Cutting Big Weight From Project STI With AntiGravity Batteries and MeleDesign Firm

While we are going through Project GD STI, repowering it and upgrading many of its systems, we thought it would be nice to replace the car’s heavy AGM battery with something lightweight that takes advantage of new battery technology.  We knew that Lithium batteries could save a lot of weight but we didn’t want a fiddly super light racing battery that would have to live on a trickle charger or be constantly on the edge of not being able to meet the car’s power demands.  After all, this is a full street car with all of the street car accessories like a stereo, AC, power windows, etc.

We made a call to AntiGravity Batteries for tech advice.  We wanted a powerful yet lightweight battery that had plenty of reserve power for a street-driven car in daily use.  We also wanted to have a secure way to mount the battery if it had a smaller than the OEM footprint.  AntiGravity recommended their ATX-30 battery in a MeleDesign Firm mounting box that was specifically made for the battery and the Subaru’s engine compartment.

The AntiGravity  ATX-30 battery has a whooping 880 cranking amps, this compares to the 650 cranking amps for a conventional lead-acid or AGM heavy duty series 24 battery that came in the car.  The capacity of the battery is 32 amp hours which is a bit less than a typical series 24 battery which is 50 amp-hours or so.  Comparing the ATX-30 to the popular PC680 lightweight racing battery, which has 550 cranking amps and a capacity of 16 amp-hours, the ATX has a lot more capability.

The ATX-30 battery has AntiGravity’s restart technology.  If your car has a dead battery because you forgot to turn the light off or something, you can push the restart button and it will activate a circuit that has enough power to start your car.  The restart battery has internal circuitry to prevent the vehicle from draining the battery below 12 volts over time. This is good for preventing “parasitic drain” issues that many newer cars have. The circuitry prevents the vehicle from draining the battery below 8 volts during cranking. This prevents it from being used in an application with too much power demand for what the battery is intended for. The circuity also protects against occasional spikes in voltage beyond 14.8. This does NOT include when a regulator has failed and allows system volts to constantly rise above 14.8.

The ATX-30 uses Lithium Iron Phosphate chemistry.  This is a variant of the common Lithium Cobalt Peroxide lithium-ion batteries found on nearly anything that needs a rechargeable battery. Lithium Iron Phosphate chemistry offers many advantages over other batteries including other types of lithium-ion batteries.  It has a longer cycle life than most other batteries. It has a very constant discharge voltage, meaning its voltage will stay high and stable until the battery is totally exhausted. It has a higher peak power rating than other chemistries.  It can also charge quickly. Lithium Iron Phosphate batteries have a very high power density and the ability to take multiple charge cycles.

The ATX-30 uses prismatic/pouch cells, this sort of cell construction is found on high-end batteries that require a lot of energy density.  This is a departure from a plastic case packed with cylindrical cells that other cheaper motorsports lithium batteries typically have.  The prismatic/pouch cells allow for more cell density and thus more capacity to be packed into an equivalent-sized case.

MeleDesign Firm came out with this awesome battery mount for our STI.  Mele makes mounts that are direct bolt ins for many popular cars that are a direct fit for many performance batteries, AntiGravity included.  They were cool enough to build our mount with the MotoIQ logo laser etched right into the case!