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12-30-2008, 05:48 PM   #1
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K200D Battery Meter Problem

4 months ago I bought a Pentax K200D and I'm very pleased with it. The lithium batteries that came with the camera lasted about a month. And ever since I've been using standard alkaline bateries for some quick shots. Of course these don't last long at all. But where my camera quickly reads these bateries as empty, my wii motes and other stuff still read them as full... (???)

So now I've invested into some GP 2700 NiMH recharable Bateries, but the camera also reads these as empty after 3-5 shots. Is there something wrong with my K200D ?

12-30-2008, 06:10 PM   #2
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QuoteOriginally posted by Zerreth Quote
So now I've invested into some GP 2700 NiMH recharable Bateries, but the camera also reads these as empty after 3-5 shots. Is there something wrong with my K200D ?
Well there's yer problem.

GP are notoriously dodgy when it comes to quality. Try Sanyo (the always-popular Eneloops), Energizer, Duracell or other well known brand of rechargeable batteries.

Also make sure you have a good charger that doesn't make your batteries explode.
12-30-2008, 06:20 PM   #3
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use slow charger
12-30-2008, 07:20 PM   #4
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Another vote to the Sanyo Eneloop rechargeables AA.

If you can't find it at retail then any other "Pre-charged" Nimh AA will be your second best option. Those regular Energizer/GP/etc rechargebles may be good for low-drain devices like the wiimote, but they don't hold enough voltage to power the K200d after just a few shots.

I use only the Eneloop on my K200d, never have a problem.

12-30-2008, 07:28 PM   #5
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Well for some reason they're doing fine now, just did a test run of 200 shots without flash, 100 with flash. (normal and burst) I just got these batteries, maybe I shouldn't have paniced so fast... (fresh from an 8 hour charge)

I'll wait and see. Tomorrow I'll do some some more tests and shoot till the batteries run dry.
12-30-2008, 10:00 PM   #6
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It's actually quite difficult to figure out how much juice is left in a NiMH cell... they have a flat discharge curve, so measuring the voltage won't tell you how much is left like it will for alkalines and lead-acid. Electronic devices do fancy things like measuring voltage over time along with temperature, and they still get it wrong occasionally.

This is why any "battery tester" is useless for NiMH. You cannot effectively measure the remaining capacity of a NiMH cell with only a few seconds of sampling.

Alkalines are pretty much useless in digital cameras, because they have high internal resistance and don't respond well to the high-current needs of the devices -- much energy is wasted heating up the battery rather than doing useful work. Cameras use energy in big gulps, while devices like flashlights consume a steady flow.

More than you ever wanted to know about batteries: Welcome to Battery University

A key reason I got the K200d is that it uses AA cells, which (among other reasons) means that I can use my high-quality chargers and infrastructure, instead of relying on a POS cheap bundled charger that doesn't actually tell you much about the state of the batteries.
01-02-2009, 08:41 PM   #7
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Pentax Needs to Fix Firmware

I am an Electronics Specialist with experience to 1958. I too find the K200D showing a premature "depleted battery" message using 2450 mAh Energizer batteries. After the K200D shows a battery depletion, I removed and checked the batteries using a 2 ohm load resistance across each cell with an accurate, high-end digital voltmeter. Each battery had a reading no lower than 1.24 volts. The nominal voltage of a Nicad or NiMh is 1.2 volts. What I found, the batteries had a huge amount of capacity left. They had not yet achieved the nominal 1.2 volts of the battery. This means the Pentax software is set too high for for a 1.2 volt battery. Pentax needs to get this fixed. I use a Maha MH-C801D charger that charges each battery separately.

Pentax....get your software fixed and issue a firmware update. Do like Garmin does with their GPS units. Make a screen entry allowing user choice between battery types offering a proper setpoint in the software.

D Messing
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01-03-2009, 01:34 AM   #8
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QuoteOriginally posted by dmessing Quote
I am an Electronics Specialist with experience to 1958. I too find the K200D showing a premature "depleted battery" message using 2450 mAh Energizer batteries. After the K200D shows a battery depletion, I removed and checked the batteries using a 2 ohm load resistance across each cell with an accurate, high-end digital voltmeter. Each battery had a reading no lower than 1.24 volts. The nominal voltage of a Nicad or NiMh is 1.2 volts. What I found, the batteries had a huge amount of capacity left. They had not yet achieved the nominal 1.2 volts of the battery. This means the Pentax software is set too high for for a 1.2 volt battery. Pentax needs to get this fixed. I use a Maha MH-C801D charger that charges each battery separately.

Pentax....get your software fixed and issue a firmware update. Do like Garmin does with their GPS units. Make a screen entry allowing user choice between battery types offering a proper setpoint in the software.

