Daniel's EVPorsche 911 conversion - Page 18

TEG · 06-07-2009, 06:58 AM

Quote:

Originally Posted by dimitri

- starting in 3rd gear is a range killer, anyone who speaks of direct drive has no idea of currents involved, direct drive is possible, but not effective at all, you need gears, especially with air cooled DC motor, which doesn't have much useful RPM band.

I think when "Direct Drive" was mentioned we just meant it is possible to have an EV with no clutch. (Although hub-motors are truly direct drive). Many EVs use gears or belts to step down RPMs but offer a fixed ratio and no shifting. (Tesla for example uses an air-cooled motor with no clutch).

If you assume that Daniel will keep his 'current' motor, then yes, having some shifting ability is probably a good thing, but there are plenty of AC motor powered EVs that offer no shifting and work just fine.

dimitri · 06-07-2009, 03:10 PM

Quote:

Originally Posted by TEG

I think when "Direct Drive" was mentioned we just meant it is possible to have an EV with no clutch. (Although hub-motors are truly direct drive). Many EVs use gears or belts to step down RPMs but offer a fixed ratio and no shifting. (Tesla for example uses an air-cooled motor with no clutch).

If you assume that Daniel will keep his 'current' motor, then yes, having some shifting ability is probably a good thing, but there are plenty of AC motor powered EVs that offer no shifting and work just fine.

Of course I was referring to Daniel's specific EV, not what can be done in general. DC conversion with air cooled Warp motors require transmission with at least 2-3 gears. Starting in 3rd gear is out of the question as it puts incredible strain on the batteries, motor and controller. You can do it, but not if you want any decent range and longevity of your pack.

Daniel, you are getting excellent advise on DIY forum, from the guy who designed and built my controller and a motor expert, I hope you will weigh all your options and seek professional help to finish your EV.

Also, forgot to mention before, your instrumentation is horrible, I would recommend at least a voltmeter to see the pack voltage, without having to use the calculator

, PakTrakr would be nice to track cell level data and SoC.

When talking about amps you always must specify motor amps or battery amps, I can't recall from your past posts if your ammeter on the motor side or battery side of the controller. All controllers are rated at peak motor amps, which is almost irrelevant to EV design or power calculations. Curtis 500amp rating is on a motor side for 30 seconds, it can only do 250-350 continuous motor amps. To get your promised acceleration you need to double controller rating and have exellent controller cooling, preferrably water cooling.

JRP3, yes 11" and 9" have somewhat similar ratings, but the extra rotational and stationary mass only make things worse, wasting precious power. Its probably not effective to downgrade the motor now, after all the work was done to install 11", that is why I didn't suggest it as strongly.

Hope this helps.

dimitri · 06-07-2009, 03:54 PM

Quote:

Originally Posted by JRP3

Hey Dimitri, good to see you here. About the power steering, I guess you're saying that the pumping losses when going straight are minimal since there is no load? What about the possibility of having an electric pump only turn on after a specified degree of wheel turn, since you don't really need power assist at speed? Not worth it? How much power does PS draw?
As to the motor, the plots for the Warp9 and Warp11 show the 11 drawing less amps at similar RPMs, and producing more torque per amp. http://www.go-ev.com/images/003_16_W...preadSheet.jpg
http://www.go-ev.com/images/003_20_W...preadSheet.jpg
Certainly the acceleration performance potential is higher with the 11, with the right controller.

JRP3,

if acceleration was the primary goal and not the range, then 11" is better than 9", no doubt, although proper controller selection is the key to get the best out of it. However, it seems that range is more important to Daniel, in which case 9" would be more efficient and still plenty powerful for good acceleration.
As for those graphs, they don't show all the dynamics involved. You may be getting better amps at certain RPM level, but how much power did it use to get to those RPMs? I don't want to get stuck in motor discussions, since replacing the motor is probably not worth the trouble for Daniel. He really needs to get a good controller and the cooling for it, that's all. As for range, he'd have to live with what he gets from that pack, since there is no room to add more cells.

I am getting 50-60 miles range from my 128V LiFePo4 pack of 160Ah cells and it's exactly what I expected based on calculations, so I am very happy. This range is at average 50-60mph, I don't need to get on a freeway in EV.

However, as a test, I will try to see what my freeway amps will be at say 70mph. I will post results soon...

My EV may not look as cool as Daniel's Porsche, but I think it has generally similar weight and air dynamics specs, and similar conversion specs, so we can compare apples to apples.

