subject: The Three fundamental Laws of Batteries: The Third Law [print this page] The Three fundamental Laws of Batteries: The Third Law
Welcome to a laptop battery specialist of the IBM Laptop Battery First post by: www.best-battery-online.com The third law is, in some sense, also a commentary on our expectations from our batteries and it states: Of the four metrics batteries are graded on for a given application (i.e., performance, cost, life, and safety), typically, only two can be simultaneously achieved. If the battery is designed to also perform satisfactorily on a third metric, it will fail spectacularly on the fourth.This law can be summarized in a single sentence: Batteries are all about compromise.If you decide to start a battery company, you go to the various VC firms and tell them you have a system that has the highest power, highest energy, longest life, best safety, and lowest cost of all systems out there.Once you get money and start doing development work, you'll find out very soon that you're doing well in a couple of metrics (say energy and safety), but your other metrics aren't looking so good, like your cycle life is really bad and your costs are through the roof.You then hit upon an amazing idea. Why not decrease the voltage to which you cycle the batteries to increase the life? This decreases the energy, but by this time, reality has set in and you (and your VCs) are willing to compromise on energy. So you lose some energy, but you gain a lot in life.But in doing so, your cost ($/kWh) just went up from astronomical to even more astronomical. But infinity+ anything is infinity, so I guess it's all fine.This compromise scenario is the reason why there's no one battery chemistry that has dominated the market for all applications. No system has yet replaced the lead-acid battery for starting your car. It's not that the lead acid is an amazing system (try leaving your car parked with the lights on and you'll know how flawed this chemistry is), but it's the best system for that application, despite its shortcomings.It's the same law that describes our lack of clarity about which Li-ion battery chemistry willdominate the electric vehicle and plug-in hybrid vehicle market .And it's the same law that prevents Moore's law-like improvements in the battery space. Try to increase the energy density too much, and your cycle life will fail spectacularly.The first and second laws, in some sense, can be considered a subset of this law in that we compromise between energy and power when we design our battery such as IBM FRU 92P1121 Battery. And we compromise between energy density and cycle/calendar life and self-discharge when we decide to maximize the voltage to go above the voltage window of the system.The third law is something we all should remember when we try to understand how to develop a business plan around batteries, or when we are trying to identify the best battery for a given application.However, one should also be cognizant that there is no fundamental reason why a compromise is needed. Researchers in national labs, companies, and in universities are working hard everyday to find the magic combination where no compromise is needed.All this leads me to a law that supersedes all these laws. It captures the nature of batteries and how we design them, our decision to push the envelope in terms of voltage despite the risks, the constant compromises when it comes to batteries, and the expectations we have from our inventions.I call this the Zeroth law, and it states:The performance of any battery will fall (just) short of our expectations irrespective of the complexity of the device it is powering.I shall not even bother elaborating this one.Note: If I had written this blog post three months ago, I would have said the Zeroth law doesn't apply to me. I consider myself a pretty evolved human with limited expectations from my energy storage devices. I had a car battery that was seven years old, a computer battery at four years, and a Bluetooth headset battery at two years all working very well and to my satisfaction. And then my world crumbled (twice), and I'm now a firm believer in the Zeroth law. http://www.articlesbase.com/laptops-articles/the-three-fundamental-laws-of-batteries-the-third-law-4504700.html
