Wednesday, December 26, 2012

Plastic Welding and First Steps Towards Lithium

The first tangible step towards converting my DIY electric car from lead to lithium batteries was accomplished today. I welded the first of two plastic battery boxes from sheets of PVC. Cutting was done on a table saw, and I used a cheap $40 plastic welding tool from harbor freight along with some PVC welding rod to complete the box.
The tool has a built in heating element, and requires quite a lot of compressed air. It has it's own regulator and air pressure is the only way to regulate temperature. A pressure of 4 PSI gives a stream of air at around 600 degrees Fahrenheit which is the recommended temperature for welding the PVC I was using. The process is fairly straightforward and once you get a feel for how far and at what angle to hold the torch, things go quite smoothly. The first box went from a 4'x4' sheet of PVC to finished in about 2 hours.
Here you can see one of the welds in the box where I was still getting the hang of it. Despite some discoloration due to overheating in some areas, the edge is very strong and I cant seem to break it with my hands alone. This box will be dropping in to an existing frame used for the lead batteries, while the next box  needs to be designed from scratch to fit between the frame under the car. I'll also need to weld an angle iron frame to support that one. This is the first step of many, the batteries get here in five weeks, so it will be an ongoing process until then. More to come soon.

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