The *ist DS can use two CRV-3 Lithium disposables, four AA NiMH
rechargeables, four AA Lithium disposables and, in a pinch, four high energy
AA alkalines. CRV-3 and AA Lithium disposables cost about $8 per set in
quantity (CRV-3s are a little more expensive, but are more convenient to load
and unload). They have excellent shelf life and generally run about 1100-1300
exposures per set in average use.
NiMH AA rechargeables are good, if more maintenance work. It's recommended to
buy at least 2300mah capacity and to also invest in a good quality charger
(the Maha MH-C204W from thomasdistributing.com is considered one of the
best). Good quality cells normally run around $15 per set, the Maha charger
above is about $29. Properly maintained, a full charge on a set of NiMH AAs
(2300mah) runs about 500-700 exposures. Since NiMH don't hold a charge
sitting on the shelf well, they should be charged every week or so if you're
not shooting enough to exhaust them sooner than that.
AA Alkalines are an "emergency use" option only. Good ones generally last
100-200 exposures, they don't have enough current to drive all the camera's
functions however, and their performance is quite variable.
(CRV-3s are also available in Lithium-Ion rechargeable form. These are not
recommended by Pentax, as many of the available batteries are over-voltage
for the DS. Some are available with 3.0V output, but they are expensive and
you're back into maintenance land. I don't use them, some others I've heard
of have used them successfully. )
Given these options, I find there are three good strategies for power:
- If you're shooting relatively few exposures per week, a set of Lithium
disposables in the camera and one backup set in your bag is an effective
setup. It's also good setup for traveling as you don't have to manage with
power adapters, chargers, etc. (On my trip to the UK, I brought 5 sets of
CRV-3 and AA Lithium batteries. I consumed the third set 3,600 exposures
later. No maintenance, light weight, very little extra space consumed in my
luggage, no juggling of adapters and cords, etc.)
- If you're shooting a regular amount per week (typically 200-400 exposures
like I do) and want to minimize costs with light maintenance overhead, one
set of NiMH AAs in the camera and a set of backup CRV-3 Lithiums in the bag
is a very cost effective and useful kit. I charge the NiMH AAs once a week,
regardless of whether they are showing low voltage or not. (I only used the
original CRV-3s that came with the DS when I went to the UK, as I bought the
NiMH AAs with the camera and never ran out of power in the field.)
- If you're shooting a LOT per day, a thousand or more exposures on frequent
shooting days, three-four sets of NiMH AAs and a pair of chargers saves money
in the long run at the expense of maintenance and management time. I've not
felt the need for this amount of rechargables yet.
Pentax makes an AC adapter for the D/DS. It's a little pricey but should work
well. Others have purchased generic AC adapters with the right
voltage/current/plug polarity instead at 1/5 the price that work well too. I
haven't seen the need for one yet, it's mostly useful if you're doing
astrophotography or tethered shooting.
Godfrey
I would agree with this with one exception. To really get the
most out of your batteries, I've found it necessary to get an
over-engineered charger. I bought the LaCrosse BC-900 because it has
four independent charging/discharging circuits, LCD readouts for each
batterys' voltage and current accumulated, and different "modes" for
charge/discharge/test/refresh. It's only a 1.0A max for four (1.8A for
two), but any more than that and you'd be abusing the batteries pretty
badly. I've found that supposedly "identical" cells have widely varying
capacity. With the BC-900 I can match cells' capacities.
... the self-discharge of the NiMH is kinda a pain if you shoot
infrequently. If it's been longer than two weeks since you charged
them, you should top them off before you use them if you expect to get
much life out of them. Still, they're cheap enough to have a few sets and
rotate through.
-Cory
--
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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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