All batteries have advantages and disadvantages and these make them more
suited to different tasks. Some of the following battery types are the
ones that are used for a particular purpose anyway (eg, hearing aid batteries),
but you may find the reasons interesting. Others are battery types that
I personally recommend. Rows with a light
blue background are applications ideal for low self discharge (LSD) NiMH
cells like the Sanyo Eneloop, which gives an indication of just how versatile
they are. For these coloured rows it makes sense if low self discharge
NiMHs are your first choice.
NiMH cells from Energizer are not recommended, in particular their 2500
mAh cells. They deteriorate very quickly, and may only give a dozen cycles
before their self discharge increases to the point where they will be
completely flat within a week of being charged. It's possible that Energizer
does this deliberately, leveraging the strength of their brand name to
convince consumers that NiMH cells are not worth using, and thereby encourage
people to use their primary cells (alkaline, lithium) instead. Energizer
does not make a low self discharge NiMH cell – they must be about the only battery company in the world not to now.
Recommended Battery Type
Reasons and Other Notes
Alkaline or silver oxide button or lithium coin
Low current drain. Small battery size. Good shelf life. Alkaline
and silver oxide cells are often interchangeable (for the same size
cells) – silver oxide will last longer but are more expensive and
harder to find.
Silver oxide cells with W or SW on the end are intended for use in watches, with the W cells lasting a little longer than the SW cells.
Alkaline or perhaps
NiCd or NiMH
rechargeable if you use it a lot
High current drain situation. It really depends
on how much current your flash uses (which may not be very easy
to measure) and perhaps how often you want to change your batteries.
Another consideration is how fast you want your flash to cycle
(how fast it will get ready for the next shot). Lithium iron disulfide
and rechargeables (Sanyo Eneloop in particular) hold their voltage much better under load, so
a flash will cycle faster.
(requiring AA batteries)
LSD NiMH rechargeable
Lithium iron-disulfide as a backup if not using LSD NiMH
NiMH cells can give high current, have high
storage density, and capacity is not much reduced under heavy load.
Reusability makes them very cost effective. LSD cells, especially high quality ones like Eneloop, tend to have a slightly higher voltage under load, which is good for voltage-fussy cameras.
For cameras that are
used often, go for the largest LSD capacity available, preferrably Eneloop XX. (Note: Apparently
Energizer ACCU Rechargeable NiMH AA cells are wider than standard
and may get wedged in your digital camera.)
For cameras that may
be used irregularly or infrequently go for Sanyo Eneloop or other LSD NiMH battery. Their
low self discharge will mean the batteries still have plenty of
life in them when the camera is next used, thereby eliminating a major frustration for many users!
For single use batteries nickel zinc/nickel oxyhydroxide batteries
rate a mention since they perform quite well. NiOOH cells
from various companies outperform modified alkalines, but don't
bother with expensive NiOOH cells - they won't perform any better
than less costly ones (sadly the inexpensive GP Digi1 is no longer available).
Although modified alkalines (such as Duracell Ultra or Energizer
e2) have been designed for this sort of high current
use I don't actually recommend them for ongoing digital camera use
because they won't last as long as a single charge of NiMH cells
or NiOOH single-use cells, so using them on a regular basis will
be very expensive. However, if your NiMH cells go flat while away
from your charger, modified alkalines will do a reasonable job as a temporary
If modified alkalines are not available and you're desperate, use
one of the top brands of normal alkaline battery (eg, Duracell,
Energizer). The cheaper brands have been known to struggle to give
enough juice for more than a handful of photos.
Low current application, but a high storage density means the
battery won't have to be changed very often. Interestingly, most
of the locally available sizes of hearing aid batteries cost the
same, although there's quite a difference in capacity. This tends
to indicate the manufacturing and distribution costs are significantly
greater than the cost of the raw materials, or maybe it's just supply
Portable power supply
Sealed lead acid
For the capacity of the batteries, cost becomes an important consideration.
20Ah (for example) rechargeable batteries are prohibitively expensive
in anything except the SLA chemistry.
