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

[joerg_rw]

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

cheers
jOERG

[peterleinchen]

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

[Alecsandru]

could swap that with a capacitor?

[LinuxCub]

Originally Posted by Alecsandru

could swap that with a capacitor?

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

[Alecsandru]

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

maybe an electrolitic one

[joerg_rw]

Originally Posted by Alecsandru

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

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

[BigLebowski]

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.

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

[nokiabot]

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

[pichlo]

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