# EV a 1965 Hillman Imp ??



## rydz (May 16, 2008)

Hi everyone

I have been reading and looking up different projects on here for a little while trying to determine if building an EV is right for me.

I have a Hillman Imp that I bought some time ago,its basically a basket case but that is not a problem.deciding if going EV or a 2 Cyl Deisel is.

The Imp is a small 4 seater british car,rear wheel drive with a rear mounted motor and gearbox,similar to an old VW bug.

So I was thinking if I replaced the dead motor with an electric ,it could make a neat and interesting EV that we could use to run around the area with and at the same time would satisfy my eldest daughter who has the desire to save the planet!

now we get to the stuff I have no idea about.

How big and how many batteries (voltage ect)

The car is about 1600Lbs complete and will carry 4 adults,I will probably convert it into only 2 adults.The original motor had about 50 HP,I dont think I need it to be that strong,but I dont want to look like a fool either and it should be able to move along at say 30 mph or so.

I will keep the transmission,no clutch,not worried about the controller yet at this point (probably use the open source controller,as I like that concept).

I figure by limiting the car to 2 people that should allow me to use an extra 300 ils of batteries where the people used to be.

I would also mount some of the batteries in the front where the gas tank used to be (this car was always nose high,this should bring it down a little)

I am not worried about suspension,brakes,or anything with the body,I have done a bunch of cars in the past,so this part is easy for me.Brakes and suspension upgrade are quite easy to find for the Imp so that is not a concern either.

How do you determine how much battry power to shoot for when building an EV.

as close as I can figure ,After stripping out the ICE parts and limiting the car to 2 people,I will have availible about 300lbs (the electric motor will weight quite a bit more than the ICE motor it replaces) without performing any uograde or increaing the normal weight if the car.

I am assuming I can go a bit higher and contain at least 400 to 450 lbs of batteries between the front center and rear of the car without too much problems.

So basically I am looking for 30-35 MPH,with a range of say 30 miles (can be less in both cases) If all goes well the entire car would weight less than 2000Lbs,all in.

what sort of motor would I need,and what sort of power would be required.

Thanks a bunch guys

Paul


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## Woodsmith (Jun 5, 2008)

Do it! It will be great!

I wouldn't think you would need much motor for your speed and range.

Have a look in the Garage for VW Beetles as the layout would be sort of the same, rear motor hanging off a small transaxle. I think the imp would be lighter though so you would save on batteries or improve the range. Handeling in an Imp would be better too.

Have you got a photo of the Imp?


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## rydz (May 16, 2008)

Hi There

no good pictures of the Imp right now,it spent a few years in dry storage,then the roof collapsed,spent a few months at my buddy body shop,then back into storage and will be moved (lost storage again!!!) next week or so.

All the interior is removed and the ICE is out already,but it was quite complete when I bought in New York many years ago.

I will probably start putting together the bits I need over the end of this winter,and get the nuts and bolts of it assembled in the spring (when its not -20C outside)

I will post some pictures when it gets a little nicer outside

Thanks
Paulo


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## electromet (Oct 20, 2009)

rydz,

An Imp sounds like a good jumpoff point. It's very light and compact. It's not especially aerodynamic, but it's got a relatively small frontal area, and your speed parameters don't require ultra-sleek.

As for the clutch, you might reconsider keeping it, as rear-engined vehicles tend to to have a rather vague feel (can you say spoon in a mixing bowl) to their linkages. Coupling that lack of precision with trying to match rpms might lead to the early demise of your transmission. You can lighten the flywheel by removing the ring gear, and possibly find an aluminum flywheel that will lessen the rotating mass. If you ask some of the T-1 VW converters, I think you'll find that they tend to favor keepng the clutch.

As for motor weight, the Imp motor is quite light (aluminum firepump motor?), but I think it still weighs over 150#. I think you'll find that an 8" DC motor weighs less than that. If you're able to keep your curb weight under 2100# or so, you should be able to achieve your performance objectives on 96V or less.

My project is similar in size and weight ('57 Metropolitan) and the EV calculator using a heavier 9" motor and 96V shows better numbers than you're asking for. I say "Go for it!"


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## madderscience (Jun 28, 2008)

A fellow with a small fleet of sunbeam imps used to have his workshop near where I live. One of them was actually an old EV conversion but it was long since inoperative and he was using it as a parts car. I spent a few minutes trying to convince him it would be neat to get it going but he was into SOVREN (society of vintage racing enthusiasts) competition and not into EVs.

with something that small and your low top speed and modest range requirements, you could get away with a 72V conversion using a 6.7" or 8" (bigger is torquier but lower peak RPM) motor. Another thought is you can get an AC motor/controller combo for 72-96V range these days. A bit pricier than DC but maybe worth it.

As for batteries, six 12V golf cart batteries would weigh about 400-500lbs total depending on the specific model and give 25 miles of usable range or so presuming you don't have too extreme of terrain. the next sizes up in lead acid would be nine 8V batteries (500 to 600lbs) or twelve 6V batteries at about 700lbs, with proportionally greater range. Of course you could go lithium for a few thousand more and have a 100AH, 72V pack that probably only would weigh a couple hundred pounds and have similar range to the 700 pound lead pack: probably 40 miles or so. 

A 72V setup can be pretty economical to build. New parts (most economical options): 1200 or so for the motor, 5-700 for controller, 300 for charger, 1200 for batteries, 500 to 1000 or so for everything else, roughly speaking. Ebay and other scrounging of course can reduce that considerably.

