# '99 Porsche 911 conversion - student project



## RIPPERTON (Jan 26, 2010)

With such low voltage you will have low motor rpm so you will have to keep the gearbox, hope its manual and also keep the clutch because you will be shifting. Those 400Ah cells should be gutsy enough to supply the current you want and the 39 odd kWh should get you more than 200 mile range if you utilise the regen function as your main cruising brake.
Looks like you are on the right track, your main challenge is fitting those cells in and ending up with the right fore aft weight bias.
You could also do a bit of research into motor rpm and choose a controller and battery voltage that will give you a similar motor rpm to the flat 6 that came out so you will get similar rev range and accel.
This could mean going to 50 series with a smaller cell like 300A.
http://www.ebay.com.au/itm/Electric...C51-Curtis-144-Volt-Kit-EV-West-/111108030421


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## mlohara (Nov 29, 2014)

Thanks for the response! The car is manual transmission. What gears do you think we'll need? I would love to be able to get rid of the clutch to reduce the weight, and make the car easier to drive. If we use 300 Ah Li batteries at 120 V, would we be able to get away with not changing gears? I don't understand how changing the voltage will affect this. Can you suggest some reading? Thank you so much!!!

Michelle


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## RIPPERTON (Jan 26, 2010)

mlohara said:


> Thanks for the response! The car is manual transmission. What gears do you think we'll need? I would love to be able to get rid of the clutch to reduce the weight, and make the car easier to drive. If we use 300 Ah Li batteries at 120 V, would we be able to get away with not changing gears? I don't understand how changing the voltage will affect this. Can you suggest some reading? Thank you so much!!!
> 
> Michelle


You wont use all 5 speeds normally, maybe starting in 2nd and shifting to 4th for normal traffic driving but you can make an aluminium flywheel for lightness and definitely keep the clutch. You wont be slipping the clutch on standing starts so you wont need the original heavy steel flywheel.
Without a clutch your shifts are very long and makes the car more difficult to drive not easier.
Single speed will need about 450 to 700 volts and a 9:1 reduction gearbox which you don't have.
300Ah and 120v will still need to shift.
Your math right now is to see how much battery you can fit into the chassis so you can configure your battery. Do different configs, 50s 300Ah, 50s 200Ah and 30s 400Ah. Measure the space you have in your car and see what you can fit in there.


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## steelneck (Apr 19, 2013)

My advice is to go higher in volts and less amps, that will make it easier to find a controller with enough amperage. Remember to chose a motor that can deliver the continuous power needed, then it will also be able to deliver enough acceleration power. Your car will be quite heavy with the range you want, so it will need quite some power on average, which calls for a reasonably big motor. If you go with low voltage the motor has to withstand a lot of amperage just to keep steady speed.


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## grip911 (Dec 14, 2011)

using a dual 35 at 144v or more wore would definitely solve your problem. 200ah batteries would be more than adequate for 100 mile range at that voltage.Save a little on batteries and spend more on the propulsion end


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## Moltenmetal (Mar 20, 2014)

Plenty of warnings here to not use the AC50/51 without a clutch. Too little torque to make a satisfactorily zippy car. A gutless 911 would be a real shame! Keep the clutch and don't sweat the flywheel- that weight in practice doesn't matter much if you retain the clutch and have regen.


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## grip911 (Dec 14, 2011)

Moltenmetal said:


> Plenty of warnings here to not use the AC50/51 without a clutch. Too little torque to make a satisfactorily zippy car. A gutless 911 would be a real shame! Keep the clutch and don't sweat the flywheel- that weight in practice doesn't matter much if you retain the clutch and have regen.


My first build was my 911 without a clutch and using an AC-50. 
Felt great at first, but when the novelty of driving an electric car wore off a little, I noticed the shortcomings of not being able to shift. .No amount of practice,while shifting with regen on does any good, especially down shifting.
I agree that keeping the clutch ,makes a way better ride. As far as running an AC-50/51 in a 3000lb. car ,clutch or no clutch, it is a little short of adequate.(but not by much) IMHO


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## mlohara (Nov 29, 2014)

Thanks for the input! The dual 35 would be awesome, but I think it's a little more than we want to spend. Any opinions on using the AC-76 at 144V? Will it be too wimpy too? 

grip911 - What do you wish you had used instead of the 50? What batteries did you use?


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## Hollie Maea (Dec 9, 2009)

mlohara said:


> Thanks for the input! The dual 35 would be awesome, but I think it's a little more than we want to spend. Any opinions on using the AC-76 at 144V? Will it be too wimpy too?
> 
> grip911 - What do you wish you had used instead of the 50? What batteries did you use?


