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01-23-2010, 06:26 PM   #1
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K7 Battery and SDM focus

Just wanna share my little experience on the SDM focusing and K7 battery.

A bit of the background.....
Fully working DA* 16-50 + K7.
Then bought an original K7 grip + 2 after market lithium battery to go with it.

Then one day.....
My 16-50 feels a bit slow in focusing in door. It made a lot of "click" "click" sound, and feels like the sdm motor refuses to turn. Then I started to worry about the dead SDM issue.

Checked battery indicator, and its full... put on the Tamron 17-50, and K7 focused fast and good. So much be the DA* issue?

Since i know I've the original battery in the K7 body, and the after market in the grip, I'll just try another theory. I took the grip off, and put on the DA* again. My DA* spring back to LIFE! Put the grip on, test again.. and the SDM motor doesn't feel like moving again.

So I guess the moral of the story is.... SDM motor seems to be a bit more fussy about the battery we use. Even the K7 thinks the batt is full, I think the internal battery supply voltage might be different.

In the end......
I still use the after market batt in my grip, as I've two. One of them cause problem, and the other one is ok.


Anyone else got similar experience?

01-24-2010, 12:42 PM   #2
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Hmm, not sure about that - but obviously you've just shown a repeatable phenomenon.

Mine hunts at the best of times indoors and is to be expected. Even an f/2.8 lens may find it difficult to accurately lock focus in dull rooms.

On my K20D, whether or not the grip is on the camera, the focusing is the same. Then again, I have the OEM grip and would suggest you get the same for your fine K-7.
01-24-2010, 01:35 PM   #3
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Remember, some of us that have had DA* failure notice that the motor starts to work intermittently. Then if you perturb the lens in some fashion, like moving the rings back and forth etc. it will come back to life again, only to fail later. It is possible that your dismounting and remounting of the lens was just another way to "wake up" the lens. This may be why we constantly read the "I cleaned the contacts and it works again!" recommendation.

Sure it may have been an event related to battery voltage. It also may be the precursor to SDM failure. Just keep an eye on it before it goes out of warranty.
01-24-2010, 10:01 PM   #4
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Yes.. my DA 16-50 needed some "help" initially like moving the rings back and forth to focus.

Then without dismounting the lens, but unattach my grip with the after market battery (and I set preference to use grip first), the lens spring back to life.

Put the grip in, and lens become sluggish in focus.. and need my "help" again.

I've the original pentax grip, and my DA 16-50 is about 18 months old... so no more warranty.

If it died... then at least I'll have Tanron 17-50 as backup.

01-25-2010, 12:29 PM   #5
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OK, just done some experimentation on this:

With my DA 17-70 SDM mounted, tried the following combinations of batteries/Grip:

Pentax in Body, after market in grip
aftermarket in body, pentax in grip
pentax in body, no grip
aftermarket in body, no grip

AF indoors (dark outside, couple of table top lamps on) works fine, SDM moving and focusing freely and effectively. For reference the K7 is on the latest firmware and my aftermarket battery is an INOV8 one.

Last edited by Goliath; 01-25-2010 at 06:57 PM. Reason: Can't spell.
01-25-2010, 05:33 PM   #6
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QuoteOriginally posted by Goliath Quote
OK, just done some experimentation on this:

With my DA 17-70 SDM mounted, tried the following combinations of batteries/Grip:

Pentax in Body, after market in grip
aftermarket in body, pentax in grip
pentax in body, no grip
aftermarket in body, no grip

AF indoors (dark outside, couple of table top lamps on) works fine, SDM moving and focusing freely and effectively. For reference the K7 is on the latest firmware and my aftermarked battery is an INOV8 one.

So this might suggest the OP is indeed experiencing the first stages of SDM failure, since what he describes can't be reproduced?
01-25-2010, 06:22 PM   #7
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Li-ion is always 3.7V

If you're using a Lithium-Ion battery (aftermarket or otherwise) in the grip, I find it hard to believe that low voltage is the culprit. Li-ion is always 3.7V no matter who makes it. I recall Apple recommending that one deeps cycles (fully exhausting, and then fully recharging) its notebook battery initially, and thereafter the power cell could be recharged at the user's convenience.
Not to be an alarmist, but I sure hope you don't have an issue with the power cell (remember the Sony Li-Ion cells that :confused burst into flames)?

Last edited by rfranner; 01-25-2010 at 06:23 PM. Reason: gif didn't work.
01-25-2010, 07:54 PM   #8
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QuoteOriginally posted by PentaxPoke Quote
So this might suggest the OP is indeed experiencing the first stages of SDM failure, since what he describes can't be reproduced?

Maybe..
I'm still optimistic... but if all failed.. I'll try to claim it under my gear insurance :ugh:


After my last post on the mini episode, I tried the after market batt again just now into the grip (after charging it up), and my 16-50 focus as usual.

The K7 battery indicator was full since the last test as well as my new test. I guess the batt was a bit weak when I use my K7 last week, . but the body stilll show full batt indicator.

I didn't bother measuing the batt voltage level, but whats the characteristic of a half depleted lithium? 3.6V instead of 3.7V?

01-25-2010, 07:59 PM   #9
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QuoteOriginally posted by rfranner Quote
If you're using a Lithium-Ion battery (aftermarket or otherwise) in the grip, I find it hard to believe that low voltage is the culprit. Li-ion is always 3.7V no matter who makes it. I recall Apple recommending that one deeps cycles (fully exhausting, and then fully recharging) its notebook battery initially, and thereafter the power cell could be recharged at the user's convenience.
Not to be an alarmist, but I sure hope you don't have an issue with the power cell (remember the Sony Li-Ion cells that :confused burst into flames)?
Yeah , same here! The fact that my screw driver motor still turn fast and sharp didn't make me doubt about my battery level in the beginning. Battery Level was full too.

Lets hope none of those flame business in all our ebay batts.
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