The downside to a 72V conversion is increasing performance requires you to change out pretty much everything: controller, charger, much of the safety equipment (fuses, contactors, etc) and there is a big jump in component prices going past that.

So if you really will be satisfied with a top speed around 40-45mph (typical for a 72V small car) then you can keep the cost down, but if you ever plan on performance upgrades you might as well build for it up front.

I agree with those who say keep the clutch.

Good Luck.


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## Duncan (Dec 8, 2008)

Hi RYDZ,
lovely idea, the Imp was a nice car,

Couple of suggestions
If you use the existing transmission and a DC motor you may have problems with top speed as the (fire pump) engine in the Imp is a real screamer 8000rpm+ which means the overall gearing is a little low

If it was mine I would go with 120v + and Lithium as it seems such a shame to turn such a neat light car into a lead sled

The motor will weigh more than the engine - I think the engine and the transmission together weigh less than 150 lbs


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## rydz (May 16, 2008)

Hi Guys

Thanks for the replies,lots of good information so far.

I do have some silly questions though,if I go with a 72,96 or whatever total voltage source does the motor requirements change or is the controller the only "responsible" item for maintaining the motor in unfried condition?

I ask because I will start with the motor purchase in order to mount that in the chassis and to the tranny,so i want to make sure I purchase the right thing first.

So if I decide to go with a higher total voltage source do I have to match that to the motor design I start with?

One of you mentioned a 72V total source and that it might fit requirements I set out,if using a 8" warp motor would that work for both a 72V and a 96V design?

Sorry for the dumb questions,but I have a habit of jumping in then making the wrong choices and having to start over again,and since we are still close to the start of a new year,I figured I might try getting it right the first time and seeing how that works for me.

Thanks again

Paulo


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## electromet (Oct 20, 2009)

rydz,

The short answer is "yes", the Warp 8 will handle either 72V or 96V. As far as the controller is concerned, you just need to find one that will fit the 72-96V parameter. Realistically, you can apply as much voltage as you want to the input of controller and adjust for the output of your choosing. That's a pretty simplistic explanation and there are others here who can flesh it out with specifics.

So, you can build for 72V with an eye for 96V at a later time. Just purchase a controller capable of handling both voltages. You'll just have to plan for placing additional batteries in the chassis.


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## electromet (Oct 20, 2009)

rydz,

Duncan is correct about the final drive ratio. My research shows it to be in the range of 4.86:1. That's going to significantly reduce both range and top speed. With the bottom end torque available with a series dc motor, there is no need for such a high gear ratio. Ideally that should come down to less than 4.0:1 to bring your range and speed up. Some of the difference can be made up with taller tires, but not enough to make a major difference without adversely affecting the handling. Some of our friends in UK might be able to tell you if different gearsets might be available. Another option might be to swap in a VW transaxle. There are motor adaptor plates availabe for the VW trans, and I'm sure there are none currently available for the Hillman.

Just my 2 cents' worth.


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## dtbaker (Jan 5, 2008)

I would suggest:
- 8" dc motor
- regular dependable inexpensive 1221c (400amp) Curtis Controller
- 96v of 100aH LiFePO4 if you can afford up-front $5k
If you go Pb, consider 12 x 8v golf cart batteries for $2k w/ watering system
- keep the clutch for alignment ease and drivability by 'anyone'

...don't under-build your power/range and be unhappy later. a 96v system with 8" motor will be great for in-town and speeds up to 60+ mph. With 10kWhr or so on board you'll have enough range where your average day will be very kind to your batteries for max life.


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## Duncan (Dec 8, 2008)

Hi rydz

more musings about your Imp

It is a light "modern" car do not get any VW bits too near it - they are at least two generations older

You need a high revving motor 
- I am using an old DC forklift motor 
In your shoes I would be looking up AC motors and controllers and keeping the voltage high 

If you do use a DC motor have a look at the "using a fork lift motor" thread,

With a DC motor the available rpm is related to the voltage, 
using a low voltage system will limit your max rpm

On the other hand having your motor explode due to over-speed will also limit your driving


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## sunworksco (Sep 8, 2008)

Pull the whole drive-train out and install an ac motor with 100volts 100amp life batteries.Use an aluminum tooth pulley/belt drive with a 7-1 gear ratio.The motor weighs around 125lbs.Mount half of your batteries up front and the rest in the rear.Try to get a 50-50 weight distribution.Put some lighweight wheels and tires with low rolling resistance and if the floor has rust and needs replacement use aluminum sheet and extrusions.Fiberglass racing seats can be had cheap if you keep your eyes open.The originals are death-traps anyway.I cut my teeth on British cars in the early sixties and really like your car.It was way under-appreciated and had a few drive-train flaws which completely go away with an electric drive-train installed.That is because the ev components can be installed low and balanced front/rear by shifting the weight.There was a very good magazine article that I read a few months ago about your car.I think it was British Sports Car magazine.


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## Ferguscarr (Mar 22, 2018)

Dear Rydz

Just wondering how your Hillman Imp project went? I am interested in buying and converting a 1965 Hillman Super Minx and was wondering whether you had any pointers or lessons from your experience. Also does it being an Automatic make it easier or harder to convert?

All the best

Fergus


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## Karter2 (Nov 17, 2011)

Very few commonalities between the Imp and the Minx..
.....other than the Hillman badge !
Throw the autobox away (or sell it) and look for similar conversion vehicles like Morris Minors with inline front engine, rear axle drive , layout etc..
...and copy them.


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