[bjsmith]

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It's funny how we all have different experiences.

That's because there are different variables under consideration.

These are the factors:
1. Operational "real-time" current delivered at full charge
2. Operational "real-time" current delivered over time, during discharge
3. Non-operational "shelf-life" and operational current delivered after storage

Most people run into #1 with most NiMH, which is why they get half or no battery at "full charge." Most NiMH batteries only deliver 1A or less "real-time" current (e.g., All-Battery/Tenergy NiMH 2600mAh seem to be "half" or "no battery"), even at full charge. The K100D clearly requires far more than 1A of current, which is the problem. Most people with Sayno Eneloop and Energizer NiMH batteries get 2A+ of current at full charge, at around 1.2-1.4V. Most people with CR-V3 (Li-Mn) and Energizer e2 Lithium (Li-Fe) get close to 3A, at around 1.5V (3.0V for Li-Mn in CR-V3). Either will do.

The next issue is #2, which is where "how many shots" come in. How long before voltage and current drops. In my experience, with Energizer NiMH 2500mAh batteries that charge (current-time) to 2600-2700mAh, I get "half battery" when the charge (current-time) drops to around 1600-1800mAh. In other words, it starts dropping towards 1A "real-time" current, which then pushes the voltage down below 1.2V, when only 1/3rd to 2/5ths of the actual charge is depleted. On the other hand, CR-V3 (Li-Mn) and Energizer e2 Lithium (Li-Fe) seem to maintain well over 1A for a long-time, down to a sub-500mAh charge "left." This is why even though most Lithium batteries are rated with less current-time, typically sub-2000mAh, than NiMH, such Lithium (Li-Mn/Li-Fe) can last much longer than NiMH.

Lastly, there is the "shelf life" of NiMH and other rechargables. NiMH can actually maintain a charge "a long time." Unfortunately, they don't seem to maintain a "high charge" with "high real-time current" for "a long time." I.e., I've run months with NiMH batteries in "consumer electronics" pulling only 100-250mA. But it's only for the first 1, 2 or maybe even 3 weeks that even a "quality" NiMH will be capable of delivering 1.2-1.4V at up to 2A. After that, the potential and current clearly decreases to sub-1500mAH and more towards 1A at 1.2V, possibly lower. Lithium technologies maintain much higher voltages, Li-Mn at 3.0V, Li-Fe at 1.5V, pretty consistently down to 500mAh.

Additionally, there is also the "AF motor" v. "microelectronics" usage. AF motors will really hit 1.2-1.4V batteries (x4 = 4.8-5.6V), like NiMH hard, whereas microelectronics don't mind NiMH. If you're using the AF motors heavily, then the 3.0V (x2 = 6.0V) of CR-V3 (Li-Mn) or 1.5V (x4 = 6.0V) Energizer e2 Lithium (Li-Fe) would be better, or at least last much longer.

I have been using Energizer 2500mah batteries for my K100 and still get about 700 shots per charge (no flash use) after about 9 months.

I've now done my first American football game. Prior to this, I used to get about 400-500 shots over a half-hour or so (no flash), turning the camera on and off as appropriate only a few times. E.g., I got 1,000 shots over about 1 hour total (spread over 3 hours -- with good 15-20 minute breaks between) of aircraft on only two (2) sets of Energizer NiMH 2500mAh rechargeables.

But this game I got about 250 shots during 6 hours of the tailgate and pre-game, turning my camera off as appropriate, not unexpected with a lot of on/off, non-shot type camera usage. But once the game started, I only got about 200 shots in the first 90 minutes, with the camera continually on and the AF.C going nuts. Same deal for the remaining 90 minutes, another set. I'm sure the use of the AF and its motors really taxied the 1.2-1.4V output of the NiMH, unlike the lower-voltage microelectronics.

So, by the end of the game, I had gone through my three (3) Energizer NiMH 2500mAh sets, and just put in an Energizer e2 Lithium Li-Fe set for the last few minutes and a few post-game shots. About 600 total with the NiMH sets, making heavy use of "non-shot" power (again, tracking with AF.C button down) and another 50 or so with the Li-Fe "backup" set.

I think the slow chargers do a better job at topping up the batteries than the fast ones though. I use a 10 hour charger and have no issues.

