[noou]

just a positive update (finally!) from my part:
my old set of Uniross 2500mAh rocks!!! Several hundreds of pictures plus a couple of short movies and they just "became" orange.
Unfortunately though, they are the only cells that work in my K-x among those I own (for now)...

[OutOfFocus]

hmmm... may be I am missing something.
Your graphs seem to show that the non-LSD batteries are doing much better?
But I think the point may have been missed -
these were batteries which were deemed depleted by the Kx - ie: would no longer turn the Kx On.

Exactly. (I did say that above the graph, but perhaps it isn't too clear.)

This means the graphs are an indication of how much charge is still left in the batteries.
So unless I've misunderstood things - the lower the measurement the "better" the battery.
ie: the battery that shows the least remaining capacity is the battery that the Kx managed to utilize the most of the existing capacity.

That's right.

So let's take the two eneloops that you could not measure - this literally means the Kx managed to drain/use the full capacity of those 2 eneloops - so that there was no measurable remaining capacity.

I could measure all the batteries. They all performed similarly within a few tens of millivolts, so I am just averaging the batteries within each set. Otherwise you'd have 4 times as many points and 4 times as many lines.

In my view the eneloops performed the "best" as the Kx was able to utilize almost all of their capacity.
The "worst" would be the non-LSD since they still show a lot of capacity - meaning that the Kx only managed to use part of their capacity - to have so much remaining.
Yes, I do see the eneloops performing "better" than the Imedions - since the Imedions has more remaining capacity than the eneloops - although as you point out with that sort of shot count - almost anyone would be pleased with them.

In my opinion they're performing similarly. I removed the Imedions when I could still turn on the camera but not take any photos, whereas I kept the eneloops (and all the others) in the camera until it would no longer turn on. Frankly, I would prefer not to discharge my batteries as far as these eneloops were. This risks overdischarging one of them, because they're in series within the camera which can't tell if one is really depleted and the others still have a bit of charge left.
The graphs also show that the camera is turning off for the non-LSD batteries much, much earlier than it is for the LSD batteries, which it can totally drain. The question is why is that? The voltage curves for the non-LSD batteries intersect somewhere near a bit over 1.2 volts at a current draw a bit less than 1 amp. Is that significant? It seems a weird point for either alkalines or NiMH batteries, but it's not unreasonable for Lithiums. Wild speculation: could the camera be mis-guessing the battery type as Lithium?

[UnknownVT]

Exactly. (I did say that above the graph, but perhaps it isn't too clear.)
The graphs also show that the camera is turning off for the non-LSD batteries much, much earlier than it is for the LSD batteries, which it can totally drain. The question is why is that? The voltage curves for the non-LSD batteries intersect somewhere near a bit over 1.2 volts at a current draw a bit less than 1 amp. Is that significant? It seems a weird point for either alkalines or NiMH batteries, but it's not unreasonable for Lithiums. Wild speculation: could the camera be mis-guessing the battery type as Lithium?

Could you validate your guess by setting the battery type to NiMH?

Sorry for my misunderstanding - just take what I said as me mumbling to myself to get my own thoughts clear

As for an explanation - only of sorts -

If we assume the Kx (and other Pentax dSLRs using AA size batteries) use voltage threshold.

Then the theoretical explanation is that both the eneloop and Imedion appear to maintain their voltage under the Kx load better than any of the other non-LSD batteries - to the point where the non-LSDs may only be partially discharged before they can no longer maintain the voltage level required to keep the Kx working. Whereas both the eneloop and Imedion can do so.

Here's an animated graph showing this comparing eneloop with the typical high capacity non-LSD NiMH -
the red-line at 1.15V - is the tested cutoff voltage for the K200D -


(NOTE: to be fair - the horizontal scale in the second animated comparison are not the same for the higher capacity NiMH, their ranges are wider (better) )

NiMH rechargeable batteries native nominal voltage is 1.2V - so this is already at a disadvantage when it comes to Pentax dSLRs - and as they are used, the operating voltage under load sags - depending on the current demand - and this can be as high as ~1.5Amps. (for more details please see this thread - K200D Battery Meter Problem specifically Post #23 )

Also as NiMH batteries age - they start to develop higher internal resistance - which limits the amount of current they can deliver - so the operating voltage under load sags even more.......

eneloops manage to maintain a higher operating voltage under load than any other NiMH rechargeables - this is trivial for almost any other application - BUT for the Pentax dSLR this is a HUGE advantage - please see post #28 (link) in the same referenced thread above. (also eneloop vs. Kodak Pre-Charged Voltage Maintenance summary post #57 , also please see #61 )

taken from my post #4 in thread:
Problem with Ni-MH rechargable batteries in K200D/K-M

EDIT to ADD -

I just did a discharge to see the remaining capacity of my eneloops depleted in my new Kx until shutdown -
it was in the 20-33mAh range (Maha C9000) so they were pretty much completely (safely) depleted.

