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We have many threads here about problems with the socalled back-up battery (memory battery)

One could also call it "CMOS-battery:


This tiny battery, a Lithium 3V Seiko MS414 is located on the motherboard of your Pentax exept the very first *ist-D which had it in a tiny compartment on the bottom of the camera, the most sensible and intelligent but also more expensive solution as you can see HERE

This tiny battery drains slowly because it keeps the date, time and all settings.
It is charged when the camera is switched on but keeps its charge only if its main-battery (either Li-Ion or 4 x AA's) remains in your Pentax!


Sony is the only manufacturer giving clear instructions concerning this battery:
Does the camera have an internal battery?:
The camera has an internal rechargeable battery for maintaining the date, time, and other settings. This information remains saved in the camera regardless of whether the main battery pack is installed or not, or whether the power if off or on.

The internal battery is continually recharged when the camera is turned on and in use
(Different to Pentax! This CMOS battery does not drain with the main battery/batteries inside the camera!)

NOTE: The internal battery discharges gradually if the camera is only used for short periods of time.
If the camera is not used at all for approximately 3 months, the internal battery becomes completely discharged.


I have to note here, that in many Pentax manuals the advice is "not to store your Pentax over a long period with the main battery inside".

Now, times have changed and most laptops, smartphones and similar devices have their main Li-Ion battery built in without being able to swap it!

Think about it: If you'd have a modern electric car, do you want to swap its battery every time you go on holidays (without car)?
Or did you ever take the battery out of your navigator?

The reason Pentax still recommends this is from old days when one used standard non-rechargeable batteries which could leak badly when drained. NiCd and NiMh rechargeables normally don't leak!

I would be more careful with no-name or aftermarket Li-Ion batteries, because I have seen those swelling which indicates cheap interior!

So back to this little memory- or back-up- or CMOS-battery:

To replace it is much more complicated than replacing the solenoid (when ABF hit your Pentax).
I wrote a tutorial for the K30/50/500 and K-r:
Tutorial: Change Back-up Battery Pentax K-30, K-50, K-500 - PentaxForums.com
It is not an easy job, because the two feet of the MS414 are soldered directly onto two thin conductive tracks on the PCB (Mainboard), a little bit too intensive soldering and those tracks go lose. Then there is no chance to repair this, only solution to remove the CMOS.

Other Pentax DLSR's such as the K7/5/3 K-S1, K-S2 and K-70 have the CMOS on the backside of the motherboard!
K7/K5 and K3 use the SEIKO MS518 which has almost double the capacity of the MS414GE.

HERE a photo of the K5 motherboard, the C-MOS battery. Similar soldering as with the K30/50 and K-r.

But on the K-S1, K-S2 and K-70 you don't want to solder at all on that tiny cramped mainboard.
I'd think Ricoh might change the complete mainboard if they have it for repair.

The CMOS battery holds it charge quite well over the first years, but like every electrical part and particular those containing Lithium they age and then drain quicker, but if not depleted, they do last quite a long time.
But if once depleted, will they not only try to charge and thus drain the main battery but they cannot "be healed" anymore.
This means every time you swap the main battery you lose date/time and your settings!

If you have complex settings, it is a pain then having to repeat this every time you need to recharge your battery.

What has to be done is to check regularely (every 2 month but also depending on climate, i.e. temperature) the charge of your main battery and
recharge it if you don't use your backup camera often and just store it. So it is with my old K10D. I hardly use it but anymore but I value it. Maybe it is some sentiment but I just don't want to let go of it. So every 2 month I check it and use it a little bit.
(Good news with the K10D and K20D is: Those are the only semi-professionals made by Pentax which use the Japansolenoid and here not using them has no affect on the solenoid, it works like a mechanical precise Suisse watch i.e. perfect!)


If your CMOS is depleted, you can try a few other methods, sometimes they work
(Me myself and others I know personally have tested and tried all those methods and no matter what anybody tries to suggest out of sheer theory, there is no danger with any of those methods for you camera!)

1.
a) In the Menu wrench-symbol: Auto Power Off: Off (so it won't switch off)
b) Leave your camera switched ON for several hours (don't worry, it will switch off automatically if the battery's voltage is too low to not endanger the battery!)

Maybe repeat this again.
Often this method will help to charge the CMOS at least to that extend that when you quickly swap batteries, it will hold your settings!

If this method won't work, try this:

2.
- plug in a full charged battery
- switch your Pentax on, do nothing but wait 30 seconds
- then switch it off and wait another 15 seconds
- switch it on again: Another 30 seconds

repeat this about 50 x times!

This will give an extra surge to the C-MOS battery.
Because there have been reservations towards this method from one member (without having ever tried it) in another thread:
No, there is no danger to your Pentax, but of course switching it 50 x on is a eeny weeny tiny bit more wear on your Pentax, basically the same as if you would have used it

50 times more during its lifetime. Is that a lot of wear? With a little bit of logic this question answers itself and any "warning" not to practice this method is based on imagined fear.
Everybody who knows me in this forum through the ABF / solenoid failure researches knows, that I do warn of misuse in many respects but here a warning is completly out of context!


