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THE LATEST ON NIMH
RECHARGEABLE BATTERIES
AboutRechargeableBatteries.Info
BASIC COMPARISONS
Sizes AAA, AA, C, D, 9v.
The
safest, most efficient, most cost-effective rechargeable on the market today is the
highly versatile Nickel Metal Hydride (NiMH) battery. We will compare
features of the new Low Self Discharge variety and the older non-LSD
variety to each other, and to other types of batteries. Note that overall quality of
NiMH batteries varies considerably by brand - and the brands famous for alkaline
batteries are generally missing from the list of superstars. Unless stated
otherwise, the comparisons shown below are based on top quality brands for each
type.
BATTERY SPECIFICATIONS: Six basic specs should be printed on the battery (or
at least on a sealed package) and be consistent with consumer findings and
advertising claims. If not, watch out!
-
Chemistry (NiMH, NiCad, LiON, Lithium,
Alkaline, etc).
-
Storage capacity
(mAh).
-
Internal
resistance (ohms).
-
Self discharge rate
(percent per
month).
-
Voltage.
-
Charging requirements
(time and amps).
LONGEVITY & ECONOMY:
NiMH batteries (LSDs and Non-LSDs) may be
fully recharged 1000 or more times, with just one NiMH battery potentially
replacing 1000 or more alkaline or lithium non-rechargeable batteries. This is a
vast improvement over NiCads and the old version of NiMH rechargeable.
TOXICITY: NiMH batteries (LSDs and Non-LSDs) are considered to be non-toxic,
which is good news for our kids, pets, and landfills. NiCads are highly
toxic. Lithium battery components are used in the illegal manufacture of
methamphetamine,
causing the sale and use
of these batteries to be restricted in some states.
CHARGE RETENTION: NiMH
Batteries (LSDs only) and NiCads stay charged for long periods of time while
idle, whereas the Non-LSD type of NiMH leak energy relatively fast while idle
and must be recharged on a regular basis.
-
Low Self Discharge NiMH Batteries: Maximum
acceptable self discharge rate is around 4% per month at
room temperature; should retain an operational charge for at least 2 years without
refrigeration.
-
Ultra Low Self Discharge Batteries: A good example of a ULSD is the AccuEvolution,
which typically self discharges at a verified rate of about
2% or less per month
at room temperature and, when fully
charged, retains an operational charge for over 4 years without refrigeration;
the half life for this battery without refrigeration is about 30 months. An ultra
low self discharge rate such as this translates to a high level of readiness, less recharging, less energy waste, less battery wear, and greater longevity.
-
Non LSD batteries: This
older type of NiMH battery typically loses about 20% of charge within 24 hours
of charging, then self
discharges at a rate of 15% to 30% per month thereafter. Some (marketed
as high capacity batteries), show a
somewhat higher storage capacity than the LSD type. Yet, because non-LSD
batteries leak energy quickly, the useable storage capacity of such batteries is
less than for LSDs in most usage situations.
-
Precharged batteries.
Almost any battery can
be marketed as 'pre-charged'. If your priority is a battery that
comes charged and
STAYS charged, select a
NiMH battery with a low self discharge rate
that you can verify. If the self discharge rate is not printed directly on the
battery, is not shown on the manufacturer's website, or is
not consistent with consumer use - you are likely getting a pre-charged
battery that will NOT stay charged.
-
Batteries claiming to retain charge for 'up to
12 months': Any NIMH battery that self discharges in
12 months or less does not approach the minimum standard for
a Low Self Discharge battery. Such battery is either the
NON LSD type that would require refrigeration to retain charge for such a period of time
OR an exceptionally low quality LSD.
STORAGE CAPACITY: NiMH batteries (LSDs and Non-LSDs) generally feature twice
the storage capacity of NiCads. Although the Non-LSD type of NIMH generally
offers slightly more capacity than the LSD, this is
usually negated by the Non-LSD's
relatively fast rate of self discharge while idle. Be a bit wary of Non-LSDs marketed as
'high capacity' batteries, as many are low quality batteries that waste lots of energy on internal resistance and
are no bargain at any price.
CAMERAS AND OTHER
HIGH DRAIN
DEVICES: NiMH
Batteries (LSDs only) excel in cameras, strobes and other high
drain devices. Brands with the lowest internal resistance are the best as they waste
little energy to heat in high drain situations. Factory fresh NiCads
(hard to
find) perform fairly in high drain situations, but must be recharged frequently due
to their low storage capacity. Although lithiums are
aggressively marketed for cameras and other high drain devices, they are inferior in
most ways to a good LSD type NiMH battery. Besides being expensive and
non-rechargeable, lithium batteries (not to be confused
with the rechargeable lithium ion batteries used in cell phones
and laptops) generate considerable heat. Such heat
wastes energy, damages equipment (suddenly or gradually), and too often results in
dangerous leakage or explosion.
VOLTAGE QUALITY:
SEVERE WEATHER USE:
RECHARGING AND
MEMORY EFFECT:
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