Thursday, February 11, 2010

Batteries, Nothing but Batteries

Another day spent fitting batteries into the car. The first part of the day, I finished up the battery box closest to the firewall.

It's surprising just how long this takes to do. In spite of being exceedingly careful, I had one mishap today that really scared me. I was installing an interconnect on one of the front batteries there. I had the bolt in, but not cinched down, so the strap was still free to move. The strap slipped out of my hand and casually swung down to land on the one below that. There were lots of sparks, my heart raced, and I think there may have been a few expletives shouted. Fortunately the two straps of copper didn't weld themselves together and short the batteries. Man that would have been bad. Instead, it bounced and landed harmlessly on an edge of plasitc. So, new method; I'm securing the first interconnect to the battery before it goes onto the stack.

With the new method, the next boxes' install went without incident.

The only change I had to make was to move the shunt from it's original position. If you look on the forward box all the way to the left side, you'll see an object made of brass on a black base. That's the sunt and it was originally going to be a little to the right and horizontal. But the batteries in the forward box would interfere with it, so I had to move it. The shunt allows the car's new Link10 meter to measure the high amps without letting out the blue smoke. You attach the high voltage lines to the big bolts, and most of the current goes between those two brass blocks over the thin plates between them. On the other side are a couple of small screws you attach the meter's wires to, one on each block. The shunt allows only a few milliamps to go down the wires attached to the screws. Since the amperage is scaled down so much, a small sensitive piece of electronics can measure 500 amps without catching fire.

Getting close. I have to install the last 8 batteries, run a bunch of high voltage lines, install the fuse and start re-assembling the inside of the car. I think my goal of getting it off the jack stands and on the road by the end of the month is totally feasible.

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