# Upscale Car Conversion



## PThompson509 (Jul 9, 2009)

Check out the metric minds website - they have siemens motors and some matching controllers. http://www.metricminds.com

Cheers! Peter


----------



## PThompson509 (Jul 9, 2009)

20hp may be true for smaller cars, but for bigger cars, more weight, more wind resistance ... this would push the need for more power on a continuous basis. Plus, it depends on where you are driving - freeway speeds in LA can range from 0 to 110mph.  Also using the LA freeway as another example, there will be times when you need to accelerate quickly to get past some moron snoozing in the "fast" lane. Hmm, and maybe a tesla coil to shock some sense into them. :-D

Cheers! 
Peter


----------



## PThompson509 (Jul 9, 2009)

As long as you can get the voltage up high enough for the controller, you're gonna have a VERY nice ride.  Does the transmission require an aux pump to keep the pressure up? I could see how that could be a problem, but only a minor one. Some of the smarter controllers can emulate an engine idle (650rpm or so), so that would also take care of the problem.

You've got me thinking about my next car (again).


----------



## aeroscott (Jan 5, 2008)

I Googled CLS550 it's curb weight is 4140 lbs, It's a E class based car. Even the S class based cars like CL550 are just 4300 +lbs. Great looking car . If it's anywhere near as strong as my E300D 1987 , it's the best body/chassis on the market . Mine was hit in a head on by a 1965 ford pickup @ about 10-15 mph , I was stopped with foot on the brake , drove me back and side about 2 feet , collapsed the frame rail about 3" but dose not seam to have displaced the entire rail or inner fender . Now for the most overly complected electric system ever .


----------



## Bowser330 (Jun 15, 2008)

Well a member "etischer" did custom make an inverter for a Siemens motor based on an industrial VFD for his passat, but he isn't providing any details to help others make their own. He mentioned Calmotors as a reason for not selling his inverter plans as well which ends up being totally bogus, as Calmotors like all the other companies doesn't want anything to do with individual DIY'ers and when contacted by Jack Rickard, Calmotors told him something like 16,000$ for a 67kw (90hp) setup (motor+inverter)...so yah...IMHO, pass on Siemens.

Metricmind has MES-DEA motor and inverters, however looking at their prices it looks like you cant get out of that joint without dropping 15,000$, again for 60-70kw

CurrentEVtech is providing an 80kw BLDC setup (motor+inverter) for 5,850$

http://currentevtech.com/Drive-Syst...lers/80KW-BLDC-Motor-and-Controller-p167.html

Dave K also mentioned in a thread that the 80kw was calculated @ 288V Nominal, however with the controller being able to take 400V, if one were so inclined they could extract 100kw from the motor, albeit temporarily. You would need more cells, but you wouldnt have to get too many AH if you didnt want too, the peak amps for the 80kw inverter is 330A, which is 3.3C on a 100AH cell, which is the continuous rating, so you could go smaller....


----------



## glaurung (Nov 11, 2009)

Hi, is there a reason for using ac? HV 11", dual Solitons to max voltage, would be cheap, powerful and ready to be picked up. Any trans would do,why not use original?
No need to invent anything, just install and go
Harri


----------



## Bowser330 (Jun 15, 2008)

glaurung said:


> Hi, is there a reason for using ac? HV 11", dual Solitons to max voltage, would be cheap, powerful and ready to be picked up. Any trans would do,why not use original?
> No need to invent anything, just install and go
> Harri


dual solitons with a single motor?


----------



## glaurung (Nov 11, 2009)

Well it´s only 1000 amps each. Not much for a big car.


----------



## Bowser330 (Jun 15, 2008)

glaurung said:


> Well it´s only 1000 amps each. Not much for a big car.


I did not think it was technically possible...do you know someone who has done this?


----------



## GizmoEV (Nov 28, 2009)

Quantum said:


> As far as voltage I'll be putting in lots of LiPo's, and maybe an ultra-cap bank in series for regen capture. Say, 350V in LiPo and 350V in ultracaps, for a max of 700V. Those ultracaps will capture virtually 100% of regen (batteries only capture 10%-15% at most), and serve for startups and passing.


You must be talking lead acid batteries in that 10-15% figure. Also, if you are going to series those ultracaps with the batteries you are going to run into a big surprise when those caps drain if a few seconds. If you parallel them then the voltage won't add.

As for AC vs DC motor efficiency you have to consider the inverter + motor for AC and controller + motor for DC and the improvement in efficiency isn't as big as you think.


----------



## aeroscott (Jan 5, 2008)

GVWR= gross weight , with you on AC , I want do a E class 4 matic wagon ,using Prius (2 of )trans . With enhanced motor cooling should be good for over 100 hp each . Heavily modded original electric system .(much simpler). The stage 2 would be 1 motor per wheel like the new gull wing MB .


----------



## Overlander23 (Jun 15, 2009)

Curb Weight vs Gross Vehicle Weight Rating...

Curb Weight is what the vehicle weighs with standard operating equipment, all fluids, and a full tank of fuel, but without passengers.

GVWR, is rated limit of weight for the vehicle (once loaded with passengers, cargo, etc)

Be happy, the curb weight is lower!


----------



## aeroscott (Jan 5, 2008)

MB is working on a ev version of SLS . I would modify the cv shafts , replace the differentials (2 in a 4-matic) with the Prius motor/trans . its taller so will cut threw the trunk floor then make a raised box to cover it , loosing some trunk space . Would think CLS came in 4-matic as the E class does . There is some MB moder's in southern Cal that know a lot about the electric systems . The electric shift trans are just shifted by powering the solenoids for the wanted gear , check out using automatic trans for ev s on forums .


----------



## aeroscott (Jan 5, 2008)

just came out , 4matic CLS , also a wagon(concept) looks great .


----------



## aeroscott (Jan 5, 2008)

understand the looks of the front end , I'm slowly worming to them . The So Cal moders are moding gasers .My point is they know how to handle the electric system . Maybe they are thinking ev too . should be with the DBM battery and other ev projects comming on like gang busters .


----------



## major (Apr 4, 2008)

Quantum said:


> I am shocked to find that I can buy 100 CALB LiFePO4 batteries (http://www.powerscaner.com/product_1.php?id=123) for only $11,200. In series this would be 100AH at 360V = 36KW. Weight would be 744 pounds. Battery volume is 7.28"x4.57"x1.8"=59.89c"
> ... so pack volume is
> 59.89c" / 1,728c"/ft = 0.0346585648148 * 100 = 3.47 cu'
> 
> Although, 36KW doesn't seem like alot for a car of this weight. Maybe I need 200 cells, to parallel?


Hi Quantum,

100 Ah times 360 V = 36,000 Wh = 36 kWh......not kW. Get your energy and power straight. Those cells are rated at 4C for 30 seconds, so that would be 144 kW, not counting sag. 

Regards,

major


----------



## frodus (Apr 12, 2008)

well, since you haven't defined what your range requirements are, it's an ambiguous question, and impossible to answer.

You said how much power you want, but not what kind of range and top speed you want. 

You have lots of high hopes with this project (huge AC motor, HV pack, ultracaps)

it's an engineered car. You're the engineer. I'd sit down and write down some design constraints, budget, distance, speed, how far you want to go at 45mph, how far at 60mph, how fast you need to charge, how much volume you're willing to give up for a large pack.... Devil is in the details.



What is your background?


----------



## aeroscott (Jan 5, 2008)

just found a 2006 SL5.5 AMG 4800 miles, 7 speed, $27k . that's almost new in my book ! What a cool conversion that would be .


----------



## aeroscott (Jan 5, 2008)

7-speed was new ,what other stuff . thanks


----------



## frodus (Apr 12, 2008)

Quantum said:


> Frodus I am shooting for as much range as possible of course, with a target of 100 miles. But I am not limiting myself to 100 miles. Never mind, I'll figure it out for myself. Let's not get into a cycle of criticism here.


Yeah, you'll need a larger pack for 100 miles. I'm not critisizing, but you're not giving any information.... its like an equation.... and you're missing a few variables.



> I am a real estate developer. Don't worry about me.


Well, then Good luck with the project. I was going to offer some advice and concerns about your aproach to the electrical system (specifically with lifepo4, ultracaps and BMS), but don't worry about it. I'm sure you have it covered, I mean, being a real estate developer and all.


----------



## frodus (Apr 12, 2008)

Quantum said:


> Yeah, that's what I thought frodus. I'm not going to get in to a whole big thing with you.


That's a very good choice on your part.

But good luck, this is an interesting project, can't wait to see the finished vehicle.


----------



## david85 (Nov 12, 2007)

Well in fairness, not many of us have any business building these cars and yet, for some strange reason we do anyway. I'm only now planning to get some formal training in electronics but had absolutely no official back round on the subject before my car project was started.

All I do for a living right now is build/install railings or install vinyl membrane decking. That doesn't mean that's all I can do though (same goes for anyone else).

Quantum, I was able to get a 100 mile range on my car (see my garage entry for specs). It was under fairly ideal conditions, but according to my meter, I only needed ~26KWH for that distance.

My car is however lighter than yours, so if we were to do a very crude comparison, you could add another 25% to that for a (very) rough equivalent range for your car (assuming similar aerodynamics and wind resistance, which also needs to be factored in, but I'm guessing its not too far behind me old saturn). That would give you 32.5KWH, but no reserve.

My battery is about 32khw already so (in theory) I had a 24% reserve when I drove that distance in my car but I never actually ran it dry so can't be sure.

Keep in mind this are very crude estimates on my part, but my gut tells me you will need about 40KWH of battery reserve for satisfactory ~100 mile performance. This would allow you to easily pass that distance on a good day, and still reach it on most other days. And IMO, you don't need to use a capacitor bank, but its your call.


----------



## frodus (Apr 12, 2008)

I think you and I started off on the wrong foot. Lets start over.

I meant no disrespect in asking what your background was. I just wanted to know a little about you so I knew where to start with helping.... either i start out basic as if you have no tech training, or a little more involved with someone that has some technical background. Sometimes if I start dumb and work up, more technical people take offense..... I was what your technical background was so I could be on the same page. You're new and unfortunately, no one here has any idea who you are or how smart you are. New guys with dreams of grandeur are a dime a dozen on here. Thanks for (finally) letting us know what your background is, that helps a lot.

And for what its worth, I was only asking for more information so I could help... hardly a "put down or argue" attitude. Lighten up, ok?


That being said......

