ALABC Research Providing Sustainability for Lead in Start-Stop Micro-Hybrids

One of the more significant technological advancements in automotive technology has been the development of the start-stop system, which shuts down the internal combustion engine when the car is stationary in order to improve fuel economy. The vehicles that employ these systems, often referred to as “micro-hybrids”, are being produced by automakers as a primary and easily-implementable step toward reduction of both petrol dependency and carbon emissions. They are also considered a boon to the battery industry because start-stop systems impose an even greater demand on the electrical system in order to keep non-critical conveniences and accessories (air conditioning, GPS, etc.) operational while the vehicle is stationary and the engine is shut off.

The introduction of this technology is advancing rapidly in Europe, where emissions regulations are tighter than anywhere else on the planet. In 2011, automakers sold more than 5 million micro-hybrids, and a vast majority of those were in Europe. Lux Research already estimates that number is expected to grow to 39 million by 2017 annually worldwide, and Pike Research estimates sales to reach 41 million by 2020. This paradigm shift in automotive technology is also starting to draw the attention of U.S. automakers, and Lux expects American domestic sales of micro-hybrids to reach 4.6 million annually by 2015.

Although there are a few unconventional battery chemistries being used for start-stop systems, nearly all micro-hybrids employ some form of lead-acid battery, in the form of enhanced flooded (EFB) or valve-regulated absorbent glass mat (AGM) designs. However, the market penetration of these systems might not have happened as rapidly or as successfully without the results of ALABC research.

* Boosting the Performance of EFBs
In many parts of the world, particularly in Europe where micro-hybrids have gained significant market share, many of the vehicles employing entry-level start-stop systems make use of enhanced flooded batteries, which are essentially a step up in the technology of the standard lighting and ignition (SLI) batteries. One key development that has enhanced the performance of flooded lead-acid batteries for stop-start vehicles – namely, the use of carbon additives in the negative plate – is a direct result of ALABC work.

Over the past 20+ years, the ALABC has been coordinating research and development programs aimed at advancing lead-acid battery technology, and its work in regard to the effects of carbon additives has helped to spur some of the most significant advancements in the energy storage industry. In 2003, ALABC-funded research showed that the addition of small amounts of certain types of carbon to the negative plate of the battery actually extended the life of the battery (because carbon inhibits sulfation) and markedly improved its dynamic charge acceptance. This discovery, along with the continued ALABC study of carbon additives, cleared the way for a new generation of energy storage devices, also known as lead–carbon batteries, but more importantly, it provided manufacturers of all lead–acid batteries – including the traditional flooded variety – with a new “roadmap” that would help to enhance the prospects of lead–acid technology in hybrid automotive applications.

EFBs, in particular, benefited significantly from the addition of carbon because it enabled this technology (favored by OEMs for micro-hybrid duty because of its low cost and ability to withstand high under-hood temperatures) to perform at a higher level in the high-rate partial state-of-charge (HRPSoC) duty necessary for start-stop functionality. Thus, EFBs have become the dominant power source in micro-hybrids across Europe and other parts of the world where cost and efficiency are key factors in market acceptance.

* Paving the Way for VRLA Batteries
During the early years of adoption, EFBs have been satisfactory for simple start-stop operation; but for more complex automotive designs incorporating regenerative braking and advanced energy management systems, several automakers have turned to the valve-regulated lead–acid (VRLA) battery. VRLA batteries have been a focus of ALABC research since the Consortium was first formed in 1992 when the industry was challenged to create an energy storage system capable of meeting automaker demands for electric vehicle propulsion. Although the market for EVs failed to develop during the 1990s, VRLA batteries were soon identified as a viable (and often preferred) power source for hybrid-electric vehicle duty, particularly in mild- and micro-hybrids. Today, these designs have raised lead–acid’s profile and enhanced its market prospects in several motive and stationary applications. Yet, if it were not for the early breakthroughs of the ALABC and its members, the market prospects for this technology might have been dead on arrival.

When the Consortium began its work in the early 90s, one of the primary areas of focus was to identify and eliminate the factors that led to the random failure phenomenon known as premature capacity loss (PCL). Two of the early mechanisms, which were more common in VRLA designs, were eventually labeled PCL-1 and PCL-2, and both were addressed within the early phases of the ALABC program. PCL-1 was caused by the development of resistive layers at the surface of the battery grid and, through ALABC research, was addressed by adjusting the composition of the grid alloy. PCL-2, which was found to be a conductivity issue caused by expansion of the battery’s positive active mass, was eventually overcome by maintaining compression of the positive active mass through specifically-designed separators. (Later in the Consortium R&D program, a third factor – PCL-3, was identified as sulfation of the negative plate, and is being addressed through current work regarding carbon additives, as mentioned above).

The ALABC R&D project results eventually paved the way for battery manufacturers to produce more effective and efficient valve-regulated designs, particularly in deep cycle applications. One of the most common VRLA designs used for automotive applications is one that utilizes a fiber-glass mat separator, and is more commonly known as an absorbent glass mat (AGM) battery. Because of its proven performance in HRPSoC operation, the AGM battery has now become a major player in the market for mild- and micro-hybrid applications. Johnson Controls Incorporated (JCI), a long-time ALABC member, was one of the first to produce enhanced AGM batteries, and have since been able optimize the technology for use in the first OEM-produced micro-hybrids in North America (2013 Ford Fusion, 2014 Chevy Malibu). Thanks to the advancements of ALABC research, VRLA batteries are now considered the standard-bearer for the industry as it continues to expand the market for start-stop vehicles.

A Foundation for the Future of Lead–Based Batteries
ALABC research has been and continues to be the basis for expanding the market potential of lead–acid and lead–carbon batteries, and nowhere is this more relevant than the emergence of these batteries as power sources for micro-hybrid applications. The advancements in battery development over the Consortium’s 20+ years of existence have directly impacted the viability of lead–based chemistries in micro-hybrids, and have provided lead battery producers with the opportunity to seize an even greater share of an emerging market.

The continued cooperation of lead producers, battery manufacturers, component suppliers, carbon manufacturers, research facilities and academic institutions is yielding technological advancements that would never have been possible under any other structure. Without it, there likely would have been little effort to mobilize the lead battery industry collectively to address the technological limitations of its primary consumer product and future market sustainability.