eneloop vs. Kodak Pre-Charged Voltage Maintenance

One of the things that has me floundering is that I am not able to take the right metrics/meausrements when it comes to batteries.

For example I report on voltages - but they are open-circuit readings which are obviously not as useful or meaningful as the actual operating voltage under load.

This became pretty obvious to me when I was trying to determine the actual threshold cut-off voltage of the Dorcy 45lumen 1AA flashlight - I could only report on the open-circuit voltage before or after the runtime tests - but not during, when the battery was being used in the flashlight.

I wanted to be able to determine the operating voltage under load for the Kodak Pre-Charged and eneloop to see if there was a difference.

So I thought of a pretty simple somewhat artificial method, but should be easily controlled and reproducible -
just get a 1 ohm resistor and read the voltage when the resistor was loaded across the battery terminals.

To start this I charged one each of Kodak P-C and eneloop AA and then allowed them to rest and cool down for approx 2 hours -

Open-Circuit readings -
eneloop #1: ... 1.454V; FA=11.6A; 1.436V
Kodak P-C #1: 1.423V; FA=10.4A; 1.409V

1 ohm load readings -
ene = 1.388V @ 1.25A (= 1.735watts)
KPC = 1.336V @ 1.22A (= 1.630watts)

End of test o-c readings
ene = 1.440V
KPC = 1.412V

Under a 1 ohm load - eneloop maintained 0.052V higher than the KPC, which is about 4% higher voltage.

From open-circuit voltages (3 sets) the actual differences were 0.031V; 0.027V; 0.028V higher for eneloop - which is about 2% higher for eneloop in all 3 sets.

So this shows that not only is the voltage higher for the eneloops under the same conditions - the KPC sags more under-load than the eneloop.

That's a good way to test cells.

From those numbers you can estimate the internal resistance of each cell:

Eneloop = (1.440 - 1.388) / 1.25 = 0.0416 ohms
Kodak = (1.412 - 1.336) / 1.22 = 0.0623 ohms

Your Kodak result is quite good. I measured more like 0.1 ohms with a similar test. How many charge/discharge cycles had your Kodak cell been through before you tested it?

You could try the same thing with partially discharged cells for a comparison. You might see a greater relative voltage drop in that situation.

For an even more representative measurement of the internal resistance you can use two different resistors, e.g. 1 ohm and 2 ohms. The internal resistance calculation then becomes:

Internal resistance = (V2 - V1) / (I2 - I1).

I love this forum...you learn so much.

Mr Happy said:

For an even more representative measurement of the internal resistance you can use two different resistors, e.g. 1 ohm and 2 ohms. The internal resistance calculation then becomes:
Internal resistance = (V2 - V1) / (I2 - I1).

Click to expand...

Actually I bought a pack of 2 (Radio Shack) 1 ohm 10watt 10% wirewound resistors so I can easily get 2 ohms (series).
Using the same batteries as in the 1 ohm test above -

2 ohms (series) -
ene = 1.400V @ 0.67A
KPC = 1.360V @ 0.65A

Using the 1 and 2 ohm readings and your formula
Internal resistances -

ene Rb = (1.400-1.388)/(0.67-1.25) = -0.021 ohms
KPC Rb = (1.360-1.336)/(0.65-1.22) = -0.042 ohms

These seem very good/low??

I can also get 0.5 ohms by using the resistors in parallel -

0.5 ohms (parallel)
ene = 1.328V @ 2.26A
KPC = 1.264V @ 2.16A

ending open-circuit voltage
ene = 1.421V
KPC = 1.390V

I thought Internal resistance was the way you originally calculated it
Rb = (Vs-V)/I
Vs = open-circuit voltage
V = voltage under load
I = current supplied to load.

However as can be seen the open-circuit voltage has dropped after my tests for both batteries.

Using this formula
2 ohm readings -
ene Rb = (1.421-1.400)/0.67 = 0.031 ohms
KPC Rb = (1.390-1.360)/0.65 = 0.046 ohms

0.5 ohm readings -
ene Rb = (1.421-1.328)/2.26 = 0.041 ohms
KPC Rb = (1.390-1.264)/2.16 = 0.058 ohms


Coming back to voltage maintenance -

2 ohm load at a current draw of about 0.66A
eneloop was 0.04V higher than the KPC or about 3% higher

0.5 ohm load at a current draw of about 2.2A
eneloop was 0.064V higher than the KPC or about 5% higher

I've probably had about 1/2 dozen cycles through both eneloop and Kodak P-C

Yes, I got the sign wrong in my formula of course. It should have been:

Internal resistance = (V1 - V2) / (I2 - I1)

The other thing I should mention is that it is important to take the two readings as close together as possible. In an ideal world it is done with two meters measuring amps and volts simultaneously. You momentarily connect and disconnect the second resistor to jump back and forth between high resistance and low resistance, to try to obtain readings that are repeatable and not drifting over time. Every time you measure the voltage on a NiMH after testing it will have moved a bit, and that movement will upset the accuracy of the result.