Go reread my initial post in this thread with a positive attitude instead, and you'll see I was just saying we need more info to answer your question on pack size. I think we have Weight (approximately), HP peak requirements, but some other things that you'll need to know are how far at XX MPH you want to go so you can back calculate how many Wh/mi you might use, and how large the pack needs to be sized.

You're on track with motor/controller. Just size it enough for the performance you need and you should be good. Viktor is a great guy to work with, he'll help set you up with something nice. There are other motors and controllers that come to mind. www.evdrive.com has a nice beemer with a Rinehart motion controller and Siemens motor. Remy, UQM and YASA come to mind as well.

Then comes batteries. Calb seem like a good choice. With 100Ah cells, go high voltage as you're saying, to keep the discharge current low. These cells are good for 3-4C continuous, so about 3-400A. Anything above that and you might need to go with larger cells in parallel, or higher discharge rate batteries. Also, you'll need some sort of monitoring system, and if you want it (I recommend it), a balancing system. Something that can cut out the charger if a cell hits high voltage, and decrease throttle if a cell hits low voltage. Elithion and Manzanita are well proven systems. I can help with batteries, chargers, BMS and depending on what you want for motor/controller, I can put you in contact with some great people, or help you directly.

The big issue will be Ultracaps. There are certain design considerations with Ultracaps that get tricky. The one's I've seen need additional circuitry to keep voltage balanced, they're bulky and very expensive for very little benefit. The ultra caps are low voltage, so you need a string of them in series to get the voltage you need (which you mentioned, and I'm agreeing). If you paralleled them with a battery, I think that might be over the voltage rating of the ultracap. The Maxwell ultracaps are absolute max 2.85V, so parallel with a battery is too much for it. You'll have a series pack of batteries and a series pack of caps to do it correctly, or break into modules that match the voltage better. You also need to make sure that while charging, the caps don't get voltage over their limit. Most lifepo4 batteries charge between 3.7V and 4.0V, so even if you break into modules, it might still go over 2.85V per CAP. Having 2 modules (one battery one capacitor) would be best, beause you can disconnect during charging, and reconnect once voltage hits a certain level.

IMHO, I think you'd be better off getting larger batteries with a high discharge or high recharge rate so that you can more effectively take in regen.


----------



## jk1981 (Nov 12, 2010)

Surely the simplest thing to do with capacitors is to run a string in parallel alongside the main battery and isolated from it by a diode rather than 2 per cell. Rate the cap string at ~2x pack voltage. Energy stored in a capacitor is 1/2CV^2 so the pack voltage pre-charge only uses up ~1/4 of the capacitors energy storage capability. Once you've recovered your energy from the cap bank the controller seamlessly switches to drawing current off the pack via the diode. Obviously there's a lot of room for refinement here! You'd need a controller capable of very high voltage input or a relatively low pack voltage. For anything but stop-start vehicles even a fairly simple solution like this seems like pointless overkill, the money and weight would almost certainly be better spent on more battery.


----------



## etischer (Jun 16, 2008)

You should check out my conversion, I am using the Ford Siemens motor in a VW Passat. I'm at 3700 lbs, it was 4010 with my original Lead pack. 

http://etischer.com/awdev/


----------



## frodus (Apr 12, 2008)

Quantum said:


> The concern is that batteries cannot capture but a fraction of regen.


And it may be only slightly more if you were trying to use caps. There's just not a huge amount to begin with, and the caps don't store a ton of energy. Add in all the inefficiencies of drivetrain, generator (motor) efficiency, controller efficiency.... you're limited. Also, the higher the pack voltage, the less regen you'll get, so it's not just battery that effects the regen.

The "recommended" charge current of the CALB is about 30A, but I'm sure for short bursts you can go higher than that, so it may not be an issue.

If you're up for a project, you can use higher discharge/charge rated cells like Headway, A123, Kokam. They'll allow a higher charge rate. They're just a little more complicated to assemble.


When I looked a few years ago, the price for CAP's and the support electronics for them was expensive compared to just adding another 10-20Ah worth of headway. I could have almost bought another complete pack of batteries for my project. Plus, The space would have required much more. 

So maybe jump up to the 180's and see if they might fit, then you're looking at a higher rate of charge for the batteries.


----------



## major (Apr 4, 2008)

frodus said:


> ..... Also, the higher the pack voltage, the less regen you'll get, so it's not just battery that effects the regen.


Hi frod,

I guess I don't follow your logic with that one  If you want to use regeneration, you have to design your system to do so, meaning the appropriate energy storage system voltage and motor system voltage.

Ultracapacitors are great. I like them. However, I don't see them as practical for BEVs, especially DIYers. 

For the OP's benefit, he might check out this thread http://www.diyelectriccar.com/forums/showthread.php/ultracapacitor-eye-candy-25994.html or read about Victor's experience here http://www.metricmind.com/ac_honda/main2.htm 

BTW, the bus used a 650 V system and regenerated at 160 kW peaks, but then it was 12 tons 

Regards,

major


----------



## frodus (Apr 12, 2008)

major said:


> Hi frod,
> 
> I guess I don't follow your logic with that one  If you want to use regeneration, you have to design your system to do so, meaning the appropriate energy storage system voltage and motor system voltage.


I mean the closer to "charged" your pack is, the more the controller is going to limit the regen. i.e. on the HPEVS systems, if the pack voltage goes too high from what it's set to, it reduces regen.


----------



## aeroscott (Jan 5, 2008)

Eric , Love the web site ( I wondered what you were up to). 75 on Sunol grade wow , I know it well . I just hooked up with Shillow III wind generator project on Friday(Birds Landing/ Rio Vista) , Starts in 2 weeks . ON the way home I rolled my Dodge/ Cummings . Looking for a body for 1st gen Dodge .


----------



## major (Apr 4, 2008)

frodus said:


> I mean the closer to "charged" your pack is, the more the controller is going to limit the regen. i.e. on the HPEVS systems, if the pack voltage goes too high from what it's set to, it reduces regen.


O.K. But if you have an appropriate sized ultracap buffer, it will take more and more energy as the voltage increases compared to a battery which needs a reduction as it nears its charged voltage. But then I wondered about that. So what if I hit a LiPo cell with 5V 20C for 3 seconds? As long as I stay well within the total charge limit of the cell  Maybe I'll give that a try. I have a lipo bag


----------



## frodus (Apr 12, 2008)

True, you could have a HUGE ultracap buffer.... *shakes head* you're fiesty this morning Major


----------



## frodus (Apr 12, 2008)

bingo....

So, not sure if you saw my posting with more quetions, but can you share some of the goals with us?

More specifically:

What range do you need at 25mph?
What range do you need at 45mph?
at 65mph?
What kind of acceleration?

We know weight (approx), but this will help figure out how to size the pack if we can estimate the wh/mile.

And I agree, either larger batteries, or higher charge/discharge rate batteries might be a great solution, and less complex and less expensive (although it doesn't look like you're too awefully concerned about cost).


----------



## major (Apr 4, 2008)

Quantum said:


> I don't see how you can back out a pack size though, given that I plan the FB Performance auto tranny,...


Hi Quant,

You're using ICE logic where it doesn't necessarily apply to electric propulsion. It takes a certain amount of energy to accelerate the mass of the vehicle, regardless of the gear ratio. And an electric propulsion system has a very wide (and high) efficiency band. Using multiple ratios to accelerate is unlikely to affect the energy requirements. If so, by such a small amount that the introduced losses in the transmission and the mass of the transmission will offset that. What a transmission may do (but not guaranteed) is increase the acceleration rate. But the rate does not affect the energy.

Regards,

major


----------



## major (Apr 4, 2008)

Quantum said:


> More torque required means more current draw.


And that would be motor current, not battery current. 

I am not sure why you came to this forum  Just to show off, or to learn some things about electric propulsion. It is quite different from ICE.

Why do the quickest EVs on the drag strip use direct drive? Why do no production EVs have a transmission? Why do you want one


----------



## Quantum (Jul 10, 2011)

No, not 'showing off'. Trust me, I do not have self-esteem issues.

Don't worry about it.


----------



## frodus (Apr 12, 2008)

Quantum said:


> But comparing direct drive with the tranny in first (2.84), the current required to start this heavier car will be massive in direct drive, compared with the tranny. More torque required means more current draw.


Major is right, it's hard to think about this as an engine.

It'l be more MOTOR side current for direct drive, true. But battery side, the difference between with or without transmission may be negligable.

They're not giving the motor full volts and full amps at low RPM. They're giving modulated voltage and lots of current.

Think of the controller as a power converter. You use the same power either way. It requires the same amount of energy to move the car. The only difference is, you're at lower "modulated voltage" higher current in a direct drive car, and lower current, higher modulated voltage on the tranny car. It has to do with PWM, waveforms and power conversion.... interesting to read up on, if you have some time.


So the thing is, you want 120miles at all speeds, meaning at 60+MPH, you're worst case. Air resistance becomes the issue. With a car that large, you'll have a high wh/mile. I'd say it'd be over 300-350wh/mile for a car that size, if not more. So 350wh/mile, 120 miles, you're at 42kWh at the minimum.

Thats why I asked, because it's all about how much power you're using while at XXX speed (we use units of watt-hours per mile). If you wanted 120miles at 25mph, it goes way down, probably below 250wh/mile.... so you may only need a 30kWh pack.

The controller is an electrical "transmission". High voltage/low current on the battery side, and you can vary it (infinitely) between Low voltage/high current for Low RPM up to high voltage/low current for high RPM.


----------



## frodus (Apr 12, 2008)

Quantum said:


> So, what y'all are saying is that whether it takes 1 newton to move a car, or 1,000 newtons, the power draw (watts/hr) is the same.


No. I'm saying just what I'm saying. The power is the same. The car itself requires the same amount of force to accelerate and maintain speed regardless of transmission. The mechanical transmission is a power converter. It converts high rpm and low torque to low rpm and high torque but the wheel speed and torque is the same between the two cases. 

The controller is an electrical version of a mechanical transmission.


----------



## major (Apr 4, 2008)

Quantum said:


> So, what y'all are saying is that whether it takes 1 newton to move a car, or 1,000 newtons, the power draw (watts/hr) is the same.


What I said was 


major said:


> It takes a certain amount of energy to accelerate the mass of the vehicle, regardless of the gear ratio.


 I'm not sure how you mix that in with your brand of physics using those watts per hour


----------



## david85 (Nov 12, 2007)

Well...if I may....

Two observations I can mention with my car.

1; Acceleration using 1st gear does seem to match starting off in 2nd, but NOT if going uphill (very sluggish off the line starting in second). Having lower gears to start off is worth while, at least in the case of my fairly underpowered car with limited RPM range (torque falls off at 3500-3800).