Going to the AC-7x series from the AC-5x won't gain you any power. All it does is give you more torque/amp at the expense of rpm/volt. That just means you will use a different set of gears to drive around. The limiting factor for the HPEVS systems is the controller, not the motors. So the only way to really get more power is to use the double motor AC-35 so that you can use two controllers.

Honestly, I wouldn't go with anything less. The single motor HPEVS systems are underpowered.


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## DavidDymaxion (Dec 1, 2008)

I have an electric 911. I'm way behind on updating my web page, but there are some good tidbits on my web page:

http://ExplodingDinosaurs.com

I think the 911 is a great choice. I'm going with 12P48S 8 Ahr Headway cells. I think I have room to expand to 12P80S, without putting cells into the passenger compartment. They were about the cheapest $/kW (good for power). I estimate with the 12P48S, 15 kWhr I'll have about 50 miles of range. It has turned out to be a lot of work hooking 600 of these little cells together, though!

Definitely keep the clutch. I found it hard to shift without. Kennedy Engineering Products supplied a lightweight pressure plate (the pressure plate is very heavy compared to other cars), and I bought a lightweight Fidanza flywheel. Don't forget to ditch the starter ring gear, it unbolts and isn't needed any more.

Here is a pic (sorry it is sideways) of my rear battery boxes, motor, and motor mount:










Note I flipped the stock motor mount to be on top, so it freed up room to sneak in the battery boxes underneath it. This also uses the stock rubber motor mounts. I think this is important, as the transmission is rubber mounted, so you wouldn't want to flex solid steel motor mounts in the back. The battery boxes are riveted to the sides and back of the motor compartment, and riveted to the square tube in front. The pics show just 1 layer of Headways, a 2nd layer will go on top of that layer.

With some coroplast I'm planning to have air come in the engine lid, go through the motor, and be blown out the bottom, similar to the way the ICE did it. This will help keep brush dust away from my controller (not shown) and batteries.

To my surprise, even with all the batteries, the motor, and me kneeling on the bumper the rear of the car is still a little high. Luckily the 911 suspensions is adjustable, or I can buy a lighter torsion bar to get it back to stock height.

Good luck with your project, it'll be a great learning experience! I'd love to see progress updates and pics.


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## Moltenmetal (Mar 20, 2014)

Not at all underpowered for my 1800 lb Triumph Spitfire, but for a 3000 lb car an AC50 might feel a tad gutless. Especially when the donor was a fast car, which can't be said in my case. The Spitfire was never any kind of performer with its garbage Leyland engine, so the AC50 is an improvement to say the least.


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## grip911 (Dec 14, 2011)

mlohara said:


> Thanks for the input! The dual 35 would be awesome, but I think it's a little more than we want to spend. Any opinions on using the AC-76 at 144V? Will it be too wimpy too?
> 
> grip911 - What do you wish you had used instead of the 50? What batteries did you use?


Actually the AC-50 was fine for my 911 because I weighed in at 2380lbs.
I did eventually siamese 2 50`s together which was more in line with the power I used to have in the ice engine. Batteries were sinopoly 200ah and ugraded to Liyuan supercapacitor hybrids for the twins.


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## mlohara (Nov 29, 2014)

David - thank you for the great info. I think I'll copy your battery and motor layout if you don't mind  I found your website incredibly helpful. It feels like I've been working on this project non-stop since Thursday (the proposal is due in a few days!), so when I'm a bit more rested I may have questions for you, if that's ok. For now, THANK YOU for sharing your knowledge!!!


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## mlohara (Nov 29, 2014)

Did you consider adding a small, cheap dc motor instead of another 50? I'm thinking about getting the 76 with dual shaft so that I have options later on, when I might be inclined to spend some more $$$ on this project.


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## DavidDymaxion (Dec 1, 2008)

You are welcome to the info, glad it was of help!


mlohara said:


> David - thank you for the great info. I think I'll copy your battery and motor layout if you don't mind  I found your website incredibly helpful. It feels like I've been working on this project non-stop since Thursday (the proposal is due in a few days!), so when I'm a bit more rested I may have questions for you, if that's ok. For now, THANK YOU for sharing your knowledge!!!


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## n1div (Jan 6, 2015)

Here's a Porsche member that just completed his. You could ask him for any suggestions/tips.

http://rennlist.com/forums/996-forum/710545-going-electric-with-my-996-a.html


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