## Why Does My Phone Battery Die So Fast?

Why do batteries die? And, why can they only be recharged so many times before they won’t hold a useful amount of charge?

And this same question has probably crossed the mind of every cellphone user trying to send one last text before the screen blinks off.

Research, like mine, continues around the world to make batteries that charge faster, last longer, and can be recharged and discharged many more times than today’s.

But as much as you and I would like, it’s impossible to make a truly everlasting battery. I have taught thermodynamics for more than 30 years.

So far, there is nothing that suggests we can break the fundamental laws of science to get that elusive battery.

Battery scientists and engineers call the main problem “capacity fade.

Regular people wonder about it with questions like “Why won’t my battery hold a charge?” and complaints like “I just recharged this thing and it’s already out again!

It’s a result of the second law of thermodynamics, which states that whenever some real process happens, it creates a certain amount of wasted energy along the way that can never be recovered.

Any time a battery is charged or discharged, there’s a little bit of wasted energy – a little bit of wasted capacity in the battery that cannot be recovered.

To envision how this works, think about battery use like transferring water between two cups.

Using a battery is like emptying the water from one cup into the other, and charging the battery involves pouring the water back into the first cup.

Even if you do it one or two times without spilling a drop, there’s always just a little tiny bit left in each cup that you can’t pour out.

Now imagine pouring back and forth hundreds or even thousands of times over a period of two or three years (for a cellphone battery) or 10 to 20 years (for an electric car).

Over time, all the thousands of little and big things that go wrong add up to quite a bit of water going missing. Even spilling a barely visible drop – say one-tenth of a milliliter – adds up to an entire liter if it happens 10,000 times.

That doesn’t even include the possibility of one cup failing in some way that loses even more water – like springing a leak or heating up and causing evaporation.

Just as water inevitably goes missing when pouring from one cup to another, more energy is required to charge the battery than it actually stores, and less energy comes out than is stored in it.

The proportion of wasted energy to stored energy grows over time.

In fact, the more you use a battery, the more energy gets wasted, and the sooner the battery will reach a point where it’s dead and can’t usefully be recharged.

I and others are studying ways to have those discharging-recharging cycles run more smoothly to reduce the amount of waste, but the second law of thermodynamics will always make sure that there’s no way to get rid of it entirely.

Pass it on: Popular Science

## This Skin Patch Can Power A Radio For 2 Days Using Your Own Sweat

Researchers have created a new skin patch that has powered a radio for two days using only human sweat. The Biofuel Skin Patch uses the sweat to provide its power – meaning it could be used to charge up devices like phones in the near future.

“If you were out for a run, you would be able to power a mobile device,” said Joseph Wang from the University of California, San Diego.

His research team at the university have been working on the technology. The biofuel patch is a few centimeters wide and sticks directly on the skin.

It works by using enzymes that act like the metals inside regular batteries, which are then powered up by feeding off the lactic acid found in sweat.

Pass it on: New Scientist

## Tesla Just Built The World’s Biggest Battery In Record Time

Elon Musk has won. The Tesla CEO made a bet that he could install the world’s biggest battery in South Australia within 100 days, and the whole installation would be free if the company failed.

Last November 23, Thurday, it was revealed that the project has been completed with 46 days to spare.

Congratulations to the Tesla crew and South Australian authorities who worked so hard to get this manufactured and installed in record time!” Musk said on his Twitter page Thursday.

The batteries are designed to provide reliable power to a part of Australia that desperately needs it. South Australia has dealt with 18 months of blackouts.

A 50-year storm event in September 2016 knocked out pretty much the entire state’s elect.

The Powerpack system provides 100 megawatts of storage to renewable energy firm Neoen’s Hornsdale wind farm near Jamestown in South Australia, holding enough power for 30,000 homes.

The two companies will join engineering company Consolidated Power Projects and state premier Jay Weatherill next week to officially unveil the battery.

The project forms part of a AU\$530 million (\$404 million) state plan to improve renewable energy production.

Last September, South Australia suffered from severe blackouts after a storm cut off production.

The state receives around a third of its energy from renewables, but the plan will boost this by building a solar thermal power plant and emergency generators along with the battery.

The world’s largest lithium-ion battery will be an important part of our energy mix and it sends the clearest message that South Australia will be a leader in renewable energy with battery storage,” Weatherill told the Associated Press.

Tesla first set itself the 100 days goal after a discussion between Musk and Australian software-billionaire Mike Cannon-Brookes.

In March, Cannon-Brookes asked if Lyndon Rive, Tesla’s vice-president for energy products, was telling the truth when he said the company could install between 100 to 300 megawatt-hours of storage in 100 days.

This led to a bidding process where the state government agreed to fund \$113 million of battery storage. Tesla beat out a number of competitors to score the contract.

Musk was a bit sly with the deadline, though. Tesla started counting down 54 days ago from September 30, the point at which the Australian energy regulator gave clearance to the project.

The company was building the battery for a while prior to this. The project came well under the January 8, 2018 deadline, but Tesla did not build a battery in less than two months.

Between now and next week’s unveiling, the battery will undergo a series of checks to ensure it meets state and energy regulations.