Electric car conversion: Project ForkenSwift

[MetroMPG]

Forgot to post this diagram after the back-and-forth last week.

Schematic v.2 - "Now with FUSES!"

[MetroMPG]

Tried the battery tester this evening. Looks like all the batts check out except possibly one dud. Maybe should have saved our money and made our own tester too. It's just a big resistor / volt meter.

Weighty matters...

Looking at batteries, we can probably - barely - get 4 under the hood (plus the 12v battery). This'll have the front overweight though, compared to OEM...

We took out approx:

- 150 lbs, wet engine
- 10 lbs, alternator
- 20 lbs, cooling system
- 15 lbs, cat/front exhaust
------
= 195 lbs, total removed (front)

Added approximately:

+ 110 lbs, motor
+ 10 lbs, adapter/coupler
+ 252 lbs, 4 floodies @ 63 lbs each
+ 45 lbs, batt cables, controller, contactors, pot box
--------
= 417 lbs, total added (front)

= 222 lbs overweight in the front. Kind of like having a big dude sitting on the hood, it'll probably have the car squatting an inch or 2 down on the suspension.

We'll be putting 252 lbs in the back (4 batts). But there's still more stuff to take out (gas tank, rest of the exhaust). Ballpark, we're probably adding about 350 lbs to the car with a 48v setup. 36v would be like adding about 214 lbs.

The car's Max Load rating (passengers + stuff) is 695 lbs.

[MetroMPG]

SW on the weight issue...

Somewhere I read that it's common for metro EV conversions to end up with the batts in back and be too heavy in the rear (and who wants that? ). I'm not sure if that's true. It'd be good if you could balance it, but it'd also be pretty good if none of the batts were in the passenger compartment.

[MetroMPG]

It's probably true, because most people put more batteries in than we are, and you can only fit 4 up front.

EDIT: most people also remove the rear seat and make a big battery box back there. But we want to try to retain stock appearance, even if we can't actually carry 4 adults

I think we'll be able to achieve a level "pitch". We'll have to make a vented battery box for the ones in the rear though, since they're effectively inside the passenger compartment.

[MetroMPG]

SW teases...

But I thought the inability to carry 4 adults was a stock feature.

j/k - I have no idea

[MetroMPG]

You've got a point. And in this day and age, you'd be hard pressed to get 4 adults in that Metro without exceeding its 695lb weight rating! Never mind any luggage. (I wonder if the GVWR changed when they switched to the Blackfly's body style - I've never looked.)

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So this evening I made up 4 cardboard boxes - "battery mockups". Easier to monkey around with these under the hood to figure out placement and rack options than with the real things. I've seen a few people do this.

[MetroMPG]

updated diagram:

[MetroMPG]

Challenge du jour: the oddball Curtis golf cart controller and the potentiometer in the forklift throttle box won't play together (its pot isn't the right spec for the Curtis). So I need to see if I can find a pot of the right physical size and specs that I can swap in to replace it.

[MetroMPG]

Played around more with the potbox & the curtis and figured out how to get them talking. Just experimented with the controller pot connections until I found a way to make it work as a 2-wire, rather than 3-wire setup.

EDIT: of course the incentive to figure it out was the cost of a replacement pot that would have been the "easy" solution: $29 US. That's pretty spendy for a pot. It sure is a lot of work not spending money!

Blah blah. All of which is to say this bizarre chimera is another step closer to ... something.

Getting this hooked up to the car's throttle cable is my next priority, because I want to try driving it sooner rather than later.



forklift potbox details.

[MetroMPG]

SW contributes...

Ah memories of cannibalizing old TV sets. If you go with a used one, make sure you get a linear taper and not an audio (logarithmic) taper pot.

OK, if I understand the potentiometer conundrum, the Curtis uses a 0 - 5K ohm variable resistor (the center and one end of a pot.), and the forklift controller came with a ~23K ohm pot. From your photos, it looks like a common part:


a single-turn, linear-taper, 1/4" shaft carbon potentiometer rated at 1 Watt (without a built-in switch I assume). Don't put an underrated part in or you might smoke pot .

Anyway, if you can't get the exact length shaft, you can always go over-size and cut it to fit (usu. aluminum).

So, which controller are you going to be using?