Voltage is voltage, and the right voltage is needed. But 7.4 V compared
to 7.2 V is small. One may wonder how a battery can differ by a small
voltage, since a battery by definition is a series of electrical cells
with voltages that add up from the individual cells that are connected
in series. For commercial usage, there are only a few kinds of cells
(i.e., chemistry) available, and each kind has a unique voltage
associated with it within a narrow tolerance. I suspect the difference
between a 7.4 V battery and a 7.2 volt battery is simply a kind of
puffery used to describe the battery since your camera will probably
require one kind of electrical cell: usually today, a lithium-ion or
perhaps a nickel metal hydride cell. (Check your camera manual to see
which kind is recommended.)
The mAh means "milliamp-hours" and measures the charge that may be
contained in a fully charged cell or battery. (The charge is also
measured in Coulombs.) Ideally, a 650 mAh battery will deliver 650
milliamps of current for one hour before becoming discharged -- or 325
milliamps for two hours, etc. Thus, a higher mAh rating ought to mean
that the battery will have a longer life in a device before needing to
be recharged.
But as the battery ages, both the energy stored and the voltage are
subject to diminish after many recharges. Eventually the battery
becomes unsuitable for your application and needs to be replaced.
So far I have gotten good results by ordering from Battery Engine, a web
store. It is not the cheapest but offers a good discount from the
manufacturer's list price. There surely are other good sources, but I
have not had good results from eBay, especially those that ship from
Hong Kong at a wonderfully low price.
Sue Cubic wrote:
I am searching online for an additional rechargeable battery for my
Nikon Coolpix 775. The original battery is 7.4V 650 mAh. I am
seeing choices of 7.2/7.4 800mAh (and 1000 and 1100). All say they
are compatible with my camera. Most are 7.2V. Does the difference in
voltage matter? Will 1100mAh last longer than 650 mAh? What is my
best choice?
I've just finished a road trip and kept killing the battery. It was
purchased in 2001, and really doesn't owe me anything! Radio Shack
sold me a non-rechargeable for $21, along the way. Rechargeables I'm
seeing online are all under $15.
Advice??
Thanks,
Sue
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