It's Sunday evening, you have to get to work early Monday morning your ride has a broken battery tray. After calling several auto parts stores whose service people tell you the item isn't available in any way shape or form (auto parts stores seem to offer a lot of excuses nowadays. I've never understood this mentality either). All you hear is this is a dealer or junkyard item. Well, on my particular car a junkyard batter tray is not an option because it's money their already broken and the dealer item will also break prematurely. I've yet to see a Buick Rendezvous where the said tray hasn't broke. One young lady whose Rendezvous needed a jump had the battery held in with a bungee cord, NO TRAY. This is very dangerous in that the battery might end up in the water pump and leave you stranded. Bungee cords tend to stretch and a 20 pound battery is going to move when the car does. It will shorten the life of the battery. I did this once with my '75 Nova and it KILLED my battery within a month. Batteries are expensive nowadays, even at Wal-Mart, so jury-rigging isn't an option, or is it?
On the Rendezvous, the tray broke off at the stationary tab toward the front of the vehicle, while the hold down with the bolt was intact. The plastic is black and the consistency of a well made laundry hamper; something easily fixed with a heat gun.
Again, this is at your own risk. Heat guns are HOT and they WILL burn you if you aren't careful. You can cause personal injury and property damage if you screw up. If you still want to do this, use a heat resistant surface like a metal workbench. I used a stainless steel sink away from the Formica counters.
The tab in question is about four and a half inches long and has a weak point that makes it easy to fail. You can heat this together, but it will break again. The the trick is to reinforce it with something, such as the same material the tray is made of. I used a piece of scrap plastic cut to fit against the tab and the rest of the tray and glued in a couple places with super glue. The trick is to heat this together until it starts to melt together, but not to get too gooey. Once the materials melt together, there will still be seams, but the parts will hold together. Take your time and let the plastic cool after a few minutes. Once you're satisfied with the result, run the workpiece under cool water and test it to make sure it'll hold the battery. This is not the time to skimp as it'll need to hold 20 plus pounds going around corners, rolling over, etc. You will have to figure out how much heat you need and when to quit. I took my time and got the materials to fuse together, heating them 'till it was the consistency of putty, but no more.
Carefully put the tray back into the car and the battery back in. Carefully tighten the hold down bolt and try lifting out and sliding the battery.There should be no movement. Any breakage will require fixing it again or biting the bullet and replacing the tray. Maranatha!