I tried modifying my earlier steel battery box to fit my new, smaller battery. It turns out that not only can I not weld, I also cannot measure. The result was still larger than needed, and too big to fit the space available behind the engine.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5776-1024x768.jpg)
To be fair, I didn’t want to shrink the size too much, because I knew I needed to leave room for some sort of cushion lining to prevent the steel edges from gouging the plastic battery housing.
I have a hot-air plastic welding gun and I keep a pretty good stock of HDPE (high density polyethylene) plastic on hand. I’d already had the idea of making non-conducting mounts when it occurred to me that I could simply make the whole box out of plastic sheet. There’d be no need to line it, and plastic is so much easier to fabricate than steel. I dug out a big scrap sheet of HDPE that had been a pistol target backer in a previous life, but still had some unperforated sections that I could use.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5780-1024x768.jpg)
If you’ve never used a plastic welder, it’s a pretty slick process. They’re not very expensive and it’s not hard to learn; you just need a bit of practice to learn the proper temperature and speed. And always make sure you’re using the correct filler rod.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5782-1024x768.jpg)
Like so many things, success mostly comes down to decent prep and proper jigging.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5783-1024x768.jpg)
Once I had a box, the next step was mounting it.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5784-1024x768.jpg)
The battery box mounts to the bike in three places. In the image below, you can see two of them. A steel angle support bolts through an existing hole in the frame right below the swingarm pivot on the right, and the inboard rear corner is supported by a post that clamps to the lower frame tube.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5788-1024x768.jpg)
The third mount is at the right front, where an angle bracket mounts to the same bolt as the rear brake line guide.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5789-1024x768.jpg)
I’m using countersunk allen screws that are flush with the tray floor.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5790-1024x768.jpg)
It might get too much engine heat as it is now. After getting everything mounted, I realized that battery could be moved slightly lower and more rearward. The current location was determined solely because of the position of the existing hole in the frame.
![](https://tanshanomi.com/wp-content/uploads/2023/05/IMG_5792-1024x768.jpg)
I still need to make some sort of door or strap, but a bit of painter’s tape will suffice for now. I’ve got a solidly mounted battery, so I can get on with making up a wiring harness and configuring the electrical equipment.