Better Batteries, and Why We Care

The Internet was abuzz for a bit today, when Engaget href="">reported
that a lithium-ion battery was in development, that could store 20
times as much energy as existing batteries, with lower cost.  

But then it was href="">clarified
that battereis could deliver 20 times more power.  

Apparently, the original article is behind a pay wall, so bloggers are
still wondering what the real story is.  Other reports say
similar things:

report said Hitachi Maxell and a number of universities and
firms in Japan have created a design for a Lithium Ion battery that
will last 20 times longer than current units.

new cell has a discharge capacity 20 times larger than that
of current Li-ion batteries, which means it's more than capable of
driving a car engine on its own.

So what is the difference, and why does it matter?

There is a difference between energy and power.  Energy is the
capacity to do work, whereas power refers to the ability to do a
certain amount of work in a certain amount of time.

Both abilities are important.  The ideal battery would store a
lot of energy, and would be able to deliver that
energy at whatever rate is desired.  Having a lot of energy
does not do you much good, if you cannot get it to move where you want
it to go at a high enough rate.

Many applications call for a battery to have the ability to delivery a
surge of energy, such as when starting a motor.  Therefore,
having a higher power rating is a good thing.  But when it
could to running time -- that is, how long a device can be operated --
it is the storage capacity that is important.

So, we will have to wait for more detailed information, to see exactly
what this advance will mean in practical terms.  It may be
that the lower cost of the new battery will be the more important
advantage.  The new batteries will use manganese instead of
cobalt.  Manganese is much cheaper.  It costs about
$1.70 per 100 grams, while cobalt costs about $21 per 100 grams. ( href="">source)

The cost of battery storage capacity is an important component of the
cost of electric and hybrid cars, and many other things.
 Reducing the cost of energy storage does not help, directly,
with the cost of the energy itself, or with the problem of energy
shortages, it can help be reducing the cost of solar and wind power
installations that depend upon batteries.  

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I find the terminology used in these reports to be confusing. "Discharge capacity" could refer to energy storage but it could also refer to peak discharge current. To clarify:

As mentioned, energy is the ability to do work, typically measured in joules. Power is the rate of energy usage, typically measured in watts (where 1 Watt = 1 joule per second). Power can also be calculated via voltage (volts) times current (amps). Batteries are, of course, constant voltage devices. Their current depends on what they're connected to. Their energy storage is usually measured in amp-hours. For example, a 10 AH battery could deliver 10 amps for an hour, two amps for five hours, or some other combo.

As a side note Amp-Hours does work out to energy as 1 amp = 1 coulomb of charge per second, so multiplying by time yields a total charge transfer within that time, and when that is multiplied by the delivered voltage (1 volt = 1 joule per coulomb) you wind up with the total energy delivered in that time (joules).

The AH rating is an idealization and there are practical limits. Internal losses will limit just how much current can be drawn over very short times. One simple way of modeling the battery is to assume that it has an equivalent internal electrical resistance. This limits the maximum current that can be produced (via Ohms Law, current=voltage/resistance). So, if they managed to reduce the internal resistance, they could increase the peak output current but this in no way means that the actual energy storage of the battery would be increased.

Bottom line, from the imprecise wording of these articles it is not clear what they've achieved here. And let me just add that as an electrical engineering technology professor I take great pains to explain the difference between power and energy to my students. Very few of them have a good grasp of the difference when they first walk in the door.

Another way of looking at power and energy is to use the example of the recently-concluded Democratic Party primary race: Hillary had the energy, but Barack will have the power.

A question for someone who understands battery technology better than me: would a higher discharge rate also imply a higher charging rate? If so, this could be extremely important even without a higher storage capacity, as it might improve the "refill-ability" of electric transportation, making it more practical for rural or isolated areas. (If you have to travel 500 miles, you often can't sit still for an overnight recharge.)

The important things just not about the abilities of the batteries but the company must know that they are one of the polluter in the environment. What about the disposal of the batteries, the wastewater from the batteries factory, the improper wastewater treatment plant and others. All that things are the pollutant sources of pollutant species especially heavy metals.

Heavy metals are very dangerous not only to the environment but to the human too. It is not biodegradable and tend to be persistence in the environment.

Think about it..the higher the ability of the batteries it still pollute the environment..

By fazlinnazli (not verified) on 05 Jun 2008 #permalink

The polution factor for batteries can be almost zero. So the comment or justification for not using batteries vs. fossile fuels due to polution is hogwash. Leaded gasoline has done tons of irreversable dammage to our soil in the Cities. Global warming is a big hint that fossile fuels need to go. Pollution from batteries? Easily controlled. Wind and solar pannels being used as a source for recharging would get alot of people off the grid if prices were reduced on the technology. Packing more energy in a battery would help as well. Replacing fossile fuels with Electricity is the only thing that makes sense. We've already done a good job of polluting our world. Lets do something about it instead of justifying the continued use of the ancient outdated use of the internal combustion engine. A device that is long overdue to disappear. Greed is the only thing standing in the way of technology change. Change....long overdue.

By Kent Taylor (not verified) on 06 Jun 2008 #permalink