# Electric Formula Vee race car



## Duncan (Dec 8, 2008)

Hi Mike
Where are you - put your location on your sign in

Prius batteries are not very good for that - better off with Chevy Volt modules - or for maximum lightness and performance (+risk) RC Lithium poly batteries

Power - a "tuned" forklift motor simply has it's timing advanced to allow higher rpms
You can put a huge amount of power through a 9 inch or 11 inch forklift motor
Several hundred horsepower - and it probably won't melt!

Controller
I'm using a prototype Paul & Sabrina OpenReVolt - 1400amps and 350v 
See if Paul has any boards left to sell you
Otherwise a "Zilla" or a "Soliton"
There is a relatively new controller from Australia - Zeva - not as powerful as the others 1000amps 150v - but that is still 200hp


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## Mike955 (Dec 4, 2016)

Hi Duncan,

Thanks for the fast reply. I live in the UK. I just have signed up for the forum. Thanks for the info regarding the technology. It looks much clearer now to me. Don't know if I can get Volt batteries cheaply as this car is very rare here compared to the Prius which is the workhorse for almost every private cab.

Once again many thanks.


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## Tomdb (Jan 28, 2013)

Since you want to do hill climbs, I would suggest going with RC lipo's if you want max preformance for the weight. Also hill climbs are short bursts and RC lipo's are great for that.

I think packaging the chevy volt batteries into the formula V chassis is going to be an challenge, but a fun one.

Quite a similair build to the one you want to do http://www.evalbum.com/2559


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## Mike955 (Dec 4, 2016)

Hi Tomdb,

I had this afternoon a look into this Chevy Volt batteries and I think they are a bit awkward. I was planning to build side pods to accommodate the batteries. Is there anything special I have to watch out when using RC lithium batteries in terms of heat etc?? As I said I'm new in this whole topic but it's really fascinating as it seems to be the future.

Cheers


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## Tomdb (Jan 28, 2013)

The rc batteries have the issue of having quite a wide spread of quality. This means that some cells will be quite weak compared to others, so a bms is required along with heat monitoring. 

These cells will also produce quite some heat, however since it is a short discharge time. Due to only the need of functioning for one run at a time a good forced aircooling setup is good enough. 

By comparison the Chevy volt/Opel-Vauxhall Ampera, the batteries are much more mature and of a higher quality so better matched. 

Where in the UK are you? I am located in Warwickshire.


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## Mike955 (Dec 4, 2016)

Hi Tomdb,

So I understand I might save money on the RC batteries but spend more on additional equipment for cooling / monitoring compared to the Chevy Volt batteries which are ready to go?

I'm located in Surbiton/ Surrey 


Regards


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## Tomdb (Jan 28, 2013)

Money should not be an issue, do a calculation on roughly how much energy would be needed to do a run. This will give you a figure to aim for in terms of KwH (energy).

Then figure out how much voltage your motor can take at max.
Then the rest will sort itself out in terms of amp hours. (Energy/voltage=Amp hours)

However then you need to take your max current draw and check if your batteries can output this.

I would personally go with a pack of A123 20amp pouch cells if you could get them for a good price. Depending on the voltage you are going to run a Chevy volt pack would be fine, or a part of a pack might even be enough. 

This guy runs insane currents out of these batteries. 1400 amps on two packs, this would equate to roughly 700 amps per pack string. A chevy volt module has cells in series to make roughly 45ah, so the draw is 15.5C (700/45). This is quite high for automotive cells but peanuts compared to rc lipo cells. A chevy volt pack is 16 KwH so two is 32 KwH.

https://www.youtube.com/watch?v=_dTmndAXsTs

If you say your run will last a minute or three and you will draw a max of 150KW then you would need worst case 7.5 KwH (3/60*150) completely untrue, but you would not want your pack to completely cave in voltage during the race because it hurts your performance.


