[HW-FIX] losing time/date on battery swap? Replace bupbat
 

some of you might never have known: N900 is not supposed to lose cmos-clock time and date ([edit] and alarms) on every battery swap. It's a tiny rechargable coin LiIon cell backup-battery (next to vibrator and power button) that's supposed to keep RTC aka cmos-clock running during months of main battery removed. Alas all those components break during a 12..24 months of usage, some even leak.
Now for the "bright" side of this story: the battery is easily replaceable when you got some moderate soldering skills (and tools), and using a
YUDEN, PAS414HR-VA5R, capacitor, 0.06F, 3.3V, STAKED COIN Coin Type Polyacene Capacitor https://hbe-shop.de/Art-2112777-TAIY...3V-STAKED-COIN will avoid having it broken again in another 12 months of time. (datasheet)

[edit]my local stock of those ran out, so the following doesn't apply anymore[/edit]
For your convenience I got some of those components as of above, and I'm willing to ship them worldwide via simple letter, for a 3EUR donation per unit to maemo donation paypal account. Contact me via IRC(freenode.net):#maemo or by mail to techstaff at maemo.org, or simply donate and give FULL addr plus your online contact (mail or IRC) in "message to account owner"

some macro-shots (taken with N900):
http://maemo.cloud-7.de/share-service/20130727_001.jpg pointing to coin cell with a red balltip fine pen http://maemo.cloud-7.de/share-service/20130727_002.jpg left black switch is camera trigger, right one (white head) is power button. The huge silver thing below the coin is vibrator http://maemo.cloud-7.de/share-service/20130727_003.jpg also see http://maemo.cloud-7.de/Gallery-N900-exploded/

cheers
jOERG

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Thanx for finding and bringing to us/community.

--
unfortunately my soldering skills are weak weaker ...
last time it was cmos batt on 486 and I dropped a bit of tin into RAM blocks :(, but hey it still ran :)
otherwise I would immediately go for one from you

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

could swap that with a capacitor?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Kondensator _means_ capacitor, that's the whole point, I'd say :-)

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

i mean a smd one , not battery , just one smd capacitor or

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

In theory yes. Though F=As/V, do the math. A 100uF might suffice for some seconds of RTC operation, and a 100uF is already not exactly a small formfactor. 3.6V voltage minimum needed anyway.
/j

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Funny, I got so used to setting date/time after swapping batteries that I assumed this had always be the case.

However, since the n900 is still my main phone (I'd like to keep it like this for the next couple of years to come) and I don't trust my soldering skills, I'm not going to attempt a hardware fix. But thanks for sharing this information with the community.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

good post.
For those considering doing the soldering themself, you should be aware of RoHS. (http://en.m.wikipedia.org/wiki/Restr...nces_Directive)
Shortly, you need higher temperature when soldering this, than with usual lead.
going to ask a good friend myself :)

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

reserve one for me as i cant find one . Long story ...

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

is there a limit per person? I'd like three...

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I got 25 originally. No limit, no volume discount. Donate (of course over-donating welcome) and in that donation paypal form state the number of cells you need, your snailmail addr, and your email or IRC nick so I can contact you. Allow for a week processing time please.

/j

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

i want one as i stated beforehand but cannot donate:)

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

:) donated 20€
Need one :) rest is donation for maemo.org maintanenece
PayPal #: 9W437295L11051929

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I'm sending out 3 standard letters with n+1 PAS414 (+1 for practicing ;-D "Dispose of properly! Please do not litter!")
N.N. By 116 3xxx F. Denmark 2
K.L. z.d.E. 21 4xxxx D. Germany 2
P.P. 1 S.E. O.14 n xx U.K. 4

/j

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

so far I hope I handled all requests. If you "ordered" and haven't heard from me for 4 weeks and not received the batteries already, please ping me joerg at openmoko org.

S.N. Il.gr. T:304 SE-2xxx L. is in the pipeline

feedback in here when letter arrived, in which condition, and how the rework panned out... all HIGHLY welcome ;-)

/j

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I don't mind using my hour/date on battery changes, but I would mind if the battery leaks. Is the hour and date backup the only function of the battery? If so, how easy is it to just remove the battery?