Alkaline or modified alkaline if NiMH not available
Moderate current draw. Modified alkaline may be
better if the device is particularly power-thirsty, but probably won't
be worth the extra expense for most equipment.
If the equipment is used frequently LSD NiMH cells will be much less expensive. If the item is used infrequently with alkaline cells left in it, check them to make sure they're not leaking.
Solar garden light
Despite having low capacity compared to NiMH, NiCd actually has
a more robust chemistry behind it. That means they can tolerate
the environment and duty cycle (a daily charge) better than NiMH
cells would. They also tolerate overcharging by a continuous trickle
charge better than NiMH cells, which they might get from the solar
panel on a long sunny day.
Because the solar panel probably won't give a complete charge (especially
in winter or on cloudy days) it can help if you periodically remove
the cells and give them a complete charge on a proper NiCd charger.
Clean all contacts before reinstalling.
Expect them to last about three years. They do wear out eventually. Recycle them when they do wear out, don't just throw them away.
Whatever works, whatever you can find, whatever
you can afford.
Note that most torch bulbs are rated in increments of 1.2V, not
1.5V. In other words, your five D cell Maglite will have a 6V bulb,
not a 7.5V bulb. A twin AA torch bulb is rated at 2.4V not 3V. This
means that with new alkalines, torch bulbs are run slightly overpowered. That's
alright - if they burn out early, replacement bulbs are normally
pretty inexpensive. It also means that rechargeables (with their
even voltage output) are well suited to torch bulb ratings.
Also, rechargeables have a flatter discharge curve than alkaline
or zinc-carbon, so non-regulated
lights will maintain a more even brightness until they go flat.
Torch/flashlight, emergency use
(eg, only used in power cuts)
3rd gen. Eneloop
The reasonably long shelf life of alkalines (when kept cool) means you will have power when
you need it, while lithium cells have a very long shelf life, and
cope with cold conditions extremely well.
Zinc-carbon batteries do not have a very good shelf life, so most
of their useful life will have expired before you use the torch,
especially if stored in a car or other vehicle which gets very hot
during the day.
Most rechargeable batteries self-discharge quickly, meaning they are likely
to be dead when you want to use the torch. (I know a couple of people
who used to find this quite often – it took them a while to learn.)
However, 3rd generation Eneloop cells will still have plenty of charge after a few years of sitting on a shelf (70% after 5 years). The expense of low self-discharge NiMH cells might make them seem unattractive
for this purpose – they'd just be sitting around doing nothing – but so would any batteries bought for the purpose. In New Zealand Eneloops cost less than the leading brand of lithium cells, and it costs a pittance to recharge them – which can be done at any time.
Many headlamps are designed to work within
the ideal current output of alkaline batteries (which is actually
quite low, <500 mA for AA, <250mA for AAA), so don't have
800-1,000 mA bulbs running off AAA cells, for example, a situation
that has apparently arisen with some 3 W Luxeon headlamps running
off 3 AAA cells. Bizarre.
However, some cavers love lithium primary batteries for their light
weight* and long life when used hard and
are willing to pay the premium for that. (Of course, some cavers
are happy spending $200 on a $50 headlamp, bless them. When one's
life depends on having light, reliability equals security.)
A set of modern NiMH AA cells such as the Sanyo XX low self discharge NiMH cells can drive an LED at 350 mA for over seven
hours, and depending on how the LED is driven may dim gradually or
die suddenly. Some regulator boards die very quickly when dropping
out of regulation, so it's good to know beforehand what to expect.
Non-LSD rechargeable batteries also have a tendency to die suddenly and
completely when using incandescent bulbs** (neither is good in a cave), which means spare alkaline batteries
should be carried if not using reliable LSD cells. An easy to reach alternative light source is
also important for changing batteries. Also see the notes under
"extra bright torch" below.