D Messing
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Not to start an argument, but rpriedhorsky already stated that NiMH batteries have a flat discharge curve. Measuring the voltage doesn't tell you squat about the remaining capacity of the battery. You're applying load, but you're not measuring available amperage, and that's where the problem is. As the cells discharge, they don't put out anywhere near 2450mAh, and cameras are high current devices. The current can only drop so low, and then the camera gives up trying, and usually there isn't a large amount of wiggle room between what the camera can use and what it can't.

The K200D isn't particularly smart about measuring batteries though, I will agree. Mine shows the batteries full until I get down to the last 10 shots or so on the set, then suddenly I'm at half power, and within 5 to 10 shots, the camera just dies. Battery life is fine, but the reliability of the gauge sucks. I pack extra batteries all the time to avoid disappointment.

01-03-2009, 02:00 AM   #9
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Pentax dSLRs using AA batteries are well known/notorious for being battery fussy/sensitive. This extends all the way back to the *istD series through the K100D and now the K200D - it shouldn't surprise anyone that there are very strong family traits in these dSLRs

The cutoff threshold voltage is set at 1.19V per cell (total = 4.76V) below that and the camera shuts down.
This cutoff threshold is pretty high since the nominal voltage of rechargeable NiMH AA batteries is supposed to be 1.2V.
(Ref: Post #49 (link) in thread - K100D - "Low-Battery" Problem gives details of the meter voltage levels)

As many report often the camera shuts down after only a few disappointing number of shots, even when there is a large amount of remaining capacity - enough to power and run other equipment.

This is because the operating voltage under-load of the batteries have dropped below Pentax's threshold cutoff voltage (1.19V/cell)

This battery problem is so prevalent that there are always concurrent threads here on the subject -
eg: K200D Batteries
k100d battery recommendation

If one reads these threads a fairly common recommendation is to use AA eneloops in the Pentax dSLRs

I posted the below in the thread k100d battery recommendation Post #62 but I'll paste it here for your convenience -

....even among Low Self-Discharge (LSD) batteries the eneloop maintains its operating voltage under load better than other LSD batteries -
I have a long (and somewhat messy) thread over at CPF batteries section comparing the otherwise really excellent Kodak Pre-Charged (LSD) with eneloops actually in the Pentax K100D -

eneloop vs. Kodak Pre-Charged Voltage Maintenance - summary in post #57

Here's an animated GIF showing the discharge curves at various current rates for 3 LSD batteries (note these were produced by SilverFox in his threads - NiMh Battery Shoot Out and Eneloop Self Discharge study - CandlePowerForums )


I've drawn a horizontal red line at approx 1.19V the cutoff threshold voltage for the Pentax K100D
(Ref: Post #49 (link) in thread - K100D - "Low-Battery" Problem gives details of the meter voltage levels)

One can see that there are more curves above the red line for the eneloop than the other two LSD batteries -
although this may seem minor, I think this is very significant for the battery fussy/voltage sensitive K100D and *ist D family of Pentax dSLR.

So although I do own Kodak Pre-Charged LSD (which are otherwise excellent) - I suspect these are re-badged GP ReCyko? - I use eneloops and confirmed re-badged eneloops in my K100D over any other batteries.

To get over 1,100 shots out of a set of eneloops and also a set of DuraLoops (Duracell Pre-Charged - confirmed re-badged enloops for the made in Japan white top versions), both having been charged 3-4 months before use - is simply incredible to me.
01-03-2009, 08:57 AM   #10
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Great Info

Thank you for the great replies. I am now curious if the set point for my K200D battery depletion is 1.19 per cell. That is a valid setpoint. Using a good regulated power supply I should be able to slowly take the voltage down to 4.76 volts showing where the trigger for battery depletion appears.

I agree the only way to check remaining capacaity is to measure the current drain with time.

Using a Fluke Scopmeter, in record mode, record current draw with time in m/sec, I plan to see what the actual current draw is for each function of the camera's operations when shutter operates, the LCD screen displays and flash operation/recharge. We will be able to calculate draw against time using actual camera operation. With that information, it will become known what the draw is and for what peroid of time. I hear the comments about the high current demands of digital cameras, is there data of what that current draw is for each camera function??
01-03-2009, 09:20 AM   #11
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That would be very usefull. I had an idea, to make a li-ion battery pack, that fits in AA storage space and directly supplies regulated, high (4*1.5..1.2=4.8..6 V) voltage. So such data would provide information on how serious the regulator should be and if it is possible and safe (because of heat) to install voltage stabilizer+liion's inside AA battery compartment.
01-03-2009, 09:41 AM   #12
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Summarizng the technical info here:

The camera needs a certain amount of voltage to run. Most batteries drop below that voltage long before they are completely drained. So it is absolutely correct and normal for the camera to report the battery as depleted (as in, not enough voltage to run the camera) while there is still enough charge left to run less demanding devices. Alkaline batteries are next to useless in these cameras, and while some ordinary NiMH rechargeables work OK, he low self-discharge types like the Eneloops work *much* better because they hold their voltage longer.