Then again, if I remove the battery I might just as well solder in that capacitor. No soldering experience, though. What soldering equipment would I need to at least remove the battery?

And thanks for providing this information and the capacitors!

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Is it possible for paying using other form of donation than paypal, for those that religiously doesn't use it? IDK, moneybookers, or whatever?

/Estel

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

You need a rather strong iron (some 40W minimum) for that. Unsoldering should be really simple, by pushing a carton or thin steel/alu sheet under the foot of battery cell while heating up the foot until solder melts. Soldering new cell needs at least basic experience with soldering. Ideally you clean the pads (use desoldering braid), (use flux and) wet them with a small amount of new lead solder (~60/40 multicore, max 1mm diameter), then likewise wet the feet of coin, again treat both the pads and the feet with no-clean SMT flux, then make sure you place the coin right way around on the pads and heat each foot until the tin reflows and foot connects nicely to the board. You should use sufficiently hot iron for that or you will overheat the battery cell (yes, since lower temperature causes longer processing time which heats up battery more than a short really hot spike). When you're an experienced solder iron artist, you may get away without flux, and you'll know how to solder that coin so it doesn't overheat. for the rest of you: everybody can do this when you use the right tools and solder and flux. But when you got one of them in the crappy variant or think of trying without flux for example - better don't!

The battery is not needed for anything relevant except RTC. Proof: N900 with broken bupbat work "flawlessly", except for losing date&time on battery swap. [edit] Note that the RTC also stores an alarm that boots up the device from power down when set. Of course this will also get lost when bupbat is defect and you swap main battery!


I hope I managed to process all orders and you all received your bupbat. If somebody didn't, please holler! This is not a planned scam

cheers
jOERG

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I've managed to rip off the positive soldering pad (the bottom side of the bupbat) while replacing it on one of my spares. Clumsy me. I am not too hart-broken about that: it was the phone with non-working telephony that I use only for testing. The old battery was dead anyway, so I have not actually lost any functionality.

Still, does anyone know if there is an alternative pad somewhere else on the board?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Ideally you use TWO soldering irons (or so called soldering tweezers) to unsolder the coin.

C4257
position M8
http://wstaw.org/m/2014/04/15/plasma-desktopTS1775.png
it's parallel to bupbat. It's the only alternative pad.

/j

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

A bit of feedback, nearly 2 years on. I replaced the bupbat on four of my N900s and it worked fine for a while, but I noticed a few months ago that the RTC time is lost again once the main battery is taken out for more than a few seconds. That would suggest that the bupbat has ran out and is not being recharged. Wasn't there supposed to be a fix in the power kernel for that?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

hmm, the charging *should* be enabled per default, afaik. You might want to check the registers, and/or probe voltage on bupbat during and after inserting main battery and attaching wallcharger
maybe useful:http://wstaw.org/m/2015/10/15/plasma-desktopiM9051.png http://www.ti.com/lit/an/swca025/swca025.pdf
actually seems it's not on per default: http://wstaw.org/m/2015/10/15/plasma-desktoppb9051.png http://www.datasheetarchive.com/SWCU050G-datasheet.html

[ SWCU050G – April 2008 – Revised December 2010 p438 "7.4.2.1 Backup Battery Charger"]
I would have expected this getting done by NOLO

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

OK, I made a few tests. Please note that I have the package, whatever it is called, that puts up the "enter date" dialog on boot up removed. My phone boots up straight to desktop every time.

Test 1: Remove main battery for 5 minutes. Put it back, power up. System tme is preserved.
Test 2: Remove main battery for 2 hours. Put it back, power up. System time is reset.

