The numbers of battery conferences are growing, but the agendas are similar — portraying a super battery that does not yet exist. With a grant of $120 million from the US Department of Energy, the Joint Centre for Energy Storage Research (JCESR) wants to develop a battery that is “five times more powerful and five times cheaper than current systems in five years.” They call this the 5-5-5 Plan. Universities are also involved but battery manufacturers are much further ahead. Additives that govern performance to a large extent are guarded as a top secret by each manufacturer.
Toyota had already been searching for the super battery in 1925. They called this the “Sakichi battery” after Sakichi Toyoda, the inventor of Japan’s power loom and the founder of Toyota Motors. He is often called the father of the Japanese industrial revolution. It is said that Mr. Toyoda promised the yet-to-be-claimed prize of 1 million yen for a storage battery that produces more energy than gasoline. To qualify for the price, the Sakichi battery must be durable and quick to charge.
Progress is being made but not without roadblocks. Lithium-air proposed in the 1970’s with a theoretical specific energy resembling gasoline is being delayed due to air-purity issues; the urban air that the battery “breaths” is not clean enough. The promising lithium-metal introduced in the 1980s still grows dendrites, leading to violent events with flame if an electrical short develops. There is much talk about the solid-state battery that shares similarity with lithium-metal, but scientists must also solve the dendrite problem here, as well as improve low conductivity at cooler temperatures and short cycle life. Lithium sulfur may be close to commercialization but the short cycle life also troubles this system. The redox-flow battery could offer a solution for large battery systems by pumping “charged” fluids from external tanks through a membrane, but this refinery-like battery suffers from corrosion. There is a glimmer of hope for Li-ion by coating the anode with graphene, a layer that is only one atom thick. This is said to quadruple the capacity, but such a battery is still miles away.
As part of a survey, a consulting firm asked me what advancements battery users want to see in a battery and he gave me list of options to choose from. Will this be a 25 percent increase in energy density; a 25 percent boost in discharge rate; a 25 percent improvement in temperature range and safety; or will this be a 25 percent reduction in size and weight?
I explained that a better battery does not rest on such enhancements alone but in knowing the performance of each pack in the field. This is seldom mentioned and a biomed technician said: “Batteries are the most abused components; staff care little about them and only do the bare minimum to service them.” He added further that, “references to battery maintenance are vague and hidden deep inside service manuals.”
Checking into battery usage in healthcare, I came across a US FDA survey that says “up to 50 percent of service calls in hospitals surveyed relate to battery issues.” Healthcare professionals at AAMI (Association for the Advancement of Medical Instruments) further stated that “battery management emerged as a top 10 medical device challenge.”
To solve these issues, device manufacturers mandate to replace the batteries on a date-stamp of 2 to 3 years of use. Batteries have improved and live longer; they also carry a higher price tag. Date-stamping has resulted in batteries being replaced too soon and a DOE report reflects this by saying that every year roughly one million lithium-ion batteries are discarded with most packs still having a capacity of up to 80 percent.
|“Where do approval-agencies stand on these issues,” we wonder? Getting a device approved is tough and device manufacturers make the best effort, including a brand new battery to pass. But once rubber-stamped, the agencies wash their hands and places the responsibility of maintenance on to the user. Rules, especially with batteries, become vague and the user will ask: “At what capacity should I replace the battery? How much spare capacity is enough? How often should I test the battery, and what are early indications of pending battery failures?”|
Agencies, such as the FDA, realize the lack of oversight on the battery for critical devices and have identified three problem areas they are trying to resolve:
Batteries in the military also fail, and often without warning. A modern soldier carries radios, GPS devices, smartphones, night vision goggles, infrared sights, flashlights and counter-IED equipment. This amounts to roughly seven battery types, with 10 packs each for a 72-hour mission at a weight of about 9kg (20 lb) per solider. Reports indicate that batteries have become the second highest expense next to munitions. Without periodic performance checks, soldiers will carry rocks instead of batteries as Figure 1 demonstrates.
Figure 1: Soldier carries rocks instead of batteries.
Batteries fade with use and age. Each pack needs a periodic performance check to ease the weight carried by the combat solider.
Courtesy of Cadex
Other uses where the condition of a battery must be supervised are drones and robots. Drones are hard on the battery and the capacity fades quickly, reducing the flight time. As drones are used for many unique commercial applications, fleet maintenance cannot be limited to knowing the state-of-charge alone but also recording state-of-health, the energy storage capability based on capacity. Knowing the anticipated flight time will prevent an expensive vehicle from crashing on a longer than expected mission, struggling against headwind or attempting a second landing.
A battery should receive similar treatments as a critical part in an aircraft or a machine where wear and tear falls under strict maintenance guidelines. The service of a jet engine, for example, is measured in flight hours and flight cycles. One cycle includes a take-off and landing, and the Airbus 330 needs maintenance after 200-400 such cycles.
Such a procedure does not apply to the battery because accepted test norms have not been established. Auditors doing quality control shy away from such ruling and only examine the outer appearance; state-of-health is mostly ignored. This allows faded batteries to hide comfortably among their stronger peers. The battery holds special privileges and evades inspections. Should it quit during a critical mission, then this is seen as beyond control.
Most failures occurring during emergencies are caused by weak batteries as heavier than normal traffic depletes them prematurely. Capacity as a measure of performance evaluation and end of life indication is poorly understood. When asking a battery user: “At what capacity do you replace the battery?” most reply in confusion: “I beg your pardon?”
The leading health indicators in a battery are:  capacity that stores the energy,  internal resistance that enables current delivery, and  self-discharge that reflects the mechanical integrity and reveals stress-related damage. With average use, Li-ion provides 300 to 500 full discharge cycles before the capacity drops to about 80 percent, marking the end-of-life. Low capacity is the most common cause of failure; the capacity level also serves as benchmark when a battery should be replaced.
While improving battery performance is important – and the high attendance list at battery seminars proves this – not enough emphasis is placed on the battery once the pack enters active duty. Product development and agency approval are only pre-operational services alike the education of a youngster. While this is important to build a career, the workforce that follows is the proof of endurance. Batteries age and capacity-fade is as certain as death and taxes, a comment Benjamin Franklin made in 1789.
Battery diagnostics and monitoring have lagged behind other technologies but an industrial revolution in batteries is in the works. In the 1970s, the world had computers but little software. Bill Gates changed this with the PC and shared software. Today, the world evolves around batteries but lacks supervision as part of control technology. Future systems will assess battery performance during charge or by a rapid-test and make the results transparent to the battery user and fleet manager alike.
About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc. For three decades, Buchmann has studied the behavior of rechargeable batteries in practical, everyday applications, has written award-winning articles including the best-selling book “Batteries in a Portable World,” now in its third edition. Cadex specializes in the design and manufacturing of battery chargers, analyzers and monitoring devices. For more information on batteries, visit www.batteryuniversity.com; product information is on www.cadex.com.
last updated 2016-06-22
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