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Rescue the backup (C-MOS) battery of your Pentax DSLR if depleted
Posted By: photogem, 09-01-2023, 03:44 AM

If your C-MOS Backup-Battery is depleted, every time you change (or charge) your battery, you lose time/date settings!


For this I already have started a few threads:

1. Why you should never store your Pentax without main battery

2. Tutorial change C-MOS

3. Maintainance of CMOS battery

One can first try, to charge the C-MOS by setting the automatic "switch off" OFF, i.e. you don't want you Pentax to switch off!

Then you leave it switched ON with a fully charged (and good) main battery for about 4 hours (don't worry, if the main battery goes beyond a certain minimum charge your Pentax will switch off anyway). Sometimes this method helps.


But here a little bit more complicated possibility to rescue this depleted C-MOS/backup battery of your Pentax-DSLR

which might help if the previous method failed:



Use a good (original OEM is best) and full charged battery (if *istD-series, K100D, K200D etc. use something like Energizer Ultimate Lithium AA's)

1. Switch your camera on (don't do anything else with it) and wait for 30 seconds

then

2. Switch your camera off and this time wait 15 seconds

3. Switch on again and wait another 30 seconds (doing nothing else with your Pentax)

4. - 50. Continue this for many times... 50 x is a good idea!

I know this is time-consuming but doing it this way the C-MOS receives an extra surge, the 30 seconds time to "store it"
Doing it this way can help to "awaken the C-MOS a little bit more" and it might keep its charge at last that long to keep your date/time settings
while swapping batteries (which means charging your battery over several hours and leaving your Pentax without battery over this time
isn't a good idea at all, you need 2 sets of batteries for sure... 2 x Li-Ion or 8 x AA)


If this method won't do anything, your CMOS is dead as dead can be.
Then you can use a method which is well explained in THIS THREAD (post # 82 ff)

And for those who want to study the CMOS Data:
MS414 / MS614 / MS621

Last edited by photogem; 09-06-2023 at 12:05 AM.
Views: 2,118
09-03-2023, 11:33 PM   #2
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QuoteOriginally posted by photogem Quote
If your C-MOS Backup-Battery is depleted, every time you change (or charge) your battery, you lose time/date settings!


For this I already wrote a few thread:
1. Why you should never store your Pentax without main battery

2. Tutorial change C-MOS


One can first try, to charge the C-MOS by setting the automatic "switch off" OFF, i.e. you don't want you Pentax to switch off!

Then you leave it switched ON with a fully charged (and good) main battery for about 4 hours (don't worry, if the main battery goes beyond a certain minimum charge your Pentax will switch off anyway). Sometimes this method helps.


But here a little bit more complicated possibility to rescue this depleted C-MOS/backup battery of your Pentax-DSLR

which might help if the previous method failed:



Use a good (original OEM is best) and full charged battery (if *istD-series, K100D, K200D etc. use something like Energizer Ultimate Lithium AA's)

1. Switch your camera on (don't do anything else with it) and wait for 30 seconds

then

2. Switch your camera off and this time wait 15 seconds

3. Switch on again and wait another 30 seconds (doing nothing else with your Pentax)

4. - 50. Continue this for many times... 50 x is a good idea!

I know this is time-consuming but doing it this way the C-MOS receives an extra surge, the 30 seconds time to "store it"
Doing it this way can help to "awaken the C-MOS a little bit more" and it might keep its charge at last that long to keep your date/time settings
while swapping batteries (which means charging your battery over several hours and leaving your Pentax without battery over this time
isn't a good idea at all, you need 2 sets of batteries for sure... 2 x Li-Ion or 8 x AA)


If this method won't do anything, your CMOS is dead as dead can be.
Then you can use a method which is well explained in THIS THREAD (post # 82 ff)
I am sure my K3-1 one is 'dead as dead' after 10yrs. of use nothing I can do to resurrect it, and I believe in normal use with main battery in already extended it's life, unlike my Protrek solar watch the battery is not like normal Lithium and can charge up via solar, I believe it's a super capacitor of some sort.
09-03-2023, 11:57 PM - 1 Like   #3
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QuoteOriginally posted by lotech Quote
I am sure my K3-1 one is 'dead as dead' after 10yrs. of use nothing I can do to resurrect it, and I believe in normal use with main battery in already extended it's life, unlike my Protrek solar watch the battery is not like normal Lithium and can charge up via solar, I believe it's a super capacitor of some sort.
No, it is not super capacitor!

