Article, August 2008
Scotty, I Need More Power!
By Alan Mildwurm, President, Diablo Valley PC Group, California
Obtained from APCUG with the author's permission for publication by APCUG member groups.
When my kids were young, I bought batteries by the bushel. All of their toys required some batteries. The phrase “batteries not included” raised almost as much terror as “some assembly required.” I still recall going out one Xmas morning in search of “C” size batteries because we missed the warning on the box. (7-11). One very cool pool toy took 16 batteries - in 3 sizes.
In those days, rechargeable batteries were garbage. Most rechargeables were nickel-cadmium and with a memory that made them useless after a few charges. Shelf life was a joke and power output dismal. For several years, I bought throw away alkaline batteries at Costco because they were cheaper than those clever bunny batteries. Not environmentally friendly, but definitely kid toy friendly. As the kids grew up, their needs for batteries diminished (actually they now buy their own), but my need for batteries is increasing. Wireless keyboards, wireless mice, gps, wireless game controllers (the Wii-mote takes 4 batteries per controller and there are 4 controllers), iPod external power units, camera accessories and on and on. I am going through more batteries now with my toys than I ever did with the kids! Luckily, rechargeable battery technology has come a long way.
Sanyo produces the eneloop (http://www.eneloop.info). According to their spec sheet, the AA battery is rated at 1.2 volts and 2000 mAh. Not bad for a rechargeable. (A disposable usually is 1.5 volts.)
There are two sizes of eneloop batteries, AA and AAA. They also produce C and D size cylinders in which you insert AA batteries.
From their site:,
eneloop is a totally new type of battery, which satisfies
in a unique way the needs and expectations of the consumers.
Consumers would like to have a battery, which
can be used right after the purchase
has a high performance
has a long shelf life with no loss of energy
can be used everywhere
is cheap in purchase and usage
is environmental friendly
is easy to use
So far these requirements could not be satisfied by a single type of batteries. The consumer had the choice between disposable batteries or rechargeable batteries.
Disposable batteries have several advantages:
they can be used immediately
they have a long shelf life with low loss of energy
they are rather cheap in purchase
they are easy to use and no charger is required
These advantages of disposable batteries however, had to be seen alongside several clear disadvantages:
can be used only once and therefore mean substantial waste and risk for the environment.
have to be purchased over and over again and are therefore expensive considering the life-time of your equipment.
are not quite powerful enough in certain applications (like digital cameras)
are being offered in many varieties and special application-specific types, which confuses the consumer.
The classical advantages of rechargeable batteries are:
high performance, especially if high discharge currents are required ( like in digital cameras)
cheap in use, because they can be recharged many times.
environmental friendly, because one rechargeable battery replaces 1000 disposable batteries.
good performance at low temperatures.
Given these advantages, rechargeable batteries also have some disadvantages, which made consumers reluctant to exchange disposable batteries by rechargeable batteries:
Rechargeable batteries lose the stored energy rather fast.
The state of charge is hard to determine.
Continuous charging or frequent charge (without complete discharge ) can destroy the battery.
Proper charging is complicated for an average consumer
The charging takes quite long and rapid chargers are expensive.
All these negative attributes have one root-cause: self discharge.
Self-discharge means, that a charged battery slowly discharges itself without any equipment consuming any current. This is the reason for rechargeable batteries being sold in discharged state. And this is the reason for that keeping charged batteries for some time did not make any sense. When you needed then, the energy was gone.
How was the self-discharge reduced? (For you techy folks!)
Modern Ni-MH batteries consist of two metal stripes (anode and cathode), which are separated by a non-conductive porous plastic foil ( separator ). These three stripes are laid on top of each other and are wound to a coil. This coil is put in a metal can and immersed with a liquid (electrolyte). Then the metal can is closed with a cap. The self discharge of Ni-MH batteries is caused by three main reasons:
the chemical decomposition of the cathode,
the natural disaggregation of the anode,
Impurities of the anode.
Now, how could the self-discharge in the eneloop been reduced?
The chemical decomposition of the cathode has been reduced substantially by the use of a new superlattice alloy. As an additional benefit the superlattice alloy increases the electrical capacity of the battery and reduces the internal resistance, which allows higher discharge currents. Another advantage of the reduced decomposition of this alloy is the fact that less Cobalt is needed to stabilize the alloy. The anode has been strengthened by another new material, which reduces the natural disaggregation. Additionally the separator and the used electrolyte have been optimized for low self discharge of the eneloop.
They really are good batteries!
I have been using eneloops for several months. They work fine. I have both a wall charger and two battery (AA or AAA) USB charger. Both chargers work very well. I like the USB charger and I love the fact that they come charged and ready to go.
The kit shown below lists for $50.00 but is available at Amazon for $32.00 It comes with 4 AA, 2 AAA, and 2 spacers each for C and D plus a charger. I have found even better deals with more batteries at Costco!!
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