Better dynamic charge acceptance
= Better fuel economy
= Lower carbon emissions
With improved DCA, Lead Acid Batteries are the obvious battery solution for tomorrow's mass market vehicles
ArcActive's proprietary carbon technology - AACarbon - delivers vastly superior charge acceptance at low costRead more
The electrical system in the car is powered by the alternator, which, in turn, is driven by a belt which is driven by the engine. In this way, the car's fuel is converted into electricity.
In broad terms, automotive engineers want to disable the alternator as often as possible, and have the battery support the electrical loads. If the battery is then recharged using the alternator, the fuel saving benefits are limited – fuel is still being converted into electricity. The fuel saving benefits are strongly enhanced, however, if the battery can be charged by converting kinetic energy available when the car is braking, and storing the energy in the battery. This energy is “free”.
The ability to recover the kinetic energy available during braking is, however, only as strong as the weakest link in the system, and right now, the weakest link is the battery. While cars may be able to generate currents of 80 to 120 amps for the 5-10 seconds of a typical braking event, a state-of-the-art Lead Acid Battery is only able to store a maximum current of around 30-40 amps.
So this is why DCA drives fuel economy:
Another key fuel saving technology is “idle elimination” or “start/stop” - when the car is at rest, the engine is switched off. Sounds simple, but this feature is incredibly challenging for the battery:
With start/stop it is therefore relatively easy for a car battery's state of charge to become so low that, if not managed, it could result in the car not starting after a start/stop event. Automotive companies naturally protect against this possibility and ensure that the condition of the battery is continually monitored. If the battery is approaching a low state of charge, the start/stop functionality is disabled until the battery recharges. While allowing the car to re-start, this clearly disables the fuel saving possibilities. Thus the better the car battery's DCA, the greater the number of stop-start events, and the greater the fuel saving.
The ability to charge a LAB typically degrades rapidly with use and within a few months it reaches a stable level. The stable level of performance is at around 30% to 50% of what car makers ideally want in order to maximise the fuel saving potential of micro- and mild-hybrid vehicles.
As with any large potential market, there are many companies actively developing solutions, covering a wide range of energy storage technologies.
But the conditions that need to be satisfied in order to have a realistic chance of becoming a relevant solution severely restricts the likely technologies. These conditions include:
These criteria effectively limit the candidate solutions to:
Of this, the two most likely products to compete for the space is an Advanced LAB or the LAB plus small Li-ion (3Ah) battery.
Some people assume that a Li-ion starter battery - which would have very good DCA performance - is the obvious technology. This is, however, an unlikely solution for the mass market due to high cost and poor low temperature performance. MHV's require “high power” batteries which are much more expensive than the “high energy” batteries used in EV’s/PHEV’s which have seen a dramatic fall in prices recently. Furthermore, Li-ion batteries cannot start the engine at low temperatures - a fundamental requirement of any "start" battery.
It is likely that the most relevant solution for the mass market will be the one that achieves heightened DCA (80A or more) at the lowest cost. With dual battery solutions, there is an immediate cost and weight penalty. It is clear therefore that a single LAB will make an ideal MHV battery ... IF the DCA can be lifted.
While the additive of carbon additives to lead acid batteries is not new, the ability of carbon to improve DCA has only recently been recognised and is one of the highest priority research topics in the industry today. ArcActive's approach is unique - we employ a carbon fibre fabric as the structural and electrical framework for the electrode's active material. While there are many innovations incorporated within ArcActive's electrode, the use of a carbon fibre fabric not only allows ArcActive's electrodes to contain much higher carbon content (by unit mass), but the electrochemically active, permanently electrically connected carbon fibre dramatically constrains sulfation (the agglomeration of lead sulfate particles) and allows for the regeneration of the fine lead and lead sulfate structures with use. This is one of the keys to ArcActive’s sustained DCA performance.
While ArcActive may be unique in using carbon fibre fabric as its electrode framework, our process of heat-treating the fabric is what makes AACarbon uniquely suited to meeting the DCA demands of tomorrow's cars.
Carbon materials used in electrodes generally have better functionality if heated and the higher the treatment temperature, the better the performance. The lowest useful treatment is for “carbonisation” and is typically at 1,200°C and “graphitisation” is typically performed at 2,500°C. We treat carbon material at extremely high temperatures of around 3,500°C - you simply cannot get much hotter without vaporising the carbon. Critically, we can do this in a continuous, low cost manner and while it’s taken us nearly ten years to optimise this, it’s been worth the effort.
While car makers want batteries with much better DCA, they cannot accept any compromise on the achievement of the traditional battery tests. This provides a very real challenge for developing new battery technologies as some of the best ways to improve DCA can often lead to serious problems in other performance areas (such as high water loss, low "cold cranking amps" (CCA), and high self-discharge rates). Through the unique combination of arc-treatment and a carbon fibre fabric in its negative electrode, ArcActive naturally avoids or minimises the issues created by other carbon-additive batteries and assists in satisfying the core traditional battery tests.
There are a number of alternative energy storage technologies that have good DCA performance, such as lithium-ion batteries and supercapacitors. However, the disadvantage of these technologies is their relatively high on-cost. It is reasonable to expect that the low cost technology that meets the automakers' requirements will become the market leading technology.
ArcActive's electrode has been designed to be a direct substitution for existing negative electrodes in flooded LABs. As flooded LABs are the lowest cost form of starter battery, even with the modest additional cost contributed by the AACarbon electrode, the resultant battery will still be a fundamentally low cost product. We expect that batteries using ArcActive's electrodes will be no more expensive than the AGM batteries that are the current start/stop battery of choice.
Being a flooded LAB design has an additional benefit: the volume of manufacturing capacity for flooded LABs is vast and ArcActive's solution will avoid the large capital expenditures currently facing the LAB industry as it builds AGM capacity to meet projected start/stop battery demand.