each motor of course. I still need to make polycarbonate covers for these.

I found a nice forward/reverse switch at an auto jumble. Originally an auto selector, I just had to reposition the switches and add the F/R indicators.

And I used some of the little Vicor DC converters and four LifeBatt cells to make a 1p4s auxiliary battery. With my limited range, 10 Ah should be plenty for now. The DC converters take an input of 36–72V volt, so two of them will be connected to one half of the pack, and the remaining two to the other half. That should ensure balanced drain on the pack and will let me go up to 144V in the future.


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## MalcolmB (Jun 10, 2008)

Made a simple frame to support the Alltrax and blower to cool the motors. Sorry about the dull picture, but sunshine is in short supply in the UK right now.
The thing just to the right of the blower is a throttle body from an MG, which is nice and light. I fitted a 0-5k throttle position sensor from RS components, as the original TPS only had a range of about 1–4k, and the Alltrax won't work with that.

I plan to upgrade to a proper controller eventually, but for now I just want to get this on the road. With the motors in parallel the Alltrax will supply each motor with 72V and 225A, for a while...


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## DIYguy (Sep 18, 2008)

Nice Job Malcolm. I like it. You're getting close to driving this thing. I love the old mini's. 
I was going to use one of the Vicor modules to charge an accessory battery . . but after some discussion with one of their engineers... I learned that there were some significant issues with this. The do have a module specifically designed for use in a battery charging application... it's called a BatMod and has the to letters BM at the end of the string. 

Here's a blurb from one of our emails. 
The input voltage range for the V300 series is 180 - 375V, so as long as you keep the input voltage within that range you should be fine. 

Assuming you intend to charge a 12V battery with the Vicor module, you will need to implement an external control circuit to limit the output current. Here is an application note for that circuit, as it applies to our standard DC/DC converters and battery charging:
http://cdn.vicorpower.com/documents/application_notes/an_ConstantCurrent.pdf

As this is a challenging circuit to implement (you will have to perform stability analysis on your system), I would suggest that you look at our BatMod series of converters (these are available with a 300V nominal input and also a version for 12V battery systems). The BadMod series requires much less design effort to use in battery charging applications than the V300 series:
Batmod datasheet: http://cdn.vicorpower.com/documents/datasheets/ds_batmod.pdf
Batmod design guide: http://cdn.vicorpower.com/documents/applications_manual/200VIJ00_Sect_11.pdf

It is OK to tie baseplate ground to ‘-IN’ and also ‘-OUT’. That is typically the configuration we see in automotive applications. You WILL need to ground the baseplate. The fuse is required to meet safety agency approvals. We also recommend that you use an input capacitor for high frequency rejection. There are further details in the design guide.

Disregard the bit about the input voltage as that is dependant on your design and chosen module.


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## DIYguy (Sep 18, 2008)

By the way, your battery pack design looks a lot like what I did for my booster pack.


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## Studebaker (Jan 22, 2012)

MalcolmB said:


> so I bought a small lathe


Laaaaathe, Been on me shopping list, since I was twelve. Envy you.


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## MalcolmB (Jun 10, 2008)

Ace_bridger said:


> Well done, very cool!!!
> Adam


Thanks Adam. I get loads of inspiration from everyone else's projects – but the mistakes are all my own.

DIYguy: Those A123 packs look great. I've not seen the large cylindrical A123s in a DIY project before. How did you get hold them?
Thanks for the info about the Vicor modules. The micro converters I'm using do current limit at 20–25A, though I wouldn't want to use them this way as they get very hot and fizz quietly. I've charged a 5p block of almost empty LifeBatt cells with a single DC converter, but it takes a lot of cooling as they're only 80% efficient. I can dig out the datasheet if you like. One useful feature is that you can parallel up to three of the converters and designate one of them as the master by adding a single resistor. This gives you a 60A single cell charger.

Studebaker:
Same here, and I wish I'd bought one years ago. Even a little lathe like mine opens up so many new possibilities. My dad was a shipyard fitter and turner, so I felt it was in the blood


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## DIYguy (Sep 18, 2008)

MalcolmB said:


> DIYguy: Those A123 packs look great. I've not seen the large cylindrical A123s in a DIY project before. How did you get hold them?
> Thanks for the info about the Vicor modules. The micro converters I'm using do current limit at 20–25A, though I wouldn't want to use them this way as they get very hot and fizz quietly. I've charged a 5p block of almost empty LifeBatt cells with a single DC converter, but it takes a lot of cooling as they're only 80% efficient. I can dig out the datasheet if you like. One useful feature is that you can parallel up to three of the converters and designate one of them as the master by adding a single resistor. This gives you a 60A single cell charger.


Thanks. The 32157's are pretty awesome. I tested them to 550 amps, 70 to 75C. I wish there were more of them. There are none to be had with screw terminals. I took some risk getting these from China. My packs have room for 4 parallel but I only have enough for 3 parallel at the moment.


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## MalcolmB (Jun 10, 2008)

Motors are in, finally! The mini has been on blocks on my drive for too long.

It's bit crowded in the engine bay, but everything fits, just. I need to cut a couple of small holes in the inner wings to make sure the motor shafts don't rub.


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## MalcolmB (Jun 10, 2008)

I've just finished top-balancing the pack. Each 24V/50Ah module has its own cell-log and relay board to provide low-voltage cutoff to the throttle input and high-voltage cutoff to the charger. The relay outputs are wired in parallel.

The fourth module is only partly populated at the moment as I'll just be running 26s to stay within the 90V max for the Alltrax controller. The battery pack will sit in a rack in the back seat of the mini, and will have a polycarbonate cover and insulators between each module.

It's taken several days of tweaking to get the cells closely balanced, but they look pretty good now. I'm using a pair of 30A 36V Curtis chargers in series. The chargers are each adjusted to finish charging at around 45.5V. All cells finish charging at 3.51±0.02V at the moment.

Just got to install the pack and finish wiring now...


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## MalcolmB (Jun 10, 2008)

Probably a stupid question but I thought I'd ask anyway...

I'm just looking at relay options for switching off my chargers. The chargers should normally cut out automatically when the current has dropped to around 1 amp, but I also want to switch off the charger supply if any cell group reaches 3.7V.