What you are trying to approximate is the slope of the line when you plot voltage and current on a graph. The slope of such a line (voltage/current) is the resistance.

The way I originally calculated it with open circuit voltage is just a special case of using two resistances, only we have one of the resistances (open circuit) being infinite giving a current of zero in that case. It gives you

Rb = (V1 - V2) / (I2 - I1) = (Vs - V) / (I - 0)

Incidentally, the higher voltage of the Eneloop with the 0.5 ohm load is starting to look quite apparent, I think.

Mr Happy said:

The other thing I should mention is that it is important to take the two readings as close together as possible. In an ideal world it is done with two meters measuring amps and volts simultaneously. You momentarily connect and disconnect the second resistor to jump back and forth between high resistance and low resistance, to try to obtain readings that are repeatable and not drifting over time. Every time you measure the voltage on a NiMH after testing it will have moved a bit, and that movement will upset the accuracy of the result.

Click to expand...

Yep, I noticed that - it's like trying to hit a moving target since I only have the one cheapo DMM - but I guess this is probably good enough just as an indication (close enough for jazz) ....

I looked up the formula you gave, and they had the sign wrong too

The other calculations were -

0.5 and 2 ohm readings
ene Rb = (1.400-1.328)/(2.26-0.67) = 0.045 ohms
KPC Rb = (1.360-1.264)/(2.16-0.65) = 0.064 ohms

0.5 and 1 ohm readings
ene Rb = (1.388-1.328)/(2.26-1.25) = 0.059 ohms
KPC Rb = (1.336-1.264)/(2.16-1.22) = 0.077 ohms

It almost seems that internal resistance increases for increasing load (lower resistance/higher current)?

Mr Happy said:

Incidentally, the higher voltage of the Eneloop with the 0.5 ohm load is starting to look quite apparent, I think.

Click to expand...

The difference in voltage maintenance for the eneloop is greater/higher over the KPC as the load increases (lower resistance/higher current).

Just to make this more obvious -

open-circuit - current draw of 0.00A
eneloop was 0.029V higher than KPC or about 2% higher

2 ohm load at a current draw of about 0.66A
eneloop was 0.039V higher than KPC or about 3% higher

1 ohm load at a current draw of about 1.23A
eneloop was 0.052V higher than KPC or about 4% higher

0.5 ohm load at a current draw of about 2.2A
eneloop was 0.064V higher than KPC or about 5% higher

Mr Happy said:

You could try the same thing with partially discharged cells for a comparison. You might see a greater relative voltage drop in that situation.

Click to expand...

I partially discharged the same 2 batteries in the Dorcy 45lumen 1AA flashlights for about 25 minutes - probably to approx half capacity - ie: about 1/2 the runtime until the lights would not turn on again (see post #11). Allowed the batteries to rest/cool down for about 1.2 hours (as those lights run noticably warm - so the batteries were warm at end of discharge).

Readings -

Open-circuit (o-c) -
ene 1.298V; FA=10.4A; 1.293V
KPC 1.273V; FA=9.9A; 1.267V

2 ohm load -
ene 1.266V @ 0.60A
KPC 1.243V @ 0.59A

1 ohm -
ene 1.247V @ 1.17A
KPC 1.220V @ 1.14A

0.5 ohm -
ene 1.224V @ 2.09A
KPC 1.176V @ 2.01A

ending o-c -
ene 1.294V
KPC 1.267V

Internal resistance calcs -
1 & 2 ohm -
ene Rb= (1.266-1.247)/(1.17-0.60) = 0.033 ohms
KPC Rb= (1.243-1.220)/(1.14-0.59) = 0.042 ohms

0.5 & 2 ohms -
ene Rb= (1.266-1.224)/(2.09-0.60) = 0.028 ohms
KPC Rb= (1.243-1.176)/(2.01-0.59) = 0.047 ohms