So this confirms the Kx is capable of utilizing almost the full capacity of eneloops.
Perhaps my lower shot count is merely me playing with a new toy and wasting battery capacity?

[OutOfFocus]

Could you validate your guess by setting the battery type to NiMH?

I'm running an NiMH test now. I hadn't charged the bad non-LSD cells I used, so I tried them in NiMH mode. They still wouldn't turn on the camera, so I put 100 mAh in each and tried again. Now they powered on the camera and took a few shots (about 20 to 30) before becoming depleted. The cutoff voltages for these cells appears to be a bit higher in NiMH mode than in Auto mode (which is worse).
In contrast, the Powerex cells are going great. They won't turn on the camera in Auto mode, but after LV I have a green indicator in NiMH mode. I haven't tried the Sanyo 2700 mAh cells or the LSD cells yet.

If we assume the Kx (and other Pentax dSLRs using AA size batteries) use voltage threshold.
Then the theoretical explanation is that both the eneloop and Imedion appear to maintain their voltage under the Kx load better than any of the other non-LSD batteries - to the point where the non-LSDs may only be partially discharged before they can no longer maintain the voltage level required to keep the Kx working. Whereas both the eneloop and Imedion can do so.

That's been the assumption, and that's what why I produced my graph. In an ideal world, all the voltage-current lines would have crossed at a single point, which would have told us the minimum required voltage at the required current drain. Now that I think about it more, however, perhaps I should be plotting volts versus power (voltage times current).
Of course, we have lots of extraneous variables which means all lines won't meet in exactly the same place.

Also as NiMH batteries age - they start to develop higher internal resistance - which limits the amount of current they can deliver - so the operating voltage under load sags even more.......

The reason the different batteries have different slopes is because of their different internal resistances when they can no longer power the Kx. I guess that that's influenced by battery age and condition, state of charge, and internal construction.

eneloops manage to maintain a higher operating voltage under load than any other NiMH rechargeables

Indeed, but I don't think that by itself is sufficient to explain the huge difference between the LSD batteries and the others. Look at the difference between the Volts versus Amps lines for the Powerex2700 and the Imedions when they were both barely able to turn the camera on. I think that for some critical load, they should have similar voltages but in no way is that the case.

Perhaps my lower shot count is merely me playing with a new toy and wasting battery capacity?

Perhaps. I used freshly charged batteries over several days of shooting, including many shots taken in multi-shot mode. About 30% of the shots before the camera shut down for the first time were with flash. At the end, I was just shooting anything to get the batteries dead.

[rawr]

This was mentioned in a thread buried in the mists of time now, but the K-x like other Pentax cameras does record battery state information in the EXIF of every shot, viz:



as viewed in PhotoMe v0.79R17

It would be an interesting project to correlate this info with a battery discharge profile.

[UnknownVT]

This was mentioned in a thread buried in the mists of time now, but the K-x like other Pentax cameras does record battery state information in the EXIF of every shot

Good call -

Red Empty battery to power off - Kx shutdown right after this shot -


Green Full battery - newly inserted eneloops top-up charged 4 days previously -


Shot with Orange Half Battery

[OutOfFocus]

This is weird.

I put a set of Duracell 2650 mAh batteries into my camera in NiMH mode. Initially they could not turn it on, but I put 100 mAh of charge into them and they could. I used them for all sorts of photo taking for a while until the batteries were "depleted". Turned the camera on again and took more photos until I was only able to get a few shots each time I turned the camera on. I took a total of just 165 shots. I took the batteries out and measured their voltage curve, which was pretty high, indicating that the batteries still had a lot of charge left.

A few days pass while I used the camera to "deplete" two other sets of batteries.

I put the Duracells back into the camera, which turns on with a red indicator. I pressed LV and the indicator turns green! I took four minutes of video and the indicator is still green! I will test until depletion again over the next few days.

