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Discussion Starter #1
Hi,I'm trying to convert a Mitsubishi Lancer, because it is not a heavy car, and also I like it and it has enough space for the batteryes.

My question is what kind of motor should I use? I've seen a FB1 4001A or a Warp 9 (they are almost the same), as you see I'll use a DC system.

Are those ok for my car? or is to much?

And then I would like to have a range of 200km - 240km with one charge and be able to drive at 90km/h - 130km/h.

So what amperage should I use? Because I was thinkin to do it with lithium batteryes but those may be to expensive...
 

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You'll need lithium (and lots of it) for that range.... lead just won't cut it. The thing would weigh as much as a tank. You're looking at a pack that is at least 38kwh worth of batteries, give or take a few percent.


I'll expand:
Amperage isn't really as important at this point in the design phase, Watt-Hours determines range. Estimate that a car like that is going to be ~300wh/mile give or take a little depending on many factors.... but it's close. Then say ~125mi (200km). 300wh/mi * 125mi = 37500watt-hours. If you need 240km, that's 150mi * 300wh/mil = 45kwh.

Speed is limited by Voltage in a DC system, acceleration is limited by torque. Top speed is limited by HP, which is a factor of volts and amps. I think you're well below what a 11" motor could produce, and if you have a pack big enough with decent quality batteries, current won't be an issue. 130kmh should be possible, but it depends on the voltage you run at, and the gear ratio of your transmission.
 

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Discussion Starter #3
Thank you very much!
Can I ask here about where's a good place to buy the lithium batteryes?

Because, I'll have to import it, and that's not an easy issue.
Calculating that W= amp(i) * volt, I suppose that W/h= a/h * volt so there is a balance between A/h and Volt.

For example: I can get my 37500W using 375V * 100A/h, or using 144V * 200A/h.

So, in my first example I will have my 37.5KW on my energy storage, but if I use 144V *33a/h (that would be 3C discharge capacity isn't it?) I'll have 4752 W moving my motor, so what you have said is that I'll have a range of 200km + or - but a speed that my motor can give me with 4752W, did I understand it well?

And the controller it's what is gonna regulate the Volts that goes to the motor?
 

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Please use correct units. Kw is power. Kwh is energy. We're talking about energy. Also amps and amp hours are different.

100Ah * 375V = 37,500Wh of energy
200Ah * 144V = 28,800Wh of energy
Completely different energy packs.

Also, 3C discharge on 100Ah cells is 300A. 2C is 200A. It's a multiplier of the Ah capacity of the cell.

If you have a 100Ah pack at 375V, and you discharge at 3C, that's 300A. The voltage will sag a little bit, lets say 12%, so down to 330V. That would be 99,000Kw of power. With a 37kwh pack, you should have no problem with power using 100Ah cells that can discharge at 3C. But realize, discharging at 1C would give you 37kwh of energy. Discharging at 3C, you'd need a larger pack to get 37,500kwh out. The higher the current you discharge, the less energy you get out of the cell.... so expect to get a larger pack to get 37kwh out. Something with at least 20% more energy at 1C.

Basically, you're going to be spending a lot of money on this vehicle to get that range, so be sure you are sold on the idea, because it's a lot of work and lots of time.

The controller regulates voltage and current to the motor, yes.
 

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Discussion Starter #5
I apologize for my mistake in the units, obviously I didn't know the difference.

Could you tell me, what volt and amperage may you use on these case?
Or perhaps, I should change my goals on these car a bit?
 

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Start by looking at prices of lithium. Right now, things are ~$1.25 per Ah. 100Ah is ~$125, and you'd need ~118 batteries @3.2V to get ~375V, so 118 * $125 = $14750 just for batteries, then add motor, controller, some sort of battery monitoring or management system to monitor the pack and a charger, contactor, fuses, cabling, DC-DC..... it's going to be well over $20k USD.... plus shipping and import fees.

100Ah batteries should be ok at that voltage, but it boils down to what motor you're using. It'l be about the same cost for batteries, but if you have a 144V motor, then you should go for a 144V pack and batteries that are ~260Ah.
 

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Discussion Starter #7
Ok, but I can't expend that money just on batteryes, so, for example I'll leave the clutch, I've been told that I can get more speed using less W, so the speed wouldn't be a problem.

Then the range would become my only issue.

I know that I'm bothering you, but it's my first convertion, and will need to import it all, so I wanna be sure about everything, so could you please explain me again what you said before, about the difference between W and W/h and also, if I've got X W/h how does the motor expend it, cos I've got a bit confused before...
 