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## Mike955 (Dec 4, 2016)

Hi,

That brings light in the dark. One run is not longer than 3mins but you might have up to 10 runs a day. So in this case it would be 75 instead of 7.5. I think first I should figure out which motor and start with the motor and then the batteries. What is your recommendation regarding the controller? Is it possible to convert one from a forklift where the motor is coming from?

I hope you don't mind so many questions!


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## Duncan (Dec 8, 2008)

Hi Mike
You almost certainly won't be able to use the forklift controller
The issue is voltage, rpm and power

My motor was 48v and 10Kw - at about 1500rpm - not very useful for a car!
You need a controller that will work at at least 150v - more is better - and the components in a 48v unit will NOT be rated at those voltages

Energy requirements
You will not cannot be using max power for your 3 minutes -
you will hit the go pedal
Your controller will supply 500amps to the motor - but that will only need 15v
So the controller will take 50 amps at 150v from the battery and produce 500 amps at 15v for the motor
As you accelerate the motor produces "back EMF" and needs more voltage until the controller is maxed out at 150v 500amps battery and 150v and 500amps motor
If your voltage is not high enough then the motor current will not stay high at higher revs
With my 11 inch motor 130v would only push 200 amps through at 100kph (about 4000rpm)
So you can't "use" full power until your speed is up - and you will almost certainly be immediately hitting the brakes for the next corner
So your actual energy requirements will be substantially less than 1/2 of your 7.5Kwhrs
Weight is not your friend! - you don't want to carry more batteries than you need


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## Karter2 (Nov 17, 2011)

Would you go to a race day without spare fuel for your ICE ?
Obviously not,.. So you need to plan on having spare fuel for your EV.
A 5-8 kW charger and 10kV generator would help if there is no high output power points available.
When you are not racing you should be charging.


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## Tomdb (Jan 28, 2013)

If I were you I would make the pack swapable. Keep the weight as low as possible so you can run with one pack and charge the other one, then swap and charge. This is the lightest solution, any other setup will be overkill and too heavy so noncompetitive.

What kind of speeds are you expecting, might be worth considering going to a single reduction.


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## Mike955 (Dec 4, 2016)

Hi Duncan,

Thanks again for your reply. I looked araound regarding a controller. Did I get this right, the more amps the controller "feeds to the engine" the more revs it will have?! I thought before that the higher revs is enabled through the advancing of the motor?! I was thinking to run on a system of 144V. 

Cheers


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## Mike955 (Dec 4, 2016)

Hi Carter,

I was thinking about this as well. It crossed my mind that solar panels could be installed on a enclosed trailer to create extra energy. 

To be honest I'm still struggling a bit with some calculations. Don't know how I can get value for how much energy I will need per run... obviously it's different from track to track, weather etc...


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## Mike955 (Dec 4, 2016)

Hi Tom, 

I'm considering a top speed of about 120mph. It could be less however as I never raced here in UK ( as I'm German. Did some sprints back at home in the past ).


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## Duncan (Dec 8, 2008)

Hi Mike

Amperage = Torque

Your controller controls current - you select the required current with your throttle and the controller reduces the voltage to achieve the desired current - until it is 100% and cant do any more

Your motor needs some voltage to push the current through (10v or so for 500amps)
But the motor develops back EMF - a voltage proportional to current and rpm

So a normal forklift operates at 1000rpm and 48v
To develop the same or more torque at 4000 rpm you need four times the voltage


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## Mike955 (Dec 4, 2016)

Thank you Duncan. I got it now.


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## Karter2 (Nov 17, 2011)

Mike, ...ref charging.
You would be doing well to get 1-2 kW from a solar trailer roof......on a very sunny day, with perfect panel allignment.!
Thats not a reliable or large enough , source for a race car to depend on.
( do you only race on sunny days ?)
Maximum performance needs the pack to be at max voltage, so you need a charger to keep it topped up.
OK a rough "Guesstimate" here....
3 min run duration, 
Average 75 kW
......hence about 4. kWh used.
So you need a charge system that can replace 4kWh in whatever time you have available between runs ?


