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Update on my EV Porsche fiasco.

12K views 13 replies 8 participants last post by  drgrieve 
#1 ·
In 2008 I bought a 2003 Porsche 911 Carrera and contracted with a conversion shop in West Palm Beach, FL to convert it to electric. The whole thing was a disaster.

I introduced myself in THIS thread.

I talked about the car in THIS LONG thread, begun when I thought all I needed was a better controller.

I asked for and got battery advice in THIS OTHER thread.

Briefly, the conversion was botched so thoroughly that the car, though drivable, was a death trap, and had hardly any power. I found a local shop willing to take on repairs, and they completely disassembled the car, totally re-designed the arrangement, and re-assembled it, including a water-cooled 1,000-amp controller, replacing the 500-amp controller that the original shop used in place of the contracted 1,000-amp controller. But it turns out that, in addition to the botched assembly, the original conversion included a severely damaged battery pack. I heard rumors about an "incident" on the bench at the original shop, but have no actual knowledge of what happened.

Now it turns out that the pack is in even worse shape than we had previously thought, and apparently failing fast.

One option would be to install a new lithium pack at around $12,000 to $15,000. One of the people who's been working on the car insists that with a new pack it would beat the Tesla Roadster that I bought almost a year ago, after giving up on any hopes that the Porsche would ever actually be finished. I don't believe that.

Four years ago, when this project was begun, with an estimated completion time of 4 to 5 months, I was supposed to have had a car with half the range, half the acceleration, considerably more seating comfort, and twice the interior space as a Tesla Roadster, and I was supposed to have it a year or more before I'd have been able to get a Tesla.

Which brings me to the point and subject of this post:

The Porsche has a completely shot battery pack, and is not worth more than about 1/5 of what I've put into it. I don't want to spend another $15,000 putting a new lithium pack into it. But OTOH, I no longer need the 125-mile range I wanted when I embarked on the project. The Roadster is and will remain my daily driver and my main car. But if I could get the Porsche back on the road, with top-notch performance, even with only 30 or 40 miles of range (for 15 to 20 miles range to 50% DoD) I could drive it to the store and back, and for occasional short errands.

So I'm contemplating putting lead-acid batteries in it. Lower cost and simpler battery management might make it worth my while, and I'd get some use and enjoyment out of the car (it is a beautiful car!) At least it would be on the road and not rusting away in the corner of a shop somewhere. The lower impedance of lead should allow high power, at the cost of greatly reduced range, now that range is no longer important to me.

I'm posting this partly to update anybody who was following the saga and is interested, and partly to see what you folks think of the idea of downgrading the car from lithium to lead. (My first choice would be to sell it, but I don't think I'm willing to part with it for what anybody would offer me for it.)
 
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#2 ·
At best you'll have about 1/2 the power of the Tesla -- if launched perfectly the Porsche might take it in 1st gear, maybe keep up in 2nd, but at higher speeds the Tesla will definitely dominate.

Something to consider is a high power pack; you can trade range for power and cost. I'll assume 144V and 1000A.

Flooded lead acid: . . . . . . $1,000, 700 lbs,. ~24 rwhp
Optima 50 Ahr lead acid: . . . $2,000, 540 lbs, ~108 rwhp
Thundersky/CALB 200 Ahr pack, $12,000, 700 lbs,. ~65 rwhp
Headway 80 Ahr pack, . . . . . $8,000, 300 lbs, ~130 rwhp

The lead acid might not drive as far as you'd want (40 miles is pretty optimistic I'd think). Also, one lithium pack should outlast several lead acid packs and could be cheaper in the long run (provided they don't get ruined by ovecharging or a failed BMS or something, admittedly lead acid is tougher).

I liiked the service I got with Manzanita Micro (still have to install my Headways, though).

http://www.manzanitamicro.com/produ...page=flypage.tpl&product_id=61&category_id=29

... One option would be to install a new lithium pack at around $12,000 to $15,000. One of the people who's been working on the car insists that with a new pack it would beat the Tesla Roadster that I bought almost a year ago, after giving up on any hopes that the Porsche would ever actually be finished. I don't believe that. ...

The Porsche has a completely shot battery pack, and is not worth more than about 1/5 of what I've put into it. I don't want to spend another $15,000 putting a new lithium pack into it. But OTOH, I no longer need the 125-mile range I wanted when I embarked on the project. The Roadster is and will remain my daily driver and my main car. But if I could get the Porsche back on the road, with top-notch performance, even with only 30 or 40 miles of range (for 15 to 20 miles range to 50% DoD) I could drive it to the store and back, and for occasional short errands.

So I'm contemplating putting lead-acid batteries in it. Lower cost and simpler battery management might make it worth my while, and I'd get some use and enjoyment out of the car (it is a beautiful car!) At least it would be on the road and not rusting away in the corner of a shop somewhere. The lower impedance of lead should allow high power, at the cost of greatly reduced range, now that range is no longer important to me. ...
 
#4 ·
What controller did you end up with? I would recommend a very small A123 pack using the 20Ah pouches, you could get something for a decent price as long as you or someone at the shop has the skills to build a pack out of them.

They are small/light and high power, you wouldn't end up with much range, (30-50 miles) but you could probably max out the controller or at least come close.

It would be a fun short range car!
 
#5 ·
Thanks for all the ideas. I'll run them by Gordy and Tim when I next talk to them.

144V was a mistake for a high-performance vehicle.
Too high, or too low???

(The fellow at NetGain said the voltage is ideal for the motor.)

The controller is from EV Source, designed in cooperation with and endorsed by NetGain. Since the Porsche is not at my home now, I cannot tell you the model name, but it's something like the third iteration of the controller. I was originally going to get one of the very first of these controllers, but because of delays in the project due to all the additional things that turned up wrong with the car, I ended up with a much-improved version of the controller.
 