2; cruising at a constant speed of 50~55 MPH nets 12~13kw of power consumption regardless of 3rd gear or 4th gear - on flat ground. However due to how the motor and controller perform, more maximum power is available in 3rd gear for hill climbing (nearly double at that particular situation). This is measured at the battery.

In terms of accelerating the the mass of the car, yes it is essentially true that it will require X amount of power over Y amount of time (energy) to get it up to whatever targeted speed. However, motors don't always have a perfectly wide efficiency range over their entire speed range, so the more time you spend outside of that, the farther you are away from the ideal calculated acceleration. A stalled motor will draw plenty of amps but that doesn't mean its contributing all of the power draw to moving the car forward in the best possible way (lots of waste heat, for example).

I think to some degree you guys are actually trying to say the same thing but misunderstanding is getting in the way.


----------



## frodus (Apr 12, 2008)

Quantum said:


> 'my brand of physics'...
> 
> 'your brand of perpetual motion'.


not in the slightest.

You have two things you're comparing. One is with a mechanical transmission, the other is direct drive. Both use an AC motor and AC controller with an arbitrary sized pack. Lets say it's a 4500lb (2041kg) vehicle. Lets say you want a 0-60 (96kph) in 6 seconds. That works out to .002777 mi/s^2

The force required to accelerate a mass is (and always will be):
F = M x A
F = 4500kg * .02777mi/s^2 = (using some conversions) is 9124N, or 2051 pounds of force.


It's the same for either situation because it's the same mass, same car, same acceleration. 

So the work being done by the motor is the same. Either you're at low RPM and high torque on direct drive, or through a transmission with high RPM and low torque. Either way, you're doing the same work through the motor because you use a controller.

Of course, you need to be in a band of motor torque along with a correct gear ratio to move the vehicle to begin with.

[edit] and David is right. Motors have a curve, so you could be in a more efficient range on a motor with a transmission, but "just" outside of it with a direct drive. It's not a huge difference like you're saying, but there is a difference.


----------



## aeroscott (Jan 5, 2008)

Picked up my buddy's 1999 S420 , all fixed shorted wires in the folding mirrors . I looked at a 2008 CLS and a new one . I see what you mean the 08 is smaller and cleaner looking more ev like .


----------



## JRP3 (Mar 7, 2008)

The caps aren't worth it, the batteries will take plenty of regen, and a transmission will not significantly increase overall efficiency, especially the overdrive. I never use 5th gear in my car, heck I never use 4th, rarely use 3rd and do 99% of my driving in 2nd, from 0-65. I'm not saying you shouldn't use a transmission as it can improve the driveability of the vehicle, depending on the motor and vehicle weight, but with or without your overall range will not be greatly affected. There is a reason most production EV's use a single speed gear reduction, and they don't bother with ultracaps.


----------



## Tesseract (Sep 27, 2008)

JRP3 said:


> ... There is a reason most production EV's use a single speed gear reduction....


Yeah, and it probably has something to do with OEMs being able to spend millions of dollars to determine whether a transmission or direct drive performs better in a particular vehicle. That's not exactly practical for the average DIYer, now is it?


----------



## JRP3 (Mar 7, 2008)

It probably has to do with a reasonable compromise between production cost and drive efficiency, i.e. a transmission might provide a very small increase in efficiency but it's not worth the cost. Since batteries are expensive and range is important OEM's must realize that adding a transmission is a poor trade off. I'm not suggesting that DIY builders skip the transmission since we get one for free in our cars, I'm simply suggesting that the OP's idea that a transmission will vastly improve efficiency, and range, such that he doesn't' even want to calculate his pack size, until he picks a transmission, is misguided at best.


----------



## frodus (Apr 12, 2008)

> So a given weight requires a given wattage to move a given distance at a given rate.


Precisely. Regardless of powertrain. The power is roughly the same at the shaft of the motor, but as David pointed out, the power the motor uses can be slightly different because of the efficiency curve of a motor. I agree a transmission will keep a motor in the efficiency band. Looks like we agree on that, and we'll stop beating that dead horse.

But the issue is raised, that it doesn't matter what gear you're in. You'll use roughly XXX wh/mile while crusing at YYmph. That's dependant on rolling resistance, frontal area, coefficient of friction. Weight is only slightly an issue, it's more the frontal area of the vehicle. Weight is more of an issue with acceleration. 

I still stand by my estimate of 300-350wh/mile for that vehicle at 65mph. It'l be lower and lower the closer you get to 0mph. wh/mile is based on speed and vehicle components (Controller efficiency, motor efficiency, drivetrain efficiency, etc). So just use that, and 120 miles and overshoot a little bit. I think you'll need 40-45kwh of batteries to get the goals you want.




> I do not buy the notion that it takes the same wattage to move 1 pound as it takes to move 1,000 pounds one meter at 1m/s, at a fixed gear ratio much less with multiple gears. This is what it all comes down to.


That's not what we're saying. We're saying that it takes the (about) same amount of wattage to move the vehicle, regardless of a transmission.



> - It seems best practice is to design battery bays/racks to fit the -car-, whether under the hood, in the spare well, behind the seat, or to replace the gas tank. Batteries are always going to be different dimensions depending on brand and technology, so design the bays/racks to fit the -car- rather than custom for a given battery. Then make up the batteries into modules, or packs, which approximately fit into the bays, and strap them down. This maximizes available space no matter the technology.


Yeah, that's what a lot of people do. Some do enclosed boxes for waterproofing, some don't. 




> - I think it's important to mount all batteries on soft rubber mounts, so much vibration is dampened. Under the hood the rack itself could be on rubber mounts and the modules then right on the rack. Other places, rubber mounts on the modules. These batteries are subject to stress fractures. (forgot the correct term for fractures due to age/vibration)


Probably a good idea. 
Not sure where you heard about stress fractures though.... can you provide a little insight on that?



> - putting batteries where the gas tank used to be exposes them to the elements, especially where it rains alot like here in Seattle. I think some effort should be made to protect them, but don't expect total waterproofing. They would stay cooler than the other modules, and so maybe do not need water cooling, assuming not totally cowled.


I doubt you'll need water cooling on any of them if you size the pack right and keep the battery current low and go higher voltage pack size. You can enclose them fine, just monitor temperature, or get a BMS that does this for you.



> - Some band their battery modules as the batteries swell when charged. Makes it difficult to then intercool with Al plates between each cell as Viktor does it. I wonder is banding/constraining necessary to preserve cell life? Sure they should be held firmly, but extremely tight?


don't intercool, you won't need to. Viktor does this because like most of his things, overkill is the only option! You can do it, but it's not neccessary if you size the pack right. The bands ARE required to keep the cells from swelling, which happens as they even slightly heat up, not much heat is required to warp the cases. There's a reason TS and CALB cells ship with them.



> - I am concerned about inductance in the battery circuit, as there have been several instances where it's blown up the IGBTs. In one case the designer was told to replace the inter-cell braided straps with bars, and it worked. Still though, there's the long lines from front to back, and other braided/stranded wire. All transistors like to see a purely resistive load, so it seems best practice to parallel capacitors onto the pack lines near the inverter. I think it's important to use braided between cells, so vibration doesn't cause stress fractures. Question is, is any C compensation built into the inverter? If not, how big a caps, to make its load resistive? Sizing depends on knowing the resonant frequency, and this is supposed to be pure DC from the batteries, so what resonant freq is causing inductance?


The controller has CAP's inside, so you shouldn't need to do that. Most of the well designed controllers use large EV rated Capacitors that take care of this issue. If you have questions, consider asking the manufacturer. If you use something like Soliton for DC, I know that the Evnetics guys will answer questions readily. Harder to get answers from larger companies, but it helps.


----------



## major (Apr 4, 2008)

Quantum said:


> I don't have unlimited time to study this, but it seems that no one is accustomed to think in terms of *watts per newton-meter*, and that's what all this boils down to.


A watt per newton-meter is an inverse second. You're right; I am not accustomed to thinking in terms of inverse time. 




> Here is a calculator which converts watts to joules (newton-meters).


Show me that please. It does not convert watts to joules. The watt is a unit of power. The joule is a unit of energy. You do not seem to know the difference.



> So a given weight requires a given wattage to move a given distance at a given rate.


I don't even want to get into this statement. 



> I do not buy the notion that it takes the same wattage to move 1 pound as it takes to move 1,000 pounds one meter at 1m/s, at a fixed gear ratio much less with multiple gears. This is what it all comes down to.


First off, I have not seen anybody say this. Secondly, I am somewhat confused by your use of weight instead of mass. When you say "1 pound" or "1000 pounds" do you refer to the weight of the vehicle, or the force needed to overcome the friction and aerodynamic drag?

Edit: It just occurred to. Quantum? Are you confusing work with torque? They do both have the units of Nm, but are very different physical quantities.


----------



## JRP3 (Mar 7, 2008)

Quantum said:


> JRP3, 'misguided'? I still don't have evidence of that. Sure, I'm guessing that I'll set the shiftpoint from 1st to 2nd very low, maybe starting in 2nd, but your denial that overdrive won't help range defies common sense.


It doesn't defy common sense, your interpretation of the way electric motors deliver power efficiently is simply incorrect. An over drive lowers the RPMs of the motor, if it lowers the RPM's too low, as most OD's designed for ICE's will with an electric motor, the motor will draw higher amps at lower voltage and will be LESS efficient, not more. It will also likely overheat. 


> - Had another big conundrum this morning at 2:00am, but the unscientific opposition here has me a bit put off and I can't remember it.


I'm sorry but the opposition here is very scientific and based on a decent understand of electric drive characteristics, which you apparently lack, and instead of learning as we all did at first you seem intent upon criticizing those of us that are trying to educate you. I'm not suggesting that you shouldn't question what we are saying, but when a group of people who have been working in a area for a while tell you where you are mistaken you might want to figure out why you are wrong instead of telling all of them how you know better and that they are unscientific. Just a suggestion.


----------



## Bowser330 (Jun 15, 2008)

Suggestion: Quantum, listen to others on the boards, they know a lot about this stuff...


----------



## Overlander23 (Jun 15, 2009)

Here's a thought experiment. Assume a drivetrain where the motor has the same degree of efficiency from 0-5000 rpm. Now take that drivetrain and power a vehicle traveling a constant 50 mph. Which will consume more energy, spinning that drivetrain through a gear ratio that yields 4000rpm to maintain the 50mph, or spinning the motor at 1000rpm to maintain 50mph?