I've ganged together the alarm outputs from the cell-logs via isolating relays and was planning to use this output (@12V) to switch off the supply to the chargers. 

Just wondering if it's OK to use a standard 12V 40A automotive 'ice cube' relay to turn off the mains supply (240V)? I know it's not a good idea to use AC-rated relays for DC applications at the same current, but can you do it the other way round and use DC-rated relays to switch AC?


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## steven4601 (Nov 11, 2010)

Generally No!

Creepage is not designed for mains voltages.


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## Woodsmith (Jun 5, 2008)

MalcolmB said:


> Just wondering if it's OK to use a standard 12V 40A automotive 'ice cube' relay to turn off the mains supply (240V)? I know it's not a good idea to use AC-rated relays for DC applications at the same current, but can you do it the other way round and use DC-rated relays to switch AC?


I would probably use a 240Vac rated relay with a 12v coil just to be sure that it will switch and isolate the ac from the dc.


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## MalcolmB (Jun 10, 2008)

OK, thanks. I was just curious. It makes sense that the insulation level may not be good enough. I've now bought a 240V relay with 12V coil.


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## MalcolmB (Jun 10, 2008)

I managed to bleed the brakes at the weekend, after rebuilding the master cylinder and callipers and fitting new discs.

Turning to final wiring now. I've been trying to work out a simple but effective way of handling precharge, and after reading various threads on this have come up with the following:

I have an EV200 main contactor in the positive leg of the power circuit, with precharge resistor wired permanently across it. In the negative leg I have a Heinemann circuit breaker, installed in the 'transmission' tunnel so it can be operated easily from the driver's seat. The breaker also has an isolated, normally open, indicator switch that closes when the circuit breaker is closed. I plan to use this switch to trigger a timer relay, which will only be powered up when the ignition is turned on.

So the sequence is:

Close circuit breaker, which starts precharge via the resistor on the main contactor.

Turn on ignition, which activates the timer relay (only if circuit breaker is already closed).

Timer relay closes after 10 seconds or so, energising main contactor coil and supplying power to controller.

The reason for doing it this way is to avoid powering the controller before precharge has completed, if (when) I get the sequence wrong.

If you can see any obvious faults with this please shout


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## MalcolmB (Jun 10, 2008)

Thanks, it's definitely simpler, but I also want precharge to be automated so that I don't have to worry about another driver skipping it.

It just dawned on me though that by putting the resistor permanently across the main contactor I've lost the ability to fully isolate the pack. Hmmm.


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## lockduke (Dec 25, 2009)

Hello MalcomB you could wire it to the ignition contact with a timed relay that would become active when you turned the ignition switch to the on position thus making it Idiot proof, and no accidents either it would then precharge and save the controller from the surge. And it would also let you know if the controller has shorted by the fact that it would try to move the car but could not because the resister would burn out trying to move the vehicle. just a thought. It would give you pack isolation that you need also. Duke


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## Ziggythewiz (May 16, 2010)

How often do you expect to have another driver operating it? Will they have to be working the breaker? If use by others is limited, you can just leave the breaker and precharge on, and they don't have to mess with either.


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## Jimdear2 (Oct 12, 2008)

Malcomb,

We use a system that has a start button on the main contactor/precharge circuit. All other low voltage stuff is, as normal, controlled by the ignition switch.

Sequence is 

Close the manual traction pack disconnect (if used)
Turn on the ignition or low voltage main switch
Turn ignition to start position or push a starter button to start precharge.
Wait until precharge is done and the timer relay closes the main contactor, this can turn on a ready light or some other notification system that the vehicle is ready.

The timer circuit can be as simple as a mechanical timer, to something as sophisticated as a circuit that senses the controller capacitor circuit voltage and waits to cycle until a preset voltage is reached.

Two of our tractors us the P&S controller board which has a timer circuit built in another has a stand alone precharge timer.

Jim


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## MalcolmB (Jun 10, 2008)

Ziggythewiz said:


> How often do you expect to have another driver operating it? Will they have to be working the breaker? If use by others is limited, you can just leave the breaker and precharge on, and they don't have to mess with either.


Not very often, and yes I would explain to other drivers that they need to close the breaker before turning on the ignition. It's one simple extra step, and I'd like to keep that step in for peace of mind. Also, if precharge was on all the time the controller would see the full charging voltage – I'm not sure my little Alltrax would like 90V plus.

Hi Jim,
That sounds like the sequence I was planning, but without my breaker interlock. What happens if someone forgets to switch on the pack disconnect first? Unless the timer circuit is a more sophisticated version that senses controller voltage it will just close the contactor after the set time without doing any precharge. When you suddenly remember to close the pack disconnect won't the controller suddenly see the full pack?

I like the idea of a sensing circuit that checks the capacitor voltage, as it's even more fool-proof, but electronics isn't my strong point. Is there a simple way of doing that?


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## Ziggythewiz (May 16, 2010)

MalcolmB said:


> if precharge was on all the time the controller would see the full charging voltage – I'm not sure my little Alltrax would like 90V plus.


Wouldn't the breaker be off? 

I would agree that if you're going automated you want voltage sensing, not just timing. Mine is just manual though. Flick a switch, watch voltage rise for a few sec, turn key to start. If someone else will be driving (say for vehicle inspection) I just leave the precharge on. They're too dumb to know (after I tell them) that the car is on if the key is turned. I wouldn't rely on them to do anything extra.


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## MalcolmB (Jun 10, 2008)

Ziggythewiz said:


> If use by others is limited, you can just leave the breaker and precharge on.





Ziggythewiz said:


> Wouldn't the breaker be off?




My wife and son are likely to use the mini occasionally and that could include charging in town, so the breaker could possibly be left on if they (or I) forget to turn it off. With the precharge resistor permanently across the main contactor like I suggested at first that means the controller could see full charging voltage. Thanks, I hadn't thought of that before. This is why I ask stupid questions.

I'm not sure this would do the controller any harm, but I'd like to be certain that the pack is isolated when the car is parked, so I'll have to rethink that.