#6 ·
Thanks for all the ideas. I'll run them by Gordy and Tim when I next talk to them.


Too high, or too low???

(The fellow at NetGain said the voltage is ideal for the motor.)

The controller is from EV Source, designed in cooperation with and endorsed by NetGain. Since the Porsche is not at my home now, I cannot tell you the model name, but it's something like the third iteration of the controller. I was originally going to get one of the very first of these controllers, but because of delays in the project due to all the additional things that turned up wrong with the car, I ended up with a much-improved version of the controller.
The controller would be the Warp Drive and is software upgradeable to different voltages and current levels, it should handle any upgrades that you want to do (at a price). 144v is low for a Warp motor with good brushes, after sag you wouldn't have as much voltage to the motor. A better idea would be to add 10-25% on top of the voltage the motor can handle and limit the motor voltage in the controller settings. The key to all this is the battery system though and keeping the weight off.
 
#11 ·
Thanks for all the ideas. I'll run them by Gordy and Tim when I next talk to them.


Too high, or too low???

(The fellow at NetGain said the voltage is ideal for the motor.)

The controller is from EV Source, designed in cooperation with and endorsed by NetGain. Since the Porsche is not at my home now, I cannot tell you the model name, but it's something like the third iteration of the controller. I was originally going to get one of the very first of these controllers, but because of delays in the project due to all the additional things that turned up wrong with the car, I ended up with a much-improved version of the controller.
Too low. The voltage is ideal for the motor, but not for the vehicle. If you want to go netgain, Warp 11HV + Soliton 1 (or maybe a netgain 1400A controller, does anyone have feedback on those?)

288V*1000A=288kw == 386 HP *.87 eff == 335 HP at the output shaft.
288V*1400A=403kw == 540 HP *.87 eff == 470 HP at the output shaft
(Caution, this is a lot of strain on the motor)

Other options are the Kostov 11" 250V or the Kostov 11 Alpha (Electric Forced Cooling).
 
#8 ·
Lead is going to be too heavy to be fun in your car. I agree with the others that a small capacity, high power lithium pack is worth looking into. The headway cells have been used successfully in a lot of cars. The A123 would be a little more difficult to integrate, but they look like very good cells. Bumping up the voltage is a good idea too, if you can get the controller upgraded. My Warp9 is rated for 170 volts max, with the brushes advanced. With neutral timing the voltage is lower. You will want to look into this so that you don't risk your motor.

Sorry to hear about your ordeal. I'm glad you are not soured on the whole project and you're willing to consider how to salvage the project.
 
#9 ·
Well, this was a short-lived idea. But I wouldn't have known if I hadn't asked, so I appreciate all the replies. The Xebra seemed to do much better with lead than lithium, but I am hearing from all sides that lead does not have the characteristics I imagined.

So Tim (who is working on it while Gordy is still busy building his house and shop) is going to get the motor re-balanced and is going to go over the pack, remove the bad cells, and see what he can put together from what's left.

I'll post again when there's news. My goals now are much more modest than they were at the beginning. Then I wanted a reliable 100-mile range. Now a local grocery and errand capability would be sufficient, since the Tesla is my main car and I don't need the Porsche to go long distances. (Though Tim wants to put together a proposal to make the Porsche into a Tesla-killer. I told him if he wants to give me some numbers, I'd listen.)

Tim thinks that with the 11" Warp motor, a new lithium pack, and a 1,400-amp controller, the Porsche would do 0 to 60 in 3.5 seconds in third gear from a stop. (Shifting through the gears would take me several seconds, so if it can't do it all in one gear it will never match the Tesla.) But the motor has a very narrow torque curve, unlike the Tesla, which has only one gear. I don't think the Porsche will ever match the Tesla, but I do know that it can perform very respectably with the present controller.
 
#10 · (Edited)
Would you be doing the 144V Warp or the Warp 11HV (something like 220V?)? The numbers below assume you have a higher voltage pack, so when it sags the controller can still deliver the max voltage the motor can take.

1400 A * 144 V ~= 200 rwhp
1400 A * 220 V ~= 300 rwhp

300 hp is not enough in a car that heavy to do a 3.5 s 0 to 60. The Cayman S, with 320 hp, PDK, and awesome traction control is "only" about 4.5 s. The regular Cayman has 265 hp and does 5.5 s.

As a counterpoint, the Tesla does 0 to 60 in under 4 seconds, with about 300 hp -- but there are some caveats. Its AC motor has a broad torque curve, and it has awesome traction control. This would be tough to duplicate with a series DC motor. The Tesla is also likely lighter than your Porsche would be.

It also depends on the batteries, high power lithium will be faster (lighter and more power) than Thundersky/CALB type batteries.

My vote would be to go for performance, but don't expect 0 to 60 in 3.5 s.
... Tim thinks that with the 11" Warp motor, a new lithium pack, and a 1,400-amp controller, the Porsche would do 0 to 60 in 3.5 seconds in third gear from a stop. (Shifting through the gears would take me several seconds, so if it can't do it all in one gear it will never match the Tesla.) But the motor has a very narrow torque curve, unlike the Tesla, which has only one gear. I don't think the Porsche will ever match the Tesla, but I do know that it can perform very respectably with the present controller.
 
#12 ·
Perhaps take stock of the parts in the conversion as see what the upper voltage limit is. From there build a pack of Headway P or HP 8 amp hour cells in a series/parallel arrangement until it should meet the power needs. Based on some testing by Manzanita Micro the 8 amp hour P cells should be good for 200 amps each. If you can handle a 48 cell in series pack and you want 1000 amps for the ground then a 5p48s pack would work for a list price of about $4500. I bet when someone asks for 250 cells (a few spares) they will get a price break.
 
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