I would never "top-off" NiMH. I always do a full discharge, recharge. Why? Because NiMH have a nasty habit of voltage-current fluctuation based on no-load, and when a load is applied, that's when you find out the NiMH wasn't really charged.

About 1 in every 10 NiMH batteries -- or basically 2 batteries in every 5 sets (of 4, 2 in every 20 batteries) I charge, mischarge. They say "full" when they are not. I do a full discharge and then see how much they actually charge -- and if I don't see 2500mAh+ I know there was a mischarge. Again, it happens in 2 batteries out of 5 sets, and I save those 1, 2, 3 or 4 batteries to re-discharge/charge again.

Li-Ion, on the other hand, can be "topped off" without issue. In fact, you never want to deep cycle Li-Ion. Of course, I strongly recommend against ever using RCR-V3 in a K100D. But that's another discussion.

I've been using Uniross Hybrios for about 6 months in my K100D. They're great, ideal in fact. I can get about 5-600 shots over a 3 week period, which is my average shooting rate I suppose, and if I put in another set that I charged a few weeks ago, they work fine for the same number of shots. That sort of behaviour makes them very easy to live with. I use a 3yr old Uniross smart charger that charges in pairs at 1A, so takes about 2 hrs for completely flat batteries which NiMh never are when taken out of a K100D so 1.5hrs would be more like the normal charge time. A set of Energizer 2500mAh I have are better though if I charge them and heavily use the camera all day long, I've had 900 shots on that basis.

BTW, I should mention that the second my Energizer NiMH 2500mAh batteries show "half battery," I change them because the AF motors definitely slow compared to "fresh." I'm sure I could get more than 400-500 shots in continuous usage if I used them until "empty battery." But "half battery" basically means the current is insufficient at the minimal voltage, so I just replace them for "good measure" on several levels. I.e., I have a long history of microelectronics design, and I like supplying the "nominal operating voltage" as much as possible.

I usually keep a set in the camera, one set as a spare, and 2 CRV3's as a backup. The Eneloops and the new Sony NiMH batteries do not have the self discharge problem of the older formulas, and they do give lots of images per charge (over 500) in both my K100d and ist D cameras (the ist D does go longer on a charge).

That is the approach I use -- multiple, quality NiMH sets with one or two Li-Mn/Li-Fe backup sets. I already have five (5) Energizer NiMH 2500mAh sets (20 batteries), which continue to give me bliss with the K100D whenever I go to shoot 1,000+ shots. With Sams Club selling the Energizer e2 Lithium (1.5V Li-Fe) three (3) packs (12 batteries) for $19, I now carry two (2) extra sets.

In all honesty, after shooting my first American football game where I continually press the button in AF.C mode and "follow the action up close," I'm really glad I now carry two (2) extra Li-Fe sets. Using that much motor action just drains the 1.2-1.4V NiMH batteries, and the 1.5V Li-Fe batteries are just better.

The CRV3's long shelf life and ability to handle in excess of 2000 images makes them ideal as a vacation set or backup.

The great thing about carrying CR-V3 Li-Mn or e2 Lithium Li-Fe is that they last until drained and give you solid voltage and current over nearly that full duration. They don't "lose charge." In fact, it's really only the regulator logic in the (multiples of) 3.6V Li-Ion rechargables that use the charge, the Lithium material holds the charge almost perpetually.

I've been using Energizer 2100mAh for a few months with good results, about 500-600 shots. They lose charge in about 2 weeks, for that I keep a backup set of Eneloops and some Energizer lithiums as well.
There is a very noticeable increase in AF speed with the 1.5v batteries, but I haven't tested it in reality, the speed is comparable to the K10 but some people report bad focus accuracy.

This is exactly the case! The higher voltage of Li-Fe of the e2 Lithium AAs or Li-Mn of CR-V3s will definitely give you better AF motor performance, especially as NiMH voltage drops down to its nominal 1.2V (or below), and even further as it goes "half battery" and voltage drops to keep current consistent. If you really value your AF motor speed, use Li-Mn or Li-Fe, or at least get quality NiMH batteries and change them the second they hit "half battery."

I wish somebody'd sell a bulk pack of 80 lithiums for £30-40.

Hmmm, here in the US, our Sams Club stores carry a three (3) pack (12 batteries) for US$19 -- or about US$1.50/each. That's not quite as cheap as you desire, but pretty close.