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## Ziggythewiz (May 16, 2010)

You might consider adding another contactor on the neg leg, and then depending on the age of the car you could use the seat switch (activates seat belt light) to turn on the neg (precharge) contactor, then the key would turn on the pos contactor. Assuming it takes a few sec to sit down, close the door, seat belt, and turn key. That way they wouldn't have to know/remember anything.


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## Jaesin (Mar 6, 2011)

I would suggest the following approach:

1. Turn on the ignition and a regular 12v relay engages the pre-charge circuit. Use an incandescent indicator bulb (or two) as your pre-charge resistor.
2. Wait... When the indicator bulb turns off, the caps are sufficiently charged. 
3. Turn the key to the start position. This will engage another 12v relay that supplies power to the contactor. Tie the output of this relay to it's own trigger as well. This will turn it into a latch on circuit so it will stay on until you interrupt the other leg of the trigger which should be tied to the ignition.

If the breaker is off, the pre-charge bulb will not light up at all because there is no current going through it.


Does this make any since to you guys?


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## Woodsmith (Jun 5, 2008)

Jaesin said:


> I would suggest the following approach:
> 
> 1. Turn on the ignition and a regular 12v relay engages the pre-charge circuit. Use an incandescent indicator bulb (or two) as your pre-charge resistor.
> 2. Wait... When the indicator bulb turns off, the caps are sufficiently charged.
> ...


That's how I had my tractor set up.
The snag I found was that when switching off the key, the caps slowly discharged back through the precharge resistor keeping the relays engaged for a few seconds (about 10seconds in my case).
Needs a diode inline with the precharge to prevent current flowing back.


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## ricklearned (Mar 3, 2012)

Jaesin said:


> I would suggest the following approach:
> 
> 1. Turn on the ignition and a regular 12v relay engages the pre-charge circuit. Use an incandescent indicator bulb (or two) as your pre-charge resistor.
> 2. Wait... When the indicator bulb turns off, the caps are sufficiently charged.
> ...


I have been looking for a latching circuit that would turn on my controller when the key is turned to the start position and remain on until the ignition switch is turned off. My VW doesn't have an accessory position but this circuit give me that. 

This means I can turn the accessories on by just turning on the ignition switch. To turn on the controller I move the switch to start to latch that relay. This makes the operation of the car pretty straight forward in the event I let someone drive my car. My Curtis controller takes care of the precharge so I don't have to worry about that.


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## jddcircuit (Mar 18, 2010)

Ziggythewiz said:


> I'm confused about the latching bit. It looks like the relay is being bypassed.


It looks to me that the upper right relay is turned on by "Start" and held (or Latched) on by "Ignition".

I don't see the problem that WoodSmith mentioned. When Ignition is removed every path is broken including the pre-charge.

The only downside I see is if someone moves to Start too early. This is where one might take preventative measures.

Thanks
Jeff


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## Ziggythewiz (May 16, 2010)

Yeah, I was just looking at it too early. You're right about the pre-charge. I think it could be an issue in a variant circuit, but as posted it can't feed anything but the controller.


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## Woodsmith (Jun 5, 2008)

jddcircuit said:


> I don't see the problem that WoodSmith mentioned. When Ignition is removed every path is broken including the pre-charge.


I might need to re-examine my set up. I might have a relay wired the other way round.


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## MalcolmB (Jun 10, 2008)

Obviously lots of ways to skin a cat. Thanks! I like the simplicity of the seat switch (though I don't think minis ever had one) and the lightbulb as precharge resistor. I'll probably use Jaesin's/Woody's setup for the time being. I'd still like to automate the process eventually though.


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## Jaesin (Mar 6, 2011)

MalcolmB said:


> Obviously lots of ways to skin a cat. Thanks! I like the simplicity of the seat switch (though I don't think minis ever had one) and the lightbulb as precharge resistor. I'll probably use Jaesin's/Woody's setup for the time being. I'd still like to automate the process eventually though.


There is this thread from a while back bit I haven't tried it yet.

http://www.diyelectriccar.com/forums/showthread.php?t=61429&highlight=pre-charge


- Jaesin


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## MalcolmB (Jun 10, 2008)

Thanks for the link Jaesin. I hadn't come across that thread before. I'll take a closer look at it.

I don't have much time to play at the moment though, as work has finally picked up after a very quiet spell, so I need to get back to the grindstone for a while.


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## MalcolmB (Jun 10, 2008)

Made a bit more progress. I tested the motors at the weekend and hit a slight snag though. These are new motors, so I've already run them for several hours on the bench at low voltage to seat the brushes. They both ran perfectly.

The motors are now hooked up to the Alltrax in parallel, and I've made sure each set of power cables is identical in length. The Mini is still on axle stands and the front wheels and their respective motors turn very easily. When I fired up the controller and applied a little throttle, one of the motors started up smoothly, but the other didn't want to turn. I could get it to run by giving the wheel a gentle push, but it didn't run very smoothly and there was a fair bit of arcing from the brushes. I checked all the connections to the motor and they were all tight.

I had a slight leak of brake fluid from the brake reservoir above this motor while I was bleeding the brakes, so all I can guess is that a few drops of fluid managed to find their way on to the commutator. I've removed four of the eight brushes and there were some small green deposits on the sides of the brushes that looked like verdigris. I gently scraped the brushes clean and refitted them, and the motor runs much more smoothly now. The commutator surface looks patchy in colour compared to the good motor. I'll do the same with the remaining brushes and run this motor in for a couple of hours more at low voltage before trying a road test.

The good news is that the chain drives run very smoothly.

I'm a bit surprised at how sensitive the commutator/brushes are to a little contamination. Has anyone come across a similar problem?


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## Jozzer (Mar 29, 2009)

Hi Malcolm,

Get some degreaser on the commutator (brake cleaner perhaps?), oil can cause all sorts of commutation problems as well as causing damage to the commutator if run at power.
TBH I've always been a little surprised this doesn't happen more often, I guess we're lucky that most EV's don't tend to be very oily..


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## MalcolmB (Jun 10, 2008)

Hi Steve, good to hear from you!

Thanks, I'll give the commutator a rub down with isopropyl alcohol. Yes, when you think of the industrial environments that some of these motors work in I'm also surprised they don't fail more often.