If this more time-consuming method won't work, here is another solution, which works very well:
*ist DL and batteries? - Page 6 - PentaxForums.com

But with all those methods you must remember:
Your CMOS battery will suck energy on your main battery because it continuously tries to charge. You will notice that your main battery will need to be charged more often and... particular when you store your Pentax over a longer period: Check the status of your main battery regularely!
The main battery does keep the CMOS from discharging even so the charge current when the camera is switched on is stronger!
And yet the CMOS (if depleted!) sucks more on the main battery compared to a healthy CMOS. This I have verified with older Pentax DSLRs using AA's as much as with those using a Li-Ion main battery! And no, I have not and never will measure the different currents on the CMOS because this will need extra soldering on the mainboard so I can place either a multimeter or an oscilloscope in series to measure quick current-changes. As Ricoh/Pentax repairshops won't unsolder the CMOS on a mainboard but replace the complete mainboard, why should I then take the risk to destroy a mainboard?

Here another hint for the main D-LI50/90/109 battery, it it is completly depleted:
!Use a 3.rd party charger!
I have noticed a few times, that a Li-Ion such as the D-LI109 and D-LI90 when completly discharged would not be charged anymore by the original Pentax D-BC chargers. But when I charged them on a third party chargers it worked and then those batteries were o.k. again! The D-BC chargers by Pentax want to read a minimum voltage which the batteries don't have anymore. But the 3.rd party chargers accept a lower voltage to start charging and thus can restore a battery to full function again.

[grhazelton]

Okay, how about whatever powers the display in my Pentax 645n, and I presume other members of the roll film Pentax family? Are there 35mm SLRs by Pentax with LCD displays, what's the word with them?
I think it thoughtless that Pentax would require a virtual tear-down of a camera to replace this button cell

[photogem]

Okay, how about whatever powers the display in my Pentax 645n, and I presume other members of the roll film Pentax family? Are there 35mm SLRs by Pentax with LCD displays, what's the word with them?
I think it thoughtless that Pentax would require a virtual tear-down of a camera to replace this button cell

Completly different theme/issue/circuit
This thread is for the CMOS backup cell in Pentax DSLR
Because they are digital and have a stored firmware/operating-system.
The first one was the Pentax *ist-D which still had a circular cover at the bottom of the camera for its CR2016. I know of Nikon DSLR which had it similar but in the battery-chamber. One could still replace it. Due to size/weight/costs this sensible solution was abandoned.

For some film Pentax one had the Pentax Data Back with it's own battery:
https://www.amazon.com/Pentax-Data-Back-ZX-10-PZ-70/dp/B00005ABA2

[rojogannon]

Hello.
My recently purchased Kr has a dead cmos battery. I'm not bothered about the date but the battery is also still trying to draw power from the main battery which therefore loses it's power over two weeks or so when camera is not used. The seller agreed to chop 50% off the original price rather than repair it as the repair cost
was far greater than the value..
I love the camera ( I like the colour blue!) but I don't want to take it apart so my question is what is the best way to use the camera conveniently without losing too much power as I use it. I wonder if there is anyway to stop the cmos battery from trying to recharge ( maybe going into support mode ) or is it a case of accepting the batteries have to be removed after each use ? If there is a clever way of retaining power without having to remove the battery I would love to know. I thought that if I bypassed the date setting request screen then at least the date would not progress but stay put at initial date and time. This was the case so I thought maybe that would save some battery use but of course the difference was minimal so that didn't really work.
Any suggestions would be much appreciated.

[photogem]

There are 3 options:
1. (which you don't want): Repair (I can't remember were the CMOS is located on the K-r, only disassembled one once or twice)
2. Everytime you put the K-r away, take the battery out (and lose time/date, meaning you have to press the shutterrelease button once, then the quest for adjusting time/date is gone for this session)
3. Leave the battery in and accept its drain: It could be that your battery has aged itself, the K-r was the first to have the D-LI109 and thus it is now
over 10 years old, not a bad time. So either a new (but original!) D-LI109 or the adapter and use it with strong Eneloops which the K-r anyway likes

[kypfer]

Hello.
My recently purchased Kr has a dead cmos battery. I'm not bothered about the date but the battery is also still trying to draw power from the main battery which therefore loses it's power over two weeks or so when camera is not used. The seller agreed to chop 50% off the original price rather than repair it as the repair cost
was far greater than the value..
I love the camera ( I like the colour blue!) but I don't want to take it apart so my question is what is the best way to use the camera conveniently without losing too much power as I use it. I wonder if there is anyway to stop the cmos battery from trying to recharge ( maybe going into support mode ) or is it a case of accepting the batteries have to be removed after each use ? If there is a clever way of retaining power without having to remove the battery I would love to know. I thought that if I bypassed the date setting request screen then at least the date would not progress but stay put at initial date and time. This was the case so I thought maybe that would save some battery use but of course the difference was minimal so that didn't really work.
Any suggestions would be much appreciated.