Dear Fellow Pentax-ians:
The PIPE Here...and when I ordered my Pentax K100D (along with the kit lens and the DA 50-200mm telephoto) I got myself two quartets of the Thomas Distributing Sanyo 2700 mAH AA cells to power my K100D ...the link to them is at Sanyo 2700 mAh Rechargeable batteries - 2700mAh Industrial AA Rechargeable Battery .
Now, these are NOT the Eneloops, but they DO have that extra 700 mAH in them, that seems like it might comie in handy when using the flash a lot, espeically in a "fill-flash" mode outdoors.

Unfortunately the rating in "current-time" means jack. It's the "real-time" current output that matters -- refer to my numbered list above.

In fact, most "current-time" is rated at typical AA usage of only 100mA (0.1A), and not the 1A+ (close to 2A at times) of the K100D. As many tests show, standard AA Alkaline batteries almost always fail to power anything that draws more than 1A, or "barely runs" and at only 1/3rd (or less) time than their rated 500-900mAh. Cheap NiMHs, even those rated at 2600mAh+, have the same issue -- unable to supply 1-1.5A at 1.2V, they are "half battery" even when "fully charged." I have seen that out of All-Battery.COM/Tenergy NiMH 2600mAh batteries -- solid 2600mAh performance when only 100-500mA load is placed on them, but horrendous results in the K100D.

[cznut]

well I have used my Uniross Hybrios for a month and have been really happy. they have lasted this whole time on one charge and i have taken about 500 pictures. I definately recommend these!

[Class A]

Of course, I strongly recommend against ever using RCR-V3 in a K100D.

Why, if they are of the voltage regulated type?

[bjsmith]

Why, if they are of the voltage regulated type?

Again, all Li-Ion batteries are "voltage regulated."

The problem is that even these alleged "3V" RCR-V3 batteries are at least 3.2V, if more like 3.3-3.4V when full.
Why? Because Li-Ion cells start dying much below that.
That's why many RCR-V3 owners report very short lifespans for their batteries.
Either that, or they are transforming the voltage internally, which takes up significant space (let alone has EMF/EMI design issues not factored into the end device), and that's why there are so few cells with so little duration.
In any case, they suck.

Just because they are modified to under-volt doesn't mean they are actually "3V".
Again, it's quite impossible for Li-Ion to work nominally that way.
The K100D/200D are designed for maximum 6.5V input, nominally 4.8-6V.
You use RCR-V3 and you utterly borderline or, far more likely, violate that, and put its own end-device regulator into a position it was never designed for.

That's in addition to the various, non-standard "3rd terminal" options.
Those "3rd terminals" are a non-standard modification so the end-device won't "accidentally" receive the nominal 4.2V (absolute minimum 4.0V) open/charge voltage that Li-Ion requires.
Yes, that makes them "safer" than the standard 2 terminal RCV-V3.
But it still doesn't remove the fact that you're still running a material that never runs at 3V.

Non-rechargeable CR-V3 is Li-Mn, not Li-Ion, and nominal 3V -- with no "charge" voltage/transient issue.
Even Energizer e2 Photo Lithium is Li-Fe, not Li-Ion, and nominal 1.5V -- again, with no "charge" voltage/transient issue.
Rechargeable Li-Ion is nominal 3.6-3.7V -- with a "charge" voltage/transient of 4.0-4.2V (sometimes 4.4V, depending on the device).
The "3rd terminal" ones with alleged "voltage regulation" only solve the latter, they don't address the former.

Under-volting Li-Ion in the hope of reaching 3.2-3.3V which is only a 7-10% over-volt (instead of 20% like nominal Li-Ion) only makes the RCR-V3 last far shorter, and have far less lifespan.

"But my AF motors are snappy!" -- Of course, you're over-volting them. That's typically okay, but ...
"Oh, if my camera locks up, I just turn if off/on again" -- Of course, you're over-volting your microelectronics by 7-10% (or even 20%+), which causes temporary "transconductance" (which destroys the semiconductors over time) while your AF is "snappy" (motors are different, with far more tolerance).
The K100D/200D is designed for 4.8-6V, maximum 6.5V, and 2x Li-Ion is well beyond that, or even "under-volted" ones are either borderline at best, but over is more typical.
Your K100D/200D should never, ever "lock up" as its semiconductors and other microelectronics are quite robust.
If has "locked up" which required a hard reset, and you're using RCR-V3s, you have your answer, even if very infrequently.

