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Revised October 13, 2002
Revised December 5, 2006
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Nickel Metal Hydride
This article originated after I had bought a camera that uses
4 AA to power it up. I tried Alkaline batteries, just because
I had been using them for a walkman and they had lasted a long
time there. But not so in my new Olympus C4040 camera, which
the sales person warned me about during the purchase. I knew
about rechargeable nickel - cadmium batteries because I have
been using them for over five years in things like: flashlights,
a walkman, and other battery powered units.
I had never used a nickel metal hydride battery and had no
idea other than it was rechargeable and that they held no memory
like the other batteries I had used. I figured that I would go
to the closes Radio Shack since I had a discount card that would
save me 20 percent off their regular price of batteries. I also
figured that if anyone knew about batteries they would.
During my visit there, I was greeted by a young lady who knew
nothing about batteries, but tried to get answers from another
sales person. The other person was so ignorant in the way that
he answered her, that my first thought was to walk out. However
it was not her fault, she was new to this store and this sales
guy must have been in the wrong profession. I bought the batteries
and a charger not knowing anything about them except that they
did not hold a memories.
However I learned quickly that they are a whole lot different
than any other battery I have ever used. If you don't use them
properly you will either have a fire or have a short lived
battery, -- which other wise are remarkable to use. So I felt
it important to learn about them and than pass this information
along to you, so that if you need a rechargeable work horse battery
that you will know how to look after them.
Rules of Life
Note to readers : This article is only
to inform you so when you do buy batteries that you will have
enough knowledge to decide if these Nickel Metal Hydride Battery
will fit your needs or not. Also I am by no means putting Radio
Shack down, they are an excellent store and at most times their
staff can be relied upon for good knowledge and accurate information.
The Olympus C - 4040 zoom camera came
with 2 lithium 3 volt CR - V3 non - rechargeable batteries. I
thought that I would use alkaline batteries first and I am glad
I did. Lithium batteries work very well in cold weather but are
costly to buy and so they should be used as a back up to Nickel
Metal Hydride Battery or Ni - MH the shorter
name for them.
NiMH are cost - effective and can offer between 500 to 1,000
charge charges per battery - provided they are properly looked
after. A few important practices to learn and your on your way.
A few Golden Rules:
Rule 1. These batteries do not
like to be overcharged.
Rule 2. Excessive heat during charging
will destroy them or cause a fire.
Rule 3. Always charge NiMH in
fixed sets, as if they were part of a battery pack. Never mix
batteries between other packs.
Rule 4. Look for a smart charger
that has a built in timer and knows when to shut off. Use the
charger in a cool, well ventilated area like a basement. Keep
the cover of the charger open, during charging to vent off the
heat created from normal charging.
Remember these few rules and these NiMH batteries, will last
for many years.
What is a Nickel Metal Hydride
Nickel-metal hydride (NiMH), batteries of course. Can
be used in place of all existing types use now, AA are common
among camera users, however there are other sizes available :
AAA, 9 volt, D and C cells too.
- Thet can be used like any (AA) battery with a life expectancy
of twice that of an alkaline battery.
- Are cost efficient because they are rechargeable and last
longer than other rechargeable on a single charge.
- They have a high capacity of 1300 to 1800 mAh per AA battery
- They perform excellent in high drain digital cameras which
have LCD monitors and flashes.
- Flat discharge curve- you can actually draw most of the rated
- They are made of different materials that make them light
- They can be recharged at any time or whenever you like without
the fear of a NiCd - like memory effect.
- They need minimal maintenance: a good charger can successfully
condition them back to maintain peak performance.
- They have a long life of 500 to 1,000 charges per each AA
- The best of all is that they are environmentally friendly,
thanks to their reusability and lack of toxic heavy metals.
How Long will they Last?
Any rechargeable batteries will lose its' charge over time
even when not in use. NiMH batteries do so even faster than lithium
rechargeable (if you can afford them to buy) (Lithium rechargeable
are most often found used with Camcorders). A satisfactory run
times of one AA set is from 3 to 5 weeks. So it is a good idea
to carry an extra set or two just in case the batteries your
using go dead.
