# What is your preferred voltage?



## david85 (Nov 12, 2007)

My feeling is that 144V is idea since most of the acceptable performing cars run that setup and most decent motors can run that voltage.

So what do you think?


----------



## ZenDaddy (Jul 22, 2008)

My feeling is that there is such a balancing act between range, performance, vehicle gvwr / battery capacity, and expense, that it is tough to label any voltage as ideal.

I voted 120v. Why, you ask?

20 6v batteries gave good range and more than acceptable performance with a 600 amp controller. They weigh quite a bit, they put my truck within 800 lbs of gvwr and I felt that was as close as I wanted to get. 4 more batteries and two hefty adults would be pushing safety karma a bit.

18 8v batteries would have given me better performance, but I would have sacrificed quite a bit of range and spent quite a bit more on components.

20 12v batteries? Cool on the drag strip, much reduced range, MUCH MUCH increased expense in controller/motor/components.

Anything less that 120v 600a would have underpowered the truck.
(I actually started with 400a, mistake)

Of course I am only referring to la batteries as I have no experience with any other.

I chose 120v because I felt it best balanced all of the goals I had for the ev and kept it within financial range.

ZD


----------



## david85 (Nov 12, 2007)

I was chatting with some one that is thinking of building motors and controlers for highway capable EVs and we were trying to figure out what would be the best system voltage to shoot for.

I figured 144V would be a good middle ground for range, performance as well as a wide variety of possible motors or controllers that already exist.

The voltages we discussed are in the poll. I'll be going with 144V.

Basically I'm looking for as close to a universal standard as we can get.


----------



## Guest (Dec 16, 2008)

I currently use 72 volts with 550 amps. It was what I started with because my controller is a 72 volt controller. Every thing works ok and speed is acceptable but I want more. Because my car has very limited space I think 144 is about it for power with standard batteries. With lithium that will change but for now 144 volts. It is also about the max any controller for the series DC motor has. Some controllers are designed and built to run more voltage but only like one or two. One is on hold so not much choice in controllers. That is pretty much the deciding factor unless you decide to go AC. Then the game changes again but many still only have room for 144 volts or less. Damn things take up lots of room and weigh a ton, literally. I like my little 72 volter but I want more. So I will be upgrading to 144 when I can. Until then I will play with my little 72 volt car. : )


----------



## ZenDaddy (Jul 22, 2008)

Don't get me wrong, I would have liked to have had the gvwr and money to have had 144v. The key word there is money by the way. A set budget is a set budget. (try to convince your spouse otherwise lol)

My argument is that all ev gliders, build budgets and performance goals are different.

I guess my question is; Is your poll intended to assume unlimited budget and carrying capacity? Or is it intended as demographic research to see what average real world builders can and will accomplish? Don't misunderstand, I respect this fully.

Unlimited budget? Higher voltage is definately better.

Average real world? Compromises for the sake of completion with acceptable results.

ZD


----------



## ZenDaddy (Jul 22, 2008)

I do think this will make for an interesting thread!


----------



## DVR (Apr 10, 2008)

For me I think 144V or it wont be worth doing. I think the worst thing that I could do would be to spend all my money on a car to end up with less performance and then have to answer all the "why did you do it then?" questions from the terminally ignorant.

GOTTDI how will your GIA's gross weight cope with the weight of 144V of lead?


----------



## DIYguy (Sep 18, 2008)

Obviously you will get a lot of different reasons for different answers. It depends on vehicle weight, performance expectations, budget... etc. etc. I want to vote for 156 .....but there is no place to put my vote...?? lol 
I would say that 144 or 156 is a spot to be as most DC motors can handle this if modified for it, without issue. 

It's an evolution in the thinking process for most ppl. We all "start" somewhere... and often evolve our thinking to another place... I guess. 

A good, thought provoking question though. It challenges us to justify our choice within our current thinking......


----------



## sailfish11 (Sep 15, 2007)

I see I'm the first to vote for high-voltage -- what's up with that?!!! 

My system is AC, which loves high-voltage. You also gain efficiency with higher voltages.

Why go with less?


----------



## DIYguy (Sep 18, 2008)

sailfish11 said:


> I see I'm the first to vote for high-voltage -- what's up with that?!!!
> 
> My system is AC, which loves high-voltage. You also gain efficiency with higher voltages.
> 
> Why go with less?