Extremely flat rechargeables may have enough power to drive a
LED at very low current but continuing to use them may damage the rechargeable
cells. Flat alkalines will almost certainly still have enough juice
to run an LED for many hours in an emergency, will be unlikely
to leak in that time, and it doesn't matter if they get damaged
internally since they will be discarded after use anyway.
Since cadmium in NiCd batteries is so bad for the environment it
seems almost sacrilegious to enjoy the great outdoors using them.
If using them, make extra sure none get lost on the trip. They also don't
have the capacity that NiMH do.
I had one multiple LED caving headlamp which used a dropping resistor
that I couldn't change. I found that single-use nickel-zinc AA batteries,
with their slightly higher voltage, was just what I wanted to run
the LED array on more current, and therefore run brighter. While using
them with the headlamp's half-voltage setting, the LEDs drew
twice as much current as they did with alkalines,
which was very nice.
Torch/flashlight, extra bright
(1 amp or more)
Very infrequent use:
NiCd or NiMH
Sealed lead acid
At high current drain lithium cells "can
exceed the power output of alkaline cells by 260%" – which
can begin to make the lithium cells about the same value for money
as top brand alkalines (since in New Zealand they cost at least
that much more). The reduced weight* of
lithium batteries coupled with less frequent battery changes and
longer life (meaning fewer spare batteries to carry around) can
make them quite attractive if the torch is not used very
If the torch is used often the high current output of rechargeable
batteries make them ideal (and much more sensible) for a high current
torch. Their voltage stays relatively constant over their output
life, so the light output of the torch will also be quite constant.
NiCd might not suit security work because of voltage depression
and the need to have charged batteries at the start of each shift,
but NiMH is great for this use.
Rechargeable handheld spotlights use sealed lead acid (SLA) batteries
with bulbs that may draw as much as 20 amps. Heavy, yes, but give
great light for everything from possum shooting to boating. (Although
I'm told that some spotlights these days are so bright they make
the opossums close their eyes, which makes finding them hard.) SLA batteries
have a pretty slow self discharge, so will be fine if not used too
Torch/flashlight, keyring with single LED
Alkaline, silver oxide or lithium button
Low current application. The size of the battery is important,
because it will often be the greatest factor in the torch size.
If designing a single-LED seldom-used torch, it might use so little
current that the shelf life of the battery also needs to be considered.
(Sadly, this tends to rule out zinc air cells for almost all applications,
which is a shame, since three zinc air 675 cells would have quite
a nice size, voltage, and capacity to drive a single white LED.)
As an emergency light in a cave zinc air cells might work well.
A long life is needed at a low current drain.
Don't even think of using rechargeable batteries in a smoke alarm
– most self discharge (and so have a short shelf life) then die
suddenly. You might too if your smoke alarm doesn't work.
If you do not presently have a smoke alarm GET ONE! They
Sealed lead acid
Rechargeable, reliable. Weight isn't an issue since these things
aren't designed to be highly portable. Needs to be tested regularly
to ensure proper functioning.
Footnotes on battery uses
* AA alkaline 23.0 grams, AA lithium 14.5 grams. AAA alkaline 11.5 grams,
AAA lithium 7.6 grams. It's been so long since I last bought any lithium
AAs that I don't remember how much lighter they felt in practice. I think
they did last quite a long time in my camera flash, although I'm not sure
they were value for money.
** When the voltage available to an LED drops, the amount of current
the LED draws reduces – their resistance increases – so an LED will likely
continue to produce at least some usable light with dying rechargeables.
The colour of light they produce also remains the same, which is quite
nice, although that can make it harder to pick a slowly dying battery,
as it's much harder to pick that the light level is dropping. On the other
hand, the resistance of an incandescent bulb's filament drops
significantly as the temperature of the filament drops, which means it'll try to conduct
more current, not less. (A bulb's resistance is lowest when it is first
turned on, before it heats up.) Also, if the power dissipated by the filament
is too low, the filament may not heat up enough to produce any usable light. I've seen completely dark bulbs drawing 200mA. This means rechargeable batteries, especially NiCd, die
much more suddenly when using incandescent bulbs compared to LEDs.