Alright recently upgraded the battery in my Miata and based on the external conditions of the RX7 battery (Ill load test both of them monday) Im thinking the RX7 battery is going to be replaced with the much smaller Miata battery, any suggestions on the easiest way to mount it in the factory location?

 

You'll need to make a new mounting braket. Since the miata battery is so small it looks like it would fit better in the storage bin then a stock 7 battery. Maybe consider relocating it?

 

Cant per class rules, can use any battery I wont so long as its mounted in stock location.

 

What I did is get an aftermarket plastic battery tray. It has holes to put one J bolt on each side of the battery and secure it with the cross brass across the top of the battery. They sell a "kit" that has both J bolts and the cross piece at almost any autoparts store. I then bolted the new plastic try to the metal factory battery shelf.

 

Big zip ties.

 

I dont see how a cheap walmart nylon strap wouldn't solve your problem. Unless its against the rules of your class then the strap might have something to offer you as you could shave off the metal weight(not that its alot). I accidently threw my stock battery mounting gear away when I got the car, as it was sitting in the hatch in 3 different pieces and I debated over a week as to what it was for. Anyway I managed to thread that strap down and around the metal battery tray and just fasten it to itself with out much trouble.

 

I use a plastic battery box bolted through the bottom to the stock tray. Also use the strap that came with the box to hold the lid on. I got the U1-size battery box on-line for $10-$12. Works great in my ITA/7.