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top speed is directly related to Volts, more volts will give you more speed and is more efficient, so you want to go as high as you can here (limited by battery space, and motor/controller/and charger limits)

range is related to Volts*ah so adding volts (cells) and ah (bigger cells) will give more range.
 

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top speed is directly related to Volts, more volts will give you more speed ........
Hi Ziggy,

This statement isn't necessarily correct. It is true if the motor, controller and gear ratio are fixed (cannot be changed). However, top speed of a particular vehicle is determined by the power delivered to the wheels. That power can originate from many combinations of motor designs, controller ratings and battery configurations (voltage and amperage). A 100 volt, 500A system could easily outpower a 300V, 100A set-up and yield a higher top speed with the appropriate gear ratio in the same vehicle. So more volts doesn't necessarily give you higher top speed ;)

Regards,

major
 

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Discussion Starter #12
But, if I'm going to keep the clutch, couldn't I get an smaller motor, or perhaps a FB1 4001 but of 96V? I mean, the clutch and the gears are made to get a better performance with not much energy, so perhaps with an smaller motor, I can handle less batteryes and get the same speed?
 

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But, if I'm going to keep the clutch, couldn't I get an smaller motor, or perhaps a FB1 4001 but of 96V? I mean, the clutch and the gears are made to get a better performance with not much energy, so perhaps with an smaller motor, I can handle less batteryes and get the same speed?
The clutch doesn't have anything to do with it. Multiple gear ratios can enable you to achieve faster acceleration and therefore use a smaller motor. This doesn't affect the battery size. It takes the same energy to accelerate the vehicle either way.
 

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Gears are made to convert high torque low RPM to low RPM, high torque.... they don't convert low energy to high energy, that stays the same.

You still need a motor with a certain power to maintain a certain speed or accelerate at a certain rate.
 

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Discussion Starter #15
I appreciate everything you guys have explained me and taught me, it is not easy for my to get these information in my country and even harder is in my lenguage.

Thank you again!
 

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Discussion Starter #16
Gears are made to convert high torque low RPM to low RPM, high torque.... they don't convert low energy to high energy, that stays the same.

You still need a motor with a certain power to maintain a certain speed or accelerate at a certain rate.

So is there any scale (an easy one) to know + or - what kind of motor do I need?

And if I use a smaller motor, perhaps I wouldn't have more speed, but if the motor needs less Volts, aren't the batteryes going to last any longer? so I could get more range?
 

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Easy? This isn't going to be "easy", not even close.

You'll need to do some work. You need to do some calculations to see how much power you need to get your vehicle fully loaded up to the speeds you want. Then work backwards. Get a motor that can handle that power, get a controller that can handle that motor, then design a battery pack that can supply the current and voltage that is required to the controller. You basically need to engineer it.

Read this:
http://www.diyelectriccar.com/forums/showthread.php/want-build-ev-do-starti-6441.html

Read all of it's links. Read, read and read some more.

We can't tell you what you're going to have to choose becuase you've given us nothing to go by. If you want help, start a post called "joamanya89's electric [insert model of car here]"

What you will want to post is:
  • Your skill level with auto mechanics and fabrication
  • The range you are hoping to get (how many miles/charge)
  • What level of performance you are hoping to get
  • How much money you are willing to put into your project
  • What parts you've already considered, if any.
Then keep everything related to your questions inside that thread. It makes it easier for people like Major and myself to figure out what your goal is, what vehicle you're doing. If I have to jump between threads to figure out what you're doing, I'll likely just skip answering questions altogether.
 

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Discussion Starter #18
Ok, I'm new at this forum, so I didn't know that I could do that.

About my level I'm an engineering student, so the electric wouldn't be a problem, the mechanical perhaps yes.

I'll do that post you've told me, but you will have to pardon me for my english, as you see I'm limited at the tecnical lenguage
 

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I'll do that post you've told me, but you will have to pardon me for my english, as you see I'm limited at the tecnical lenguage
You are doing quite well so keep at it. You might try google translate or something when you can't think of the English word you are after. I do not know how good Google Translate is at technical language, however.
 

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Hello joamanya89

I am a newbie on the matter, just like you :)
still I will try to give some input.

It seems to me that your aimed range is rather ambitious, in particular for a first conversion. AFAIK the larger dc motors are not exactly the most efficient ones. Given your range expectations, maybe you should give efficiency a bit more weight in your "motor choosing procedure". However, the most efficient motors tend to be quite expensive (it would be helpful to know your budget for the whole conversion).

There is no way a clutch or a gear box (or for that matter any mechanical system) could improve your range (assuming the drive train was not completely bad/inefficient design to start with) since those systems do not add any energy to your car (worse even, any gearbox will transform some of your energy into heat..).

rgrds,
sokon
 
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