Electric car conversion: Project ForkenSwift

[MetroMPG]

Originally Posted by MetroMPG

Finished securing the front batteries yesterday. Also started on the rear rack.

Ivan's basically out of the picture for helping on the project for the foreseeable future: baby due any day, and he started a new job with a 200 km daily commute (nutbar!) rather than the 8 km r.t. commute for which the ForkenSwift's minimum range requirement was originally made.

and from the peanut gallery...

You're going to need more batteries. :-)

Nutbar indeed, I guess it's your job to drive it then?

[MetroMPG]

Got out the stuff today to work on the rear batt rack. Did a few welds... and then ran out of welding wire . And the parts store was closed. D'oh!

I spent more time driving the car up & down the street this week than I did working on it. I wonder if the parts store sells discipline too?

I'm going to be away for 10 days at the start of Aug. I'd like to get something accomplished on the old FS before I go.

[MetroMPG]

Got some more flux core wire and did a bit of welding after supper. Got the base of the rear tray done - basically a big rectangle made up of about 6 scraps of angle iron (no, not 4 - that would be too simple).

Now I'm thinking about the best way to mount it. In mounting the batts, I've been giving some thought to 2 issues:

1) the easy part, which is simply securing them so they won't jump out of the tray if they're jostled/turned over.

2) the harder part, which is designing things up so there's more strength in the trays/attachment points in the direction of force from a "sudden stop".

I'm not saying the trays are crash proof, or even crash worthy, but I tried to set them up with that in the back of my mind.

Also the rear tray will cover some of the opening to the spare tire well - probably enough to make getting a tire in & out impossible. So I've been thinking maybe I could cut out the bottom of the well & hinge it for access from below.

[MetroMPG]

Another EV converter arrives on the scene...

Hey there. Yet another future EV-er your project has inspired. I just bought myself a Baker 12" motor almost exactly like the one you sold off recently. Look Familiar? Square drive and all. I'm hoping to swap it into an Audi Coupe GT. I've got a bit of an electrical background, so I am attempting to make my own 'home-brew' motor controller to run this beast. While I intend to use the car for commuting and require 30mile range and 65mph+ speed, I too am doing mine on 'the cheap'. Cost so far (haven't even gotten the car yet) is $291.75, and includes the motor, and everything I need for 2 PWM controllers (assuming they work).

Thanks for documenting your project so thoroughly! Perhaps when I have something to show, I'll start my own thread and do the same.

[MetroMPG]

Hi BigMouse

Yup, that motor end cap looks very familiar! If you do go ahead with the project, I hope you'll post a thread.

Building a PWM controller is way over my head. A contactor controller perhaps... What kind of controller specs are you aiming for?

I'm still keeping my eye out for a bigger Alltrax. Missed out on a 650A 48v unit a few days ago. (By "missed out" I mean "decided to stop bidding".) 650A would have been a massive increase in power for us. Eventually something will turn up in the ForkenSwift price range with a little more oomph than the controller we've got.

I just got back from holidays so will be puttering away at the battery rack work a bit more this week.

[MetroMPG]

Bigmouse replies...

Quote:
Originally Posted by MetroMPG
What kind of controller specs are you aiming for?

With a small PWM circuit driving an IGBT, the capacity of the controller is dependant on the capacity of the IGBT, since that, and that alone is carrying the load of the motor (in theory). I ordered some 400A 1200V IGBT's on eBay. If I run two of them in parallel, I should have a capacity of 800A. The specs on the IGBT's are such that they will be able to handle the 16khz PWM frequency with no problem. And if not, they frequency is selectable with that chip. Really looks to be pretty simple. I hope it ends up being as simple in reality as it is in theory.

That MR2 project sounds very cool. I'm running megasquirt on my 1990 Audi Coupe Quattro with a turbo engine swap in it. Such an awesome little box that is.

[MetroMPG]

Agreed - I'd much prefer a web-based EVDL.

But there are some incredibly smart, helpful & articulate people on there which make it worth following (if you can stand the volume of messages, which is another issue).

[MetroMPG]

Spent a couple of hours tinkering today: worked on the rear batt rack.


(click, zoom)

This will hold four batts. It's positioned as far forward as possible, to try to keep the suspension level. Until this afternoon, the batts were piled (actually wedged in place with pieces of wood & empty gallon paint cans) against the rear of the hatch area, and the rear of the car was sitting lower than the front. Hopefully moving them forward and losing the cantilever effect will fix that. The rack will have them nearly in line with the rear shocks.

I was thinking of placing 2 of the 4 batts down in the spare tire well, but decided I wanted to retain that space for the tire.

Unfortunately the rack will prevent getting the tire out the usual way, so I'm thinking I'll cut out a section of the bottom of the well, and hinge it to get the wheel out from under the back of the car if needed.

[MetroMPG]

saggy butt cured


Put in some more time working on the rear rack. Test mounted the batts and the car sits nice and level with everything mounted as far forward as possible (snug against the rear seatback). Thumbs up - cured the ForkenSwift butt sag!

Rack will be done and secure by the end of the week. Next on the list is cutting cables to the proper lengths and making new lugs for the cut ends.

[MetroMPG]

People chime in with suggestions about making a tilting battery tray...

If that rear seat folds forward you could put the batt rack on hinges and fold it forward as well to get at the spare tire. might be a bit heavy but how often do you need a spare anyway.

That's a neat idea.

I'd have to get some good leverage to fold it forward though, since the rack, batts & cabling will weigh around 280 lbs together. But that's not impossible.

Another thing I'd have to check is the angle the batts need to be at to get the tire out from underneath - don't want to tip them so far that acid could leak from the caps.

BigMouse:

If you put two hinges on them like this....

____
/.../

(periods are your floor, underscores are your battery tray, seatback is to the left)

Then you can move the batteries forward without tipping them at all. The leverage wouldn't have to be as much either.

Sorry for the ACSII art. I hope it makes sense.

SW:

Cool idea, especially if counterbalanced somehow. How much cable flex can you afford though? You don't want to change your flat tire only to knock a cable loose... or worse, break a terminal.

BTW, very elegant illustration, that ASCII art.

One of Wayland's Datsuns actually has an entire rear tray that slides in and out of the trunk area electrically.

That parallelogram hinge idea is nice. But truth be told, I'm going to stick with plan A just to keep things moving along. I already work slow enough - don't need to be re-engineering things on top of that!

SW:

...way to fend off creature feap.