Stop-start Idle Elimination Crossed The Chasm While Everyone Was Distracted

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John Petersen

John Lennon once quipped, “Life is what happens to you while you’re busy making other plans.” A classic example of the phenomenon is the quiet emergence of stop-start idle elimination as standard equipment on new vehicles while politicians, pundits, the media and mechanical monkeys beat the drum and played the kazoo for the amazing EV sideshow.

Stop-start is more than a vague promise of hope and change. It’s a reality that’s sweeping through the auto industry today and will conserve more gasoline in 2013 than all of the worlds HEVs and plug-in vehicles combined. It’s proof positive that a huge number of baby steps cover more ground than a couple of giant leaps.

Stop-start is one of the most sensible ideas you can imagine. Turn off the engine while a car is stopped at a light and then restart the engine when the light changes. In heavy traffic, this simple economy feature can improve gas mileage by 5% to 15% while eliminating emissions from idling vehicles. It’s a win for the driver, a win for the environment and a win for the people on the sidewalk who don’t have to choke on exhaust fumes. There are no losers and no hidden costs.

While early versions of stop-start technology date back to the ’70s, the first modern stop-start systems were introduced by Peugeot-Citroën in 2006 and BMW in 2008. What began as a modest baby step with little or no fanfare is taking the auto industry by storm. In its 2011 Power Solutions Analyst Day presentation, Johnson Controls (JCI) used the following graph to show how automakers plan to implement stop-start as standard equipment over the next five years. The subtext of their presentation was “we sure didn’t see this one coming.”

9.27.11 Global SS.png

Regardless of how you judge the merit of an automotive efficiency technology, a production ramp from zero vehicles in 2005 to planned production of 15 to 22 million vehicles a year by 2015 is extraordinary. While most investors don’t even know that stop-start exists, the technology has already crossed the chasm and is certain to have a significant impact on the future earnings of a handful of public companies that are currently trading at huge discounts from their 52 week highs.


Stop-start is a classic disruptive technology; a simple baby step that opens the door to improvements in fuel economy that nobody even considered a few years ago. The only fly in the ointment is the reality that yesterday’s automotive batteries are simply not durable or robust enough for the immense electrical loads stop-start systems require them to carry.

The battery problem is easy to understand. In a conventional car the battery starts the engine when you leave for work and it has to recover enough charge during your commute to restart the engine when you head home at night. With a stop-start system, the battery has to start the engine when you leave for work, carry the accessory loads during engine-off intervals, restart the engine on demand, and recover its state of charge as quickly as possible in preparation for the next engine off opportunity. The pattern repeats on the trip home. The following table highlights the differences in battery duty cycles for a 15-mile commute with an average of one engine-off event per mile.

Conventional Stop-Start
Initial engine start 500 Amp Seconds 500 Amp Seconds
Engine-off accessory loads 45,000 Amp Seconds
Engine restart loads 4,500 Amp Seconds
One-way battery load 500 Amp Seconds 50,000 Amp Seconds
Round-trip battery load 1,000 Amp Seconds 100,000 Amp Seconds

Think about the table for a minute. An optimized stop-start system requires 100 times the work from its battery; two full orders of magnitude. This is not a simple problem with an easy fix.

Recent studies from BMW and Ford show that flooded lead-acid batteries start to degrade in a matter of weeks and more expensive AGM batteries start to degrade within a couple months, but the batteries don’t simply die. Instead, their charge recovery time increases from 30 seconds with a new battery to four minutes or more after a few thousand miles. Since stop-start systems disable themselves until the battery regains an appropriate state of charge, longer charge recovery times make the mechanical systems less efficient and eat into potential fuel savings. In many cases, stop-start systems lose most of their functionality within six months. It’s sure to become a huge problem when pollution control inspectors start testing for stop-start functionality. Finding a solution now is a major challenge for both automakers and the battery industry.

In an effort to compensate for the shortcomings of conventional lead-acid batteries, automakers are upgrading from flooded batteries to AGM batteries, or to dual battery systems that use flooded batteries for starter loads and AGM batteries for accessory loads. The first big beneficiaries of these battery upgrades will be Johnson Controls and Exide Technologies (XIDE). Both companies are building new AGM battery manufacturing capacity at a blistering pace and it’s easy to see why. Historically the automakers spent about $60 per car on a flooded starter battery. AGM batteries in comparison cost about $120 and dual battery systems cost about $180. Anytime a manufacturer can double or triple its per vehicle revenue and widen its margins by selling premium products wonderful things happen to the income statement. So far the income statement impact has been small because production volumes have been small. Over the next couple years the impact will become dramatic and it’s already baked in.

While AGM batteries and dual battery upgrades are the best the automakers can do with current technology, they’re a still a compromise and there’s a growing recognition that the automakers need a more durable solution for the basic stop-start systems they’re selling today and a more powerful solution for the advanced stop start systems they want to sell tomorrow. That dynamic has created a compelling business opportunity for two technology developers whose products can integrate easi
ly with existing battery manufacturing infrastructure and are better suited to the demands of stop-start systems.

The first advanced energy storage system for stop-start was introduced last year by Maxwell Technologies (MXWL) and Continental AG. It combines a supercapacitor module from Maxwell with an AGM battery from Continental to provide the extra cranking power required by stop-start diesels from Peugeot-Citroën. The dual device architecture complements current automotive battery technologies instead of competing with them. Shifting the starter loads to the supercapacitor slows the rate of battery degradation and extends AGM battery life by up to 30%. It’s not a perfect solution because it can’t address the accessory loads that are over 90% of the problem, but it’s clearly a step in the right direction with a product that’s available today in relevant scale.

A second advanced energy storage system for stop-start is the PbC® battery from Axion Power International (AXPW.OB). The PbC is an asymmetric lead-carbon capacitor that replaces the lead-based negative electrodes in a conventional AGM battery with carbon electrode assemblies. The end result is a hybrid device that offers extraordinary charge recovery times while eliminating negative electrode sulfation, the principal failure mechanism of conventional lead acid batteries. Like the Maxwell supercapacitor module, the PbC complements current battery technologies instead of competing with them because the PbC electrode assemblies have been designed to work as plug-and-play replacements in any AGM battery plant. The PbC hasn’t scored a design win yet, but extensive data generated in over two years of bench and vehicle testing by first tier automakers shows that the PbC is a very promising solution for basic and advanced stop-start systems.

A dark horse energy storage system for stop-start vehicles was introduced this year by A123 Systems (AONE). This one kilowatt-hour lithium-ion battery pack offers the cold cranking power of a quality lead-acid battery, the exceptional charge acceptance of lithium-ion and a weight reduction of about 20 pounds. While A123 has not released pricing information on its Nanophosphate® Engine Start Battery, its average unburdened cost of goods sold for the quarter ended September 30th was $1,015 per kWh. Even with significant future economies of scale, I believe it will be difficult for lithium-ion batteries to compete effectively in the low-end stop-start market because automakers must carefully weigh the trade-off between battery cost and fuel savings. As you move to the high-end market with very heavy accessory loads, the A123 solution could be compelling.

Stop-start creates an unusual business dynamic in the battery industry because the additional revenue from doubling or tripling the battery capacity of every new car leaves plenty of room for the old line competitors and the new technology entrants to thrive. The following table provides summary market capitalization and stock price data on the five companies that are likely to compete in the stop-start market.

11.27.11 Data Table.png

There isn’t a stock in the table that I wouldn’t feel good about buying at current prices.

Disclosure: Author is a former director of Axion Power International (AXPW.OB) and holds a substantial long position in its common stock.


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