Picasso · 06-07-2009, 04:32 PM

If "Paul" was working on this car for a year he had all the time he needed to get the zilla if that is what he planed to install. I wonder why he didn't order that a year ago?

daniel · 06-07-2009, 05:20 PM

Quote:

Originally Posted by dimitri

Daniel,

I read this entire thread and I have to say that I am very sorry for your EV conversion experience. I have done 2 EV conversions so far and I am offering EV conversions in Tampa Bay to people like you, who are fascinated by electric propulsion, but not DIY type.
I have taken many points from your experience with Paul of what NOT to do with my customers.
I applaud that you remained positive after all that experience, it takes a lot of character...
Biggest issues to learn from here is that it takes a lot more effort to build freeway capable EV with good range, much more than to build a decent EV. You got a decent EV , ridiculously overpriced, but decent EV, not freeway capable and not a lot of range, but still a decent EV conversion. Not much decency in Paul's behaviour towards you, but that it impossible to know up front unless you checked many references, sadly it doesn't sound like you did.
A lot has been said here of possible improvements, many things from people who never built an EV, although they tend to think they understand the challenge very well. With 2 EVs under my belt, recent one being practically the same specs as your Porsche, I can point out things that make a big difference and things that make very little difference.
Big things:
- 11" motor is a huge overkill for this car, it carries extra 50Lb of metal and eats huge current at acceleration, none of which is good for the range.
- Curtis controller is a huge underperformer, although it is very dependable, but not suitable for the specs of your EV
- any controller that puts out the power you need for freeway will have to be water cooled, especially if you keep that 11" monster of a motor
- starting in 3rd gear is a range killer, anyone who speaks of direct drive has no idea of currents involved, direct drive is possible, but not effective at all, you need gears, especially with air cooled DC motor, which doesn't have much useful RPM band.
- your battery config is OK, its not even close to promised range and was grossly miscalculated, but its the best for this car, you wouldn't get any better battery of LiFePo4 chemistry, unless you wanted to pay the premium for small cylindrical cells, but its not worth the trouble IMHO.
- the best possible DC conversion of this car would give you perhaps 80-90 miles of low freeway speed with modest driving style. So promised 120+ range was always out of the question, no matter what Paul was hoping for.
- it takes 2 times energy to travel at 70mph vs. 50mph, due to exponential nature of air drag, that's why I said that freeway capable EV is far far away from a decent around town EV.

Small things:
- changing AC and PS from belt to separate electric drives is not going to save you. Results will not be as impressive as cost and labor to implement them. PS pump does not waste energy while driving straight line, nor does AC unless its turned on. Mechanical losses in belt drive are so small compared to overall energy levels involved that its negligible.

Your best bet is to improve this EV with help of local EV club guys, get a better controller, at least consider what it would take to switch to smaller 9" Warp motor, this might be too much of mechanical work involved to adapt plates and shaft couplers.

Synkromotive controller is very promising , but I am not sure it can drive 11" motor at freeway speeds with air cooling.

I am a lucky beta tester of EVNetics controller, which would do the job perfectly, but only when water cooled and it still won't help with the range issue.

Also, I wanted to mention that your conversion should not cost more than $25K, although I am sure you paid Paul much more, unfortunately.

Hope this helps.

Dimitri
Clean Power Auto - Home
Dimitri Butvinik's 2002 Mazda E-Protege5

Dimitri:

Thanks for all your comments. Yes, I am weighing everything I'm reading here and over on the DIY forum, as well as what I'm getting from Gordy and Tim (the local guys) Richard (the battery importer) and Paul. I believe Paul was acting in good faith, but that he had no idea what would be involved with a late-model car and lithum batteries, and I feel that he grossly overcharged me. I did ask around about him, and heard only good things.

Originally, I wanted both range and acceleration. If Paul had told me that what I wanted was unrealistic I'd have reconsidered. However, I do drive this car on the freeway to Coeur d'Alene and back (a 50-mie round trip) and have done so 3 times. Most recently today, when I maintained a speed between 60 and 65 mph, probably averaging around 61 or 62, and consumed 130 of my total 200 amp-hours. It is sluggish getting up to speed, and I'd like to correct that, but it makes the trip fine. I used 367 wh/mi, which translates to a range of 63 miles to 80% depth of discharge.

As you assumed, I probably won't change the motor. That sounds like it would mean practically starting from scratch.

I was pretty much convinced to switch to a 1,000-amp controller, but then one of the local guys talked me out of it, but then after talking to Richard and reading what you and others have posted, I am again convinced that it the way to go.

On the p/s pump, some folks (including Richard) say an electric pump would only run when needed, and so would save a lot of power; others say it would run all the time and save little power if any. But that's something I'll look at after the controller. I think the controller is the big thing.

I think I paid way too much. But Paul has been in business for a very long time and I think he just bit off more than he knew how to chew with this project. I am disappointed with the range, but I can live with it if the acceleration issue is addressed.

I have two styles of driving, and I want a car that can do either, at my discretion, and I am well aware that they work against each other: For trips out of town I want range, and acceleration only matters for getting onto the freeway. One burst of power is not going to cut much from my range, and once on the freeway I don't need much power. For trips in town, range is not an issue and I'd like to have power so I don't have to wait until there are no cars within two city blocks before crossing, as I have to do with the Xebra.

Quote:

Originally Posted by dimitri

Of course I was referring to Daniel's specific EV, not what can be done in general. DC conversion with air cooled Warp motors require transmission with at least 2-3 gears. Starting in 3rd gear is out of the question as it puts incredible strain on the batteries, motor and controller. You can do it, but not if you want any decent range and longevity of your pack.