It is a 3V Lithium battery by Seiko!


If you study the other threads supplied: It is all explained there.

I have several Pentax bodies here which are older than the K3: K10D, K200D and K5 but all with functioning CMOS battery.
So one must learn to keep a healthy main battery in the body!
09-04-2023, 09:17 AM   #4
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I have five bodies. Based on algorithm the whole process of renovation will take more than three hours. Still I should find the time and do it.

09-04-2023, 11:31 AM   #5
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None of these things have any bearing on how cameras and their lithium time/date batteries actually work.

The camera does not need to be turned on in order to charge the time/date battery, and in fact, if manufacturers actually mention it in their instruction manuals, they specifically say to leave a main battery in the camera with the camera turned off.

Turning the camera on will not "surge" the lithium time/date battery, and even if it did, doing that repeatedly would not do any good to charge it, and in fact would harm it and reduce its life.
09-04-2023, 06:31 PM   #6
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QuoteOriginally posted by Strangways Quote
None of these things have any bearing on how cameras and their lithium time/date batteries actually work

Turning the camera on will not "surge" the lithium time/date battery, and even if it did, doing that repeatedly would not do any good to charge it, and in fact would harm it and reduce its life.
On the one hand it is sad there is no cheap way to prolong life of CMOS battery. On the other hand I got more then three hours of free time . Still it would be nice to read the discussion with OP to find the truth.
09-04-2023, 07:08 PM   #7
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QuoteOriginally posted by jumbleview Quote
On the one hand it is sad there is no cheap way to prolong life of CMOS battery. On the other hand I got more then three hours of free time . Still it would be nice to read the discussion with OP to find the truth.
Well, whatever you do, don't apply this "advice" to other things and try to "surge" a Lithium-Ion battery on a charger - that can seriously damage the battery and possibly even start a fire.

09-04-2023, 07:46 PM   #8
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As far as I recall my one on the K3 failed at the 7th yrs. or so and it's long enough, it's about the same time I purchased my Protrek solar watch. I did actually see the watch battery completely ran down, and I gave it a couple hours of sunlight to 'resurrect' it, that's why I said it's supercap of some sort, or why not to use supercap as battery on that low consumption device ? it's too much of a task to replace the K3 CMOS battery, so I'll leave it as it is and adjust the time clock every time I change the main battery.
09-04-2023, 07:50 PM   #9
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Doubtful this is the issue, but have you thoroughly cleaned your battery contacts on the battery and in the compartment? A Q-tip and some methanol are pretty cheap and quick so it wouldn't be much of a waste of resources or lifespan.
09-04-2023, 11:10 PM   #10
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QuoteOriginally posted by Strangways Quote
None of these things have any bearing on how cameras and their lithium time/date batteries actually work.

The camera does not need to be turned on in order to charge the time/date battery, and in fact, if manufacturers actually mention it in their instruction manuals, they specifically say to leave a main battery in the camera with the camera turned off.

Turning the camera on will not "surge" the lithium time/date battery, and even if it did, doing that repeatedly would not do any good to charge it, and in fact would harm it and reduce its life.
All your posts in this thread (including your first one which was deleted by the moderatior because it was very rude)
are just based on theory and not "real life tests" / i.e. practice!


Since years many have resorted to the more simple procedure, which is leaving the camera switched on over a longer period and they have have managed to get the CMOS working for this short time so they wouldn't lose date/time settings.

