Tuesday, 16 July 2013

Charger build picks up the pace!

Now that I have a definite deadline for completion of this EV it has become critical to speed up the charger build.

I spent some time this weekend  wiring things up, Mainly crimping the HV cables and cutting down the massive heat sink slightly so that it will fit the Ali charger box I had made, It is as large as I could make it to fit the mini boot of the Honda Beat.

I have changed the planned internal layout (of the charger) several times in the course of the charger build, I think I have now settled on a workable internal layout.

I also 3D printed another toroidal ABS custom bracket now that I have a better idea of how this might work, It is basically a plastic ring the same size as the toroidal inductor with 3 (was 2) oblong rods fixed to the bottom of the ring and spaced exactly to slot into the fins of the heat sink, The length of the rods is exactly the size of the internal dimensions of the Ali charger box (front to back) so that the bracket prevents the  toroidal inductor moving either forward or backwards, left or right? (shit! see comment below photo)


However I have literally just realized that my original orientation of the heat sink meant that the toroidal inductor would  have been held from moving up or down by the (insulated) lid of the charger box.

Since then I have reoriented the heat sink due to the position of the driver board in respect to the power board.

This close positioning is a requirement of high frequency high power electronic switching circuits, according to a comment I read somewhere, not sure if it was on the DIY EV site or in the build instructions or most likely on EmotorWerks’s Charger build pages.

This now means that there is nothing other than friction holding the plastic rods into the slots (gravity and the lid did this in the previous orientation of the heat sink).

This will not do and I will have to come up with a better way of securing the 3D printed toroidal bracket to the heat sink, hmmm back to the drawing board!

Or maybe I will resort to a few high temp zip fasteners (I was going to order some to secure the toroid to the bracket anyway)

Oh yes, and I had better not forget the electrical potting  silicone required to prevent vibration of the large capacitors.

(Just found some on Maplin’s Website, http://www.maplin.co.uk/silicone-adhesive-sealant-46001 £5.00 for 80ml, ouch!)

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