NiMH batteries that are removed from the charger when fully
charged, will lose about 10 percent of their capacity in the
first 24 hours and 1 to 2 percent daily at room temperature.
If batteries are stored in warm temperatures this will increase
discharging, while cooler temperatures will slow discharging
down. At about 1.5 percent per day after the 1st day, that leaves
a residual charge of 58 percent at the end of the first month.
If you're coming down from, say, 1600 mAh, the remaining 928
mAh per AA will still power quite a few shots.
No memory what so ever .
No worries about recharging your NiMH AAs before they die
in your camera or palm computer. Avoid overcharging your batteries,
and you will never see a memory effect like we all have came
to know and hate in NiCds batteries.
Charge your NiMH AAs whenever it's convenient but less is
still better. Waiting till they are at the end of their power
cycle is not necessary with these batteries.
Why Keep Batteries in Sets
I never had to keep any other battery before these ones in
sets. However with NiMH it is important to keep them in sets.
Depending on what they are used for in my case it was a camera
that uses four AA battery cells and an extra four batteries as
a spare. It is important to keep those four batteries in the
camera together. So I labeled the first four bateries as set
One. Each battery had on it set one battery "A", set
one battery"B" ect. The back up set I labeled as set
two, battery "A" , set two battery"B" ect.
Why bother keeping sets of batteries together? Here's why:
Charging multiple batteries in different states of discharge
can easily damage the batteries, and the charger.
Here is what you need to do: put together in dedicated groups
of 2 batteries or 4 batteries of complete sets. A complete set
means that the batteries all started out together as brand new.
Mark each battery as in a set of four like this: Set1 battery1,
Set1 battery2, Set1 battery3, Set1 battery4 and the second set
is marked like this: Set2 battery1, Set2 battery2, Set2 battery3,
Set2 battery4. Mark all additional sets the same so that you
can not easily mix them up when using or charging.
It is important not to mix these battery set because you want
them to discharge over time equally. So never, ever break your
sets up. When you need to replace batteries in a set, try to
get the new and the old batteries in sync separately as best
you can before charging
them together. It is better to replace the group of batteries
than to add a new battery cell to the older group.
A Good Charger
A good charger will do most of the work for you and help your
batteries last through many charging cycles. Most will charge
Nickel - Cadmium as well, but never charge the two of them together.
Charge one or the other in the charger at one time only. For
better comparability I suggest that you uses the same manufacture
for both your batteries and charger.
A smart charger will be able to conditioning and charger your
battery with in a short period. I picked up a charger from Radio
Shack that will charge eight "AA" cells in under two
hours. It uses a pulse conditioning charge which is suppose to
lessen the chance of causing harmful gas bubbles. The charger
has an indicating light which tells you that you are in the charge
mode or that the battery is dead. The charger allows you through
a switch to charge batteries in sets of 2, 4, 6 or 8 at one time.
It has a timed charge and will never over charge. It also has
a short- circuit protection and senses batteries that have been
place in the charger backwards and in a reverse polarity.
Points of a good charger are:
- It uses a microprocessor to sense temperature and charging
- It will fully charge 4 AAs from dead to full charge in about
2 to 3 hours.
- It will not overcharge
- It will condition your AAs.
- It is small and light weight to transport and store.
What Should you look for in a
Look for a charger and batteries from battery manufactures
rather than the one offered by the camera manufactures. These
usually cost much more however, Kodak chargers and batteries
seem to be an exception. I recommend going with the Universal
Battery Charger catalog number 23 - 422 from Radio Shack.
Buy a fast charger for your NiMH AAs, and an extra set to
have on hand. Look for one that will monitoring the batteries
temperature so that you batteries are not harmed.
Shop around for a NiMH chargers,
- Fast (500 mA) NiMH/NiCd
- Some will charge AAA/AA and 9 volt charger,
- Radio Shack AA battery cell rated at 1600 mAh
- 110-120V AC adapter
- A 12V cigarette lighter charger is good for those long holiday
trips. The car adapter is used.
- The is a built- in conditioning circuit activated when needed.
- A trickle charge rate is safe for indefinite charging.
- Has individually charging AA/AAA bays.
