Sunday, April 13, 2014

Custom Interconnects

I finally got a couple of weeks to work on the ElectroJeep.  First order of business was finalizing the battery layout and interconnects.  Here is the final layout:

You can download a PDF of the ElectroJeep battery layout here.  From left to right, the five battery boxes are named "front", "passenger's side under seat", "driver's side under seat", "upper rear", and "lower rear."  One significant change from the previous version is that the most positive terminal is now in the upper rear box rather than the lower rear box.  This was done to simplify the HV cable tangle at the front left of the lower rear box.

Note that there are several "odd" interconnects in the upper rear and lower rear battery boxes.  The task a couple of weeks ago was to actually manufacture the interconnects.  I created some patterns which I printed out on 8.5x11 paper.  The first is for the "turnarounds" - the two spots in the upper rear box which require a parity reversal on the cells' positive and negative terminals:

The PDF file for the turnarounds is here.  The second is for the "odd interconnects" - the L-shaped interconnects and the longer interconnect in the upper left corner of the lower rear box:

Again, the PDF for the odd interconnects is here.  I used double-sided tape behind each thing I wanted to cut out, stuck the pattern to a sheet of 0.02" copper, and cut them out with sheet-metal shears.  I then used my hole punch to punch out 5/16" holes, then stacked them together and used heat-shrink to bond them.  Here are the completed turn-arounds:

Each one is made from a stack of six cut-outs.  I designed them to be 22mm wide - basically, 0.9" - and 0.9" times 0.12" (the combined thickness) is 0.108 in^2, the cross-sectional area.  This is approximately the same as 2/0 gauge welding cable (0.105 in^2), which is what I'm using as the main cable size.

I also used a double stack of 1/16" by 3/4" copper straps in two places - between the EV display and a cell terminal, and between the CamLok inlet to the upper rear battery box.  This is 0.094 in^2, which is a little smaller than 2/0 cable (but about the same as the copper interconnects that come with the cells).  Here is the double strap behind the EV display:

You can also see the massive 400A 500VDC fuse to the left of the EV display, and the edge of a 30A 500VDC fuse holder on the right (which protects the charger wiring).  These are shown on the updated HV circuit diagram:

The PDF for the HV circuit diagram is here.  And, finally, here are the interconnects in their places (you can also see the CamLok connector in place in the upper rear battery box):

Next up (finally!) - interconnecting the cells.

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