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Pentax D-LI109 test

Using AA batteries was very convenient, but newer Pentax cameras use special rechargable Lithium-ion batteries. D-LI109 can be used in several Pentax bodies ( K-R, K-S1, K-S2, K-30, K-50, K-70, K-500, ... ).

The original D-LI109 is quite expensive, approx. $50-$60. Replacement batteries are much cheaper, I bought 2 VHBW batteries at ebay for $20 total (including shipping). I wanted the test the batteries and compare the original and the replacement.

Pentax
Pentax 7.8Wh
VHBW
VHBW 6.5Wh

The test

I'm using my K-70 for the test. There are several ways to test the batteries. It would be possible to use interval shooting and create a new image every minute. After that I chould check the pictures using exiftool. This method would create lots of useless images. I was looking for a way to test it without increasing the shutter count.

I was using pktriggercord (my Pentax tethering software) after I connected the camera to the computer using an USB cable. The program can read battery voltage. It returns two values (V1 ├ęs V2), even the well-known exiftool calls these value simply voltage1, voltage2. Probably these are the unloaded and the loaded voltages (V1 > V2 is always true).

The program read the camera status twice every minute, the camera was doing nothing else. I was testing freshly charged batteries. Brand new ones, I was charging/discharging the batteries only once or twice.

Of course this method does not test quite a few things: What will happen after 100 charge/discarge cycles? What is the temperature is extremely low...

Results

It took 6 hours and 15 minutes for the original battery to deplete. I only took 4 hours 42 minutes for the VHBW battery. I've created a graph (using gnuplot) to show the voltage change during the test.

To summerize the results: