Ideas for my first EV.

[cRiPpLe_rOoStEr]

Have you never considered to get rid of the transmission, as electric motors can have their rotation reversed?

[Frank Lee]

Originally Posted by Alex77tj

How come?

Because available energy is relatively small so the vehicle must be efficient.

Adding gear meshes adds driveline friction. And weight. And width. All because you are guessing the motor wants to rev higher. Since you are leaving the transaxle in, why not simply cruise in 3rd gear?

Running alternators off the motor: someone already explained it. It's inefficient. Perpetual motion machines don't work.

[Alex77tj]

Let's say that my comute to work is 35 miles each way.
The idea is to wire the alternators to the batery before the control box

[Frank Lee]

Oy. See what I mean?

[oldtamiyaphile]

So really the question is why stop at one alternator?

Then you could run the car on a 9V smoke alarm battery

[Ryland]

Again, a dc to dc converter is going to be far better...

But as others have pointed out, ringing an alternator as you suggest is called perpetual motion... is not real, It doesn't work, it's been tried billions of times, the patent law even says that you can not patent a perpetual motion machine because they are not real.

Now that we have that out off the way, tell us abuot the rest of your idea.

[RedDevil]

Why use a car at all?
We can use a small battery to power a motor to power a generator to power a bigger motor to power a bigger generator to power a really big motor, etc.
Free energy, we all are going to be rich!
Why hasn't anyone thought of this before?

Seriously, if you want to build an EV the wanting it part is not enough to make it happen.
You need to know at least:
- what your budget is,
- what range you need,
- what performance you need
- what batteries you'll use
- what battery management system
- which motor
- which motor controller you'll use
- how you are going to charge it
- what charge controller you'll use
- how to get your EV road legal
- how to insure your EV
- how to do the build and operation in a safe way
- how to deal with all the odds and ends that rear their ugly heads over a build.
- I probably missed a few essentials; you must keep track yourself.

And then you read, search, look, investigate, check, recalculate, plan, test and keep doing this over and over again.

Do not underestimate the size of the challenge!
I'm building a parallel booster pack for my hybrid.
Way easier than a complete EV build.
I do have a lot of experience with electrics and a solid physics background, still I am struggling hard!

If I had to build an EV I would avoid complexities with a vengeance.
I'd go with an existing design and parts off the shelf, maybe re-purposing an existing EV appliance.
MetroMPG has done a forklift conversion on his Metro. That is a nice example of how to build an EV cheap (provided you can get an electrically functional forklift on the cheap).
There are limitations, like reduced top speed and range.

You do have a 35 mile single commute.
A lead acid battery pack can barely make that one way. And wears out after a few hundred full charges.
A used Leaf pack would give you the range both ways, but needs a good BMS - and you'll never know how much life is left in the pack.

Heat is a problem with most battery technologies. You don't want your car bake in the Mexican sun all day and then drive off with batteries at 70°C / 158°F. You won't make it home after a few times that.

Whatever you do, focus on the essentials.
If your plans don't give you the range you need then make a new plan.
Don't lose your head on alternators; an EV does not need them.
If you want to harvest braking energy the motor can do that, working as an alternator on deceleration. Even so, that is hard enough to make many EV builders skip it altogether! And you need conventional brakes anyway.

[elhigh]

Alex,

There you have it.

PLEASE PLEASE PLEASE read the preceding messages very carefully. I am hoping that you are unlike so many others who come along with wild-eyed enthusiasm and the absolute certainty that the way around short range and battery drainage is to just run an alternator off the drive motor, or add extra gearing, or some other scheme.

Think about this: hundreds and thousands of people, virtually all of them much smarter and better equipped than me, have dug VERY deeply into how to make an electric car. How to make it faster, how to make it go farther, how to make it better in so many different ways. And do you know what NONE of them have ever done?

Put an alternator on the drive motor.

Now, why do you think that is?

I'll let you think that over.

When you come to the (hopefully) right conclusion, there are other people here who have built their own EVs, or else done lots of work rebuilding/refurbing existing ones to either return them to productive service or else improve on existing but obsolete work. I am certain, once you step out of the Unicorn Corral, that they will be willing to provide tips. And before you ask, no, none of them have put an alternator on the drive motor either.

Good luck with it.

Frank, my apologies.

[Ryland]

There are people who put alternator's on their motor...
When you see an EV conversion like that, it's always because the person didn't any reach and didn't understand it would hurt their range.

[RedDevil]

Originally Posted by Ryland

There are people who put alternator's on their motor...
When you see an EV conversion like that, it's always because the person didn't any reach and didn't understand it would hurt their range.

More like to make a cheap build work.
If you don't have a decent DC-DC converter but you do have an alternator, and it is still hooked up to the remaining parts of the original engine, and your range does not matter, why not?

It would just power the 12V bits, albeit at max 75% efficiency versus the 90% from the DC-DC converter.
It would thus eat into the range more than the DC-DC converter would.

You could also charge a separate battery for the 12V system and not use alternators or converters altogether. But then you'd have to watch both battery charge levels.