Installing a Lightweight Genesis Battery
By: Blitzo 

Introduction

With the autocross and track day bug firmly attached to my jugular, any chance to drop 10 lbs from the rear of the Spyder is a welcomed mod.  I selected the Hawker Energy Genesis G13EP Sealed Lead Acid battery because of it's small size, good reliability, and reasonable cost - oh yeah - and It's incredibly low weight.

 

I bought the Genesis from Portable Power Systems (www.gotbatteries.com).  Current pricing is $69.96 plus shipping (varies, but cost me about $10).  Other automobile sites that were touting the Genesis generally use the 16 AH model, but I decided to try the 13 AH model (the smallest and lightest in the Genesis lineup) to test the extreme.

You can see in the picture to the right just how much smaller the Genesis is than the stock battery.  It is also much lighter - under 11 lbs versus over 27 lbs for the stocker.  Removing 16 lbs from the rear of a mid-engine car is a pretty good accomplishment for $70.

 
Here is the G13EP sitting atop the stock battery.  Notice how much smaller it is.
 
There's not too much to do for installation.  Since the battery is much shorter, I hade to make a new hole in the battery support riser for the battery clamp to slip into.  The old and new holes are circled in orange. 

I bought a new hold down bolt from NAPA - the smallest I could find - and had to cut it down further (outlined in blue).  I had to cut more threads on the rod to give the nut room to clamp down tightly.  It would probably be easier to cut the other end and make a new bend at the end instead of dealing with threading the rod.

The battery terminals I just unbolted from the battery clamps, flipped them upside down, then used the bolts that came with the Genesis to bolt them to the battery (circled in red).
The installation uses the stock mounting with very little modification.
 

I have seen conventional post battery terminals that bolt atop the Genesis, but I thought the flip and bolt solution was pretty elegant, albeit a little bizzare looking.  The reason the terminals have to be flipped is because the bolts are far enough from the edge of the battery that the downward bend of the terminals would not clear the battery case if you try to bolt them on right side up.

I have been using the battery daily for nearly six months without any problems.  I did put the stock battery back in for a week long driving trip just for extra security, but put the Genesis right back in once I returned.  My initial fears of using a starting battery as a full-time battery and not just a racing battery is that there would not be sufficient reserve power for starting on cold mornings or longevity if I were to allow the battery to run down by leaving the lights or radar detector turned on.  An automotive deep cycle battery is designed to be able to withstand repeated deep discharge and recharge without weakening the battery - a starting battery is not.  I have since left my detector on once and completely discharged the battery and the battery is still working fine after a quick recharge.  I have also recently had several opportunities to start the car below freezing (only about 29 degrees) and there was just the very slightest of detectible slowness to the starter.  I'd guess it was about 95% or the warm weather cranking speed.  I don't remember how much the stock battery would slow down in cold weather, but I'm guessing it is similar.

For the really dedicated, a battery as small as this one could be placed almost anywhere to further improve the weight distribution of the Spyder.  The more weight you can remove from the rear or transfer towards the front, the better.  Getting the weight closer to the ground is advantageous as well.  Relocation to the lower firewall right close to the transmission sounds like a good idea for weight, but would make servicing the battery more difficult.  Relocation to the storage bins is also a fair solution - very minor cable lengthening and a sealed lead acid battery releases hydrogen slowly enough to be used in living spaces, but a bit more work.  Relocation to the front may sound like a good idea, but the additional weight of lengthening the thick cables probably puts you over the stock weight - so scratch that idea.

So if you're looking to lose a quick 16 lbs from the Spyder when your stock battery dies, consider a racing battery.  I don't expect the battery to last as long as a full sized battery, but the stock battery is known to last as few as two years in service.  If the Genesis would last for two years, I would be happy with the additional cost to get the benefit of weight savings - and also the strange looks I get from technical inspectors that can't believe such a small battery can start and power the car reliably.