----------



## frodus (Apr 12, 2008)

> At this point I can only accept this as reasonable heuristically. I just don't have time to study it deeper.


 Fair enough. They're estimates. Without R&D and dyno numbers, it's hard to tell.





> Stands to reason. The travel of a car over all kinds of surfaces will cause vibration of many frequencies, including the resonant freqs of the batteries. Maybe in an M-B running on airbags it's not really a problem, but if in 5 years guys are getting dead cells for unexplained reasons, I think I can explain them.


Well, the lithium is a paste, it's not crystaline, so I don't think there's much issue with stress fractures. The metals used inside are foil and carbon. If it breaks through the coating of the anode/cathode, it will self heal. Something to look into though. Putting it on rubber mat, or mounting the box on engine mounts (rubber for vibration) may not be too hard. I think if you use a BMS mounted on the cell, they'll be more sensitive to strong vibration than the cell.



> Eric doesn't cool them and I respect his design skill. Viktor does and is in my neck of the woods. I will have to have a cooling system anyway, for the motor and inverter. I expect to use the OEM radiator, in place.


Where do you live?



> As to BMS I do not like that centralized. A whole hash of wires everywhere. OTOH a distributed system generates alot of heat right at the cells, although maybe only at first until they are essentially balanced.


well, depends, I know elithion is in the mA units of current, so it depends on the BMS. Some others shunt amps of current. The shunt usually turns on towards the end of charge, so it's not for a huge amount of time. They're not on during discharge, so that is good for cell over-heating.



> Certainly need as much intel as possible at the cell, hopefully temp, voltage, current, with the cell having a unique address to send info on a single line to the BMS monitoring board, which can be interrogated. Need to be able to easily ID a dead/underperforming cell and where the heck it is...


Elithion comes to mind, contact me if you want more info. It's distributed with a central control module that reports all of what you want.



> Say, with the cells banded, it's going to be damned hard to replace a dead one. Hate that.


You could test them before you install, to keep the bad ones out to begin with. I'd say it's a bigger risk without a BMS.



> Straw man argument. I never said RPMs too low, and that's not the meaning. I am saying shift from 1:1 to .7:1, which is well within the range of the power band. Lower RPM, same speed, only a tiny bit more load at that speed, it must draw less current. I can't prove it though, as I am very busy with other things and you shouldn't use a straw man.


lower RPM, same speed, more load would equal slightly more current motor side, but battery current MAY stay unchanged, depending on the RPM and load change.... so yeah, both of you can't prove it, but looks like it could use some research. Most of that is going to come from the motor torque curves. So once you chose a motor, that will come into play.




> What I've seen so far is what I call 'street knowledge'. It's, "don't do that, do this because it just works". I'm looking for theoretical underpinnings, and I'll have to find them myself. That's why I say don't worry about it


as long as you dont rush too much, we're here to help if you'll take SOME of our advice. We spend a lot of time helping people, and I have a consulting business doing just that.... so anything you need, let me know, I'll try and help. If I can't, I know people that can.


----------



## aeroscott (Jan 5, 2008)

Y0u were looking for metal fatigue , Particularly bad do to harmonics structural and harmonics electrical (ringing) , which can become structral . MB does a great job on harmonics in general , ie rubber donuts in the drive line instead of u-joints , etc. vibration / shock mounting would help component life . I'm a big fan of single speed ev's for simplicity sake , but tesla was able to get a higher 0-60 speed( in 1st gear) with a 2- speed . As a high end ev it's nice to have lower speed motor at the cruse speed . Also nice is a very low ratio diff (2.25/1 extreme for ev's) , keeps the drive shaft vibrations down . As is done on the high powered MB's . But means bigger motor /controller .and higher c rate on battery , bigger pack or 2 speed. If trans is 2/1 in low effective 4.5/1 overall , 1/1 in high effective 2.25/1 for (2000rpm's @ 60mph)and those 100+mph bursts . What a ride


----------



## Overlander23 (Jun 15, 2009)

Quantum said:


> Yeah, I agree.


Was there an answer in there?


----------



## frodus (Apr 12, 2008)

Quantum said:


> How does Elithion do this? How does it measure current, with a shunt? How prone are these to failure? With 120 cells in series, one shunt or cell fails, I get towed home. Another good feature is auto-bypass.


www.elithion.com for more info
It measures current with a hall effect. Not on the cell level (the current is the same for all series cells unless you parallel them). So just one sensor coming out of the pack is needed. The shunt resistor is small because you don't NEED a huge shunt unless your pack is way out of balance. If you properly equalize before you install the pack, this shouldn't be an issue. Elithion is a full fledged BMS system, like the Manzanita system. The Manzanita has boards in groups of 4 or 8, and is also a great system. I can help quote a system for both (work for both companies).

If one cell fails, you'll know about it via the BMS, it'l fault. If it faults, you'll know and can stop. You can bypass, but you won't want to do that. If it measures a cell too low, you don't want to drive. 

They're not very prone to fail once they're installed. Some fail, but you know as you're installing and setting them up. 




Quantum said:


> And what about these synchronous motors they mention? WTH is that?


It's a BLDC motor, brushless DC, or also called Permanent Magnet AC. it's not an induction motor, it has magnets in the rotor.





> NP. I'm grateful for help. (although impatient with ego) Must split pretty soon, as things are piling up.


yeah, lets all relax a bit, we'll get ya sorted.


----------



## aeroscott (Jan 5, 2008)

IF MB hasn't changed there ways , they use 2 or 3 sizes of diff . depending on power /weight . within a size they will have from 3.75/1 to 2.25/1 ,the smaller engined cars will have higher numbers . My 2.25 was in a E420 and will go into my 300d for better mileage .


----------



## frodus (Apr 12, 2008)

> their site is dead.


wait a day or two, Davide is making some site changes.



> Eh, ideally measurement should be at cell or multi-cell level. I'll look at both systems when tech info and time permit. I have alot of respect for Manzanita equipment, but (at least years ago) Rich was a bit testy, as so many of them are.


Well, that doesn't really work out too well in the real world. Monitoring cell current would be VERY expensive, one sensor per cell. If you only have say 200Ah cells in series, then it's not so bad. But consider Headway 10Ah cells, 20 in parallel, then it gets pretty messy.

It's at the cell group level, i.e. batteries in parallel are all at the same voltage. They'll measure the same voltages. There's no way to detect a bad cell in parallel unless you monitor all cell temperatures. No BMS that I know does that, although the Manzanita has temperature probes and the Elithion monitors board temperature of the cell modules.

These will tell you if they see anything fishy, i.e. the voltage or temp of that group looks out of place.

Rich is a very smart guy, but has little patience sometimes. He's very busy so don't take offense, thats just how Rich is.





> Knowing _which_ cell has failed is important.


if you're only using 120 in series and not paralleling them, then these BMS will do that. If you have 240 cells (120 series, 2 parallel) then these can detect a bad group. No BMS that I know of will detect a bad cell in a group of parallel cells, but that bad cell WILL effect the other cell voltage if it shorts, and you'll immediately know about it, but you wouldn't be able to do anything about it unless you can quickly remove that battery so that the good cell doesn't discharge into it. I've never heard of that happening.





> OK, like those big-diameter motors you can gang up. Well warrants looking into, but if not exceptionally better than or more accessible than AC (or if lacks regen) I'll stick with AC. I was a strong proponent of AC at SEVA back before it'd entered anyone's consciousness, therefore I turned out to be a PITA. Nobody will remember me tho, as I didn't stick around not being able to learn anything and all...


Well, kinda. Those are versions of BLDC motors (sound like axial flux PMAC), but there are many flavors. Not just that kind. Some of the BLDC has better performance per weight because of the magnets. You don't have to generate the flux in the rotor. And it "IS" AC, it's just a different type of AC motor. AC Induction (Siemens) is Asynchronous. PM AC (UQM, Remy) is synchronous. Accessable depends on your pockets.


----------



## JRP3 (Mar 7, 2008)

Elithion seems to work without the www.
http://elithion.com/


----------



## JRP3 (Mar 7, 2008)

Quantum said:


> Overlander, you posed a very good question, and I +1 that question. I don't know the answer, but it gets at the center of the issue.


It was a rhetorical question. The answer is they would be the same, which as you say gets at the center of the issue.


----------



## major (Apr 4, 2008)

Quantum said:


> No, it wasn't...


It was obvious.


----------



## major (Apr 4, 2008)

Quantum said:


> ...
> And no, it isn't.


Can you explain what you mean?


----------



## Overlander23 (Jun 15, 2009)

Quantum said:


> Overlander, you posed a very good question, and I +1 that question. I don't know the answer, but it gets at the center of the issue.



Ahh, OK. The answer, in this particular case is that both configurations would yield the same energy consumption. It's down to the physics of moving an object. In this case, the factors acting to consume energy are primarily rolling resistance and air resistance. You could say that the motor presents an inefficiency, but since we're talking about the same level of inefficiency regardless of motor speed, you can cross that out of the equation.

Power, for our purposes is referred to as the amount of instantaneous wattage. Energy is power over time.

Watts (power) are simply volts * amps, the latter being current. Volts dictates the speed of a motor, and amps dictate the torque generated by the motor.

So given the previous scenario, what you'd see is a higher voltage necessary to spin the motor at a high rpm (in this case 4000rpm), and a lower voltage to spin the motor at a slower rpm (1000rpm). Conversely, the current required to maintain speed with the motor spinning at 4000rpm would be less than the current used at 1000rpm. In both cases, the amount of power remains the same.

You're either doing 10 amps at 100 volts to use 1000 watts of power, or 100 amps at 10 volts, being 1000 watts of power, to achieve the same goal of maintaining a vehicle velocity of 50mph.

Theoretically, you can examine the system and determine differences in energy consumption factors which would then yield inequalities in power usage. In the drivetrain example, both scenarios have equal efficiencies (as a dictated condition)... so you can throw them out of the equation. That leaves rolling resistance and air resistance. Again, both of these situations have identical drag factors (a vehicle traveling 50mph). So you can throw those out as well. What do you have left that's different between the two examples? Nothing. So, the two examples would consume the same amount of power.

If one of those factors was different between the two examples the outcome would be different. If, for some reason, the drag resistance of one example was higher than the other, the energy consumption would be higher. Or if the efficiency of spinning the motor at 1000 rpm was higher than spinning it at 4000 rpm there would be a higher energy consumption at the higher speed.

