Electric conversion: Project ForkenSwiift - Page 49 - Fuelly Forums

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Old 04-03-2007, 08:53 AM   #481
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Originally Posted by MetroMPG View Post
SW: good idea! But which half? The "ding" or the "dong"?
I'm not even going there...

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Oldie: re the Spitfire - watch for Toecutter's thread. That's his plan.
I thought he was a making a GT6-EV, though I'd prob go for the spitfire, in fact I recently saw an EV kit for one.
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Old 04-03-2007, 08:56 AM   #482
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You're right. GT6. Excuse my ignorance, but are they not the same chassis, one hard top, one convertible?
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Old 04-03-2007, 09:00 AM   #483
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You're right. GT6. Excuse my ignorance, but are they not the same chassis, one hard top, one convertible?
...and a 6 vs. a 4 cyl.
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Old 04-03-2007, 10:10 AM   #484
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Vid

I just had a chance to watch the vid (sorry a bit late -- couldn't do it at work )

I love unsolicited reaction by the guys on the street when it's explained as electric.

Bystander: "Bull****. Really? Awesome!"

Meanwhile back at the repair car, $20 is exchanged for an "I told you so" between buddies.

BTW, do you cut your own vids? Good background music.

So regarding the battery pack inequalities, what can be done (cheaply and easily) to prevent this problem?

Do you need all batts to run? ...or can you run on x-number until discharged, switch to the next set, etc (or would that discharge them too quickly?) Or you could alternate among them -- guess this would let some "rest" while others were in use, but put a lot more strain on the cables. ...would probably require a series of heavy-duty solenoids or relays.

Do you (or have plans to install) a Voltage readout inside?

OK, I'm done with my 20-questions

Keep up the great stuff.

-Rick
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Old 04-03-2007, 12:11 PM   #485
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OK, so what Metro parts are leftover to sell?
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Old 04-03-2007, 04:20 PM   #486
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OK, so what Metro parts are leftover to sell?
Not enough to pay for replacing the batteries we're sure to murder as we figure all of this out!
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Old 04-03-2007, 10:58 PM   #487
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Been following this for a while now and thought I'd chime in. Firstly, congratulations on what is shaping up to be a fantastic conversion, and on an affordable budget too! Now about those dodgey flooded batteries. I suggest you buy a hydrometer (couple of bucks), battery load tester ($50) and build yourself a desulphator or two (about $20 worth of parts each).

I just finished my second one, which is also my first ever attempt at etching a PCB. I've been testing on a 220CCA 12V flooded battery. Over the course of a week or so the specific gravity of the electrolyte in the cells has shown improvement (moving from "Fair" into "Good") which is enough to make me think this thing actually works.

A desulphator is by no means a magic bullet, it can't recover all batteries, and the one I built is quite slow - we're talking progress measured in weeks or months, not hours and days. But, you don't seem to be in too much of a rush, you've got a great supply of cheap/free batteries at your disposal so I'd say it's worth a shot.

The plans for the desulphator I built are here: http://www.shaka.com/~kalepa/lowpower.htm

Here's an article by the inventor describing how it works:
http://homepower.com/files/desulfator.pdf

There is a low activity forum as well. I didn't post there, but by reading through the messages you can learn a lot:
http://p198.ezboard.com/Lead-Acid-Ba...erydesulfation

The Alastair Couper plans @ http://www.shaka.com/~kalepa/lowpower.htm are for 12V batteries, for 6V, simply double R2 to 44k. I strongly suggest anyone contemplating building one reads this: http://www.shaka.com/~kalepa/faq.htm There are kits available too if you just want to solder one up.

If you're considering a commercial solution, the only one I've heard of that is reported to actually do anything is from: http://www.batterylifesaver.com. I can't speak for or against it, but I can say I bought one of these http://www.batterylifeplus.com/pulse.html and it didn't do anything, while the one I built myself for much less has produced measureable results. I'm cautiously optomistic.

Anyway, good luck and I look forward to more updates!

Cheers,
Ash
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Old 04-04-2007, 07:49 AM   #488
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Nice exposé by Jerry at evconvert.com
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Old 04-04-2007, 09:24 AM   #489
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Ash: thanks very much for chiming in with that info & those links. I had a quick look through. Will delve in further, later. I did buy a hydrometer, but haven't tried it yet (been relying on the DMM alone to this point).

SW: Jerry's funny. For all the "Forkenlookers" out there...
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Old 04-04-2007, 04:12 PM   #490
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No worries. I found it pretty heavy going (I'm an electronics dunce) but over the course of about a month I've progressed to the point where I'm able to make working versions with their own PCB's. If I can pick it up, anyone can A DMM is good for showing you the OCV of the batteries, and if you can juggle it, the voltage under load, but a hydrometer will give you a better indication of the actual condition of a flooded battery.

A brief note about electric motors (I apologise in advance if you already know this), their torque curve is very different to an ICE. As motor rpm approaches peak, torque approaches 0. So, the faster they rev, the less torque they have, though obviously there's a sweet spot between rpm and torque. While we're talking torque, current is roughly proportional to torque, and voltage is roughly proportional to rpm. So more amps = more torque and more volts = more rpm. The tradeoff is that too much current = excess heat and too many volts (above the rating in a brushed motor) = accelerated brush wear and arcing on the commutator. In extreme cases overspeed will cause the rotor to come apart which is why you must never run a series wound motor at it's rated voltage with no load. Again, there's always a sweet spot.

I generally treat the ratings as a rough guide If you go too far over them, some forced air cooling via a fan to cool the windings is a good idea. Electric motors are rated at their continuous power output anyway, peak output is normally at least twice the continuous. I guess what I'm trying to say is find out how much current your controller is rated to deliver, use some Ohms Law[1] to figure out how many Watts you're delivering to the motor. Voltage sag under load will effect things significantly, but it give you a starting point to play around with anyway.

You might want to consider an ammeter and shunt (I got mine from
http://www.evparts.com but maybe you can get one from another forklift or something). You could use a friend holding a DMM plus the ammeter readings to get an idea of voltage sag under load, and also how much current your batteries can actually deliver to the controller.

Gerrys evconvert.com site is what brought project forkenswift to my attention. I've been hooked ever since I'd love to do a car, but not gonna happen in the foreseeable future (getting a modified car registered here is nothing that bulk $$ can't fix )

BTW, I just watched your video (forgot to yesterday). I loved it! There's nothing so sweet as the sound (or lack of it) of an EV cruising down the street. I especially loved the EV1 rip off at the end, classic

Cheers,
Ash


[1] i = v/r where i = current in amps, v = volts and r = resistance (watts)
http://en.wikipedia.org/wiki/Ohm's_law

You can shuffle things around like in any equation and I prefer to think of it this way: Watts = Volts * Amps. So if your "ESS" is 36V and it's delivering 100A to the motor; Watts = 36 * 100 = 3600W (incorrectly assuming no voltage sag under load).
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