I agree. Perhaps the poll should have mentioned motor type...? Higher is better I think in almost all cases... I vote for the higher end practical DC motor voltage. AC is again another kettle of fish..


----------



## DIYguy (Sep 18, 2008)

sailfish11 said:


> I see I'm the first to vote for high-voltage -- what's up with that?!!!
> 
> My system is AC, which loves high-voltage. You also gain efficiency with higher voltages.
> 
> Why go with less?


I agree. Perhaps the poll should have mentioned motor type...? Higher is better I think in almost all cases... I vote for the higher end practical DC motor voltage. AC is again another kettle of fish..


----------



## david85 (Nov 12, 2007)

Currently there are 3 different types of motor that are currently most likely to be use in an EV. Brushed DC, Brushless DC and Brushless AC (all versions may or may not have perminant magnets). The voltage range I show here does cover all of them, hence the 192V or higher option.

From what I've seen, 144V will work reasonably well for all of the main options (or is at least most likely to work). However, a motor can be made to run well on nearly any voltage you want if it is made from scratch. The higher voltage can mean less metal used for conductors to carry the current, but getting more than 144V can be hard with lead acid, and isn't much easier with lithium when you consider the BMS and charger that is needed.

I set the poll to expire in 30 days. What we could do is use this one to develop the discussion further and maybe to another poll later on with more detailed questions once the backround has been established here.

Does that sound OK?


----------



## dtbaker (Jan 5, 2008)

I would vote for 96v in many cases, but thats not a choice in your poll..... 
My issues were limited space, and 'reasonable' range and cost tradeoff. I would prefer higher voltage like 120 or 144, BUT with the suzuki swift I really nly have room for 12 batteries without sacrificing cabin space.

given that, and wanting to avoid 12v batteries.... my choices were Li or 8v Pb. Reasonable cost dictates Pb still, and a DC system. The cost of components drops considerably with 96 versus 120v, so I stuck with 96v FLA with DC motor.

This would be different with a bigger car, or truck. But for the sub-compact, I would vote for 8" DC motor, 96v using 8v golf cart batteries is a well balanced choice.


----------



## tj4fa (May 25, 2008)

DIYguy said:


> ...I want to vote for 156 .....but there is no place to put my vote...?? lol


I'm using 144V FLAcid in my Ranger (24ea X 6V) but notice first thing in the morning when I unplug and the voltage still is settling down from 160V it is a lot peppier.

I wouldn't mind going to 156V but it seems that's just more weight to haul around.


----------



## david85 (Nov 12, 2007)

Any more thoughts in this?


----------



## TheSGC (Nov 15, 2007)

I like 96 volts as it is a good middle ground between budget build and a standard EV package. The parts are easily affordable, and it has upgrade potential.


----------



## david85 (Nov 12, 2007)

Next time around I will include that option.

Any other voltages that should be included?


----------



## JRP3 (Mar 7, 2008)

156 156 156!  That way you cover the 144 crowd but you've got a little extra for the 156er's.


----------



## david85 (Nov 12, 2007)

I can certainly see how it could end up being a 2 controller solution. One for 72V-120V, and another one for the higher voltages. Not sure if a third one would be needed for over 300V.....


----------



## JRP3 (Mar 7, 2008)

Curtis already has the 120 market covered, and Alltrax up to 72, so I wouldn't bother targeting that range. What does not exist is 144 and up high amp controllers. As for multiple controllers, that's exactly what Zilla did, 1k amp Low voltage, 1k amp high voltage, 2k amp low voltage, and 2k amp high voltage.


----------



## dtbaker (Jan 5, 2008)

david85 said:


> Next time around I will include that option.
> 
> Any other voltages that should be included?


you might wanna separate DC from AC builds....

d


----------



## david85 (Nov 12, 2007)

Well actually the custom motor I'm getting will be a brushless DC. He tells me that he is also working on a DC controller comparable to the zilla though....if for no other reason, than there is demand for it. He prefers to work with BLDC but seems to have the ability to make almost anything motor related. Time is the only thing in his way at the moment and thats why it could be a few months before my motor and controller are ready, but OMG its gonna be awesome according to his specs.