0.5 & 1 ohm -
ene Rb= (1.247-1.224)/(2.09-1.17) = 0.025 ohm
KPC Rb= (1.220-1.176)/(2.01-1.14) = 0.051 ohm

the other way of calc using the o-c voltage (I used the ending o-c V)
2 ohms load -
ene Rb = (1.294-1.266)/0.60 = 0.047 ohms
KPC Rb = (1.267-1.243)/0.59 = 0.041 ohms

1 ohm -
ene Rb = (1.294-1.247)/1.17 = 0.040 ohms
KPC Rb = (1.267-1.220)/1.14 = 0.041 ohms

0.5 ohm
ene Rb = (1.294-1.224)/2.09 = 0.033 ohms
KPC Rb = (1.267-1.176)/2.01 = 0.045 ohms

Voltage maintenance -

o-c ene was 0.025, 0.026 & 0.027V higher than KPC ~ 2% higher
2 ohm ene 0.023V > KPC ~ 2%
1 ohm ene 0.027V > KPC ~ 2%
0.5 ohm ene 0.048V > KPC ~ 4%

In this round of using approx 1/2 discharged batteries -
although the eneloop still showed consistent higher voltage maintenance than the KPC - it was only about 2% higher for loads up to 1 ohm or about 1.2A current draw.
It was only using the 0.5 ohm load with current draw of about 2A that the eneloop once again pulled away from the KPC by almost 0.05V and about 4%.

It would seem from this limited testing that the higher voltage differential is more pronounced when the batteries were nearer full capacity and lessens with diminishing capacity - it remains that the eneloop hold voltage better than the KPC with higher loads (ie: lower resistance/higher currents)

Update - I used the Pentax K100D dSLR today with the same (continuing) set of Kodak Pre-Charged and took over 46 shots all with flash.

I saw half charge signal 11 shots in and it stayed there (except for an occassional bounce back to full) eventually I saw the low ("empty") battery icon (there is one more stage when that flashes - but that would be close to shutdown) about 38 shots in - however the batteries manage to keep going.

The shot count on these Kodak Pre-Charged is now 540 - when I checked just before I started this post the indicator was back to full charge icon and remained that way even after two test shots no flash - but long exposures.

readings Kodak Pre-Charged
#5 1.264V; FA=9.4A; 1.260V } more recently
#6 1.265V; FA=9.6A; 1.262V } charged pair
#7 1.253V; FA=9.4A; 1.248V
#8 1.253V; FA=9.6A; 1.248V

Of course when I returned the set to the dSLR after the flash amps the indicator showed half-charge.

Interrupting this post - I went and checked the indicator was back to full-charge - but a single test shot dropped it back to half charge again.

However a shot count of 540 is only 27 short of the eneloop total of 567 - this is a sterling performance for a battery that definitely has lower operating voltage and higher internal resistance than the eneloops.

The eneloop shot count of 567 was over a much longer period just short of 5 months - whereas the KPC is only over a period of 1- 1.5 months (but this is more typical of my usage - with the eneloops I had previously been charging up and using a set of regular NiMH on day of shoot and kept the eneloops as backup and standby in the dSLR).

I used more flash with the eneloop set, and did more flash amp readings.

But I am now very impressed with these Kodak Pre-Charged.

Update - I used the Pentax K100D dSLR today with the same (continuing) Kodak Pre-Charged and managed another 126 shots (almost all without flash) until power-off .

So the accumulated grand total for this set of Kodak Pre-Charged is 671 shots - this exceeds the eneloop total by 104 shots.

But the conditions were different as outlined already in my previous post above.

However I would say these Kodak Pre-Charged are at least roughly equal to the performance of the eneloops I recounted previously.

Reading of the Kodak P-C after 4 hours rest -

#5 1.251V; FA=9.3A; 1.243V
#6 1.252V; FA=8.7A; 1.246V
#7 1.240V; FA=9.1A; 1.232V
#8 1.238V; FA=9.2A; 1.231V

With the 4 hour rest these probably would power up the dSLR and be able to take a few shots - but the state of these KPCs are about the same as the eneloops after power-off and 10 hours rest.

I had the impression that the dSLR signalled the low ("empty") battery icon for quite a while before the camera powered down - seemed longer than for the eneloops - perhaps this was another indication that the KPC voltage is lower/sags more under load than the eneloops -
however we have already shown the higher voltage maintenance of the eneloops by using static 0.5, 1 and 2 ohm loads.