I fully agree that 4x NiMH is too low of a voltage (1.2V/battery, possibly 1.3V/full charge), too many brands have inadequate real-time current (the K100D/200D easily uses 1500mA real-time current at around 5V), to make the AF peppy.
But going the other way (RCR-V3) is far, far worse for camera longevity, let alone just jacks up risk a couple orders of magnitude.
That's why I only use non-rechargeable 2x CR-V3 or, more inexpensive yet, 4x AA Li-Fe (Energizer e2 Photo Lithium), which are 2 x 3V and 4 x 1.5V, respectively, and can output more than 2A (2.6A specifically from Energizer's charts).
They cost a whole $6/set at Costco/Sam's Club in packs of 3 sets (12 batteries), and last a lot longer than the under-volted RCR-V3s (let alone are much, much safer of a material for the unit they were never designed for).

Again, there is not one (1), single end-user device on the planet certified for Rechargeable CR-V3.
I'm more than willing to be shown such a unit, but the actual end-devices (not the "battery's marketing") always either use non-rechargeable 3V CR-V3, 1.5V AA or, in the case of rechargeable Li-Ion, are explicitly designed with a specific battery that is a multiple of 3.6-3.7V (not 3V).
Why? Because Li-Ion is incapable of reaching 3V, and most marketing out there is not reality (much less not certified for any device on the planet).

It's one thing not to use a certified battery for an end-device, people debate that all the time, but at least the end-device was designed for 7.2-7.4V Li-Ion (or some multiple of 3.6-3.7V).
What you're talking about with RCR-V3 in the K100D/200D is purposely and willfully over-volting the unit with a material it was never designed for.
Again, virtually all "3V marketed" RCR-V3 devices are, at best, 3.2V, and typically much closer to the natural 3.6-3.7V of Li-Ion under load/nominal.
If they have the "3rd terminal" for charging, that just means it removes the possibility of the 4.0-4.2V (possibly 4.4V) transient that's required to charge, and Li-Ion batteries have been known to sometimes output their charging voltage when full/recently removed from charger.
Devices designed for Li-Ion batteries handle this, and have much better/stronger regulation logic in that end-device, whereas more inexpensive devices that take AA/CR-V3 do not, and NiCD/NiMH are lower voltage (not higher), don't have the swinging issue (or combustion possibility for that matter), etc... like Li-Ion.

It's your camera. The chance may be low, but I've still heard many people with RCR-V3s admit they've had to cycle the power more than once every now and then, like maybe once every few swaps.
And that's in addition to the complaints about battery longevity (which can be for many reasons above).
Just pointing out reality, even if the "AF is more snappy," not worth it to purposely cause transconductance in the more sensitive microelectronics.
Try over-volting your PC's CPU from 7-10%, and then 20%+, exact same difference -- only at least your power supply is regulating that output much, quite removed, and much better than a cheap Li-Ion battery is directly.

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Last edited by bjsmith; 10-20-2008 at 07:37 AM.

[Class A]

Thanks Bryan, you pretty much put me off ever trying rechargeable CR-V3. Excellent posting. I put a link to it from my "K100D Tips & Tricks" thread.

However I wonder why

a) there is no way to make the CR-V3 undervolt in a safe way. Are you saying that any means to get them close to 3V makes them stop operating? A voltage divider would give them the wrong working resistance and voltage transforming electronics would be to space consuming / costly?

b) the K100D engineers haven't designed the voltage regulator circuit with a bit more tolerance so that it could withstand 8V or similar. They should have known that rechargeable CR-V3 would be an attractive option to K100D users. 2V doesn't seem a lot of energy to burn or would this require a much more extensive cooling system?

In what way do you think 4 x 1.2 V (from NiMH) are too little? After all the K100D is sanctioned to use this type of battery. Is it just the AF performance that suffers a little? I don't shoot action and the AF performance with my 4 2500mAh Energizers seems just fine.

Thanks again for your very informative posting!