And because I have repaired many Pentax cameras which had aperture-block-failure I came across this problem a few times (because people don't store their camera with the main battery). With the K30/50/500 I replace the CMOS, it sits on the frontside of the mainboard. And yet it is tricky to do the soldering work (I have over 40 years of soldering practice) and I wouldn't recommend it to just anybody. Much more difficult than to solder the wires to the solenoid.
But with the K-S1,2, K70, K7/5/3 and also a few older Pentax bodies the CMOS sits on the backside of the motherboard and requires much more tricky work,
the modern motherboards being smaller and parts very dense/tight. This is why repairshops just replace the motherboard and don't do any soldering anymore.


I have made it clear that it isn't possible to really rescue a depleted CMOS. But sometimes it can be brought back to function enough so that when one changes batteries one doesn't lose time/date-settings. No matter if it.... based on theory... shouldn't be possible.


After all, we know that the replacement of the CMOS battery is the only 100% perfect solution but if one send the camera in, it is very expensive, often the camera is less worth than the costs.


Your argument, that switching the camera On/Off in intervals would be dangerous is again just based on pure theory.

Because then "continuous shooting" would be even more dangerous! Every intense use of a camera is using it up, but we are not speaking of a car or motorbike here, were start/stop is 90% of the total wear (the reason why some switch it off on modern cars if it is possible).

QuoteOriginally posted by Strangways Quote
Well, whatever you do, don't apply this "advice" to other things and try to "surge" a Lithium-Ion battery on a charger - that can seriously damage the battery and possibly even start a fire.
You're mixing things up:

The CMOS isn't a Li-Ion battery but a 3V Lithium-battery cell. Very different characteristics, behavior, etc.!

Nobody has recommended to "practice this method" with a Li-Ion battery and my warnings regarding 3-rd party Li-Ion batteries such as D-LI109, D-LI90
and respectivly their clone chargers always made it clear that one doesn't gamble with Li-Ions.

Nobody will take any remote risk trying to rescue a 3V Lithium battery!

You argue with warnings here which have zero connection to the CMOS battery.
Kind of what is called alternative facts, i.e. arguing with wrong facts.

The only danger with 3V Lithium buttoncells is kids swallowing them.
"Honey, I shrunk the kids.... so they can crawl into my Pentax...."

Last edited by photogem; 09-05-2023 at 11:27 AM.
09-05-2023, 06:12 PM   #11
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Seeing as you have opened several Pentax cameras up, have you used a multimeter to see what current is applied to the clock battery when the camera is off, versus when it is on, and what the peak is when it is initially switched on?
09-05-2023, 07:10 PM   #12
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My K-01

QuoteOriginally posted by photogem Quote
If your C-MOS Backup-Battery is depleted, every time you change (or charge) your battery, you lose time/date settings!


For this I already wrote a few thread:
1. Why you should never store your Pentax without main battery

2. Tutorial change C-MOS


One can first try, to charge the C-MOS by setting the automatic "switch off" OFF, i.e. you don't want you Pentax to switch off!

Then you leave it switched ON with a fully charged (and good) main battery for about 4 hours (don't worry, if the main battery goes beyond a certain minimum charge your Pentax will switch off anyway). Sometimes this method helps.


But here a little bit more complicated possibility to rescue this depleted C-MOS/backup battery of your Pentax-DSLR

which might help if the previous method failed:



Use a good (original OEM is best) and full charged battery (if *istD-series, K100D, K200D etc. use something like Energizer Ultimate Lithium AA's)

1. Switch your camera on (don't do anything else with it) and wait for 30 seconds

then

2. Switch your camera off and this time wait 15 seconds

3. Switch on again and wait another 30 seconds (doing nothing else with your Pentax)

4. - 50. Continue this for many times... 50 x is a good idea!