Is your MX-5 still running well?


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## Jozzer (Mar 29, 2009)

MalcolmB said:


> Hi Steve, good to hear from you!
> 
> Thanks, I'll give the commutator a rub down with isopropyl alcohol. Yes, when you think of the industrial environments that some of these motors work in I'm also surprised they don't fail more often.
> 
> Is your MX-5 still running well?


 Just giving the MX5 a service after it's first year of use - the heater element died (actually it melted the plastic and dropped out of the airflow) and it's getting to that time of year when you really WANT a heater!
Also lost a cell (or 1 bank of parallel cells) - though luckily the LVC system caught it before I poked 1000A through it! Easy to swap these lipo cells over however, it will be back on the road this week.


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## dougingraham (Jul 26, 2011)

MalcolmB said:


> The motors are now hooked up to the Alltrax in parallel, and I've made sure each set of power cables is identical in length. The Mini is still on axle stands and the front wheels and their respective motors turn very easily. When I fired up the controller and applied a little throttle, one of the motors started up smoothly, but the other didn't want to turn. I could get it to run by giving the wheel a gentle push, but it didn't run very smoothly and there was a fair bit of arcing from the brushes. I checked all the connections to the motor and they were all tight.


I just read your entire thread and it wasn't clear that you had set the advance on the motors in opposite directions since they are turning in opposite directions. I will go look at the photos again after I post this. Having one motor advanced by 8 degrees and the other motor retarded by 8 degrees would give one motor that ran well and one that would have terrible arcing from the brushes and not want to turn well. Double check that the motor that is having problems has advanced timing for its direction of rotation.


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## MalcolmB (Jun 10, 2008)

Thanks Doug, the same thing crossed my mind, but both motors are neutrally timed at the moment. I reset them to neutral a while back as I'll be using a low-voltage pack for a while - until I win the lottery.

I test ran the motors on the bench for several hours in their current configuration and there was no problem at all.


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## MalcolmB (Jun 10, 2008)

She works!! 

I've just had my first drive in an electric car  Drove up and down my street this morning in the Mini. I've got to say after all the time and thought I've put into this project and all the imagined problems, it was almost an anti-climax. No fireworks, no clouds of smoke, no wild surges of power. She just glides along serenely accompanied by the sound of an old milk float and the odd thump from the suspension 

My main worry was torque steer, since the motors are wired in a parallel to a single Alltrax. I did a couple of full-lock turns and the steering feels just the same as it did with the ICE. Obviously I'll have to do more testing, but it looks encouraging so far.

The performance isn't anything to shout about at the moment, but it feels perfectly adequate for town driving.

I did find one small problem though. I installed a forward/reverse gear lever in the transmission tunnel just in front of the handbrake. The handbrake was on when I did the installation, and I never thought to check clearance with the handbrake off. Now I can only select reverse when the handbrake is on... I guess that's one way of making sure I've come to a complete stop before I go into reverse 

Still a few little jobs to do, minor details you know, such as wiring the instruments and chargers, fitting the dash, interior carpet, exterior paint...


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## tylerwatts (Feb 9, 2012)

Excellent news Malcomb! Been looking forward immensely to this! How about some pics?! Keen to see your final motor installation, and some pics of what your plan is for mounting batteries. Love the thought of an EV Mini! Was looking at the thread about the Toyota/Lexus electric rear transaxle and thinking that would drive a light fiberglass Mini a treat! Be a little rocket!  
Congrats sir!


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## skooler (Mar 26, 2011)

Great news!

Video?


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## toddshotrods (Feb 10, 2009)

Congrats!


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## MalcolmB (Jun 10, 2008)

Thanks gents 

No video and very few pics at the moment, I've been too busy. Here are a couple of pics of the engine bay though. I still need to fit terminal boots and tidy up the wiring. I've just sent details off to PlugInsure to get an insurance quote. They'll be getting sick of us UK tinkerers soon...


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## Studebaker (Jan 22, 2012)

Top notch Malcolm.


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## Ziggythewiz (May 16, 2010)

Looks like lots of motor for a little car. Must be loads of fun!


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## MalcolmB (Jun 10, 2008)

Ziggythewiz said:


> Looks like lots of motor for a little car. Must be loads of fun!


I'm hoping it will be when I get lots of battery and lots of controller to match them. At the moment they just sit there yelling feed me!


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## Jaesin (Mar 6, 2011)

Awesome. Glad to hear you're on the road!


- Jaesin


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## mizlplix (May 1, 2011)

Nice job! Malcom.

Every time you drive your car will feel like that first time. That is part of the reward too.

Miz


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## MalcolmB (Jun 10, 2008)

Big day tomorrow, I have the Mini booked in for its MOT (roadworthiness test)! I've got loads of little jobs done, fixing lights, replacing the windscreen washer and a seat belt etc. Hopefully I haven't missed anything.

Only running on 60% of the battery pack at the moment, so the battery installation isn't complete. The batteries are secured in an angle iron frame with heavy-duty lashing straps and a square-section restraint bar. Since there's plenty of space either side at the moment I've installed the chargers here. I need to make up a proper cover for the fuse 

I charged the pack up yesterday and the cells are closely enough balanced that the chargers shut down before any cell can trigger the cell-logs. The highest cell was around 3.53V and lowest around 3.47. The chargers just shut down for a minute or so and then repeat the charge cycle. I plan to use a timer to prevent them cycling endlessly. If any of the cells does get far enough ahead of the other to trigger a cell-log (3.6V) it activates a mains relay that shuts off the chargers.

Instrumentation is minimal right now. The speedo is the original tachometer, taking pulses from an inductive proximity sensor on the tail shaft of one of the motors. I worked out the speed at given rpm and then printed off a new dial for the tach.

I've fitted the old Cycle Analyst from my motorbike but realised that the new 400A 50mV shunt I fitted is outside its calibration range, so I'll probably get one of the ZEVA fuel gauge drivers. I'm also tempted by the EMW Android tablet display.

Still need to wire up a pair of analogue ammeters, one for each motor, just to check how they are sharing current under different conditions. I don't need accurate current reading, so I'll just use identical lengths of motor cable as shunts for each meter, to give readings for comparison (thanks for the tip Jozzer).