In the case of an ICE vs an electric motor, the efficiency curves vary greatly. From a drivetrain perspective, there's significantly more frictional drag with an ICE than an electric motor due to significantly more moving parts in the former. There are also pumping losses in the ICE that just don't occur with an electric motor. And, significant efficiency in an ICE is lost to heat both radiated from the engine block and via the exhaust. It's claimed that the Bugatti Veyron's W16 actually produces 3000 hp, but 2000 of it is wasted to inefficient heat. Electric motors have no exhaust, and produce significantly less heat for the amount of energy they convert to motion (which is why they're anywhere from 75%-95% efficient.)

The upshot is that the ICE has a very narrow band of high efficiency (which is still, unfortunately, pretty mediocre). And, it's why all EV range extender engines are designed to operate within a fixed rpm band, why the industry is moving to 8-speed gearboxes, and why the CVT transmission generally yields the most efficiency. Conventional transmissions are used to keep the ICE in its most efficient rpm band.

An electric motor has a much, much wider efficiency band. It starts off low (but still at around 75% efficient), slowly rises to peak past max power (around 80-85%), and then starts to drop out past its rotational limit. It's really a very broad efficiency curve. Reference any manufacturer's motor curves to see this.

Take your example of using a transmission's overdrive gearing to drop the speed of the motor. In this case, the voltage drop required to spin the motor at the slower speed would actually increase the current requirement to maintain the same vehicular velocity. Power consumption remains the same. If, though, a motor is most efficient past peak power and higher in its rev range, then you actually risk dropping efficiency by slowing the motor down.



Quantum said:


> But comparing direct drive with the tranny in first (2.84), the current required to start this heavier car will be massive in direct drive, compared with the tranny. More torque required means more current draw.


Yes, this is correct. But see below for a more complete description of this.



Quantum said:


> And with overdrive, essentially giving it 30% longer legs on the freeway at virtually no current cost... there is a big savings on a heavier car, and so much more complex to calculate.


This isn't so much correct for the very reasons you've given. As you know, lower gears increase torque multiplication. Higher gears lower torque multiplication. Using an overdrive lowers torque multiplication which would raise current draw/cost.

But current draw isn't everything. Power is. And as stated earlier, power is current * voltage. In the case of acceleration from rest you have high current (torque) but at a low but increasing voltage. You may have a 400v system, but the 400v isn't delivered all at once, it's pulsed (using PWM). So, over the course of one second of acceleration you will only see a much smaller voltage average, but at a high current. And this, of course, translates to less but increasing power.

As long as the system can handle the current draw, everything is OK. In the end, it'll either be high speed with less current, or lower speed with more current.

In fact, different motor designs cater themselves to different characteristics. A high-speed AC motor like the Tesla's motor (14,000 rpm) requires a large gear reduction to be used practically in a vehicle, while most series DC motors come in at around 5000 rpm, require a much smaller gear reduction, but produce similar power by having more torque. The gear reduction gives the Tesla torque from its higher speed. The design of the slower DC motor provides more torque at lower speeds. I believe the only real design constraint to higher rpm DC motors is the brushes bouncing off the commutator becoming impractical.

Theoretically, the most efficient system doesn't involve any gear reduction at all (since energy is wasted in the gearbox.) But unfortunately, designing a motor to compensate for the amount of torque needed yields a somewhat inefficient motor. So you take your pick, a high efficiency, high spinning, low torque motor that uses an energy sapping gearbox, or a lower efficiency, low spinning, high torque motor that doesn't waste energy with a gearbox. Argueably... it's usually a wash.


----------



## Duncan (Dec 8, 2008)

Hi Quantum,

When looking at the vibration isolation on the MB remember that things like engine mounts on IC engines are very soft to isolate the firing vibrations, the drive-line is also soft torsion-ally as an IC engine gives a pulsating torque,

Electric motors are not totally smooth but they are a lot smoother and the impulse frequency tends to be a lot higher.

The net result is that the MB vibration system will be much too soft, you should think about stiffening it up where practicable


----------



## etischer (Jun 16, 2008)

Quantum said:


> As to BMS I do not like that centralized. A whole hash of wires everywhere. OTOH a distributed system generates alot of heat right at the cells, although maybe only at first until they are essentially balanced.


I would avoid centralized BMS if you can, but when cells are mounted under the car, in the spare tire well, and generally impossible to reach places, centralized is more practical. Centralized BMS also keeps the circuit boards in a clean dry environment. It is also convenient when you want to measure cell voltages, since all the cell voltages are centralized. 

The battery pack in my car is sized for range (99 x 100Ah). My average battery current on the freeway is about 0.5C so not much heat is generated. Smaller packs will be pushed harder, higher current draw will produce more heat, and these are the instances when you need water cooling for the battery. My pack doesn't get much above 5 degrees above ambient, a water cooling system would just add additional points of failure. You might consider battery warmers if you live in a cold climate. 

Inductance in the battery wiring isn't what blows up IGBTs, it's the inductance between the IGBT and the DC capacitor bank in the motor controller. 

Duncan makes a good point about driveline rigidity. With the instant torque from an electric motor, the soft squishy ICE mounts are too soft. The ones in my Passat were liquid filled and ruptured within a week. I highly recommend solid rubber mounts.


----------



## drgrieve (Apr 14, 2011)

Overlander23 - that was a really good post. Maybe you could add that to the wiki.

Quantum - I'm also pretty new to the electric game but after several months of reading and watching evtv videos I can say I agree fully with all what these guys are saying. My advantage is that I also don't know much about ICE cars so I have less pre-conceived notions. Less to unlearn.

I have one thing to add to the conversion. Several build threads mention that the drivers also prefer lower gears when freeway cruising to keep the motor in the peak efficiency band for their pack voltage and also if the motor relies on an internal fan the RPMs must be kept higher or the motor will overheat on a long or arduous drive.

Putting it another way - I haven't read a ev build thread were the builders mentions they use 5th gear legally on the road - whereas in my daily driver I'll use it at 80km to save some fuel.


----------



## JRP3 (Mar 7, 2008)

CALB's are rated at 3C max charge, which for 100ah cells means 300 amps of regen. I rarely see more than 200 amps of regen for a couple seconds in my 120V system and that can stop me quite quickly with the final bit done using the brakes. I could turn it up but the few seconds of friction braking would equal minimal amounts of energy. In a higher voltage system you'd see even lower current. I don't think it's worth paying substantially more for cells that could take a small amount of additional regen, though there are other reasons to get higher C rate cells.


> Clearly everyone knows motors get hotter at higher RPMs, don't we?


No we don't, since we all know our motors run cooler at higher RPM's. 


> And if the motor's speed is held constant, comparing overdrive and third, the car goes 30% further in overdrive for about the same amount of energy used.


Think about what you are saying here and why it's not only wrong but impossible.


----------



## Woodsmith (Jun 5, 2008)

A motor spining at high RPM uses a higher voltage and a lower current.
Reduce that RPM and you are reducing the voltage and increasing the current to provide the same power output. That is what you are doing when you go into overdrive gear. Road speed stays the same but motor speed reduces.

If the motor speed stays the same then the road speed increases but that requires more power, it has to as the resistances increase. To increase the power to the motor at the same RPM means the current increases but not the voltage.

The problem with increasing current and running overdrive instead of increasing voltage and running a lower gear is the I²R losses.

Increased current creates heat due to the I²R losses so the motor producing the same power output becomes less efficient and hotter when run at a lower RPM then at a higher RPM.
It is the opposite way round to an ICE.

In my ICE car I run at very low RPM for efficiency and a cool engine. If I run at high RPM I use more fuel and create more heat. So in this case running a higher gear ratio is beneficial. It is not beneficial in an EV as the motor is more efficient at high RPM with low current and less heating.

When JRP says the motors run cooler at high RPM he means they actually generate less heat, and hence less losses, then when they are running slowly.


----------



## dtbaker (Jan 5, 2008)

Woodsmith said:


> A motor spining at high RPM uses a higher voltage and a lower current.


and the internal fan moves more air


----------



## Woodsmith (Jun 5, 2008)

dtbaker said:


> and the internal fan moves more air


We haven't even got to that bit yet.


----------



## etischer (Jun 16, 2008)

Quantum said:


> At higher RPMs there are far more losses given up as heat. Clearly everyone knows motors get hotter at higher RPMs and consume logarithmically more amps, don't we?


Depending on what the load is, the opposite is true. Maintaining 60 mph on flat ground, you need a fixed amount of power. Your motor will use more amps if it is at 1000 rpm, compared to 8000 rpm. 

If you are comparing motor amps at 60mph vs 70mph using the same gear ratio, then yes, higher rpm = more amps = more power.


----------



## major (Apr 4, 2008)

Quantum said:


> Woody, look at the torque curve in my long post above. The sweet spot is just around 4,500rpm. Get above or below (particularly above), and* ever-decreasing efficiency* and more waste.


Is this the curve you refer to? http://www.evdrive.com/bmw_project/specifications.html Please show us how you determine efficiency from it.


----------



## major (Apr 4, 2008)

Quantum said:


> Please show us why you peck-peck-peck, rather than using your considerable resources to contribute positively to the discussion, major? Your tone is petulant in every post lately. I think you have some significant life frustrations outside this board. I am not interested in contending with that.


So you can throw any BS you want up on this board and then get offended when someone questions it? You don't like my tone. Then put me down with facts and reference material to support your erroneous and incorrect statements. Don't just insult me. You can keep on posting BS, and I have every right to point that out. Post correct and factual items, and I will likely disappear from your thread.

This thread has over 1900 views. Has there been a single post which has supported your views on electric motors? And doesn't the name of this thread, Upscale Car Conversion, kind of put down the rest of the folks here who have done conversions? Like you're better than they and can do a better up-scale car.

Give me a break and answer my questions. How did you determine motor efficiency from that curve?


----------



## major (Apr 4, 2008)

Quantum said:


> Your tone is petulant in every post lately.


And you were so nice to me first  


Quantum said:


> You don't see how a transmission gears down and gives mechanical advantage?
> 
> Or how a lower gear requires less torque for the same work?
> 
> Or how in torque matching mode the controller keeps the torque (current draw) the same for both motors?


----------



## Elithion (Oct 6, 2009)

Quantum said:


> Ya, their site is dead.


Sorry about that. We use a shared server, and another tenant was a bad boy, which made all of our sites nearly unreachable for a few days.

We just changed hosts, and the site is now fully up, including the support forum.


----------



## major (Apr 4, 2008)

Quantum said:


> I noticed earlier you suggested I was "bragging".


I think you have me confused with some other post. I do not remember this.

Anyway, I asked a simple polite question. 


major said:


> Is this the curve you refer to? http://www.evdrive.com/bmw_project/specifications.html Please show us how you determine efficiency from it.