Anyway - I am now very pleased with the performance of these Kodak Pre-Charged - 671 shots on the Pentax dSLR exceeds even the spec'd shot count for Lithium AAs withOUT flash of 660.

Summary - Superceded - please see New Summary in Post #57 (link)

EDIT to ADD -
Important - please see Post #56 - where I managed to finally show that the lower operating Voltage under load of the Kodak Pre-Charged causes my dSLR to shut Off even though there was still remaining charge to take many more photos.

This thread admittedly has been a hodge-podge of ad-hoc experimentation.

My initial objective was to try to show that eneloops maintained a higher operating voltage (under load) than the Kodak Pre-Charged - by demonstrating some difference in usage in voltage level sensitive devices.

Although I started this thread with what I thought was a pretty clear demonstration of the advantage of higher operating voltage under-load of the eneloop - subsequently after more (ad-hoc) experiments/test I was NOT able to do this conclusively.

(1) I have demonstrated that the eneloops do maintain a higher operating voltage under load than the Kodak Pre-Charged by using static fixed resistors - 0.5, 1, 2 ohms (with current draws of about 2+A, 1.2A, 0.6A respectively) using fully charged and about 1/2 discharged batteries - Posts #41, #44 , #47

(2) Calculating the internal resistance of the batteries showed eneloops had lower internal resistance than Kodak P-C - Post links above, + Mr Happy's post #42

(3) Use in flashlight with high voltage threshold cut-off - Dorcy 45 lumen 1AA - runtime with 4 min On and 1 min Off - attempting to show a difference when the light was turned back on (lower voltage may fail to turn light on) - showed that eneloop and Kodak P-C were basically neck and neck - if anything the Kodak P-C may have had more remaining charge/capacity than the eneloop Post #11 -
caveat - although these were two samples of the same flashlight - there might be some difference due to sample variation - so this may not be quite as conclusive - I may have to re-do the runtimes using just one flashlight.

(4) Use in well regulated flashlight Fenix L1D-Q5 (on High in general mode) - the straight runtime results were basically neck and neck post #27

(5) (**see below addendum) Use in dSLR - Pentax K100D (notorious for being battery fussy) with relatively high voltage threshold cut-off. Much to my pleasent chagrin - the Kodak P-C seem to do as well as the eneloops in the one device where I thought higher voltage would really matter. The Kodak P-C actually well exceeded the shot count of the eneloop - but there were different conditions - however I would regard the performance of the Kodak P-C and eneloops as "sterling" - far surpassing specs and my expectations (especially considering the notoriety of the dSLR on batteries) Posts #38 , #49 .

Overall I am now very pleased with the performance of the Kodak Pre-Charged and would regard them basically "the same" as eneloops for most of my practical usage.

But I still feel that eneloops are intrinsically "better" due to the higher operating voltage and lower internal resistance - but other than resistance testing - I have not been able to demonstrate any notable difference in any real practical usage - even when using devices that were known to be voltage level sensitive.

EDIT to ADD **-
Important - please see Post #56 - where I managed to finally show that the lower operating Voltage under load of the Kodak Pre-Charged causes my dSLR to shut Off even though there was still remaining charge to take many more photos. So point 5 above is NO longer valid.......

eneloops are better than the Kodak Pre-Charged in the Pentax K100D dSLR due to eneloop's higher operating voltage under load.....

Note: this summary has been superceded - please see New Summary in Post #57 (link)

Nice work Vincent.

A lot of good data provided by all your various hands on tests.

Black Rose said:

A lot of good data provided by all your various hands on tests.

Click to expand...

Thank you Black Rose for being so kind and generous.

I felt this thread was not very well organized on my part -
it almost felt like I was "making it up as I went along".

Because I ended up doing so many different types of "ad-hoc" experiments
- I thought a summary was needed
- even if it was only to clarify things for myself

Hello Vincent,

Don't worry... Testing is often like this. Sometimes you have to make it up as you go along. In the end, it often works out fine.

People often get better with practice, so what's your next project?

Tom

SilverFox said:

Don't worry... Testing is often like this. Sometimes you have to make it up as you go along. In the end, it often works out fine.
People often get better with practice, so what's your next project?

Click to expand...

Kind words indeed Tom - thank you.

Yeah coming from a science/engineering background I do understand that experiments are exactly that, and even a negative result is worthwhile.