Loads of cosmetic work still to do, as you can see. It looks as if the Mini is going rusty, but that's just glue from the old carpet. Fibre glass doesn't rust as far as I know


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## Jozzer (Mar 29, 2009)

Good luck on the MOT!

Did you try both of the range settings in the Cycle Analyist?

Great way to bring an old classic back to life. I look forward to seeing it at one of the Brighton Mini runs one say


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## skooler (Mar 26, 2011)

good luck!


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## MalcolmB (Jun 10, 2008)

I'm road legal  Passed the MOT with no advisories at all. I'm still waiting for the DVLA to approve the change of fuel type, but in the meantime I'm going to tax the Mini as an ICE, then claim back the road tax when the new log book comes through.

It was only a couple of miles to the testing station, but enough to confirm that I want more power. I'm still weighing up controller options, but at the moment leaning towards a Synkromotive. I really like the features and support of the Soliton Junior, but I don't think 600A split between the two motors will give me the performance I want. A Soliton 1 would be very nice, but is physically too big for the space I have available.

Steve: It's not actually a Cycle Analyst I'm using, it's the earlier version – the Drain Brain – and it only has one calibration range according to the manual.
It's a pity you live way down in the uncivilised south, I'd really like to drop in and see what you're up to 

Mike: Thanks, hope you get your charger sorted out soon.


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## DawidvC (Feb 14, 2010)

Congratulations


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## Jozzer (Mar 29, 2009)

Congrats!
Have you applied for the change to electric by post? Down here they usually give me a tax disk to walk away with and the docs follow later..

Shame indeed - you'd like it here, it's like an EV toyshop


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## Yabert (Feb 7, 2010)

MalcolmB said:


> It was only a couple of miles to the testing station, but enough to confirm that I want more power. .


How much power do you really have with your small battery pack?
450A and 50v after sag (22 Kw)? I guess it's the main cause of underpower, right?

About controller, why don't simply add another cheap AXE 7245? Or trade your controller for a SPM 72650 (740A peak)?


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## skooler (Mar 26, 2011)

Congrats!

enjoy


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## MalcolmB (Jun 10, 2008)

Jozzer said:


> Congrats!
> Have you applied for the change to electric by post?


Yes, I sent the V5 off by post a couple of weeks ago. Called them today and they haven't processed it yet. I'd probably have been better off going to the local office.




Yabert said:


> How much power do you really have with your small battery pack?
> 450A and 50v after sag (22 Kw)? I guess it's the main cause of underpower, right?
> 
> About controller, why don't simply add another cheap AXE 7245? Or trade your controller for a SPM 72650 (740A peak)?


Not sure about the power output yet. The lowest voltage I've seen so far is 67V, so possibly a bit more than 22 kW. Yes, another AXE 7245 would definitely make a big difference in low-speed acceleration for relatively little cost. I'm not really interested in going above 110 kph, but I would like decent torque from 0 to 95 kph, so I reckon I'll need more than 72V. I built the pack as 24V 50Ah modules with the intention of going to 120V as soon as I get a higher voltage controller. I have enough cells to go to 36s right now, so I'm looking for some more Lifebatt/PSI cells in good condition if anyone has any spare.


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## Yabert (Feb 7, 2010)

120V, 900A in this little thing!!...


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## MalcolmB (Jun 10, 2008)

Yabert said:


> 120V, 900A in this little thing!!...


Not at the same time, obviously, but it should be fun n'est ce pas? After all, I reckon it's our duty to prove that EVs are a little special


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## Jozzer (Mar 29, 2009)

MalcolmB said:


> Not at the same time, obviously, but it should be fun n'est ce pas? After all, I reckon it's our duty to prove that EVs are a little special


 It deserves no less!


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## favguy (May 2, 2008)

Congrats on the MOT Malcolm!


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## RIPPERTON (Jan 26, 2010)

Excellent engineering Mal good to see it on the road.
I just bought a Diahatsu Mira as somewhere to put my $12k worth of LifeTech's that have been sitting in the spare room for 2 years and also want to do a twin DC but running a series parallel switch.
Lots of planning ahead.
Dan


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## MalcolmB (Jun 10, 2008)

RIPPERTON said:


> I just bought a Diahatsu Mira as somewhere to put my $12k worth of LifeTech's that have been sitting in the spare room for 2 years and also want to do a twin DC but running a series parallel switch.


Thanks! $12k worth of LifeTech eh? You've got too many toys mate, you need to share more 
I was originally going to do series/parallel switching as well, but the wiring is messy enough already with two reversing contactors. I'm sure it could be simplified with a bit more planning though.


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## RIPPERTON (Jan 26, 2010)

Im thinking 2 PM motors (maybe ME1003's) with a kelly controller as they have electronic reverse and regen, then making a mechanical series parallel sliding switch.
but then there may be arcing during the shift as the magnets might be inducing current on throttle off.
Can anyone clarify this ?

Also when 2 motors are in series are the number of turns effectively doubled ?


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## riwe (Nov 17, 2011)

Congratulations on a job well done! Looks fantastic. So you can acctually get it approved as a electric car? How complex is the process? I think its impossible to do that with fiat in Sweden.


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## MalcolmB (Jun 10, 2008)

riwe said:


> Congratulations on a job well done! Looks fantastic. So you can acctually get it approved as a electric car? How complex is the process? I think its impossible to do that with fiat in Sweden.


Thanks Rikard, and congratulations to you on getting married.

It's only classed as an electric car for taxation purposes in the UK. You notify the licensing agency that you have changed the fuel type to electric, and then you no longer have to pay annual road tax. I think it's a relic of the days when we had electric delivery trucks.


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## Jozzer (Mar 29, 2009)

MalcolmB said:


> Thanks Rikard, and congratulations to you on getting married.
> 
> It's only classed as an electric car for taxation purposes in the UK. You notify the licensing agency that you have changed the fuel type to electric, and then you no longer have to pay annual road tax. I think it's a relic of the days when we had electric delivery trucks.


Actually I think it's a new directive to encourage low carbon cars - when I registered my Apriliia a few years back they told me I was only the fifth person to do so..