 But you cannot provide an answer, so you start insulting me. Forget the drama and show us how you determined motor efficiency from that curve like you told Woodsmith.


----------



## major (Apr 4, 2008)

Quantum said:


> I will address your question when you admit you are motivated by jealousy.
> Until then NO MORrE SOUP FOR YOU.


Very adult response


----------



## major (Apr 4, 2008)

major said:


> I am not sure why you came to this forum  Just to show off, or to learn some things about electric propulsion. It is quite different from ICE.


O.K. I didn't use the word brag. And I was actually being facetious as to you showing off your knowledge.


----------



## rwaudio (May 22, 2008)

Sorry I haven't read the whole thread, the bickering wasn't worth wading through..... have you chosen a donor Quantum, do you own a CLS?? What kind of performance are you looking for? My daily driver is an '07 G35 and I think it would make a great EV, other than being a bit overweight to start with, but I don't know about the stock transmission.... the car may have 306hp as a gasser but it's always in the wrong gear (an auto) to use much of it even when driving in "sport" mode. To get any real performance out of the car you must drive in manual mode, I don't know if the newer G's would be any better with their 7 speed auto's.... it would give lots of gear ratio choices though. How's the tranny in the CLS? Or the one you mentioned in your first post?

The Porsche is my first EV, smaller/lighter/cheaper/manual. I'd like to see a few higher end conversions, especially newer cars to see how well the EV drive train integrates and what it delivers as far as driving experience.


----------



## JRP3 (Mar 7, 2008)

Quantum, the only "progress" being made in this thread, very slowly, is that you might be starting to see how wrong most of your assumptions are. All of us posting, including Major, already know the facts we are presenting. You have brought zero new information, we are simply trying to improve your knowledge, in spite of yourself.


----------



## EVfun (Mar 14, 2010)

Quantum said:


> Eh, part right. The power curve drops as RPMs increase, so dropping that motor's speed brings it to a happier place in the curve. At higher RPMs there are far more losses given up as heat. Clearly everyone knows motors get hotter at higher RPMs and consume logarithmically more amps, don't we?
> 
> And if the motor's speed is held constant, comparing overdrive and third, the car goes 30% further in overdrive for about the same amount of energy used.


"The power curve drops as RPMs increase" 
Yes

"dropping that motor's speed brings it to a happier place in the curve" 
No, the motors happy place for efficiency is generally in a higher rpm range than the happy place for power. Of course, in extremes that could be true. The motor is likely more efficient at 2000 rpm than 7000 rpm. For a typical one gear change in a car you are often better off in the lower gear.

"At higher RPMs there are far more losses given up as heat"
No, There are higher fan losses in an aircooled motor, There are increased bearing losses and magnetization losses. However, the big heat in a motor is I^2*R, resistive losses. These losses go up at the square of the motor current. When operating a motor at a fixed power level but 2 different rpms the motor current is higher at the lower rpm. 

"Clearly everyone knows motors get hotter at higher RPMs"
No, experience says otherwise. Motors get hotter than the blazes when you insist on operating them at low rpms for any length of time. Search the site for newbie EV owner stories and you will find more than one case of motor failure related to operating the EV on the freeway in high gear. I've built a few EVs and know firsthand that freeway one gear below high results in a cooler motor when compared to freeway in high gear. I have not noticed any difference in range.

AC induction motors change things a little, but underneath the basics are the same. You make torque with amps, you make rpm with volts. You make heat with amps. As far as going down the road at a steady speed, the battery amps will be nearly the same in any gear. It will vary slightly for changes in motor efficiency at different points on the curve.

I'm attaching the performance graphs of a typical series wound motor. The top set of curves are for 100 volt operation. Notice where the peak efficiency is at, about 3800 rpm. Also notice how lowering the voltage lowers the whole efficiency curve.


----------



## david85 (Nov 12, 2007)

Well, in general, electric motors want to be run in their efficiency band. For some motors that will be 1750 RPM. For others it may be above 7000. The map posted by EVfun demonstrates one example of the sort of information you need to take into account when trying to setup a powertrain for a conversion.

If however you decide to retain the original 4-7 speed transmission, its pretty much a given, that you can keep it well inside that rather wide operating zone with an even wider overlap between gears. I don't have much overlap with my relatively low RPM motor, but something like a siemens that can run efficiently over 7000 RPM will not benefit from having that many gears to choos from. I don't see how it would hurt very much either however.

And can we try to avoid these personal jabs maybe?


----------



## david85 (Nov 12, 2007)

Quantum said:


> Well I have many things to do, so will analyze EVFun's post later. Offhand though, I don't see any references or annotation except that old DC motor chart.


This is taken from Metric Mind's website for the siemens motor (unfortunately, they don't show an efficiency plot on here):


----------



## david85 (Nov 12, 2007)

With apologies for the size of the image, here is the plot for the MES motor, including efficiency:

Note how the efficiency and holds fairly steady well into the upper end of the RPM range. This is generally how most AC motors perform. The rated RPM on this motor is stated as 2800 on the Metric Mind website (right where efficiency peaks).

More info here:

Motors: http://www.metricmind.com/motor.htm
Full website w/sidebar: http://www.metricmind.com/


----------



## Overlander23 (Jun 15, 2009)

Unfortunately/fortunately in the time it took me to write as much as I did, several people posted with supporting posts. Eh, I'll post anyway...



Quantum said:


> Eh, part right. The power curve _drops_ as RPMs increase, so dropping that motor's speed brings it to a happier place in the curve. At higher RPMs there are far more losses given up as heat. Clearly everyone knows motors get hotter at higher RPMs and consume logarithmically more amps, don't we?


Yes, the power curve drops as RPM increases... but I'm not sure how that links in with efficiency. Rarely is max efficiency to be had at max power (this isn't even the case with an ICE). See links below for where a motor does produce its max efficiency in relation to power.

I'm not sure everyone does know that motors getter hotter at higher RPMs and/because they consume logarithmically more amps by design or innate characteristics. In fact, they don't. If this were true it would mean that the motor was getting logarithmically more inefficient at higher speeds. And I agree this would be the case if you ran the motor outside of its designed operating parameters. An efficiency curve would prove this; I've linked to several below.

Notice that all the efficiency plots start low, increase with rpm, and then they trail off with higher RPM. Also notice how broad the efficiency curve is... and how high a level of efficiency they begin with.

Here's a Kostov Series DC motor curve: http://kostov-motors.com/files/productattachments/e2dd0a6a56533b75d3fb6ce7a96d2dee_perf11-192V.pdf

Here's a Siemens AC motor curve: http://metricmind.com/line_art/efficiency.gif

Here's a Netgain Series DC motor curve: http://www.go-ev.com/images/003_15_WarP_9_Graph.jpg

If you're seeing a logarithmic increase in power usage or energy consumption then it's down to the application, or you're pushing the motor too hard, above its rated capability. And pushing a vehicle through air does indeed increase aerodynamic drag exponentially.

_major's_ question was a good one... and trust me, I'm not writing all of this to ***k with you. Nor is he. How are you determining peak efficiency? What information or anecdotal evidence do you have?

This comes down to the vast difference between ICE and electric. In electric, peak efficiency does *not* arrive at peak torque (as with an ICE under WOT), rather it arrives at about 75% of the rated speed of the motor, it comes after the power peak, and typically at less that 1/2 the stall torque; cited here, http://www.fastelectrics.com/elecmotorbasics.htm and here, http://en.wikipedia.org/wiki/Electric_motor#Efficiency

For that matter, a motor's torque curve peaks at 0 rpm, but slower speeds is exactly where a motor is inefficient. So, you can't tie a motor's efficiency with torque the way you do with an ICE.



Quantum said:


> Woody, look at the torque curve in my long post above. The sweet spot is just around 4,500rpm. Get above or below (particularly above), and ever-decreasing efficiency and more waste.


Given the sources above, and the three ways in which to guestimate peak efficiency, I would wager that, given that graph, with the power peak at around 4700 rpm and the max rpm to be 10,000 rpm, the actual point of peak efficiency would be closer to 7500 rpm. Add in the idea that peak efficiency is typically less than 1/2 stall torque, and I'd say that agrees even more (peak torque 317 lb/ft, torque @ 7500 rpm 150 lb/ft).



Quantum said:


> And if the motor's speed is held constant, comparing overdrive and third, the car goes 30% further in overdrive for about the same amount of energy used.


 I'm confused by your quote, can you help clarify? Keep in mind that to keep the motor speed constant in third and in overdrive the vehicle has to travel faster in overdrive (which leads to aerodynamic drag losses, and more energy consumption). We're talking a gear reduction here, so I don't know how this particular scenario works if the vehicle is meant to, alternatively, stay at a constant speed.

Why does the car go 30% further for the same amount of energy? Is it because the overdrive gear moves the system into a 30% more efficient motor state? I don't see how this is possible if the motor speed stays constant. Or because the gearing creates 30% more efficiency within the gearbox? Or because the gearing creates 30% more efficiency in the flow of current, or power, or something else? I will admit, this last sentence is a baited one, forgive me.



Quantum said:


> More complicated than this friend. Current is actually what is pulsed (actually conditioned)(transistors can only control current) to the motor in three phases. (PWM is DC) The full voltage is applied (conditioned), but it is pulled down by the load to deliver the current. Well done though.


(Bare with me here. I know you know something about this, but as you've mentioned, there are others that may not know who may learn something. It may get slightly pedantic.)

I never claimed differently. I wrote, voltage is pulsed (in my particular example, 400v). You can't have current flow without voltage, ergo, current is pulsed. I'm not in disagreement there. Let's agree to state that "energy is pulsed". 

What I said was, the amount of voltage over time the motor sees is less than full voltage over the same period of time. This is, of course, due to the PWM duty cycle. 

If the energy is pulsed such that it's only "on" 10% of the time, then over one second the motor, on average, sees 40v. If, on the other hand, the duty cycle is raised to 100% than the motor sees 400v, on average, over the same one second period. What are the effects? Well, since voltage determines motor speed (not current), in the first case, the motor runs slower... in the second case the motor runs faster.

But we all know that's the effects of PWM control.

Current is determined by load. If the motor is unloaded and asked to run at a 10% duty cycle, it will dutifully spin slower while consuming little amps. Move the duty cycle to 100% and the motor will spin faster similarly consuming little amps. After all the load hasn't changed.

