These are some notes and pictures of a Red Top Optima Battery install in my '94 Miata. Because I've had problems with my 2 previous Westco batteries, I decided to switch to an Optima Red Top battery instead. The Red Top model features some pretty cool technology. It's not that much more expensive than a Westco battery, yet it's a much better, higher capacity battery than the Westco.
First a warning: I make no guarantee that this battery will work for you or fit in your car. I'm not responsible if your battery explodes or you have an accident and manage to arc-weld your hand to the inside, of the trunk. This isn't mean as a general how-to install guide - just a write up of how my install went.
Now that's out of the way, the complete technical spec for the Red Top Optima 74/35-925 battery is available as a PDF file. The battery weighs 33.1 lbs compared to 25 lbs for Westco. It's also a larger battery than the Westco. You can compare it's dimensions by heading over to the Westco's spec page. The Optima has a capacity of 44 Amp-hours compared to 31 for the Westco. The Optima has a power of 720 CCA compared to Westco's 475 CCA.
The size of the Optima battery is the key problem when putting it into a Miata. It's designed for a bigger car. It's footprint is bigger than the OEM or Westco replacement, and it's also a little taller (which actually doesn't present much of a problem). So without modifications of the base plate of the Optima battery, it simply won't fit in the area that's bounded by the 2 metal brackets (see picture 03) where a battery normally sits.
Fortunately, a solution to this is to trim the Optima battery's plastic base plate so it can fit in the space. In miataforum.com, I've read about some people who've done this. They've purchased a normal Optima battery, trimmed it with their table saw, and made it fit in their car. Unfortunately, I don't have a table saw so I can't do this at home. I also read about some people's concern regarding warranty issues. It's been rumored that Optima may not warranty your battery if you go hacking it up, even though you're trimming a non-functional plastic trim piece.
Luckily, a solution exists for both problems. There was a thread over at miataforum.com, in which someone found a store that was willing to sell an Optima Red Top Battery, and more importantly, trim the base plate. Since the store was the one cutting up the battery, it's reasonable to assume that they'd handle warranty claims with no hassles.
I contacted the folks over at Optimabatterystore.com (they're also know as Batteriesareus.com, and on the receipt that I got, they were listed as Parts & More Inc). Like the miataforum.com thread, I asked for the Optima Red Top 75/35-925, "Miata version", with the plastic base plate trimmed. Their price was $94.95 which included UPS shipping from their store in Nebraska. Payment was via credit card using Pay Pal.
(Note: 11/20/03: There's a thread over in miataforum.com that discusses some recent problems people were having with this store. Note: 04/02/04: Here's another thread. Buyer beware!)
My goal with the installation process was to keep the stock locations of the positive and negative posts of the battery. Also, I didn't want to cut or bend any of the existing OEM brackets, just in case I needed to use them and go back to a stock battery size some day in the future. For my install, these goals were achieved. I just had to expand the 2 holes of the L-shaped battery bracket. Also, I had to kludge up a different horizontal hold-down bracket since the stock one wasn't big enough to fit the Optima, without modifications. Although it holds the battery down just fine, I may rig up another one that's shaped more like the original OEM hold down bracket. Finally, I was glad that the stock battery cover still fit over the Optima battery. I was prepared to leave the cover off if it didn't fit, but luckily, it didn't come to that. Incidentally, the Optima comes with a plastic carrying handle that can be easily slipped off the battery before installation. This way it doesn't get in the way when you connect the power and ground cables to the battery.
In the few days I've had it in the car, the battery is working as expected. The car feels like it's starting stronger/quicker now and it also seems like my power windows move up just a little faster now.
Questions? Comments? Send them to me at jaimev@panix.com