[Class A]

How do I recognise a good charger? I'd be happy to just buy one someone recommends but it may not be available round here (New Zealand) so I'd appreciate some parameters to look for.

I currently have one charger that charges each battery individually with deltaU detection. It can discharge accumulators and is specified for 7.2 hours of charging for 2300mAh AA accumulators. Higher capacity accumulator charging times are not specified. I believe that is too slow for NiMH, right?

I have another (ultra-)fast charger that came with some accumulators (TRONIC). It outputs 2.4V, 1500mA/400mA or 6.0V, 60-150mA. The trouble with this one is you can either charge two or four accumulators. It doesn't seem to sense the charging status for individual cells.

I'm pretty sure I should get another charger but wonder what to watch out for.

[K Logan]

eneloops work great for me.

[bjsmith]

Thanks Bryan, you pretty much put me off ever trying rechargeable CR-V3. Excellent posting. I put a link to it from my "K100D Tips & Tricks" thread.
However I wonder why
a) there is no way to make the CR-V3 undervolt in a safe way. Are you saying that any means to get them close to 3V makes them stop operating? A voltage divider would give them the wrong working resistance and voltage transforming electronics would be to space consuming / costly?

It just takes up space.
I mean, if you get a RCR-V3 with a transformer, it's going to have far less actual cells.
As far as using resistance, I asked a guy who has designed power cells and regulators (my experience is microelectronics and integrated circuits) and he stated it's also going to cause issues, including added heat and drainage, no matter what the design (and there are bad ones).

b) the K100D engineers haven't designed the voltage regulator circuit with a bit more tolerance so that it could withstand 8V or similar. They should have known that rechargeable CR-V3 would be an attractive option to K100D users. 2V doesn't seem a lot of energy to burn or would this require a much more extensive cooling system?

No, not cooling, regulation.
If would require them to put in a far more expensive regulator to handle multiple voltage dividers for the microelectronics/ICs.
The greater the range, let alone range introduces more risk (among other things), the greater the cost.

In a nutshell, no one designs end-user devices for RCR-V3. No one, period.
They will always design a proprietary battery of multiple 3.6-3.7V Li-Ion cells.
This includes for safety, certification, size, etc...

E.g., the K10D/K20D get great AF motor pep because they take in the 7.2-7.4 of the battery, while the voltage gets divided correctly for the far more sensitive microelectronics/ICs.
And the volume the K10D/K20D Li-Ion batteries take up is seemingly less than 2 x CR-V3 or 4 x AA (at least overall).

If you're going to design for RCR-V3, you might as well put in a real, well-designed Li-Ion battery.
There are many out there for vendors to design around, and then certify against.

You can use an after-market battery that is uncertified, but at least the voltage is similar.
That's far less of a risk that intentionally putting in more voltage than the regulator is designed for.

In what way do you think 4 x 1.2 V (from NiMH) are too little? After all the K100D is sanctioned to use this type of battery. Is it just the AF performance that suffers a little? I don't shoot action and the AF performance with my 4 2500mAh Energizers seems just fine.

I definitely can feel a difference between the 1.2-1.3V of NiMH and 1.5V of Li-Fe (e2 Lithium).
I also found that when I have my K100D in AF.C, it just totally eats up the battery and drops the charge to a point the Energizer/Eneloop NiMH batteries cannot sustain the 1.5V required.
When I'm going to use the AF.C for hours, I have the choice of rotating NiMH, or going multiple hours with a single Li-Fe (e2 Lithium) set.
For the price, the latter is worth it, especially without the headaches of ensuring the NiMH are still near full charge and producing enough current for the K100D.

But NiMH is "within specifications" and there are no issues.

[UnknownVT]

The Pentax K100D is notorious for being very battery fussy - mainly as pointed out - due to too high voltage threshold/cutoff levels -
Ref: Post #49 (link) in thread - K100D - "Low-Battery" Problem gives details of the meter voltage levels.

Primary Lithium AA's are probably the best - like the Energizer e2 lithiums - as they maintain higher operating voltages - but they are expensive and use-once only.

For rechargeable eneloops are the way to go - please see -

Summary Post #57 (link) of this thread eneloop vs. Kodak Pre-Charged Voltage Maintenance

where I used a Pentax K100D to show that eneloops maintained a higher operating voltage under-load than the Kodak Pre-Charged (otherwise great LSD NiMH).