So forget that alkaline or ordinary NiMH cells were ever invented and use Eeneloop-type rechargeables (low self-discharg / "precharged") or Lithiums and you'll get hundreds of shots per charge.
01-03-2009, 10:39 AM   #13
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QuoteOriginally posted by Marc Sabatella:
Summarizng the technical info here:
I don't think this is a good summary, because the thread has quite a lot of anecdotes and repeated anecdotes, but little actual data.

First, the notion that the K200d battery meter works by monitoring the battery voltage and then stopping when it reaches 1.19V per cell does not appear to be grounded. Here's the relevant quote from the other thread:

QuoteOriginally posted by SteveB:
I'll just add a few facts as measured with my particular K100D........

Battery meter shows full charge at > 1.25v per cell, i.e. >5.00v
Battery meter shows half charge at 1.25v per cell, i.e. 5.00v
Battery meter shows empty and camera shuts down at 1.19v per cell, i.e. 4.76v

I'm an electronics engineer and took great care in taking these readings by the way, it's very easy to get it wrong. Other K100Ds could be a bit different of course, and temperature may be a factor possibly, I'm not going to repeat these measurements to find out.
There are two problem here:

1. SteveB is using an assumption about how the battery meter works (that it's purely voltage-based) but hasn't presented any evidence for that assumption (or stated his assumption, for that matter).

2. There's nothing about his methodology, just that he's an "electronics engineer" and that he "took great care".

Another reason I'm skeptical about that is that the batteries are in the camera in series, so it's not meaningful to quote per cell voltages -- the sum of all four cell voltages is what matters (to the extent that does).

Later in that thread is another anecdote from someone saying they get great results from "cheapo" non-Eneloop NiMH cells.

Now -- knowing how the battery meter in the camera works would be tremendously useful. But, I don't see how we're going to find that out by speculating, only by learning it from Pentax or disassembling the firmware.

Second, the cited analysis by SilverFox seems to have tested only a single set of each type of cell (please correct me if I'm wrong). Generalizing based on a sample size of 1 is extremely risky.

I've got several different brands of NiMH cells and can report on my experiences in a few months, but that's just more anecdotes.

Finally, FWIW the battery meter on my Canon A530 and my FW's Canon A570 both work as drewdlephone decribed -- reads full until the camera quits. I deal with this by assuming the meter is meaningless and carrying extra batteries.
01-03-2009, 12:37 PM   #14
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QuoteOriginally posted by rpriedhorsky Quote
Second, the cited analysis by SilverFox seems to have tested only a single set of each type of cell (please correct me if I'm wrong). Generalizing based on a sample size of 1 is extremely risky.
Agreed - but in his thread -
NiMh Battery Shoot Out (follow up NiMh Battery Shoot Out Part II )
would reveal some of his methodolgy. I believe he normally uses sets of 4 and checks their consistency and rejects or doesn't even test unless they are consistent (see post #14 ) since the threads are long running SilverFox is often notified of any differences from other people's testing - (eg: Posts #26, #27, #28 )

I am not being "defensive" about SilverFox's work
but these are long running threads over at CandlePowerForums (for flashlight enthusiasts)
where there would be a great deal of interest and knowledge about batteries -
although there might be a "sacred cow" or even "emperor's new clothes" syndrome -
I don't really think this is the case, considering how many true experts and electrical/electronics engineers are over there. I believe the threads contain some really good information and has stood the test of time and scrutiny of others better than me.

But then, by definition anything I say has to be anecdotal.......
01-03-2009, 12:51 PM   #15
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K200D Battery connections

Before, I do any current draw measurements and capturing instantaneous current peaks down to the millisecond range, I wanted to verifiy if the batteries are used in series configuration.

The batteries appear not be in a single, straight series only configuration, here is what I found.

Laying the K200D upside down with the lens pointed away from me, I numbered the battery compartments in the following manner. Most foward was #1, going CCW, #2, then #3, then #4. Using an ohmmeter I found #2 and #4 are a direct short (a jumper internal inside the camera).

Then using the same numbers for the battery cover, it is plain to see a jumper between #1 and #2 and a jumper between #3 and #4.

Drawing that out, #1 down in the camera is the most positive voltage source of battery pack and #3 is the most negative source.

Then using a regulated power supply I connected a range of 4.8 to 6 volts positive to #1 in down in the battery compartment and the negative to #3.

The camera would not turn on.

That seems to indicate the camera is using a connection at the #2 to #4 internal jumper at half voltage potential.

If it were just a true parallel connection, then the camera should come on with just two batteries at the #1 and #2 slot, or two batteries only at the #3 and #4 slot.

I would be interested in thoughts on this before I proceed to current measurements, which may clear up some of this.

dmessing
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