- The Kodak PhotoLife Charger Kit, is also available from most
camera shops of 4Q2000), which includes a compact, lightweight,
smart, fast (650 mA)
compact charger and a set of 4 Kodak 1450 mAh NiMH AAs. The 110-120V
fold-down wall-socket prongs on this one-piece unit make it a
choice for travel to civilized portions of Canada.
Do not buy a cheap charger because it is the charger that
will help make those batteries work to their peak and last for
many cycles and years. The rule of thumb is that you get what
you pay for. Cheap fast chargers are seldom smart enough to use
without careful supervision, but it is usually safe to leave
your AAs in an inexpensive trickle or overnight chargers for
extended periods. Just make sure the trickle charger's current
is rate in milliamps (mA) and is no more than 10% of the rated
capacity (C, in mAh) of the batteries you intend to charge. For
example, it is safe to leave C = 1500 mAh AAs charging indefinitely
in a trickle charger rated at C/10 = 150 mA or less. NiMH AAs
will safely tolerate a long - term charging currents in mA up
to C/10. These slower chargers generally do not need to be smart
and most overnighters fall into this category.
Cheap and slow may be safe, but slow charging promotes crystallization
within NiMH cells and reduces overall service life.
Smart, fast chargers are well worth the extra cost over time.
Over Charging is a No No
NiMH AAs are very hardy as rechargeable go, but overcharging
is a sure way to ruin both run times and service life. Overcharging
causes overheating, which literally will
cook the batteries chemistry and basically destroys them. Conditioning
can sometimes reverse the symptoms of overcharging, but it's
not a safe bet. Prevention is your best bet.
If the battery is often overcharged a noticeable decline in
NiMH performance will be seen. Known all to well for NiCds is
the "memory effect" which occurs only on abused such
as over charged NiMH batteries. The "memory" can be
caused by a battery which appears to have been overcharged and
thus has its internal chemistry changed. NiMH batteries should
never be subjected to overcharging other wise memory like symptoms
will develop in their dying days.
Not All Chargers Are Equal
Have I stressed this enough yet, to try not to overcharge
but if this is happening look at finding a charger which senses
a full battery and will not over charge. But running batteries
down to the point where it will not power your device efficiently
is a good indication that it is time to recharge. When it comes
to overcharge prevention, some chargers are a lot "smarter"
The smartest chargers, monitor and respond to several different
overcharge indicators. When overcharging is sensed, they throttle
back to a safe trickle current that NiMH batteries can tolerate
indefinitely. Since fast chargers are more prone to overcharge
and overheat batteries than slower ones, they'd better be pretty
smart, but the really cheap fast chargers are often anything
A simple charger will rely on the user to know when it is
time to remove the batteries. For a slow overnight charger that
starts out at a trickle (well under C/10) and stays there,
it's fairly safe to be dumb, but buying a dumb fast charger is
just asking for trouble. The reality is that few of us can be
trusted to babysit battery chargers, myself included.
Do not hold back when purchasing a charger. Cheap can be destructive
when charging battery sets. Spend a little more and get a charger
that will not over charge thus not overly heat batteries up too.
Once again we know that heat destroys these batteries.
Hot Is Bad
When charging NiMH batteries heat is generated, this can not
be helped, but if any of them become hot to the touch, they must
be remove from the charger immediately. On average 130°F
(54°C) is the maximum safe charging temperature. To the touch,
normal is equivalent to hot // warm tap water.
If during charging a NiMH battery get hot, have the charger
checked out or your sets have gotten mixed up or a battery in
the set has gone bad. If you notice melting of any battery
parts, including the plastic jackets, discard the affected batteries
immediately; an internal short is likely.
Warning: Never, ever install
overheated batteries in your camera while they're still hot!
There could be seriously damage to electronic equipment.
Cool Is Good
Charge batteries in a cool and well ventilated place.
If the charger has a cover , leave it open during charging.
Overnight and Maintenance Charging
When charging over night, make sure your charger's trickle
current rating is in milliamps (mA) and is no more than 5 to10%
of the rated capacity (C, in mAh) of the
batteries to be charged. For example, it is safe to leave C =
1500 mAh AAs on a trickle charge for days at a time in the charger
at a rated of C/10 = 150 mA or less.
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