K100d battery issue again: facts and figures

Started Feb 9, 2007 | Discussions thread
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boyd2 Contributing Member • Posts: 659
K100d battery issue again: facts and figures

Hi,

As discussed here often, many K100D samples have their battery low voltage set to high, causing a early shutdown with perfectly normal NI-MH batteries. Some can't even get the K100d to power up, while others with a good sample report hundreds (sometimes even over 1000) pictures per charge.

Really wanting the K100d (already bought 2 lenses), I'm getting a bit desperate trying to find a good sample. Tested 3 faulty samples already and have to test in the shop, due to lack of return policies here. So I tried to get to the bottom of this. (Please refrain from 'eneloop and CRV3 answers', already know all that).

I called a technician at Pentax Belgium and discussed the problem. BTW, the problem they find most is dirty contacts, which causes much more problems here, due to the fact there are 8 battery contacts in the camera (camera's with lithium-ion batteries only have 2 or 3). Often polishing the battery ends with fine sand paper cures problems.

In their procedure to calibrate battery voltages, they have to apply 6 and 5.6 volt, but don't directly set the battery low mark. So he took a K100D and figured out the exact voltages with a variable power supply:

  • 1/2 mark: 5 volt

  • battery low mark: 4.7 volt

  • shutdown: 4.66 volt

Now this was a sample he took of the self, not one he knew was set optimally, their could still be some margin. But this confirms the samples I tested are real lemons: one shutdown just below 5 volt, one at 5 volt and one at 5.2 volt. The search continues, it seems the Netherlands got a bad batch

This is the little rig I bring to the shop, here shown with full batteries.

The trick is to bring NI-MHs which are depleted to 40% or so and put them in the camera. As soon as the camera shuts down, I put the batteries in here as quickly as possible. Speed is important: as soon as the batteries don't have a load, voltage will rise again, but the measurement will be within 0.01 to 0.02 volt accurate.

It would be nice to know what figures people with a good K100D measure at the point of shutdown.
Some general info:

For a device to work with almost all NI-MHs, shutdown voltage should be about 3.75 volt. To work with most high capacity batteries (say 2300 mAh and above) shutdown voltage must be at least 4 volts. With shutdown at 4.25 volt, choices are already limited to the lower capacity batteries, around 2100 mAh. Some good data can be found at http://www.users.on.net/~mhains/Reviews.html

So when the typical shutdown voltage of the K100D is around 4.66 volt indeed, choices are limited to the highest voltage NI-MHs. 4.25 volt would make many NI-MHs work OK and 4 volt or a bit lower would be ideal.

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