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06-09-2015, 06:57 AM   #1
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D-Li90 & D-Li109 Battery Compatibility

I'm a little puzzled by the voltage ratings on the D-Li90 and D-Li109 batteries. The D-li90 battery used in my K7 is labeled 7.2 V and 1860 mAh. The D-Li109 battery used in the Kr, K30, K50, KS1 and KS2 is labelled 7.4 V and 1200 mAh.

The battery grip for the K7 uses 6 x AA batteries, which would provide 9 V (nominal) if they are connected in series. The battery adapter for the Kr, K30 and K50 uses 4 x AA batteries, which provides 6 V (nominal) assuming a series connection. I'm a little puzzled why the K7 uses a lower voltage battery if it needs more AA batteries? Perhaps the AA battery tray uses a parallel configuration of 2 x 3 x AA batteries to get 4.5 V (nominal)?

If I measure a fully charged D-Li90 I am seeing 8.312 V. Just curious. Thanks!

06-09-2015, 07:12 AM   #2
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I think the constant current is more important. The voltage is more tolerable.
06-09-2015, 07:20 AM   #3
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I have a K-30. The original battery is 7.4V (Li polimer I think), but I bought some inexpensive replacements. The replacements are 7.2V (Li ion I think). I have a battery adapter too, I use it whith 1.2V NiMH batterys (4*1.2=4.8V) I think the internal supplay converts everything to 3.3V. The batterys should be messured whith load to get the nominal voltage. If the internal messurement circuit can't guess correctly the type of the battery then it can messure wrong remaining capacity, but the camera should work fine since the input current is enough. The replacement batterys are goes to red very quickly but gives power for hours in this state. So they aren't messured correctly.

The D-Li109 and D-Li90 aren't compatible.
06-09-2015, 07:21 AM   #4
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The cameras have a range of acceptable voltage they will operate on, and provide the ability to regulate the power of a battery source to what it needs.

06-09-2015, 09:20 AM   #5
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QuoteOriginally posted by 08amczb Quote
I think the internal supplay converts everything to 3.3V. The batterys should be messured whith load to get the nominal voltage.
The D-Li109 and D-Li90 aren't compatible.
QuoteOriginally posted by crewl1 Quote
The cameras have a range of acceptable voltage they will operate on, and provide the ability to regulate the power of a battery source to what it needs.
Thanks for the responses. It makes sense that the camera would drop the battery voltage to a lower voltage (probably several) to run the internal logic. I also agree that loading the battery will result in a lower reading. I was just trying to get some idea how close the battery voltage was to the labelled 7.2 V. A discharged battery (camera would not turn on) measured 7.091 V.

I was contemplating the idea of adding a spacer to a generic K7 battery grip, to fit a D-Li109 battery. The terminals on the batteries line up, so the only concern would be any difference in voltage. I haven't measured a D-Li109 battery voltage to see how it actually compares. Obviously the smaller battery wouldn't last as long but may allow me to consolidate to one size.
06-09-2015, 12:43 PM   #6
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If you use rechargeable AA,s you'd get 1.2x6 or 7.2v, which is much closer to the Li-ion voltage. In any case, the tolerance in voltage has always been there.

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06-09-2015, 01:17 PM   #7
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QuoteOriginally posted by Adam Quote
If you use rechargeable AA,s you'd get 1.2x6 or 7.2v, which is much closer to the Li-ion voltage. In any case, the tolerance in voltage has always been there.
Good point on the 6 x 1.2 V rechargeable AA being closer to the 7.2 V D-Li90. There must be quite a bit of headroom on the power input, since it also needs to handle alkaline AA too, which will be closer to 6 x 1.6 V or 9.6 V when new. The Pentax AC adapter also appears to output 8.3 V. I'm going to assume they use a switcher to drop the voltage down, otherwise they will be wasting a lot of battery power generating heat in a linear regulator.
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