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## Studebaker (Jan 22, 2012)

Congrats Malcolm. Make some video clip of driving the mini for us, please.


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## Ingineer (Nov 22, 2012)

Are your motors both timed neutral? Some motors have different timing, so because you have one running forwards and one backwards, you would need to offset the timing (rotate the brushgear) to the negative offset instead of the positive on one motor.

You can determine this by running each reverse and forward at a constant voltage and determining if the speed is the same in each direction. If it isn't, they probably are not neutral timed and one will require adjustment.

The motor manufacturer could also shed light on this.

-Phil



MalcolmB said:


> I've been playing with my motors a little today and noticed something odd. I have the motors wired in series with a 12 V battery, with both fields switched by a single reversing contactor. I found that one of the motors spins a good deal faster than the other, in either direction. When I measure the voltage across the armature I get around 7.5V across the faster motor, and around half that across the slower motor.
> 
> I expected a slight difference between the motors, but not this much. When I turn the hubs by hand the mechanical resistance feels very similar. It just occurred to me while writing this that I can easily check how similar they are by adding a torque arm to each hub and hanging a weight from it...
> 
> I'm just wondering if this difference is solely down to slight electrical and mechanical differences between the motors and drive trains, will it become less significant as I increase voltage and load?


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## MalcolmB (Jun 10, 2008)

Ingineer said:


> Are your motors both timed neutral?


Hi Phil,
Yes, I believe both motors are neutrally timed at the moment. I checked them with a tachometer and ammeter when I first got them, and got very similar readings in both directions. I don't think there's any need to advance them yet as I'm only running on 72V. But I have drilled and tapped each of the casings with two sets of holes at +8 degrees and -8 degrees, so I can advance them if/when I go to higher voltage.

I'm fairly sure the difference in speed I noticed earlier was just due to slight differences in friction loading.


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## MalcolmB (Jun 10, 2008)

Hi guys. Time for an update.

I put very few miles on the Mini over winter as the low temperatures meant my little pack was struggling. I've now installed the rest of the cells and reconfigured the battery to make a 77V 80Ah pack. It's still small of course, but it'll have to do for now. I originally planned to go to a higher voltage, but realised that it's good deal cheaper to stay below 90V.

I got a free J1772 charge point installed a few weeks back. It's from Pod Point and they did a very neat job of installing it. I bought a matching socket and AVC2 module from Modular EV Power. The AVC2 takes care of the handshaking with the charge point. There's just one problem though: the charging process starts up fine, but after 20 seconds the Pod Point shuts down. I mentioned this on another thread and electricmini suggested it might be because I'm using a pair of Curtis chargers in series. Apparently the combined leakage current can be enough to trip the RCD. Sure enough, when I disconnect one of the chargers the Pod Point no longer trips (thanks Richard!). Anyone have any ideas how I can get round this, other than buying another charger? In the meantime I've gone back to charging with a regular UK mains plug.

Other stuff I've done recently is to fit a Sevcon 300W DC converter and a little back-up battery made from sixteen A123 28650 cells. I top-balanced the cells first, and the Sevcon keeps them nicely charged at 13.4V.

The coolest addition is an Android dashboard unit from emotorwerks. I just hooked this up yesterday and I'm really pleased with it. I've run the app on both an Asus 10" transformer tablet and my old Google Nexus phone, and it works well on both. I've driven about 15 miles today, mostly stop and go in town plus a few miles at 50 mph, and it tells me I'm getting around 200 Wh/mile, which is about what I was expecting.

The next job is to fit a bigger controller. The performance around 40-50 mph is surprisingly good, but low-speed torque is just not good enough. I was considering replacing it with a Synkromotive controller, but since I'll be sticking with 72V for some time I've decided to settle for the bigger Alltrax SPM 650. This is supposed to be able to deliver 740A for a few seconds, which should give me around twice the maximum torque. Anyone here used one of these yet?

Enough for now, here are a few photos. Yes, my Mini is seriously in need of a paint job...


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## skooler (Mar 26, 2011)

Looking good Malcomb.

Could you not swap the RCD for a less sensitive one?


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## MalcolmB (Jun 10, 2008)

skooler said:


> Could you not swap the RCD for a less sensitive one?


Thinking about this again, it's not the main RCD that's tripping. The electricians fitted a new (more sensitive) RCD between the distribution board and Pod Point when they installed it. This doesn't trip when the Pod Point cuts out, but to get the Pod Point to reset I've been turning the RCD off and on again.

I hear the relays inside the Pod Point click open about 20 seconds after the chargers start up, then the green LED on the front of the unit turns red. This doesn't happen when I disconnect one of the chargers.

Is there some kind of additional earth leakage detection inside the Pod Point unit?

... I'm beginning to wonder if it's the additional load of the second charger that's causing the problem rather than earth leakage, though that seems unlikely, as the chargers output a steady 30A at 80V (between them), and the charge point is rated at 3.5 kW.


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## skooler (Mar 26, 2011)

Ah! got it!

It's a PodPoint right?

There is a jumper on the inside of the unit. By default I believe it is set to 13 amps. You can change this to anything up to 40 from memory.

Do you have the manual? (if not I can email you a copy) There are instructions on how to do this. but it's pretty obvious, just open up the unit and play with the jumpers, on the one at work it's all labelled on the PCB tracks.

Hope this helps.

Cheers,

Mike


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## MalcolmB (Jun 10, 2008)

Thanks Mike, but I don't see any jumpers. Maybe the one you looked at was the 7 kW version? Mine is 3.5 kW.


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## skooler (Mar 26, 2011)

MalcolmB said:


> Thanks Mike, but I don't see any jumpers. Maybe the one you looked at was the 7 kW version? Mine is 3.5 kW.


Ah, sorry that's a different model to the one I've played with.

Perhaps there is something in the manual?

Cheers,

Mike


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## Redi (Aug 13, 2013)

This is the most amazing thing I've ever seen in my entire life 

I'm now also in the stage of thinking about electric Mini, preferably 2 motors solution. But since electric cars and Mini Coopers in general are scarce in Czech Republic I have a lot of questions to ask 

First things first, why DC motors and not AC? Is it just because of the price or is there another element? Also, were the rear seats completely removed?