This is where the concept of power comes in. The controller pulses energy to create an amount of power (under load). You may not know it, but you tend to speak very little of power, but quite a bit about current. Current alone is not power, therefore it cannot account for an amount of energy used. Current, by itself, if largely irrelevant. Current *with* voltage (electrical potential) *is* an amount of power and *can* account for an amount of energy consumed over time. It's much more useful. Here are two examples: 

Ex #1
A) 1000 amps at 10 volts for 1 sec
B) 1000 amps at 1000 volts for 1 sec

Which scenario produces more power and/or consumes more energy? 

Ex #2
A)1000 amps at 10 volts for 1 sec
B)10 amps at 1000 volts for 1 sec 

Same question, which scenario produces more power and/or consumes more energy?

So back to the controller and an unloaded motor. Ramp the duty cycle from 0-100%. 400v is pulsed through the controller (along with an amount of current). If the motor has a constant efficiency curve across its speed range (which it actually doesn't, but we've done this already), then as the motor speeds up the amp draw will actually decrease as the PWM duty cycle approaches 100%. Why? Because an unloaded, constantly efficient motor, has to do a constant amount of work... spin itself up. Therefore, it requires a constant level of power consumption. And due to the inverse relationship between current and voltage in creating power, as average voltage increases with the increasing PWM cycle, the only thing that can happen is for current to inversely drop. 

I get the impression that you think of amp usage as a potential raging current. But you have to characterize it. Is it a raging current of air, water, molasses? Each presents a completely different power and energy consumption scenario.


----------



## Overlander23 (Jun 15, 2009)

david85 said:


> With apologies for the size of the image, here is the plot for the MES motor, including efficiency



Wow, can you change the image to a link? Or resize the image? It's wreaking havoc with the page formatting.


----------



## david85 (Nov 12, 2007)

Overlander23 said:


> Wow, can you change the image to a link? Or resize the image? It's wreaking havoc with the page formatting.


Yeah sorry about that. Should have just attached instead of linked to it from the start.


----------



## coulombKid (Jan 10, 2009)

glaurung said:


> Hi, is there a reason for using ac? HV 11", dual Solitons to max voltage, would be cheap, powerful and ready to be picked up. Any trans would do,why not use original?
> No need to invent anything, just install and go
> Harri


 I swapped email last week about with metric mind about the hole in AC products availability. They project that their big inverter will be ready in 2012. When its released it will only be paired with one of their motors. 400hertz engineering is in the same boat. They want about $25K for their big motor inverter combo.


----------



## JRP3 (Mar 7, 2008)

Quantum said:


> Redacted, because none of this matters.


 Looks as if someone erased himself from history. Interesting reaction to receiving information that contradicts your assumptions, you go back and erase all your posts. I think we see what we are dealing with here, in case there was any question.


----------



## major (Apr 4, 2008)

JRP3 said:


> Looks as if someone erased himself from history. Interesting reaction to receiving information that contradicts your assumptions, you go back and erase all your posts. I think we see what we are dealing with here, in case there was any question.


Hi JR,

This behavior really irritates me. How fair is this to those who took the time and posted lengthy replies trying to help this guy? We've seen others erase themselves or selected posts. It is why I try to use quotes in my replies. They can't erase quotes in others' posts.

And it is hard telling who Quantum really was. Not that it matters. But maybe some teenager in his mom's basement? Maybe some millionaire?

Oh well 

major


----------



## Quantum (Jul 10, 2011)

So of all the issues I've covered with this conversion, we are going to concentrate on power vs rpm, which everyone seems to think I have _wrong_. Awesome. Well *I've* learned alot in this thread, but it looks like nothing else I've said matters so I've kept it to myself. Matters to me. 

So let's talk some red beans and rice, then I'll get out of here because this is a definite bummer.



EVfun said:


> "dropping that motor's speed brings it to a happier place in the curve"
> No, the motors happy place for efficiency is generally in a higher rpm range than the happy place for power. Of course, in extremes that could be true. The motor is likely more efficient at 2000 rpm than 7000 rpm. For a typical one gear change in a car you are often better off in the lower gear.
> 
> "At higher RPMs there are far more losses given up as heat"
> ...


How does any of this argue against my contention that an automatic tranny would help at lower speeds, and at higher speeds? Makes things easier at lower speeds, raising RPM and increasing efficiency, and at high speeds lowers RPM reducing heat losses. The point is to keep the motor in its most efficient range, and you cannot do that with direct drive.




EVfun said:


> When operating a motor at a fixed power level but 2 different rpms the motor current is higher at the lower rpm.


You had better take another look at your chart. What _I_ see is at 3,000rpm current is 60A, and at 4,000rpm current is 80A. Of course at the lowest rpms the tranny will have you in a lower gear so rpms are much higher than they would be with direct drive. This was a waste of time.


Exactly, david85. OK so now we have a graph for my specific motor. The torque curves show that it's almost perfectly suited to EV use. Now in actual use, power draw will be a combination of Pmax and Pcont, Pmax being more dominant at lower rpms. This being wattage, we can't suss out the fact that amps will be way high and voltage low at the lowest rpms, and amps is what drains batteries. (I'll stop asking for others' confirmation as I seem to be alone) I have to say, the Pcont line is suspiciously flat from 4,000-10,000 rpm, which I don't understand, but it does destroy both arguments that overdrive helps/ hurts.

Now the MES motor, I'm not sure which one the chart is for, nor the % of nominal power, so am discounting the chart. Let's look at the MES 200-330W motor at 30kW (75% of full nom power, 240 VDC inverter input). You'll note that above 6,000rpm current does increase, although not nearly as much as I'd expected, and motor efficiency slightly declines above 7,200 rpm, supporting my position for overdrive although not nearly to the degree I'd expected. 




Overlander23 said:


> Given the sources above, and the three ways in which to guestimate peak efficiency, I would wager that, given that graph, with the power peak at around 4700 rpm and the max rpm to be 10,000 rpm, the actual point of peak efficiency would be closer to 7500 rpm.


Actually, that's not what the Siemens chart shows. Check it and you will find that just as I said, peak efficiency is around 4,500rpm (88%), and this is for the combined inverter and motor system. There are no efficiency curves above this, implying that Siemens does not consider the upper rpm range for normal use.



Overlander23 said:


> Quantum said:
> 
> 
> > And if the motor's speed is held constant, comparing overdrive and third, the car goes 30% further in overdrive for about the same amount of energy used.
> ...


Now I have proof with your chart. Hypothetically we are cruising at 60mph with 7,000rpm at 1:1 tranny gear ratio. Shift into overdrive (.7:1) and we maintain rpm so go 30% faster at 78 for the same distance and energy. Sure, higher aerodynamic losses in this case. Or we reduce rpm 30% to 4,900 to go 30% further and our power goes down from 22.5KW to 20.5KW (mechanical, don't have electrical), bringing us to peak efficiency though. Again this isn't as much a drop as I'd expected, but such is life.



JRP3 said:


> Looks as if someone erased himself from history. Interesting reaction to receiving information that contradicts your assumptions, you go back and erase all your posts. I think we see what we are dealing with here, in case there was any question.





major said:


> Hi JR,
> This behavior really irritates me. How fair is this to those who took the time and posted lengthy replies trying to help this guy? We've seen others erase themselves or selected posts. It is why I try to use quotes in my replies. They can't erase quotes in others' posts.
> And it is hard telling who Quantum really was. Not that it matters. But maybe some teenager in his mom's basement? Maybe some millionaire?
> Oh well
> major


You jumped the gun JRP3 and major. It's taken me a while to assemble this.
Why would I stick around for you two to pettily peck-peck-peck?
Life's too short and I'm going to enjoy it.

Two-headed snake a danger to itself
"A two-headed snake in a Ukraine zoo demands extra attention while being fed because its heads compete for food. (Yes, it has only one stomach.) Zookeepers have to place a divider between the heads at feeding time."


----------



## aeroscott (Jan 5, 2008)

I've driven a diesel with a egt(exhust gas temp, 5 speed & Gear vender) and double overdrives (the one I reshaped the body on last week) every time I shift to higher gears the temps. go up ( more load) on the engine , but at lower engine speed .


----------



## major (Apr 4, 2008)

I am copying this post so it cannot be erased.



Quantum said:


> So of all the issues I've covered with this conversion, we are going to concentrate on power vs rpm, which everyone seems to think I have _wrong_. Awesome. Well *I've* learned alot in this thread, but it looks like nothing else I've said matters so I've kept it to myself. Matters to me.
> 
> So let's talk some red beans and rice, then I'll get out of here because this is a definite bummer.
> 
> ...


----------



## Quantum (Jul 10, 2011)

You mean, just in case someone can find something wrong with something I've said? Since you can't?

No, I'm not going to delete that one.


----------



## EVfun (Mar 14, 2010)

I wrote previously:


> When operating a motor at a fixed power level but 2 different rpms the motor current is higher at the lower rpm.





Quantum said:


> You had better take another look at your chart. What _I_ see is at 3,000rpm current is 60A, and at 4,000rpm current is 80A. Of course at the lowest rpms the tranny will have you in a lower gear so rpms are much higher than they would be with direct drive. This was a waste of time.


You clearly don't understand how to read that chart. Using the 100 volts curves, at 4000 rpm the motor is drawing 240 amps while at 3000 rpm it is drawing 460 amps. Its efficiency at 4000 rpm and 100 volts is 85% while at 3000 rpm it has dropped to about 82%. Of course, since the power required to go a given speed in a given vehicle is fixed the motor voltage will be lower at 3000 rpm. This tends to lower efficiency too.


----------



## Quantum (Jul 10, 2011)

You're right, I did just take a cursory look at that chart, because it's a) for a DC motor, b) of the wrong size, and c) a low voltage, and so is irrelevant to the issue. Also the chart is ancient. Interesting that efficiency markings start at 60% for 4,000 rpm (*400 AMPS?!*), and go to 80% at the top rated speed of the motor. That motor must be 50 years old. No wonder everyone thinks what they think...


----------



## JRP3 (Mar 7, 2008)

Quantum said:


> You jumped the gun JRP3 and major. It's taken me a while to assemble this.
> Why would I stick around for you two to pettily peck-peck-peck?
> Life's too short and I'm going to enjoy it.


And yet you took the time to go back and erase all your posts, which clearly showed you didn't know what you were talking about, and also showed that you're a bit of a tool. I'm sure you'll keep doing the same, so I won't waste any more of my time on you. Have fun. Unsubscribing.


