Mazda MX5 Conversion Blog


9 May 2008: The wiring begins! (Among other things..)

It's been a pretty productive few weeks with the MX5, and it's starting to feel like the end is in sight!

TIG welding of the aluminium motor frame and battery boxes was completed about a week ago by Morrison Engineering in Kewdale. They did such a great job that I'm also getting them to help with fabrication of the coupler between motor and tailshaft, so that's away being done at present. It certainly takes a load off one's shoulders, getting help from people who know what they're doing with such things!

In the meantime there has been plenty for me to get on with. I had the original driveshaft lenthened by Driveshafts Australia down in Maddington to suit the new motor frame. I've also started tidying up the 12V wiring again, having finished removing unnecessary cables and identifying the wires for some of the factory instrumentation I may want to interface with later.

I've added a "missile switch" on the dash for forward/reverse. It seems a little strange having such a tiny switch for forward/reverse, but as best I can interpret NCOP14, it is perfectly legal so long as it has the cover preventing accidental switching.

I installed the MES-DEA vacuum pump in the left hand side of the engine bay and attached a tube to the brake master cylinder. No vacuum reservoir for now, but I may add one later. They're generally a good thing to have so the pump isn't turning on and off every time you step on the brake!

I've run a large conduit of tough black tube down the old transmission tunnel (plenty of space above the driveshaft itself), which carries the power cables back to the rear battery box, 8-gauge wiring carrying full pack voltage back to the rear accessory shelf (for the charger, BMS and DC/DC) as well as an 8 gauge wire forwards from the 12V battery (which is in the rear of these cars) to the primary fuse box in the engine bay. (Legally all high voltage cables must be outside the cabin, so the transmission tunnel is a good place for them.)

The rear battery box is now all installed and wired up. The battery box is bolted down securely, the batteries are in there pretty tight, and there's an aluminium bar running across the top middle to prevent the batteries from going anywhere.

You can see the EVPower TS90 BMS modules mounted on each cell, though they're not yet wired together. As you can see I've got a 350A connector for disconnecting the pack (for isolating the rear pack while working on the wiring), and a fuse to protect the pack from short circuit.

And the latest thing I've been working on is the rear accessory shelf which includes the charger, BMS master unit and the DC/DC converter. They will be enclosed but visible from the cabin through a polycarbonate cover, and should look pretty flash upholstered in black carpet to suit the rest of the vehicle's interior.

Hopefully the drive coupler will be done in the coming week and I'll be able to hook the motor up to the wheels - that'll feel like quite the milestone! Once that's in, I can wire up the engine bay, reinstall the interior, and it'll be done!

As I said.. it's starting to feel like the end is in sight :)


(1) The lengthened driveshaft, test fit between diff and prototype motor frame

(2) The old 12V wiring is much less intimidating once it's tidied up again

(3) The 12V wiring behind the dash

(4) A pic of the reversing switch, which controls the reversing contactor and the car's reverse lights

(5) The vacuum pump installed in front of the brake master cylinder, joined with a pressure hose

(6) The conduit containing power cables, just before installation in transmission tunnel

(7) The rear battery box, during installation

(8) The rear battery box, installation and wiring completed

(9) The rear accessory shelf, under the old parcel shelf, with DC/DC, BMS and charger (left to right)

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