Thank you for your answer


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## MalcolmB (Jun 10, 2008)

Hi Redi,

Thank you. Take a look at some of the other conversions here and you'll be even more amazed 
Yes, I went with DC mainly because of the lower cost. Off-the-shelf AC drive systems are much more expensive and I don't have the knowhow to build an AC system myself. Yes I removed the rear seats as it was the easiest place to install the batteries. 
I've actually been thinking of redesigning this to use just one motor - it would be a lot simpler in many ways and I realise now that a single motor would give me adequate performance. I still have a few 'experiments' I want to try with the dual setup though, mostly to satisfy my curiosity.

Have you got any particular motors in mind?


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## Redi (Aug 13, 2013)

I have no idea yet  (I've checked Prestolite webpage, but it seems that the AC motors are too long.)

Well, there are two ways IMHO. 1st the two motor solution like you did or the older solution with stock gearbox and one motor (which is "more dirty" and definitely heavier). Or is there any other alternative? 

As I don't have the necessary equipment nor the space to do this conversion by myself I would give the car to 3rd party company to do the conversion for me. (There is enough skilled people in here, but I bet none of them ever did anything to a Mini, mostly Škoda cars are being converted here, for obvious reasons.) That's why I was asking about AC motors, the people who handles the conversions are skilled enough to make the adequate wiring, electronics etc.

Also there is the problem with the batteries, not being able to use the two seats at the back is quite unfortunate but I guess it's better solution than storing them in the trunk because of weight and handling. I would probably use LiFePO but still...

What will be the max range of the car with all the battery packs fitted? I was thinking about at least 90 miles range with max speed at 70/80MPH for highway use. Is that even doable? Also, how is the handling? Did you already tried some longer route?


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## johnjcbs (Oct 10, 2012)

I like that android gauge setup,I have an extra tablet to try that with.


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## MalcolmB (Jun 10, 2008)

There are several alternative solutions: Here are a few other Mini threads just to give you some ideas:
http://www.diyelectriccar.com/forums/showthread.php?t=71039
http://www.diyelectriccar.com/forums/showthread.php?t=67066
http://www.diyelectriccar.com/forums/showthread.php?t=78125
http://www.diyelectriccar.com/forums/showthread.php?t=48283
http://www.diyelectriccar.com/forums/showthread.php?t=64941

Your speed and range requirements are both possible, but would need a heavy battery pack that takes up a lot of space. To get 90 miles of range, including some highway driving, you would need a battery pack with a capacity of (very roughly) 30 kWh. Using readily available prismatic lithium cells that would weigh around 270 kg and take up all the boot and rear seat space. If you can reduce your range requirements it makes things a lot easier and cheaper.

My Mini handles well, but the battery pack only weighs around 75 kg. To keep costs down I've chosen to use the smallest pack possible. The range is a little over 20 miles, but charging time is just two hours.


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## anachlores (Sep 8, 2012)

How does the car handle at speed? I've been working on a dual motor-independent drive system and I'm worried about motor timings/rpms. Do you notice different rpms at the same voltage for the two motors (i.e. does it pull in one direction over the other?)


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## MalcolmB (Jun 10, 2008)

Hi Anachlores,

I've tested the motors in three different configurations now:

*Single Alltrax driving both motors in parallel*
I've only tested this up to 50 mph, but the straight line stability was excellent. There was no tendency to pull to either side – I can take my hands off the steering wheel on a neutral camber road. In low-speed manouvering there is a slight increase in the self-centering effect of the steering, this is not a problem though.

*Single Alltrax driving both motors in series:*
Because each motor only sees 36V from the Alltrax controller in this configuration the top speed is limited to about 35 mph. As you might expect, the handling feels much as it did with the original engine and open differential. Low-speed manouvering is easy and straight line stability is good, with no tendency to pull to either side. It's quite easy to spin one of the wheels when climbing kerbs, which does not happen when the motors are configured in parallel.

*Two Alltrax controllers connected to a single throttle and driving each motor independently:*
Steering is extremely twitchy under acceleration, the car tries to pull to one side or the other. I don't know if this is due to the speed control response of the Alltrax AXE controllers (they don't have a torque control setting), but it is not safe for road use. It is possible that you would not notice this twitchiness if the motors were driving the rear wheels, but I still would not recommend it. I checked the motor currents and voltages with the car on axle stands, and they are within 5 percent of each other throughout the rev range under no load.

Right now I'm running the car in series mode, as it's fine for town use and accelerates well up to the speed limit (30 mph). I prefer parallel mode, but the acceleration is poor with the current setup. I need a decent battery pack and controller to unlock the potential of the motors.

Can you tell me more about your plans?


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## anachlores (Sep 8, 2012)

Thanks for the detailed response. I'm surprised the series configuration worked as well as it did. I agree that the two-controller solution is very dangerous. Even if you managed to get the voltage-rpm curves exactly the same, if one controller fails on the road, you would be in a world of hurt.

My plan was to run a pair of L91-4001 7" motors on 530 chain with a ~3.7:1 reduction at each wheel using sprocket size as my reducer. Driving the motors in parallel would be a soliton 1/jr so no shortage of power there. The setup would be on a rear engine, rear wheel drive custom chassis with independent front and rear suspension.

More info here: http://www.diyelectriccar.com/forums/showthread.php?t=78394


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## lockduke (Dec 25, 2009)

Hello MalcolmB any further progress on the mini


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## MalcolmB (Jun 10, 2008)

Hi Lock

Sorry for the slow reply but I've been up in the Scottish highlands for a few days. No real progress on the Mini, apart from giving her a coat of paint. I'm at the stage where she runs, but not very fast and not very far. I want to install a decent-sized battery pack but don't have the cash to spare right now, so I'm going to be ticking off those little jobs in the meantime – instruments, carpets and so on.