Exactly as photogem has described ^^^
My K-01 "forgets" it's date and time whenever the main battery is changed and the main battery discharges a lot quicker in my K-01 than either of my other cameras with a D-Li90, when stored.
I have a spare battery which I use as necessary, but in the case of the K-01 I don't leave the battery in the camera when unused, so I've always (usually) got a usable battery to put in the K-01 if I want to play with it
All of my other cameras are stored with batteries fitted, but are checked fairly rigorously, every couple of months or so.
Any batteries that need recharging are dealt with at that point … none of them, including the AA's where applicable, will have gone totally flat in that interim, so no clocks need resetting
For my purposes, I don't consider having to reset the clock occasionally to be a problem … just "one of those things" that needs to be accepted when using older equipment.
Agreed, having to effect a fairly major repair to replace a known-to-fail component might be considered a design fault, but, in the wider scheme of things, these 'CMOS' batteries do have a life expectancy in excess of 10 years, when used regularly (my *istD S, bought new in 2005, is still totally reliable!)

[rojogannon]

Great ideas thanks photogem and kypfer.

I'll go for the same option but although I have eneloop batteries and holder I may decide to use pentax lion battery . I have two of these so keep them charged in the bag and pop one one in when I want to use the camera. I can probably afford to keep battery in for the rest of the day and take out at the end of the day if there is still juice left. Then charge up ready for next time. The only reservation I have is that the pentax batteries lose charge over time whereas the eneloops last longer in that respect. So I'm not totally decided yet I'll just have to play it by ear. Also I'll set the time etc as that can be useful because it only takes a few seconds.
In a way I'm really pleased just to accept the fault since I gained the use of the camera for an extremely cheap price given the partial refund. I've used this retailer before and they have been extremely good for after sales service. If anyone wants to know who they are then I can give a reference. Some in UK might even guess.

[photogem]

Agreed, having to effect a fairly major repair to replace a known-to-fail component might be considered a design fault, but, in the wider scheme of things, these 'CMOS' batteries do have a life expectancy in excess of 10 years, when used regularly (my *istD S, bought new in 2005, is still totally reliable!)

It is so, they can live longer than 10 years but only if the main battery (AA's for the *ist-DS; K100D, K200D etc) stays in the camera when stored away.
And even then one has to check every time and then that the main battery isn't depleted.

Because the CMOS is Lithium, as soon as it is below a certain voltage, it is lets call it "hurt". One can do something to bring it back to life but not to it's original state.

[rojogannon]

Is it worth the effort to bring it back to life? Which method has been proven to work best?

[photogem]

Is it worth the effort to bring it back to life? Which method has been proven to work best?

It might be worth because then it holds charge just for the time you need to exchange batteries.
See main post and post #11

[rojogannon]

Yes but would this process render the cmos battery charged to the extent that the main battery is no longer depleted whilst sitting in the camera because it is constantly trying to charge the cmos battery?
I for one am not at all bothered about having to set the time and date every time I change batteries. What I am really bothered about is finding that the main batteries are depleting whilst sitting in the camera. I don't believe there is a solution for this that avoids opening up the camera and replacing the cmos battery.
Unless there is a way to charge the dead cmos battery into fully charged life then I must accept that I must take the main battery out of the camera when I store the camera because I am not willing to open up the camera.

[photogem]

That you need to find out by try and error.

[Fluegel]

Of two K10d bodies with failing CMOS batteries I managed to restore the BU battery in one of those bodies.
A friend in Australia also tried to charge the BU battery of his K10d without succes.

It looks like bodies that were left long time without charged battery will not pick up any power in their BU batteries.
I am happy the BU battery in one of my two K10d bodies could be saved.
From now on I will keep bodies that I do not use fitted with a fully charged battery.

I thank photogem very much for his explanation of the memory system in our cameras.

[The Jannie]

Photogem: thank you for sharing your knowledge once again. My question is - can you tell me of a supplier of MS414GE? I'm waiting for the arrival of a (new to me) K-R which needs one but am struggling to find a supplier - UK, Europe or USA would be fine as I can trade with those easily.
bfn
David

[photogem]

https://uk.farnell.com/seiko-instruments/ms414ge-fl26e/battery-button-lithiu...eRedirect=true
MS414GE-FL26E 3V 0,5mAh batteria Lithium Rechargeable Battery -POSTA1- | eBay
just google Seiko MS414GE FL26e

[The Jannie]

Photogem: thank you again. I had checked fleabay and searched and found Farnell. Unfortunately any link I found seemed to want to sell me hundreds of them! Once the K-r arrives and I've tried all your recommendations I'll be able to put the link you gave to good use.
bfn
David