I get shot counts of between 550-650 shots with well over 50% flash using eneloops - this well exceeds the K100D specs for 2500mAh NiMH - in fact approaches the specs for Lithium batteries without flash.

[Deni]

I got this grip for my k100d and it has a 2200 mah lion battery. For $57 shipped I think it's quite a good investment.

I have to shoot a wedding on friday and will check how it performs. I checked it's voltage and it's 5.99 volts. I also have 8 eneloops and 4 2500 mah for back up and to use with the hot shoe flash. I will also get 4 Energiser e2 for backup.

[Ex Finn.]

[

"I get shot counts of between 550-650 shots with well over 50% flash using eneloops - this well exceeds the K100D specs for 2500mAh NiMH - in fact approaches the specs for Lithium batteries without flash."[/QUOTE]

Last time I actually checked my shot count with Energizer e2s, it was beyond
1300 exposures. Not much flash, 1 sec. preview, AF always nice and "snappy".
I am happy.

[UnknownVT]

How do I recognise a good charger?

Over at CPF (CandlePowerForums - for flashaholics) they have a Flashlight Electronics - Batteries Included section - where there are lots of enthusiasts and some real experts on batteries and chargers.

Thread: Charger Comparison

The concensus over there are for the Maha C9000 and the LaCrosse BC-900
- both are really good chargers with good analysis capablilities.

On a much more modest note there is also Soshine SC-C3 Intelligent Rapid Charger (review) for all of US$13.98 delivered worldwide

[Class A]

Thanks UnknownVT, these are great links!

[wipearl]

I have used numerous rechargable batteries with my 1st DS, however about a year ago I got a set of Ray-O-Vac Hybrids and have had excellent results from them. A couple of months later Circuit City ran a special on 8 Enloops for like $12.00 or $13.00, so I got them also. Since I have gone to all hybrid AA rechargable batteries. Since then I have done several weddings and commercial shoots, and have never had a battery problem since.

bp

[bjsmith]

The Pentax K100D is notorious for being very battery fussy - mainly as pointed out - due to too high voltage threshold/cutoff levels -
Ref: Post #49 (link) in thread - K100D - "Low-Battery" Problem gives details of the meter voltage levels.

When the batteries are unable to output the current required, the voltage drops. All it takes is a single AA in the series circuit to produce inadequate real-time current to cause this to happen.

It's very, very important to have your NiMH batteries fully charged so they can output the real-time current required. Real-time current in NiMH drops as they are depleted, unlike Lithium battery technologies. As I've stated many times here and elsewhere, the Pentax K100D/K200D is a current pig. You really need 1.5A at 5V (4 x 1.25V) at a minimum. Far more ideal for AF.C is 2A at 6V (4 x 1.5V).

In my personal experience with Energizer NiMH 2500mAh, I found that they were "fine" when charged to 2400-2600mAh. But once they were depleted down to 1500-1700mAh charge left (verified by discharging them in a 900), real-time current dropped. The real-time current dropped enough that voltage dropped as well, resulting in half battery and clearly had slower AF.

So I would say that 4 x AA Energizer NiMH 2500mAh batteries only give me about 1000mAh at 1.5A real-time -- that's about 40 minutes continuous. Now that's in AF.C, used on and off over about 1-1.5 hours (sporting event). I could get far longer duration out of them in AF.S. I.e., I could easily go a full day and get 500 shots when doing scenery, but I definitely had to have two sets of NiMH to get 500 shots at a sporting event over 3 hours.

Lithium, on the other hand, really maintains excellent current until near empty. The 4 x AA Energizer LiFe (e2 Photo Lithium) is rated at 2.6A output at 1.5V. I've gone a good 2 full games (2 x 3-4 hours in AF.C) with the e2 Photo Lithiums -- definitely worth $6-7/set versus my time in discharging-charging four (4) sets of NiMH to guarantee they actually charged to the full 2400-2600mAh. The only way to guarantee that is to do a full discharge-charge, especially since I found a mis-charge in 1 out of 10 NiMH (one battery in every 2.5 sets).

Again, not worth my time.