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## lockduke (Dec 25, 2009)

Yep I know what you are going through. I have the floor pans out of my 60 Ford Falcon getting ready to fabricate aluminum frame rails, to lighten the car and get better range and speed . My intended batteries were to be the 200 amp hr Winston or (snyoplies?) can't remember the correct spelling. I intend to install them in what was the drive-shaft tunnel by making it slitly wider and taller by lowering the floor pan to the actual bottem of the frame rails. The 11 inch (Kostov?) will be mounted in place of the 8.8 housing in the independent rear out of a mustang. Hoping to get a solaton controler and install it in the trunk to keep it dry and out of peoples prying eye's and find legs and walk away if it were out under the hood that will now be used for a luggage compartment or extra battery space if needed I intend to use 176 volts so there is room for voltage drop with decent miles and highway speeds. Our weekend home is 92 miles away, we can go the back roads which is what my wife likes, but some times you need to get there in a little faster pace that requires 70 mph on the highway here. Oh well I have bent your ear long enough I like your build and fab skills, you do tremendous work. Duke


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## epyon (Mar 20, 2008)

You did it an now we can all do it , you are the man . GREAT JOB !!!!! Just one" I told you so" ? I know you want too !!


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## haim (Feb 22, 2017)

I just join.
I am looking to convert a 2009 mini cooper clubman 
At this point I have two sets of Prius Battery packs.
Any one have any suggestions where I start??
thks


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## galderdi (Nov 17, 2015)

Excellent project you have there. I can't wait to hear how it all comes together. I wouldn't try it for the first time on the snow or ice.


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## MalcolmB (Jun 10, 2008)

Hi galderdi,

Thanks for the prod. I've not posted here for a long while but I still check the forum regularly to keep up to date with everyone's projects. Your autocross special looks like great fun and I really like the video updates.

After a long timeout I've just got back to working on the mini again. I was never happy with the chain drive system – even though it worked well it always seemed a bit clunky and was likely to need regular maintenance. I recently bought a small VW gearbox and I'm busy working on an adapter plate to couple one of my 7" DC motors to it. I reckon this should give me up to 50 hp at the wheels, which should make a decent runabout for use in town. I'll post some pics when I've made some progress.


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## jacksdad (Apr 13, 2015)

Hi MalcolmB

I was interested in your comment about the chain drive, i have just sent my car to get the controller and BMS setup and I have a two stage chain drive and quaife differential - what did you mean by cluncky ?? starting to get worried now - their have been some doubters but i have always been optimistic !!


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## MalcolmB (Jun 10, 2008)

Hi jacksdad,

All I meant was that chain drive seems a bit of a backward step in terms of automotive development. There's no reason why a well-engineered chain drive shouldn't be reliable – just look at all the high-powered motorcycles that use them.

Part of my aim when I started thinking about an electric conversion was to build something that was clean and maintenance-free, and although chain drive doesn't need a lot of maintenance it's still not fit and forget. Because of space restraints I was also forced to use 3/8" pitch chain and sprockets to get the gear reduction I needed, which is on the small side and was likely to wear faster than usual.

I'm looking forward to seeing your Rocket hit the road for the first time – with dual AC35s it should live up to its name!


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## galderdi (Nov 17, 2015)

I have a similar dilema on my next project. I stopped in at an industrial drive line engineering shop thinking I would be talking about chain drive. They convinced me that belt drive is the way to go. They sighted examples like Harley Davidsons and Superchargers using a broad band. Apparently they are more robust than chain. 

Then I was at a car/bike show a few days later so I looked over the Harleys. I was surprised by the diversity in the drive lines. There was even a wide range of sizes in the belt drives.


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## WolfTronix (Feb 8, 2016)

Here is another data point for belt drive, dual motor:










Note: Sprockets are rusty since this pic is from the restoration back in 2007:
http://www.wolftronix.com/E10/index.html

Hope that helps,
Wolf


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## MalcolmB (Jun 10, 2008)

galderdi said:


> I have a similar dilema on my next project. I stopped in at an industrial drive line engineering shop thinking I would be talking about chain drive. They convinced me that belt drive is the way to go.


I spent a lot of time looking at belt drives as well. Unfortunately the range of gear ratios achievable with a single reduction was too limited for me. Accurate alignment and tensioning are also more critical than for a chain drive. Here are some links with feedback from users:
http://amphibike.org/blog/scion-xb-ev/scion-xb-ev-construction/scion-xb-ev-drivetrain/
http://www.diyelectriccar.com/forums/showthread.php/noise-htd-belts-127226.html

What's your next project?


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## dcb (Dec 5, 2009)

just a suggestion, belt seems good once you are sure you have a ratio and everything sorted out, and can be retrofitted. Start with sprockets so you can experiment most affordably.


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## galderdi (Nov 17, 2015)

MalcolmB said:


> What's your next project?


At first glance my next project is very similar to my current one. Except this one will be much smaller and lighter. It will be a single seater with the batteries along side my legs so I can make the rear wheels much narrower. The front wheels will also be narrower but not as narrow as the rear. The cage will look very similar except narrower. I am aiming for sub 300KG. So I need more attention to detail. But now that I know what to watch for I am fairly confident.

This diagram isn't quite right but it is close enough to give the idea. See where my legs narrow up, that is where the batteries will sit. They won't go all the way back to my back. That way I can bring the rear wheels forward slightly. I am going to use an ADC 8 inch for the power.


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## MalcolmB (Jun 10, 2008)

I don't know much about vehicle design or your intended application, but the track looks quite narrow compared to the length. Is your priority straight-line speed?

If not, another possibility would be to increase the width and place the batteries and motor next to you, a bit like this:








(Taken from Dennis Palatov's inspiring website).


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## galderdi (Nov 17, 2015)

I agree, the guy that drew the diagram for me likes to take things to the extreme. Narrower is better for slalom. But the constraints of scavanging and working with second hand parts will mean the front will be wider than pictured. 

I am also reconsidering the engine/ gearbox configuration. I am going to take some measurements using the inline method I used last time around. in other words instead of chain or belt drive, the motor output shaft would have an adaptor straight to the gearbox input shaft. It will make the front wider that pictured. But it will take a lot less time, effort and money to build. so long as it isn't more than a few inches wider and so long as the steering isn't limited as a result I think that will be the way to go. 

I am 6 foot 4 and we are limited to a minimum wheelbase of 1810mm so I doubt that design would be suitable. Even the design I posted would need to be longer to allow my leg room.


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