So it looks like the bupbat keeps some charge but not for very long.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

which bupbat you are using? The polyacene capacitor type is not supposed to provide nearly as long a backup as the original LiMg cell. Anyway I'll try to find the data and do the math how long actually

to start with:
http://wstaw.org/m/2015/10/15/plasma-desktopAq9051.png

PAS414 CAP PAS COIN-TYPE 3.3V 0.07F
0.07 As/V * 3 V * 3 V = 0.63 VAs; aka Ws aka J (actually * 0.5 since voltage drops linear with discharge)
0.63 Ws / 7.2E-6 W = 87.5E3 s = 24 h (* 0.5; assuming the capacitor could power the VBRTC domain until voltage = 0, so actually probably another time half of that, ~6h in the end)

Anyway BB_CFG register reset default is 0b00000000, for polyacene cap PAS414 (!!!) I suggest setting it to 0b00011111 as soon as possible during boot

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I am using the ones from you. If this is as expected then fine. I think my test proves that the bupbat does get recharged, otherwise the time would be lost right away and not after two hours. I was under a misconception that an RTC backup battery should last for days, if not years. We used some RTC chips back in mid-1990's, can't remember the type number, that had the battery built in. So clearly not vety big. IIRC, the catalogue page claimed the battery should last 10 years.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Infamous DALLAS chip, had a Lithium battery which had quite a few more Ws than the polyacene. Probably something like 100mAh * 3V = 18Ws. And the clock in DALLAS was less "greedy" than the TPS65950

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Looking for new bup, Tayo Yuiden part is out of production. Could be ELNA DSK-414-HL a suitable replacement?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

yes, looks like a perfect match, though I didn't check the exact specs (millimeters etc), anyway generally it should just work as long as it fits.
Thanks for the pointer
/j

The N900 has a clock backup battery? All these years of ignorance I assumed it was just s lost technology and reseting date/time when changing battery wss a feature. Thanks to this recent activity in this thread I'll see if I can find that potential replacement.

The things one learns every day here!

And digikey stocks the Elna part. Makes it easy to get just one.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

It's probably realted to broken firmware in mine case, but does Nokia N9 got similar RTC battery?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Hi guys

My N900 dont save the time and date anymore after of remove the battery for few seconds adn suppose i need replace the bupbat capacitor coin.

Do you know any store on internet where i would buy it??

I could not find nothing on stock with the info give by @joerg_rw

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

http://www.mouser.de/Passive-Compone...yznegtZ1yzvmag

http://www.digikey.com/product-searc...=0&pageSize=25

http://www.elna.co.jp/en/capacitor/d...f/dsk414_e.pdf looks good

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

For the record, it's `i2cset -f -y 1 0x4b 0x12 0x1f b`.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Looking for a replacement backup battery available today.

Seems to me that there is enough room around the battery to replace it by something slightly bigger.
Did some/one of you replace it recently?
With what?

Finally, after some years experience, li-ion battery or capacitor?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Hah, is there anothner battery? Loosing time and date while removing battery - I thought it as a device character. Are there some other problems if it's dead?

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Yes, another battery. You can see it on the first page of the thread.

There aren't any other problems if it is dead. They all seem to die after one or two years.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

I guess no answer means nobody knows but just to be sure, I bump this:

Do someone know with what we could, today, replace the backup battery?
Capacitor, li-ion? Bigger size?
thanks

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Any battery that has the same voltage?
If you can fit it in there nicely (no stray contacts to other components), I don't see how this could break your machine.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Yes, there is a small battery, about 3 mm across and 1 mm high, as a backup for the system timer while you are replacing the main battery (or the main battery is dead). It is supposedly rechargeable but it is never recharged (rumours are that an updated kernel enables the recharging but this did not happen in my experience), so it eventually dies after a few years.

The only negative effect is that, if you let your main battery discharge (or take it out), then the first thing the phone does the next time you switch it on is ask you to enter the current date and time.

I have been wondering about that too. Particularly the capacitor idea, but the lack of recharging put me off that. Another battery might help, as nonsuch says, but it seemed too much hassle to me to bother.

Re: [HW-FIX] losing time/date on battery swap? Replace bupbat
 

Sure, lot for few. Especially if the battery is not recharged. I thought there was a way to enable the charging by sending some bits somewhere (sorry) with I2C-something. Gotta find and try that. (unless you are sure it doesn't work).
EDIT: oops, instruction in post 33, just above.

On the orher hand, I often remove the battery and am a bit bored to each time.