Last thrash before the $2009 competition
August 20th, 2009 by Bryce, posted in Fiero | No Comments »My last build update showed where I was planning on putting the batteries. I was hoping to reuse the Prius battery cases in that position, but it just wasn’t meant to be. Caalon, Aaron, and I tweaked those battery cases for about a day before I finally threw in the towel and gave up on them and went back to the drawing board.
I ended up using 2″ angle iron under the batteries to serve double duty. Each battery attaches to the angle iron with one small screw, which keeps the batteries from shifting around relative to each other. The angle iron also supports the weight of the batteries and is strong enough to meet NHRA battery mounting requirements. The angle iron is mounted to the chassis with several grade 8 bolts. Here’s how things came out:
As you can see, the small battery pack ended up between the shifter and the big batteries. A lot of things factored into this, but I decided that this would make the battery box, high voltage wiring, and contactors more safe in the long run. I may end up changing things eventually, but for now I thought this was the safest route with the batteries on hand. Jessica had watched me assemble the big packs and was feeling bold, so she tackled her high voltage phobia and assembled the smaller pack for me. Jessica was a HUGE help in the last few days of building, I’m lucky to have her!
Speaking of contactors, I ended up completely rebuilding the contactor box to fit that small space between the a-pillar, the batteries, the dash pad, and the fender well. I was previously using an 8″x8″x4″ waterproof box that Al had assembled with some heavy duty contactors. This time around I wanted to use a 6″x6″x4″ waterproof box and the lighter duty Prius contactors. The Prius contactors came in the big battery assemblies I have been fetching from the craigslist wrecks, there are two per battery pack (one for positive, one for negative). Because the Prius contactors aren’t rated for the kind of current this motor can pull, I decided to double up and use four (two for the positive, two for the negative). The output sides of the contactors are connected so that when the contactors are open, the two battery packs are isolated from each other. This took a lot of head scratching to figure out how to squeeze into that little box:
Once I finally figured out this rubik’s cube, the covers can go on and it actually looks pretty clean and simple. This shows the insulated pass-through connectors and case that I sourced from Home Depot, surprisingly enough. In the end, this assembly was fairly cheap and looks well sorted, it just took some attention to detail. More importantly, this makes the high voltage wiring much safer because there aren’t any exposed connections, the contactors getting damaged, etc.
It’s not shown in this picture, but I should make note that there are also fuses in the middle of the battery packs so that both strings are individually protected. This way, in case something shorts out or is hooked up wrong, the fuse will pop instead of the batteries starting a fire. It also allows you to remove the fuse during service so that you have a lot less risk of shorting things out (or hurting yourself). This is very important! The fuses, fuse holders, and all the high voltage wiring to the batteries was reused from the Prius wrecks. Interestingly, it’s worth noting that the Prius uses copper cables between the batteries and the contactors, but for the long wires that run from the back of the car to the front, larger aluminum wire is used. This is how the high voltage cables end up coming in and out of the box I made when it goes into the car.
Here’s me doing final hookup on the battery cables. I went through and zip tied all of the high voltage cables securely, then zip tied the battery post covers securely over those. There’s no risk of anything shifting around and shorting out.
Of course, now that I’ve given safety some face time in this post, now is a chance to show how I learn the hard way some times. I was showing Jessica how to use a razor blade to do some clean up work, and as it turns out I was the wrong guy to show her. Don’t wield razor blades when you’re tired kids, mmm-kay?! I’ve never cut myself so bad, there was blood EVERYWHERE. Fortunately I’m not squeamish. An hour of hand-in-ice, some butterfly bandages, a popsicle stick, and some painter’s tape had me back in action. Of course, with only a couple of days of building left, I would soon come to miss that hand A LOT. I should have got stitches, but super glue works wonders and I didn’t have time/money to be doing stitches.
While I buttoned up the final details on the mechanical stuff, Jessica took charge on getting things ready for paint. I stripped everything out of the front end (again…) and she masked everything off and started painting. We used some chassis black paint so that it would look like the factory paint. All of the attention to detail that we had put into the build was starting to finally take form…in that now nothing really looked custom.
I don’t have any pictures from under the hood when things were finally assembled, I’ll have to get some soon.

















