I know this is time-consuming but doing it this way the C-MOS receives an extra surge, the 30 seconds time to "store it"
Doing it this way can help to "awaken the C-MOS a little bit more" and it might keep its charge at last that long to keep your date/time settings
while swapping batteries (which means charging your battery over several hours and leaving your Pentax without battery over this time
isn't a good idea at all, you need 2 sets of batteries for sure... 2 x Li-Ion or 8 x AA)


If this method won't do anything, your CMOS is dead as dead can be.
Then you can use a method which is well explained in THIS THREAD (post # 82 ff)
So, my K-01 developed this problem, probably because I do not use it much and the battery it was stored with finally completely ran down, and then the internal battery ran down.

I charged up a battery and tried leaving the camera on. No luck. I tried this with several batteries. No luck.

I tried powering it on and off many times. No luck.

Finally, I charged up a battery and left it for weeks, checking it every 3 - 4 weeks to replace the battery before it ran down.

I can now change a battery without losing the time and date.

However, if I leave the battery out for 10 seconds, the time and date are reset. If I change the battery within 5 seconds or so (easily done) it retains the time and date.

I did have a quote from an independent shop to change the part and it was reasonable (around $150).

Last edited by Ray Pulley; 09-05-2023 at 07:16 PM.
09-05-2023, 10:01 PM   #13
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QuoteOriginally posted by Strangways Quote
Seeing as you have opened several Pentax cameras up, have you used a multimeter to see what current is applied to the clock battery when the camera is off, versus when it is on, and what the peak is when it is initially switched on?
Big words!

Why not show us how you do it and you show us how this is to be done with a mainboard unsoldered.

To measure current you have to unsolder one leg of the 3V battery, solder 1 wire to this leg and another wire to the PCB-track.
I want to see how you do this and how you later on unsoldered the wires and replaced the battery against a good one:
HERE
You can see how fragile those PCD tracks are. A tiny bit too much head and they come lose from the board itself. You don't want to mess with those.

Once unsoldering, once soldering, that's about as much as they can take.

So you do it and show it to us!

And I want particular to see how you do it on the board of a K-S1, K-S2, K-70, KP and KF as well as K3 or K1.

What a lot of nonsense!

Last edited by photogem; 09-06-2023 at 01:36 AM.
09-05-2023, 10:07 PM   #14
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QuoteOriginally posted by Ray Pulley Quote
So, my K-01 developed this problem, probably because I do not use it much and the battery it was stored with finally completely ran down, and then the internal battery ran down.

I charged up a battery and tried leaving the camera on. No luck. I tried this with several batteries. No luck.

I tried powering it on and off many times. No luck.

Finally, I charged up a battery and left it for weeks, checking it every 3 - 4 weeks to replace the battery before it ran down.

I can now change a battery without losing the time and date.

However, if I leave the battery out for 10 seconds, the time and date are reset. If I change the battery within 5 seconds or so (easily done) it retains the time and date.

I did have a quote from an independent shop to change the part and it was reasonable (around $150).
The K-01 mainboard is easy to access for the CMOS.

Also independent shops usually charge less.


But your experiement shows that the CMOS is charged when the camera is switched on (which I know is the case)
If the main battery is left in the camera, it does not charge but just keeps the status.
But... because the CMOS is depleted, it tries to charge!
This is the very reason what the main battery runs down quicker with a depleted CMOS.

I have observed this many times.


So one could say, your K-01's CMOS has 1% life left.

But according to @Strangeways you experienced something that is impossible.
You must be a wizzard.


The trick with the electrolytic condenser applies of course to the K-01 as well.
09-05-2023, 11:12 PM - 1 Like   #15
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QuoteOriginally posted by photogem Quote
... But... because the CMOS is depleted, it tries to charge!
This is the very reason what the main battery runs down quicker with a depleted CMOS.
...
The CMOS battery used to keep time and setting does not have high consumption to cause the main battery to runs down quicker by charging it, and I doubt the one used on the camera is rechargeable. It is just like PC CMOS battery can keep running at least for a year, but it could be the CMOS battery short-circuit or damage to cause the main battery losing charge quick.
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