My motor could end up being the prototype of his line of high speed BLDC motors, so thats why I'm asking for imput on his behalf.


----------



## dtbaker (Jan 5, 2008)

david85 said:


> Well actually the custom motor I'm getting will be a brushless DC.


I DON'T know a lot about motors.... can you give a short run-down on the pros/cons of brushless vs regular brushed DC traction motors vs AC ? ie. cost, low-speed torque, efficiency, cooling requirements, invertor/controller 'package' cost, regen, etc?

d


----------



## david85 (Nov 12, 2007)

dtbaker said:


> I DON'T know a lot about motors.... can you give a short run-down on the pros/cons of brushless vs regular brushed DC traction motors vs AC ? ie. cost, low-speed torque, efficiency, cooling requirements, invertor/controller 'package' cost, regen, etc?
> 
> d


There is no performance disadvantage with DC brushless compared to a conventional warP 9" or other series wound brushed motor. Cost is typically the only real problem.

No problem adding a regen feature with BLDC. All you need is the controller to do it.

Power band.....
You know how with a series wound DC brushed motor you have peak torque at or near 0RPM? thats great, but as the motor increaces speed, the torque bleeds off and by the time you are at 6000 RPM there is almost no torque left compared to 0RPM. With brushless 3 phase AC motors and BLDC motors (which are structurally almost identical), the torque doesn't fade with higher RPM, so it has WAY more power and the torque range is as wide as the RPM range of the motor. Also since there are no brushes to arc at higher RPM, the motor can run at high speed at high power without any problems at all.

The other thing is that efficiency is also much higher and over a wider range, so you get better driving distance for the same battery pack.

Motors are also smaller and lighter for the same power of brushed DC series wound motor.

Brushless DC are also maintenance free, since there are no wear parts on them.

Depending on the application, cooling might be needed, but its still not as big a problem as with brushed motors. Higher efficiency means less heat produced. My motor might have an auxiliary forced cooling fan for the power output that I want. 

The big problem is that so far, they have been fairly restricted to specialty applications and there really was no suitable motor than any of us could afford. That might be about to change though.


----------



## dtbaker (Jan 5, 2008)

so why aren't BLDC motors widely available (in sizes for EV) if they are so much better?


----------



## david85 (Nov 12, 2007)

The simple answer is they are more expensive to build. Currently the only real purpose made EV motors that are available to us are not much more than starter motors.


----------



## JRP3 (Mar 7, 2008)

david85 said:


> The simple answer is they are more expensive to build. Currently the only real purpose made EV motors that are available to us are not much more than starter motors.


Forklift motors, actually  (but yes, I know what you're getting at). Of course there are purpose built AC traction motors available as well, not cheap either.


----------



## ElectriCar (Jun 15, 2008)

Ideally the higher the better. Higher voltage = smaller cables = less weight = less cost to build? (not sure about that) and less weight to drag around. More voltage = more available torque as well for a given motor. That's one reason I wanted AC.

However the most practical I think is 144V for a DC system. Here's my reasoning. 

1. My DC-DC is rated at 190V max.
2. The Curtis 1231C is rated at 180V max.
3. The 1500W heater element I'm using is rated at 120V. It works fine on 144V and puts out about 2000W with the fan on high. Just hope it lasts.

During the final stages of charging the voltage is nearing 180V. A 150V system would be over 180V max therefore you can't drive immediately after charging until the surface charge dissipates. Otherwise the controller could get toasted or the converter with a little higher voltage. All you'd have to do is forget once or have an emergency and roll the dice then...Boom, 2 grand or so up in smoke.


----------



## tj4fa (May 25, 2008)

ElectriCar said:


> Ideally the higher the better. Higher voltage = smaller cables = less weight = less cost to build? (not sure about that) and less weight to drag around. More voltage = more available torque as well for a given motor. That's one reason I wanted AC.
> 
> However the most practical I think is 144V for a DC system. Here's my reasoning.
> 
> ...


Are you sure the Curtis is rated at 180V Max? I haven't seen that anywhere.


----------



## ElectriCar (Jun 15, 2008)

tj4fa said:


> Are you sure the Curtis is rated at 180V Max? I haven't seen that anywhere.


It's in the manual in the back somewhere, which I learned after I called EV-America where I bought it.


----------