Daniel, you are getting excellent advise on DIY forum, from the guy who designed and built my controller and a motor expert, I hope you will weigh all your options and seek professional help to finish your EV.

Also, forgot to mention before, your instrumentation is horrible, I would recommend at least a voltmeter to see the pack voltage, without having to use the calculator

, PakTrakr would be nice to track cell level data and SoC.

When talking about amps you always must specify motor amps or battery amps, I can't recall from your past posts if your ammeter on the motor side or battery side of the controller. All controllers are rated at peak motor amps, which is almost irrelevant to EV design or power calculations. Curtis 500amp rating is on a motor side for 30 seconds, it can only do 250-350 continuous motor amps. To get your promised acceleration you need to double controller rating and have exellent controller cooling, preferrably water cooling.

JRP3, yes 11" and 9" have somewhat similar ratings, but the extra rotational and stationary mass only make things worse, wasting precious power. Its probably not effective to downgrade the motor now, after all the work was done to install 11", that is why I didn't suggest it as strongly.

Hope this helps.

Starting in 3rd was an attempt at a zero-to-sixty test, since shifting is so slow. Normally I start out in second. It is extremely difficult to shift into second while moving, so starting in first is problematic, though I do it if I really have to zip into traffic.

I am very disappointed in the instrumentation. Paul was going to give me nothing but a volt meter. That is not acceptable. Once I get to having some work done on the car, I will want to have more instrumentation added.

I do not know where my ammeter is connected. I'll ask Paul.

Quote:

Originally Posted by Picasso

If "Paul" was working on this car for a year he had all the time he needed to get the zilla if that is what he planed to install. I wonder why he didn't order that a year ago?

I presume he was planning on using the Logitech. When those went bad it was too late to get a Zilla. I only found out about this two hours before my car arrived. He told me nothing before he shipped it. I do not know when he decided to change controllers. He did not consult me. This is not acceptable, but at this point I'm more concerned with solving the problem than with laying blame.

Daniel

JRP3 · 06-07-2009, 08:54 PM

Quote:

I was pretty much convinced to switch to a 1,000-amp controller, but then one of the local guys talked me out of it, but then after talking to Richard and reading what you and others have posted, I am again convinced that it the way to go.

Even if you can't get a 1000 amp controller, a 600 amp or higher controller that can actually work without overheating as the Curtis does would make a positive difference. The nice thing about changing controllers is it shouldn't be too hard to replace one with another, and the used one will have some good resale value.

Quote:

On the p/s pump, some folks (including Richard) say an electric pump would only run when needed, and so would save a lot of power; others say it would run all the time and save little power if any.

I'm pretty sure an electric PS pump can be setup to only run when the wheel is turned a certain amount.

William3 · 06-07-2009, 11:07 PM

Porsche : 911:eBay Motors (item 190312545943 end time Jun-11-09 14:02:16 PDT)

Porsche : 911:eBay Motors (item 190312548377 end time Jun-11-09 14:15:11 PDT)

TEG · 06-07-2009, 11:31 PM

https://www.junglemotors.com/

dimitri · 06-08-2009, 05:34 AM

I can speak a lot on a subject of PS pumps, since I have done both electric and mechanical PS in my EVs. Most people get hung up on saving energy from PS pump, not realizing that amount of energy used by either electric or mechanical PS system when driving straigt line ( 99% of the driving time ) is so little that its not even worth discussing, let alone doing something about it.

I used electric PS pump from 2000 Toyota MR2 in my first EV. It was connected to run at all times while the car is on. I measured amount of energy it uses while idle. It runs idle until you turn the steering wheel, since there is no pressure inside PS rack when its in straight position. Same for belt driven PS pump, it doesn't create pressure until you turn the steering, so it basically idles most of the time.

So, I measured about 5-7 amps at 12V on electric PS pump while idle, which means 60-80 Watts are wasted in idle. Same EV uses 14,000 - 54,000 Watts when it moves. So PS losses account for 0.1% - 0.5% of energy used in EV.

Some people propose contraptions to sense when the wheel is turned and use a relay to only turn on the pump then, but it complicates things, adding cost and introduced a risk of getting into an accident if contraption fails to operate in a hard turn. Even if it works perfectly, and saves 0.5% of energy stored in the pack, you will gain a quarter to a half of mile of range, woohoo

Hope this helps

dimitri · 06-08-2009, 05:38 AM

I forgot to mention, there is definitely a benefit in using electric PS pump in manual transmission EV conversion like Daniel's. It allows full use of PS function while motor is not running or running at very low RPMs. This is helpful in navigating into and out of tight parking spaces. When I design EV conversion with manual transmission, I would definitely consider electric PS pump. However, in Daniel's case, when PS is already implemented in a belt system, ripping it out and replacing with electric doesn't seem very beneficial, unless he values above mentioned benefit enough to consider the work.