----------



## etischer (Jun 16, 2008)

Quantum said:


> So of all the issues I've covered with this conversion, we are going to concentrate on power vs rpm, which everyone seems to think I have _wrong_. Awesome. Well *I've* learned alot in this thread, but it looks like nothing else I've said matters so I've kept it to myself. Matters to me.
> 
> So let's talk some red beans and rice, then I'll get out of here because this is a definite bummer.
> 
> ...


Nobody here will recommend going direct drive to increase efficiency. Changing gears would help keep the motor in it's peak efficiency region (high rpms). Looks like you would gain 3-5% by using 1st gear instead of 2nd. For most of us, starting in 1st gear will just spin the tires, so 1st is never used. I use 2nd gear which covers 0-80 mph in my car. 




Quantum said:


> You had better take another look at your chart. What _I_ see is at 3,000rpm current is 60A, and at 4,000rpm current is 80A. Of course at the lowest rpms the tranny will have you in a lower gear so rpms are much higher than they would be with direct drive. This was a waste of time.


The graph shows max amps, this does not translate to efficiency. It doesn't mean at that RPM, that will be your current draw, it means you cannot exceed that current. 



Quantum said:


> Exactly, david85. OK so now we have a graph for my specific motor. The torque curves show that it's almost perfectly suited to EV use. Now in actual use, power draw will be a combination of Pmax and Pcont, Pmax being more dominant at lower rpms. This being wattage, we can't suss out the fact that amps will be way high and voltage low at the lowest rpms, and amps is what drains batteries. (I'll stop asking for others' confirmation as I seem to be alone) I have to say, the Pcont line is suspiciously flat from 4,000-10,000 rpm, which I don't understand, but it does destroy both arguments that overdrive helps/ hurts.


Motor amps does not equal battery amps. If you had 100 amps at 10 volts at the motor, you would have roughly 10 battery amps if you had a 100 volt battery.

A motors continuous power rating is basically measuring how well a motor can remove it's heat. Think of it like a heating element. You can put a certain amount of power in, the element reaches a certain temperature. PMax is the max power you can put in without overheating the motor. 



Quantum said:


> Now the MES motor, I'm not sure which one the chart is for, nor the % of nominal power, so am discounting the chart. Let's look at the MES 200-330W motor at 30kW (75% of full nom power, 240 VDC inverter input). You'll note that above 6,000rpm current does increase, although not nearly as much as I'd expected, and motor efficiency slightly declines above 7,200 rpm, supporting my position for overdrive although not nearly to the degree I'd expected.


From 2000 - 9000 the efficiency is between 90-92 percent. This supports the notion that overdrive will have virtually no effect on efficiency. Overall vehicle efficiency will likely go down due to the added weight and frictional losses of the over drive unit. Adding overdrive to gain 2 percent efficiency doesn't make sense. 



Quantum said:


> Actually, that's not what the Siemens chart shows. Check it and you will find that just as I said, peak efficiency is around 4,500rpm (88%), and this is for the combined inverter and motor system. There are no efficiency curves above this, implying that Siemens does not consider the upper rpm range for normal use.


I think you are miss reading the graph. Look at it like you would a topographical map. System efficiency would be "altitude" on the topographical map. The peak of the mountain is around 15kw north, 6000 rpm east. 

At 15kw, 88% efficiency starts at 4500 rpm and carries out till 10,000. 



Quantum said:


> Now I have proof with your chart. Hypothetically we are cruising at 60mph with 7,000rpm at 1:1 tranny gear ratio. Shift into overdrive (.7:1) and we maintain rpm so go 30% faster at 78 for the same distance and energy. Sure, higher aerodynamic losses in this case. Or we reduce rpm 30% to 4,900 to go 30% further and our power goes down from 22.5KW to 20.5KW (mechanical, don't have electrical), bringing us to peak efficiency though. Again this isn't as much a drop as I'd expected, but such is life.


You're confused with the max motor current rating, this is not a measure of what your actual current will be while driving, it is the maximum current you can deliver to the motor without damaging it. 

Picture yourself on a bicycle. Let's say you are in the highest gear pedaling as hard as you can at 30 mph. If I double the diameter of your crank gear, will you now be traveling 60 mph?



Quantum said:


> You jumped the gun JRP3 and major. It's taken me a while to assemble this.
> Why would I stick around for you two to pettily peck-peck-peck?
> Life's too short and I'm going to enjoy it.
> 
> ...


----------



## major (Apr 4, 2008)

Quantum said:


> You're right, I did just take a cursory look at that chart, because it's a) for a DC motor, b) of the wrong size, and c) a low voltage, and so is irrelevant to the issue. Also the chart is ancient. Interesting that efficiency markings start at 60% for 4,000 rpm (*400 AMPS?!*), and go to 80% at the top rated speed of the motor. That motor must be 50 years old. No wonder everyone thinks what they think...


a) Characteristic performance charts and curves are very similar for DC and AC motors.

b) Size matters in the scaling, but the shape of the representative curves remain much the same.

c) Voltage will affect scaling, but again the shapes of the representative curves remain similar.

Yes, the chart is old. Drawn in 1978 I think. What's your point? Modern motor characteristic performance curves look the same. What is relevant is the fact that you do not know how to read and interpret the curve.

At 4000 RPM and 96V, efficiency is indicated at 84%. Current draw at that point is 200 amps, not 400 as you say.

And the motor is likely about 30 years old. What's wrong with that? EVfun is still using it to power his EV.

I don't know what you think everyone thinks and don't really care. It is obvious that you don't really want to learn anything here, just to bitch at those who were attempting to help. Thanks a lot.


----------



## major (Apr 4, 2008)

Quantum said:


> That's an interesting interpretation, but I don't think so. They define efficiency as a definite number, which would be at an edge, not in a continuum like a topo map. I suggest most likely 88% is along the dotted line.
> 
> Yes, although I couldn't power it. But a car at cruising speed has a good deal of inertia and requires little horsepower to keep it going. In that speed band, lower gearing would bring higher speeds, or longer distance at lower rpm, with virtually no power cost (given the chart), excepting aerodynamics.
> 
> (major you'd better copy this one)


O.K. Two little gems from you forever here.


----------



## Quantum (Jul 10, 2011)

You little prick.

I'm outta here.


----------



## aeroscott (Jan 5, 2008)

The motor chart does not represent real load .It is a given load that gives a indication of the motors safe conditions and eff. If at a given speed in your car the amp load will vary as you go up or down hills , change gears or hit a head wind or tail wind . The motor responds to the load not to the chart .If I push another car the load could double and the motor amps would go off the chart , trying to match the load .Put another way the chart is more about safe heat handling ability and eff.


----------



## aeroscott (Jan 5, 2008)

And efficiency is a definite number only at that load /speed .: Need those 3D motor charts .


----------



## EVfun (Mar 14, 2010)

Quantum said:


> Redacted, because none of this matters.


[Redacted]


----------



## david85 (Nov 12, 2007)

Guys, guys, please......ease up a little.

You're making way too much out of this.


----------



## aeroscott (Jan 5, 2008)

I hope I didn't come across negatively ,my apologies if I did .


----------



## Overlander23 (Jun 15, 2009)

No one is arguing the benefits of transmission use. I think some people are just confused by what the transmission really does. Though, in every case it's designed to keep an engine/motor within its efficient range. It just happens that an electric motor's range of efficiency is significantly broader than an ICE... so much so that having a 6-speed transmission is largely irrelevant.

Even the Tesla gets away with a single ratio (which is the same thing as saying a gear-reduced, direct drive).

The best EV transmission would be the one that allowed for the full use of the motor's efficiency band. Such a transmission, ideally, would have few gear ratios (due to the wide efficiency band of the motor) and therefore be lightweight (due to the fewer number of parts due to less gears).



Quantum said:


> Now I have proof with your chart. Hypothetically we are cruising at 60mph with 7,000rpm at 1:1 tranny gear ratio. Shift into overdrive (.7:1) and we maintain rpm so go 30% faster at 78 for the same distance and energy. Sure, higher aerodynamic losses in this case. Or we reduce rpm 30% to 4,900 to go 30% further and our power goes down from 22.5KW to 20.5KW (mechanical, don't have electrical), bringing us to peak efficiency though. Again this isn't as much a drop as I'd expected, but such is life.


I'm a little confused by the claim of how a .7:1 overdrive can yield a 30% reduction in energy consumption by moving the motor into a 0.9% (percentage difference between 22.5kW and 20.5kW) more efficient operating state... but I guess we won't be exploring that anymore.


----------



## rochesterricer (Jan 5, 2011)

FWIW, Brammo is putting a 6-speed gearbox on one of their new bikes. I'm not sure if they are doing to please traditionalists, or to enable them to get away with using a cheaper, less powerful motor, or what.


----------



## frodus (Apr 12, 2008)

So, what'd I miss Major? JRP3? David85?

So hard to read this thread, did someone delete their posts?


----------



## DawidvC (Feb 14, 2010)

frodus said:


> So, what'd I miss Major? JRP3? David85?
> 
> So hard to read this thread, did someone delete their posts?


Major quoted some of the posts because of deletions - it is hard to make sense of this all 

Check Major's post on page 10, and David85's nearby, hopefully that explain some of what happened.

[edit - might be mistaken about David's posts -oops! /edit]

Dawid


----------



## Tesseract (Sep 27, 2008)

Everyone in this thread is acting like a [REDACTED]

Sorry, couldn't resist... but the salient lesson here is: Do Not Feed The Troll.


----------



## frodus (Apr 12, 2008)

Oh Jeff... you're the best at feeding them though.... I mean, Remember JM?


----------



## major (Apr 4, 2008)

frodus said:


> So, what'd I miss Major? JRP3? David85?


I guess Quantie got POed because everybody kept telling him his views on electric motors were incorrect. I was actually politely asking him to explain how he derived efficiency from a motor chart containing no such information. He resorted to quantum mechanics and even string theory  First time I heard that one, but guys who can't grasp Newtonian physics often rely on quantum mechanics.

Anyway, he tried to delete himself from history. Then came back for another try. And repeat.

Hey I had nothing against this guy at first. I didn't even care about his up-scale thread here. But he came over to that dual motor thread and posted pure BS. So I called him on it. Several others did also. He gave up there, but never admitted he was wrong. So I checked out this thread. He was spreading the same BS. 

Tess is right 

major


----------



## Tesseract (Sep 27, 2008)

frodus said:


> Oh Jeff... you're the best at feeding them though.... I mean, Remember JM?


I have no idea what you are talking about...  



major said:


> Tess is right
> 
> major


Even the blind squirrel finds a nut now and then!


----------



## frodus (Apr 12, 2008)

Man, I go camping for the weekend and you guys have all the fun


----------