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## Mike955 (Dec 4, 2016)

Hi Karter,

I wasn't considering the solar panels as a main charging source. It's a good idea to have fast removable battery packs... I'm planning to visit some competitions to see how much time there is to charge. 

I hope that some clubs would allow to let the car compete. I asked one and they said already no  

Is there a method to measure the required energy to run the motor let's say for a minute on a lower voltage on a bench? Don't want to spend thousands in batteries just to find out that I bought too many.


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## Duncan (Dec 8, 2008)

Hi Mike

I used to do sprints and hill climbs in the UK (back in the 80's)
There were limits about the length of the events - 2 minutes was a long long event

We used to get 1 practice run and two timed runs -

Top speeds - these were mostly lower speed events - on some venues you would get past 100mph - on a lot of venues only about 70mph

You need to get yourself a competition license and a copy of the "Blue Book" - see what you need to do to be legal

As far as the Club is concerned - you will need to be a member of a club - when I "went electric" my club made me work as Club Secretary for five years as a penalty for not using an engine

Energy usage - how much fuel would you burn in a run?
Petrol has 46 MegaJoules per Kg = 12.8 Kilowatt hours - because an IC engine is only about 30% efficient that is the equivalent of about 4 Kilowatt hours electrical

So if your formula V would burn 1Kg/run that would be 4 Kwhrs -


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## Mike955 (Dec 4, 2016)

Good morning Duncan,

I took in consideration to enter the Javelin Sprint Series. They claimed to be able to get up to 8 runs but I asked them if they would allow an EV and they said no. 

I will contact the MSA regarding the topic with EV. I read in a thread that they created a workshop of how can be used in competition. But that was 2010.

When I used to do sprints in Germany ( we call it Automobilslalom ) it was mainly on kart tracks and followed the same principles. 1 practice run and two timed. But we used to do 2 or 3 laps...

so I should be ok with 12kwh-15kwh for the whole race...


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## Duncan (Dec 8, 2008)

Hi Mike
You will probably not be allowed into a specific championship series as it will quite restrictive
As a "weird car" you will be competing against yourself and any of your pals that you want to compare with - it's fun just to beat them even if you are not in the same class
So I would expect them to let you drive - but if you start beating people in the class they put you in expect to be promoted to the next class


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## Mike955 (Dec 4, 2016)

...hi Duncan, that's what I thought. My hope is that more people are following... it's sad that this Javelin Sprint Series wouldn't allow EV unless it's built by a car manufacturer... they claim they are not under the MSA and thought they would be therefore more approachable...


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## galderdi (Nov 17, 2015)

What you are trying to do is kinda similar to what I am doing. A light weight car with the electric power to take advantage of standing starts. My car is 530kg when I do a khanacross (think of a hill climb without the hill) I can manage about 12 - 14 runs comfortably. That is running with 7kwhs of Chev Volt battery.

But I do agree with the previous feedback, the volt packs are going to be trouble to fit.

Apparently there is a another gent around here who has run an electric race car in our local hill climb. I beleive he had LIPOs. He had an incident where he was knocked out and the batteries overheated and caught on fire. The first responders tried to put it out with their standard extinguishers which only agrovated the flames. I personally feel more comfortable with Lithium Ion as they are more stable plus the volt batteries have the cooling built in. 

Take a look here:
http://www.diyelectriccar.com/forums/showthread.php/autocross-ev-special-166009.html


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## Mike955 (Dec 4, 2016)

Hi,

Thanks for reply. I had a look into this Volt / Ampera batteries. I guess you run on 3 modules and 144v in total?! I agree that the Li-Po's are a bit dangerous.

I found a motor which is relatively small,made in Germany and not too pricey. Unfortunately I don't know how far you can stretch this engine. And if it's therefore suitable for my vehicle. It's called perm PMG132.

I tried to open the link but the page was empty. I'll try it later again!

Cheers


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## galderdi (Nov 17, 2015)

I'm not sure what is going on with the link. It still works for me.

My pack is 3 of the 2KW modules and 1 of the 1KW modules
In total it is 42S3P


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