Mazda MX5 Conversion Blog


22 March 2008: Emergency Stop, Heater and Rear Shelf Components

So, what's been happening over the last couple of months..

After finishing the MDF prototypes for the motor frame and battery boxes, I drew them up in CAD and sent the plans off to be laser cut and TIG welded together. This was around 6 weeks ago, and I'm still waiting for them, which is very frustrating because there's not much I can do about it! It reminds of the expression "if you want something done right, you have to do it yourself", and I look forward to the day when I can fabricate everything in-house.. though it might be a while, the laser cutter they're using apparently cost over $1M!

So in the meantime I've been pottering away at a few other tasks. Firstly, installing an emegency stop button. It's a legal requirement for every EV in Australia to have an easy and obvious way of shutting down the power circuit in an emergency. I decided to install my emergency stop button where the old gear lever used to go. Pictures 1-3 show the fitting - the switch is mounted in the centre of a polycarbonate (aka lexan/plexiglass) plate, and I can wrap the old shift boot around it to keep that factory look.

Another legal requirement for Australian EVs is to have a heater for the ventillation system, primarily for demisting the front windscreen. The heater core in petrol vehicles is heated by the circulation of the engine coolant, but most EVs are air cooled so you have to find another way. The easiest solution is to use an electric heater core in its place. Picture 4 shows the old heater core top, and the electric heater below - mounted to a piece of engineering plastic to make it fit tightly in the same place, with relay and microswitch for turning it on and off.

Picture 5 shows the installation in the ventillation box. The microswitch is screwed to the housing in a position such that the old mechanism for changing the flow of air through the heater core (silver lever) now closes the microswitch instead. The two nylon levers which used to move flaps inside the box are now fixed in place, so air is always directed through the heater core, though the heater is not always on.

I've also been stripping out more of the unnecessary wiring, and there sure is a lot of it! See picture 6. This has included identifying the function of wires going to the original instrumentation. Hopefully I'll be able to reuse the original instrumentation (the obvious example is interfacing an amp-hour counter for reading battery state-of-charge with the old fuel gauge).

The final task of note was some more pruning with the angle grinder, this time to the area under the rear parcel shelf (part of the old fuel tank cavity), to give me a good place to install a few of the auxilliary components such as the DC/DC converter, charger and BMS. I plan to add a polycarbonate cover above this new shelf so you'll be able to view the components from the cabin - primarily for demonstration purposes.


(1) The emergency disconnect unit, and the hole for the old gearbox lever

(2) The unit mounted in place

(3) With the original centre console in place

(4) The old heater core (top) with the new electric system (bottom)

(5) New heater core and switching system installed

(6) The wiring that's come out.. so far

(7) The rear parcel shelf with carpet removed

(8) Rear parcel shelf with shield and soft top removed as well

(9) Part of the shield removed, to be replaced by plexiglass

(10) Another big hole in the car..

(11) Test fitment of charger and DC/DC converter in new rear shelf

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