But it's taken me several tries in this one to come to the eventual conclusion that probably most people would get intuitively without all this messing around -
that LSD batteries mostly perform about the same for most practical usage.

I failed to demonstrate that higher operating voltage (under load) of the eneloop showed any significant practical advantage over the Kodak P-C -
despite clearly showing that eneloop has higher operating voltage and lower internal resistance.

So for me eneloop and Kodak Pre-Charged perform about the same -
even in devices that I thought were more critical about voltage levels.

Follow up -

It's taken me this long to deplete the set of eneloops in the Pentax K100D dSLR - the final shot total was 650 - this is similar to the outstanding result I last got on the Kodak Pre-Charged (671 shots).

So as far as use in the Pentax K100D dSLR (battery fussy) is concerned my Kodak P-C and eneloops show very similar performance - they both exceed the Pentax K100D specified shot count for 2500mAh NiMH in fact do as well as the specs for lithium AA batteries.

This is outstanding - eneloops (do v well, as most would expect) and are matched easily by the Kodak Pre-Charged - for the time being a bargain of sort at $8.97/4 at WalMart (just noticed the increase in price from $8.47 to $8.97, which used to be the price of the RoV Hybrids at WalMart).

A point to note - the KP-C (last charged May/25/2008) I just put in the K100D, did show 1/2 charge indicator after trial shots - which then would recover to full charge - I think this is similar to what I first observed in my opening post.
So it would appear that the K P-C may well have lower operating voltage which would cause the 1/2 charge indication - this time it's just over 3 months storage from last charge - I'll keep a note on how this set lasts (total shot count).

UnknownVT said:

A point to note - the KP-C (last charged May/25/2008) I just put in the K100D, did show 1/2 charge indicator after trial shots - which then would recover to full charge - I think this is similar to what I first observed in my opening post.
So it would appear that the K P-C may well have lower operating voltage which would cause the 1/2 charge indication - this time it's just over 3 months storage from last charge - I'll keep a note on how this set lasts (total shot count).

Click to expand...

This is disappointing......

I used the Kodak Pre-Charged today in the Pentax K100D dSLR it showed 1/2 charge only after a few shots and continued in that state - then it started to show low charge -
and at shot count 177 the camera shut Off!!
But simply turning the camera off and immediately back On - showed the 1/2 charge indication and the camera would continue to shoot, and would even occassionally show Full charge (very confusing).

Then after another 72 shots the camera shut Off again!
- again merely turning it Off than On - seem to get the camera working without shut Offs for the rest of the shoot (another 18 shots).

So I think this is pretty conclusive for me -
after just over 3 months' storage from last charge - these Kodak Pre-Charged started to show lower charge (just as described in the opening post)
- and although they still "work" in the dSLR - the operating voltage would dip low enough to cause the camera to shut Off - only a momentary rest (in turning Off then On) was enough to have the batteries back to working again - which shows that there is still capacity
- but the lower Voltage under load would cause the camera to shut Off.

The shot count on this set of KP-C is now 265 do far - so there seems to be "good" capacity
- but the lower Voltage under load caused the camera to shut Off twice so far.......

Even though it is inconvenient - I'll persist with this set of KP-C - just to see how many shots I can squeeze out of them until final shut Off (ie: turning Off and On will not resuscitate).

The main difference between this usage and the previous report of the KP-C - this time the batteries were charged just over 3 months ago - whereas previous report of 671 shots was with the batteries charged only 4 weeks before for one pair, and the other pair only about 1 week (see Post #38 about 1/2 way down). The total duration of the previous shot count for the KP-C was just under 1 month (so the batteries were just under 2 months from charge for one pair and just over 1 month from charge for the other - so no where near the 3 months from charge for today's use, and 4 months from charge for the opening post.

It would seem that after a few months the KP-C drops in voltage level - more than eneloops. The 1st shot count for the eneloops of 567 shots at that point the eneloops were nearly 5 months from charge (see first part of Post #38) when I first started this thread those eneloops were already over 4 months from charge.....

However it's ironic this is bascially the conclusion I initially tried to postulated in my opening post #1
- the lower operating Voltage (under load) of the Kodak Pre-Charge would cause premature low battery, or even shut down in the Pentax K100D dSLR
- whereas the eneloop having better voltage maintenance under load should do better.

This has now been shown to be the case.

eneloops are better than the Kodak Pre-Charged in the Pentax K100D dSLR due to eneloop's higher operating voltage under load.....

