# Budget ev build



## alex156jtd (Sep 11, 2014)

hi everyone, I've been thinking of converting a car to ev since 2014 and recently i decided to go through with it ,
Previously i had some unrealistic goals but now i reevaluated things and here is what i came up :
i will use a bmw e46 coupe or a volvo s60 mk1
range of 80-100 miles
capable of doing 80 mph
decent acceleration something like 8-9s 0-60
i will use a 13'' dc motor from a forklift
the donor car must be manual as ill use the original transision
ill make my battery pack out of 18650 cells , already got 2k cells(still buying them, i know i need more  )
i am pretty good with tools so i will do most of the work myself 
budget as little as possible,
I know that i need something like 30kwh battery pack to achieve my starting range.
i know that i need a charger 
i know that i need a motor controler
i don't know how to build them or where to get them from
What voltage my battery has to be, and is there a way to diy the motor controller and the charger, do i need motor cooling ,do i need battery heating?
i really want to learn this and buid myself and understand it, because when its done and something broke on it can't just roll in the first garage and ask them to fix it....
so please if you can shed some light on my build or have any sugestion let me know please
i also plan to keep extending the battery pack until i reach the limit that the car can hold,so the range will keep growing , 80 miles is the starting range .
Please dont try to suggest to chose a little car or something light etc as i do 40-60 miles a day in it and also put a large chunk of money into it so it will be one of the above state cars.
thank you


----------



## puddleglum (Oct 22, 2008)

http://www.diyelectriccar.com/forums/showthread.php/1-000-euro-ev-build-193217.html
Check out these and his E39 conversion videos. A little slow but really good info.


----------



## Duncan (Dec 8, 2008)

Hi
With a 13 inch motor you can throw away the transmission and use direct drive to the diff

You may be able to enlarge the transmission tunnel a bit to put the motor in there - which then leaves the entire engine bay for your batteries

80 mph with a 13 inch motor may require a higher voltage

My car with a 130v battery and an 11 inch motor would terminal out at 59 mph


----------



## alex156jtd (Sep 11, 2014)

Ok, what determines my voltage? The motor controller , the dc motor ? 
I do follow Damien and his new project gives me a lot of hope that I’ll find answers for my questions.


----------



## Duncan (Dec 8, 2008)

With a DC motor the controller will set the motor voltage to get the commanded current

UNTIL the controller is 100% - then it can't go any higher and the battery voltage = motor voltage

What will happen is that as your speed goes up the controller will raise it's percentage so that you still get the commanded current

When you get to 100% and keep accelerating the current will start to drop

My car with the 130v pack would take off like a Tiger with 1000 amps - but by about 50 kph the current was down to 500 amps and by 100 kph it was down to 200 amps - which was just enough to maintain 100 kph


----------



## alex156jtd (Sep 11, 2014)

So my battery pack, I was thinking to put 100 cells in series which gives me 4.2vx100=420v and 3.7v x 2Ah x100= 740wh. That gonna be 1 cell and I just parallel idk 40 of those cells to get the desired capacity. Is this a good way to wire my batteries or not. This way I have high voltage and every time I grow my pack just make another cell and parallel it on the system. Please let me know if this will work or if not what other options I should consider. Thanks


----------



## alex156jtd (Sep 11, 2014)

I bought today the motor, it’s a 12” dc motor out of a Smith electric milk float .Direct current, series wound, 1750 rpm.12/72volt input range.
I’ll collect it tomorrow


----------



## Duncan (Dec 8, 2008)

Sounds good - post pictures!


----------



## alex156jtd (Sep 11, 2014)

Duncan said:


> Sounds good - post pictures!


I just got home from collecting it 300mile round trip.
He also gave me a dc to dc converter maybe I can modify it to be usable in my project.
Here are some pictures


----------



## alex156jtd (Sep 11, 2014)

That motor is on the back of an suv not a little hatchback . It’s over 100kg. I don’t know how people move those motors so easy on these YouTube videos. I consider myself fit train regularly but that motor is heavy.
Is that good or bad?


----------



## Duncan (Dec 8, 2008)

Hi
My 11 inch Hitachi was 102 Kg - so about 100 Kg is normal

I went direct drive - no gearbox just a driveshaft to the diff


----------



## alex156jtd (Sep 11, 2014)

I want to keep the gearbox as I have to travel every day 60 miles on motorway plus the city and B road drive to and from work


----------



## alex156jtd (Sep 11, 2014)

I even think to get a 6 speed diesel gearbox as its geared for lower rpm


----------



## Duncan (Dec 8, 2008)

Hi Alex
What advantage do you think that your gearbox will give you?

Gearboxes gear things down top gear is normally 1:1 (or close)

I can spin my rear tyres in "top gear" - as in without a gearbox

Your motor will give tons of torque - and as long as you give it enough volts will give enough rpm
A gearbox will give you more torque - which you probably won't need (spin tyres) but won't give you any more speed


----------



## brian_ (Feb 7, 2017)

Duncan said:


> Gearboxes gear things down top gear is normally 1:1 (or close)


Modern transmissions have overdrive (output faster than input) ratios for the top ratios - in any 4-speed automatic there's typically one overdrive, 5-speeds have two overdrives (about 0.7:1 for the tallest), and with more ratios there are more overdrives, although the tallest ratio isn't much higher.

Similarly in manuals, the top one or two ratios are typically overdrive.

On the other hand, adding a complete transmission is a heavy and bulky way to get a moderate overdrive, if that's the only ratio that is useful to you. There have been separate overdrive transmissions (a single-speed, or a two-speed with direct and overdrive), but they're hard to find now.


----------



## alex156jtd (Sep 11, 2014)

I will keep the gearbox, it’s easier for me that way. I have my reverse gear mounting point for gearbox etc , I only have to make a plate to mate the gearbox and the motor. I don’t have a garage, lift etc. This build is happening on a driveway and a shed. I try to take the easy route .


----------