One of the battery sets I tested in between the above was a set of partially discharged Powerex 2700 mAh cells that were "depleted" in Auto mode. They also turned green in NiMH mode and went for a long, long time (mostly in video) before becoming depleted again. Their voltage curve was very low, indicating they were really exhausted. I will test these again starting from a full charge to see whether that affects how the cells are recognized.

[UnknownVT]

This is weird.

No, this is really interesting.

Past Pentax dSLRs using AAs were all battery fussy (eg: K100D)
eneloops solved most people's problems with those -
this was probably due to eneloops' higher voltage maintenance under load.

However your experiments seem to show that when the Kx is set on NiMH -
it does recognize the lower operating voltage of NiMH and is acting accordingly.

However on the negative side -
it may also mean that Auto-Detect is not quite as effective as one would hope for -
but then as someone pointed out earlier if the Kx detects battery type by voltage level -
then how can it tell a NiMH recently charged at about 1.35V from an alkaline that's been used or a lithium AA that's depleted?.

This is the reason why I have set my Kx to NiMH -
hopefully your experiment shows this is the right thing to do.

[opiedog]

i used the autodetect with my panasonic and my k-x came up green
switched it to NiMh and it went to red.

there's really something funky about the battery circuit and software in the k-x.

i was also hoping that setting it to NiMh would force the K-x to lower the orange, red and battery depleted levels, but it seems like it doesn't do that, at least to the batteries that i have.

ok pentax. please come out with a fix for this!
thanks.

[HogRider]

I just did another quick battery test today.
I had used Lithiums (been using them in my Samsung Gx-1S on and off for a couple of month), freshly charge ENELOOPs (charged with MAHA charger yesterday) and a set of Alkalines (never used, but about 1 year old).
I did wait 30 seconds when changing batteries after closing the door. Battery detection was set to AUTO.

Lithiums show green as expected, and everything works as it should.
Eneloops show green as expected, and everything works as it should.

Alkalines: Camera boots up and is orange. Taken a few pictures and it stays orange. Turning LIVE view on and the I get the message "Battery depleted" and camera turns off. I can get the camera to boot again in regular shooting mode and it is orange again. I have not tested this any further, but I assume when you are out in the Boonies without Lithiums and Eneloops, the camera will be able to take a couple of pictures with regular Alkaline AAs, as long as Live View and Video isn't used, at least as an emergency backup.

[deadwolfbones]

Got my new navy blue K-x today. Put the supplied Energizer lithiums in and got full green battery as expected. Several dozen shots and a few hours later, exchanged the lithiums for a brand new set of Eneloops, fresh out of the packaging. Battery indicator showed full green for several dozen more shots with the Eneloops. I then switched back to the lithiums, which were still full green, and then back to the Eneloops, etc etc. No issues whatsoever.

All in "Auto" battery mode, serial #3506xxx

[piesforyou]

I can confirm Maplin's own brand Ni-MH hybrid batteries work fine. Green indicator when switched on. Havn't tested how many shots I can get yet.

[opiedog]

have you tried w/ non-eneloop nimh's?

energizer, duracell, etc.?

[deadwolfbones]

I don't have any, so no...

[sideshow]

Hi,

I'm new to the forum (K-x is about 30 mins old to me) and just browsed this thread, but I didn't see anything about anyone using a voltmeter or multimeter to measure the AA battery voltage.

Mine is a 346XXXX serial and is having issues with some old NiMh. I was reading the battery section of the owners manual and even though the table shows the NiMh batteries can be used the "caution" section says Not to use NiMh LOL. I thought that was funny/interesting.

Anyway.

I measured the voltage of the Lithium batteries that came in the box and they are all at 1.80V. Pretty high since I think "spec" voltage for AA's is 1.5V. The 4 NiMh batteries I tried (fresh charge in a "smart" charger) that have worked fine in other cameras measured 1.39V, 1.39V, 1.39V, and 1.45V.

If the camera is spec'ed to see 1.80 nominal voltage then 1.40V is a big time drop and would definitely make it think the batteries are low, especially if it's configured for Lithium batteries which are suppose to have a super flat voltage curve as they discharge (the lithiums will be at 1.8V until right before they are completely drained).

I think measuring individual voltages will be more telling rather than just going by advertised mAh battery life since I see some of the batteries from the first post listed in the "working" and "not working" categories.

long first post, thanks for reading if you did.