of folks have trouble understanding the energy characteristics
of batteries and the differences between them. Why does one
light take 123A batteries and another take AAA? What's the
deal with lithium AA? What makes one battery better than another?
Well, here are some answers for you.
to focus on lithium and alkaline batteries here and add in
rechargeable near the end.
very hard to explain the energy capacity and characteristics
of batteries, but I'll use an analogy that seems to work pretty
of it this way:
have a bucket of marbles. The marbles run out through a
spigot at the bottom. The marbles then flow over a waterwheel
that they spin.
bigger the bucket, the more marbles you can hold.
marbles spin the wheel faster than small marbles, but any
particular bucket is designed to hold only one size of marbles.
bigger the spigot, the faster the marbles can pour out and
the wheel spins faster. However, the bucket also runs out
bucket is fairly fragile and can only be used once.
sense doesn't it? Now let's apply the analogy.
characteristics of a battery are usually described as Amp
Hours, Voltage, and Internal Resistance. All three of these
factors affect how the battery works.
That's the work that the energy is doing.
That's the battery. The "bigger" the battery (bucket),
the more electricity it can hold. The size of the battery
is measured in Amp Hours (Ah for Amp Hours or mAh for milli-Amp
of the marbles? That's the voltage. Bigger marbles = higher
voltage. The higher the voltage, the more effort it can put
into getting the work done.
of the spigot? That's the internal resistance. Lower internal
resistance (big spigot) means that the battery can dump out
more of its electricity over any given period of time. Higher
internal resistance (small spigot) keeps the electrictiy from
flowing out of the battery as quickly.
apply this knowledge.
cells are bigger (have greater mAh) and hold much more electricity
(hold more marbles) than a AAA battery, so can do the same
work much longer. Larger batteries are needed for when you
need longer runtimes.
the voltage, the more "effort" the electricity can
exert and the more work it can do at any given moment (bigger
marbles make the wheel spin faster). Using the same batteries,
a 3 volt light will not be as bright as a 6 volt light. The
batteries are doing more work (spinning the wheel faster)
and giving us a brighter light as a result. We can either
get a higher voltage battery or we can tie a bunch of batteries
together to increase the voltage.
Hours vs. Voltage:
though, that any given bucket can only hold one size of marbles.
When we compare the 123A and the AA, the 123A has twice the
voltage but only has half the capacity as the AA. The 123A
holds fewer large marbles while the AA holds more smaller
batteries have lower internal resistance (bigger spigot) than
alkalines (smaller spigot) and can dump out all of their electricity
(also called: "deliver high currents") much faster.
This makes them good for when you need your effort (voltage)
applied VERY QUICKLY. Very high output lights and electronic
devices take advantage of this characteristic of lithium batteries.
Hours vs. Internal Resistance:
the alkaline battery (bigger bucket), the lower the internal
resistance (bigger spigot). So the spigot on bigger alkaline
batteries is naturally larger than the ones on smaller alkaline
batteries. Why is this important? Because some devices RELY
on the internal resistance of the batteries to limit the amount
of Amps that are sent through the device. Reduce the internal
resistance and the device cooks itself. This is why you absolutely
do not want to replace alkalines with lithium batteries unless
the manufacturer specifically says you can. With Lithium AA
available from Energizer, some folks think you can just plop
them into anything that takes AA batteries. Not true! Always
verify that it is OK to do so first with the manufacturer.
Otherwise your expensive electronic device may turn into an
subject of Lithium AA batteries... Lithum AA also carry higher
voltage (bigger marbles) than alkaline AA cells. They're 1.7
Volts each, not 1.5, and they maintain more of that voltage
even under load. This can cause serious problems in devices
designed to use Alkalines which dip to about 1.2 Volts under
load. So the lesson here is: be extra careful as to what you
stick Lithium AA batteries into and always get manufacturer
approval before doing so.
what about rechargeable batteries?
batteries include NiCad (Nickel Cadmium), NiMH (Nickel Metal
Hydride), and Lithium Ion.
apply the bucket analogy to these batteries:
all have big spigots, are easily refilled, but they all
we empty them out too much they won't hold the marbles any
more. We have to leave a minimum number of marbles in the
bucket to keep it working.
time we refill the bucket it gets damaged. The faster we
dump in more marbles, the more damage is done. Dumping in
marbles slower generally minimizes the damage.
eventually the bucket is damaged to the point where it won't
hold marbles anymore.
apply this information in real terms:
of these types of rechargeable batteries are capable of delivering
high currents (dumping their electricity out) very rapidly.
like to hold a charge when not used for a long period of time
(the bucket leaks). They lose some of their charge on a daily
basis. Lithium Ion is affected the least by this characteristic.
them should not be over-discharged (don't completely empty
the bucket) or they can be damaged and won't hold a charge
well any more (bucket gets damaged).
a slower charge rate is better for making them last longer
overall (refill the bucket slowly to avoid damaging it).
it's a simple analogy, but hopefully it makes sense and brings
some clarity to the relationship between batteries and their