- so I will do as I previously said - use eneloops in the Pentax K100D dSLR and keep the KP-C for other uses.

New Summary - superceding the one in Post #50 above.

I was able to show using fixed resistors that eneloops maintain a higher operating voltage under load than the Kodak Pre-Charged.

eneloops also had a lower internal resistance than the KP-C -
all these were good things.

In practical tests -

1) I was unable to show advantage of these aspects when the respective batteries were recently charged in flashlights unregulated and current regulated.

2) When recently charged the Kodak Pre-Charged did as well, and better than the eneloops in the very battery fussy Pentax K100D dSLR.

3) BUT - after storage of about 3 to 4 months from charge the Kodak Pre-Charged did show low battery signal and shut down the dSLR "prematurely" when there was obvious remaining charge - enough to continue shooting a significant number of shots
- whereas the eneloop did NOT suffer from this.
This shows me that the high operating voltage under load maintained by eneloops makes them better suited than the Kodak Pre-Charged - which had otherwise matched the eneloops step-for-step when recently charged.

Opinion - although one could just say the Kodak Pre-Charged lost more charge/capacity in the 3-4 months storage than eneloops - I don't think it is loss of capacity - from the self-discharge tests I've read about KP-C - they seem to hold up well in comparison to eneloops, in one case showing more capacity throughout the 90 days.

So I think the KP-Cs have not actually lost more capacity -
but just have lower voltage maintenance than the eneloops -
causing the low battery signal and even shut down on the dSLR -
the fact that the KP-C would work again with a mere momentary rest (turning dSLR off then on) shows there still is good remaining capacity - but the camera shows low battery and even shuts down.

Therefore - when recently charged the KP-C easily match eneloops -
but after about 3 months from charge the eneloops clearly show an advantage of higher voltage maintenance -
in voltage sensitive devices (eg: Pentax K100D dSLR) this makes a real practical difference.

UnknownVT said:

I think the KP-Cs have not actually lost more capacity -
but just have lower voltage maintenance than the eneloops -
causing the low battery signal and even shut down on the dSLR -
the fact that the KP-C would work again with a mere momentary rest (turning dSLR off then on) shows there still is good remaining capacity - but the camera shows low battery and even shuts down.

Click to expand...

FWIW - a follow up -

I still have the "disappointing" set of Kodak Pre-Charged in the Pentax K100D dSLR - and today I used it for a few trial shots to see if the KP-C's were still holding up.

First note was that on turning on the dSLR battery indicator showed full charge - and did so even after a few shots including flash.

Eventually showed 1/2 charge - but simply turning the dSLR off then On restored it to full-charge.

So I think this would appear to confirm the KP-C probably still have good amount of remaining charge - but may not be able to maintain high enough operating voltage under load - which then causes the low battery signal and even shut-down of the dSLR reported previously.

Given rest the KP-C's restore their voltage level - but put them under load for significant amount of use - the KP-C's voltage will dip below the dSLR's operating voltage threshold to cause the shut-down.

Hi Vincent,

I just wanted to chime in here and say I've really enjoyed this thread. When I get on my LSD soapbox with my friends and family, I can confidently recommend the Kodaks thanks to your fine work here.

I'm also the proud owner of a new K200D, a purchase I probably wouldn't have made without your verification that Eneloops feed the Pentax cameras quite well.

geek4christ said:

I just wanted to chime in here and say I've really enjoyed this thread. When I get on my LSD soapbox with my friends and family, I can confidently recommend the Kodaks thanks to your fine work here.
I'm also the proud owner of a new K200D, a purchase I probably wouldn't have made without your verification that Eneloops feed the Pentax cameras quite well.

Click to expand...

Thank you so much for the kind feedback (I was wondering if anyone was still reading this thread ).

I'm embrassed to say that this thread bounced about all over the place.

I started by thinking I had found a way to show the advantage of the higher voltage maintenance of the eneloop over the KP-C (using the Pentax K100D dSLR) - but all of my subsequent tests failed to do that conclusively.

However storing a set of Kodak Pre-Charged for 3 months, managed (finally) to show the eneloop advantage - much to my own chagrin - just the way I tried to do initially .

With hindsight - I should have just tested that initial set of 4 months from charge KP-C in the K100D, and that should have shown the eneloop higher voltage maintenance advantage.

Hopefully with the K200D, Pentax may have improved the over-sensitivity of their (too high) battery threshold... nevertheless I would use eneloops.

Enjoy your K200D - it's a fine choice.