The PbC battery is a hybrid device that uses the standard lead acid battery positive electrode and a supercapacitor negative electrode that is made of activated carbon. The activated carbon has an extremely high surface area (1500 m²/g) and has been specifically formulated by Axion for use in electrochemical applications.

Micro-hybrid vehicles currently utilize a start-stop system which automatically turns off the engine when the vehicle comes to rest, and then automatically restarts the engine when the brake is disengaged. Next generation micro-hybrid vehicles will, and in some cases already do, include added features such as regenerative braking, sailing (i.e. turning the engine off as the vehicle slows or coasts below a pre-determined speed) and perhaps some form of battery assist to the initial vehicle acceleration.

The conventional lead-acid battery is not designed to suitably provide the dual function required in micro-hybrid vehicles, let alone handle the added loads of future micro-hybrid vehicles, Axion says. The dual feature includes working with the alternator generator to start and power the vehicle while the engine is on, and then separately, powering the vehicle’s ancillary load when the engine is off.

The lead acid (PbA) battery shortcomings with respect to powering the ancillary load are directly attributable to the battery’s rapid decline in charge acceptance over time due to sulfation. This occurs in the PbA after just a few months of usage. Axion’s PbC battery, on the other hand, has been shown to quickly accept full system charge (i.e. no loss of charge acceptance) for more than 5 years of usage. This advantage translates into much greater engine off time resulting in greater fuel economy and reduced CO₂ emissions.

As more demands are placed on batteries for hybrid vehicles that require a significant amount of partial state of charge (SOC) operation by the battery, a dual battery approach seems to offer the most efficient solution, Axion suggests. The SBIR award is designed to demonstrate that the PbC battery and PbC technology will provide a cost-effective solution to at least part, if not all, of the dual battery proposition.

The SBIR grant was for the maximum allocation under Phase I, but it is the first step in the DOE grant approval process that could lead to significantly larger awards in future Phases of the program, suggested Axion Power CEO Thomas Granville. The award of the grant for Phase I enables Axion to apply for larger Phase II awards. Successful completion of Phase II automatically qualifies an awardee to apply for additional DOE funding beyond the SBIR program. The Phase III funding provisions do not contain predetermined award limits.

Axion Power was one of 75 companies out of a total of 764 applicants to earn an award in the first phase of the DOE's program. Grant funding is expected to be available to Axion Power by late June of this year and Phase I will conclude 10 months from that date. According to DOE documents, Phase II awards will be granted to approximately 50% of Phase I awardees and will conclude in 12-15 months. Phase III will follow shortly thereafter.