The stock liquid lead/acid battery in a Corvette weighs about 45 pounds. Up high near the front of the car, it does everything wrong - it's big, it raises the COG, increases polar moment, and just weighs. Replacing the battery with a smaller and lighter one is an good way to lose about 30lbs off the nose of your car. And, as it turns out, with this nice battery from Hawker, it's also an easy and fast way. Even in physical size, they are a world apart. (Figs 1 & 2).
Most folks will relocate their battery to the rear for improved weight distribution, but I didn't think that 13lbs was worth the time, cost, and effort. Plus, I didn't want to deal with all the rules involving relocated batteries, battery boxes, cutoff switches, and all that nonsense. So, I bought this battery, and installed it in my in the stock battery tray, lying down.
This battery is marketed under a number of different brand names - Dynabatt, Genesis, Odyssey, and such. They vary in price, but are all the same battery. The 3/S Stealth guys have done a good writeup, which you can read Here. I found the cheapest price I could at gotbatteries.com, and since they're local to me (Denver), delivery only took one day.
Installation Notes
This installation took me two afternoons after work, including time for pictures, having the terminals turned down, and trying out a few ideas. To do an install like I've done, you'll need a drill with some bits, a dremel tool, and a few extra fasteners. I used 3 12mm bolts and nuts I had leftover from my Eclipse spare bolts bin, but you could go to a fasteners store, or an Ace Hardware, and get some 13mm head metric bolts, to stay consistent with the car's bolt sizes.
The rear of stock battery is held down with a small lip at the bottom rear of the battery that corresponds to a lip on the stock battery tray. In the front, a small trapezoidal piece of plastic is held down with a bolt, and it holds down another lip on the front bottom of the battery. Since the replacement Hawker does not have a lip like this, we'll have to fab up a mount to make it fit.
Fortunately, the battery fits nearly perfectly in the tray lying down, and the positive and negative terminals line up properly as well. This is fortunate, as we don't have to re-route any cabling.
Once we have a mount fabricated, the last hurdle is that the threads on the new battery are a smaller thread size - M6x1.0, than the stock bolts. So, we must find new bolts to fit the new battery, or else modify the stock posts/bolts to fit.
Getting Started
The first thing to do is to disconnect your battery. The heads on the stock posts are 8mm. Start with the negative (black) cable, and then unbolt the red positive cable. You'll see some sparks and such, but don't worry. Next, take a 13mm socket with a deep extension, and unbolt the trapezoidal looking plastic thing from the battery tray. The battery should now lift out with some effort.
Once the battery tray is gone, the center of the tray is exposed, and you see 4 13mm bolts that hold the tray to the upright where it mounts. Unbolt these four bolts, and carefully worry the tray up and out of the car. There are four metal clips that have threads in them, (fig 3) which allow the tray to be attached to the car, and make sure to save all four of these. they tend to like to fall down into the PCM area, or get otherwise hidden. One of the $2 pen magnets from AutoZone comes in handy if one falls off of your tray.
Now that the tray is removed, you can start with fabbing up a bracket with some 1/2" aluminum from Home Depot. I chose this size because it was the easiest to bend with my relatively hoopty bending apparatus, and the lightweight means I'm getting the maximum of weight savings over my old ol' Yeller Optima Yellow-Top. It cost around $4 at Home Depot, from their bar-stock rack.
To actually bend the bracket, in the absence of any suitable bending tool, I put the aluminum between two blocks of wood, marked the edge where I wanted to bend, and then bent the aluminum by banging it with a hammer until it made a right angle. Simple enough :-).
For the second problem - getting new bolts for the battery - I chose to have my stock posts turned down to fit the new threads. The bolts are have a special head on them, that fits very nicely in the stock rubber boots. Once they are unbolted from the battery, you can remove them from the rubber boot by prying up gently on the rubber boot, and pulling the bolt out the top.
The Bracket
I decided, ultimately, to make the bracket in two parts. First, a bracket holding the battery solidly from side-to-side, and another to control its movement longitudinally.
To design the side-to-side bracket, (we'll call it bracket "A"), I realized that once the tray was in the car, I was going to need some way to remove the bracket, and to be able to keep the fasteners in place for when the bracket went back on. So, I used somewhat of a "stud" approach, whereby the bolts in the side of the tray are never removed, and all it takes is two nuts on top of the bracket, on top of the "stud", to keep things down and snug in place.
To do this, I bent the bracket such that it fit the battery perfectly, but came up a bit short of getting to the floor of the battery tray. I drilled two holes through the tray near the rear of it, and put my two bolts through the holes, from the bottom and put a nut on them to keep them in place. Now, I drilled two holes in the bracket, and it fits just perfectly on top of the nuts that hold the bolt/stud in place. (Figs 4,5). As you can see, once the tray is back in the car, they simply act like posts that I can just slip the bracket over, making removal and reinstallation no more difficult than a factory bracket. (Figs 6,7,8)
For the front-to-back bracket, "Bracket B", I had the factory mounting hole as one option, but no good way to have a fastener in place for the rear. So, I cut a hole in the back of the battery tray, under the 'lip' that was there for holding down the factory battery, and let that be a notch for a bracket. (Fig. 9) Don't worry too much about cutting into your battery tray - I had to replace mine when I first got the car, and I think I paid $25 for a new one from GM. To use that bracket, I slide the back of it through the notch in the back of the battery tray, and then bolt down the front of it using the factory hole. (Fig 10) It works wonderfully.
After bending, you might want to spray-paint them black to make them a bit less noticable in your engine compartment. Tech folks tend to notice bright shiny aluminum, but two black metal brackets look a lot less "custom" then aluminum ones do, and it helps avoid attention. All it takes is a coat of black Krylon, and a few hours of drying time in the sun. (Fig 11)
For modifying the factory studs, I simply took them to a machine shop, and had them turned down on a lathe, and re-threaded to the proper pitch. I reinstalled them in the factory rubber boots, and now it looks completely OEM. You can see the difference in the figures 12 and 13.
Impressions
Not a lot can be said here. The new battery in at only 13.5 lbs, versus my stock Optima at stocker at 45. The aluminum bracket weighs less than a pound, so I've dropped 30 lbs off of the car, and lowered the battery's location in the process (since it is now lying down) That's a lot of weight to have off the front end.
The battery absolutely does not move with these two brackets, and has passed SCCA Solo 2 tech 3 times now without any hassle. The cables go in roughly the same spot, so fitment is not a problem there either. It really worked out quite well, and I took some shots of the completed product, which are figs 14-17.
As far as longevity and strength, I had the same battery in my Eclipse, and it suffered through two cold winters, and never caused me a single problem. Even after nearly six months of not being used, sitting in my frigid garage, the car fired on the first try with this battery. Very cool, and losing 30lbs for $70 is a pretty good mod in my book.
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