That's why LiFe (AA) and LiMn (CR-V3) at 1500mAh typically "outlasts" NiMH at 2500mAh in high current sucking devices. The current already starts to drop on the NiMH as they are partially discharged while the Lithium compounds continue on-ward at full output. As current drops, voltage drops, voltage hits the current-off, and then bam! They "seem" depleted. But you can take those same NiMH batteries out, put them in a lower current sucking device at 100-500mA and still get many hours (or tens of hours) out of them.

It's all about providing real-time current.

Primary Lithium AA's are probably the best - like the Energizer e2 lithiums - as they maintain higher operating voltages - but they are expensive and use-once only.

It isn't just the 1.5V, it's the 2.6A. So 6V at 2.6A is over 15VA (~15W). Compared to 1.25V at 1.5A with a good NiMH set (Energizer, Eneloop, etc...), you're only getting 5V at 1.5A, possibly 2A if you're lucky, or 7.5-10VA (~7.5-10W). Night'n Day, especially when the NiMH real-time current drops as they are partially depleted.

I wouldn't call them "expensive" as they do give you 1,000 shots for about $6-7/set. That's well under a penny per shot. Considering I click my shutter 10,000-15,000 times per year, that's $60-70/year (basically 3-4 packs of 12 batteries from Costco/Sams Club) for consistent output that I don't have to discharge-recharge and can be shelved for months without worry of any discharge. Plus they are available everywhere. If I'm not sucking down current in AF.C, then I can get close to 1,500 shots. I have them in my AF-360FGZ and have yet to replace them (I haven't fired it over 100 times yet).

For rechargeable eneloops are the way to go - please see -
Summary Post #57 (link) of this thread eneloop vs. Kodak Pre-Charged Voltage Maintenance

Most other brands except the Energizer NiMH and Sanyo Eneloops are just horrendous. The Eneloops maintain their charge better than Energizers on the shelf, but they still don't equal the current of LiFe (e2 Photo Lithium).

I tried the cheap Tener "All-Battery" NiMH 2600mAh and found that even when I could get them to discharge-charge to 2600mAh, they couldn't muster much more than 1A. I.e., fully charged, put in the K100D, they registered half-battery because the current was inadequate and voltage dropped under 1.2V/battery.

The Tener "All-Battery" NiMH units are absolutely great for 100-500mA duties where Alkaline wears out way too fast. E.g., in my various remotes, Nintendo Wii, etc... They are even great for many types of compact cameras that only need 2.5V at 1A = 2.5VA (~2.5W). But not for the K100D/K200D.

where I used a Pentax K100D to show that eneloops maintained a higher operating voltage under-load than the Kodak Pre-Charged (otherwise great LSD NiMH).
I get shot counts of between 550-650 shots with well over 50% flash using eneloops - this well exceeds the K100D specs for 2500mAh NiMH - in fact approaches the specs for Lithium batteries without flash.

Real-time current is the key, and traditionally NiMH doesn't cut it.
Only a few brands seem to deliver the 1.5A+ at 5V that the K100D/K200D need, namely Energizer NiMH 2500mAh and Sanyo Eneloop NiMH.

Last time I actually checked my shot count with Energizer e2s, it was beyond 1300 exposures. Not much flash, 1 sec. preview, AF always nice and "snappy". I am happy.

Again, that's because using Energizer LiFe (e2 Photo Lithium) gives you around 15W power while Energizer or Eneloop NiMH will always give you under 10W power, when they are still more than half-way charged. As you discharge your NiMH, you start to lose current, and then the "lifespan" of that charge becomes reduced for your high-current use in the K100D/K200D. The LiFe keeps on chugging along (at its full 6V outputting its full 2.6A) until virtually empty.

That's why I said I can get 500+ shots out of NiMH in AF.S when doing infrequent scenery shots over a day, but I can't get even 300-400 when in AF.C at a sporting event over 1-1.5 hours (a good 40 minutes shooting). And the batteries will eventually discharge on their own, even if Eneloops are slower at that, it still happens. At the same time, I can easily get 1000+ shots out of LiFe in AF.C over two (2) different, 3+ sporting events. If I shelf them, they will still be where they left off in liespan when I come back too. Unlike rechargeable Li-Ion (which has regulator logic that uses power on the shelf), non-rechargeable Lithium compounds (LiFe in 1.5V AA, LiMN in 3V CR-V3) don't have regulator circuits in them that eat power.