[noou]

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.

actually, in this thread and others, also from different forums (e.g. dpreview), there's plenty of data provided by voltmeters/multimeters...

[opiedog]

i think the pentax manual says not to use NiMn nickel manganese, not nimh

[piesforyou]

I've been shooting like mad the past day, using my Maplin Ni-Mh hybrids. So far I've got 630 shots, with maybe 10 shot in live view, and 2 short (30 seconds combined) videos. The battery indicator is still on green when you start it up, though it went orange this morning.

[OutOfFocus]

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.


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.

First off, my K-x works really well with good quality NiMH. I've taken 2600 shots in one test with 2100 mAh batteries, and I've taken over 2 hours of video in another test of 2700 mAh batteries and I still have an orange indicator! I'm totally satisfied with my K-x battery performance (and every other category of performance as well), provided I use really good NiMH.

To get a good indication of NiMH performance, you need to measure the voltage under load not just the open-circuit (unloaded) voltage. The problem with high current devices such as digital cameras is that the internal resistance of the battery becomes very significant, which is why alkalines perform so poorly. As NiMH age they tend to develop (relatively) high internal resistance, and some brands (i.e. the battery's internal materials and construction) have higher resistance than others. Mistreatment (excessive over-charging and dis-charging) can also increase internal resistance, quite quickly.

A theory I have about the K-x's battery problems is that it incorrectly classifies some batteries as not NiMH, even if you tell it they are (i.e. it treats the battery type field as a hint, not the truth), based (in part) on the battery's internal resistance.

So, to get a better idea of your batteries' true state, measure both their open circuit voltages (as you have) and their voltages under a couple of different (significant) loads. If you look above (post 194) you'll see a graph I made using four different loads: open circuit, 3.33 ohms, 0.77 ohms, and 0.434 ohms. The voltage versus current plots are pretty much straight lines, so it wouldn't matter what resistances you used. I would suggest getting two 1 ohm 10 watt resistors, and then you can measure voltages under 2 ohms (resistors in series), 1 ohm (one resistor), and 0.5 ohms (resistors in parallel).

The graph I made above was at the point at which the batteries could no longer power the camera. I am in the middle of constructing another graph for batteries fresh off the charger. So far it shows that the low resistance batteries can power the camera for a very long time and are completely drained, while the high resistance batteries can only power it a short time and still have a lot of charge remaining.

If you'd like to post/pm your voltage measurements under load, I could add them to the graphs I'm building.

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Last edited by OutOfFocus; 12-02-2009 at 12:15 PM. Reason: fix typo

[deejjjaaaa]

Kx w/ serial = 3434xxx

Duracell 2650 mAh from WalMart - all batteries are 2-3 years old - I was using them w/ my *istDL since 2006 - charged in a cheap Targus charger (200mA current per battery) - so far they are working OK, powering camera in "auto" and "nimh" settings - I did not have a chance to see how long will they last though...

[rawr]

Wow. All this info and data.

There's enough here for someone to do a PhD on the K-x's battery usage characteristics and NiMh battery issues in general.

[jerrymouse]

There is a new firmware for K-x that should address battery issues.
Pentax releases K-x firmware v1.01: Digital Photography Review

[noou]

There is a new firmware for K-x that should address battery issues.
Pentax releases K-x firmware v1.01: Digital Photography Review

WOW! great, thanks!
Looking forward to trying it as soon as I come back home.

[RMabo]

Blue K-x running new firmware 1.01.
Uniross 2300 batteries and Uniross charger.
Working well.
K-x serial no starting with 3487

[OutOfFocus]

The following two figures show how the voltage of freshly charged NiMH batteries with different internal resistances depends on the load. The plotted circles represent measurements. The lines represent models of the batteries consisting of an ideal voltage source in series with an internal resistance, and fitted to the measurements. (Many of the batteries in this test have been used extensively, sometimes abused, and this may explain a large part of their high internal resistance. Do not use these figures as a guide to the relative performance of new batteries.)

The first figure plots voltage against current draw. (Note that the horizontal axis is not time. This graph says nothing at all about how the voltage of any battery decreases as it is used.) The linear decline of voltage with current drawn is a direct result of the internal resistance.


The amount of power delivered, however, equals the voltage multiplied by the current, so getting a specific amount of power from a battery with lower voltage will require an even bigger current draw and hence an even lower voltage. The following figure plots voltage against the power supplied. (Again, the horizontal axis is not time, and this graph says nothing at all about how any battery's voltage will decline with use.)

Note how all the batteries have a similar voltage under no load, but that there is a wide difference at high power levels (for instance 2 watts), and that unloaded voltage readings are not a good predictor of voltage under load.

In the original firmware (1.00), only the top 4 batteries (under load) delivered very long runtimes (thousands of shots or hours of video) and finished being completely drained. The others could only power a couple of hundred shots or a few minutes of video at the most, and even when "depleted" still contained a lot of charge.

I haven't yet had time to do extensive testing with the new firmware (1.01), but so far the Energizer 1850s are showing much improved runtimes.

[deejjjaaaa]

The following two figures

so that is what I expected - Duracells 2650 are pretty much Eneloops, just in a modest clothes...

[OutOfFocus]

so that is what I expected - Duracells 2650 are pretty much Eneloops, just in a modest clothes...

In this one test, yes, but there are lots of other differences. White-topped duracells, the so-called duraloops, are something else.

[UnknownVT]

so that is what I expected - Duracells 2650 are pretty much Eneloops, just in a modest clothes...

In this one test, yes, but there are lots of other differences. White-topped duracells, the so-called duraloops, are something else.

Have to be careful here folks.

The Duracell 2650mAh are regular (high capacity) NiMH - without any special LSD (Low Self-Discharge) properties.

It is the Duracell Pre-Charged which are the LSD batteries and they are rated at 2000mAh.

Admittedly it is somewhat confusing - which most battery manufacturers have not made any great effort to differentiate.

The white-top made in Japan Duracell Pre-Charged are the confirmed re-badged eneloops nicknamed "DuraLoops".

[UnknownVT]

An update -
Kx serial # 34348XX
received Nov/24/2009 from Newegg.
second set of eneloops for my actual normal usage.
Firmware version: 1.00
Starting frame # 0664
Current frame # 1791 << NOTE: this is for so far (batteries are NOT finished)
Current Battery Status = Half Orange
EXIF info from PhotoMe below



This set of eneloops is NOT depleted -
the shot count so far is 1,128.

I am still on Firmware version 1.00 -
I do not intend to upgrade until this set of eneloops is depleted.

I'll report the final shot count.

[noou]

WOW! great, thanks!
Looking forward to trying it as soon as I come back home.

firmware 1.01 preliminary results:
previously non-working batteries seem to work
working batteries that made the camera turn off, even with some residual charge, now can turn the camera on and go orange.

so far I'd say I'm pretty satified
the test goes on, though...