Has anyone measured how much a cell degrades over time, even if they're not being used? There are some studies on batteryuniversity / cadex about this but I wonder if anyone has done so on their n900's -- is it worth stockpiling batteries despite them being perishable?

The cell I'm currently using (an authentic Nokia BL-5J) has LMD of 1029mAh (bq27200.sh) or 1080mAh (bnf), it's got about 2.5 years of use on it as it's been used in my Nokia 5230 before I stared using it in my N900. I think I may need to get a new one sometime - but I wonder if the cells on the market have not been made for years, they must be NOS and likely we're buying these now?

I tested it in practice with ~1500 mAh scuds (bluedream and yellow ones, doesn't matter, as they're same cells, anyway) - after 1,5 years of *proper* storage, capacity loss was negligible. Seriously. Made dual-cell from one such pair, and it gave me ~3400 mAh relative capacity (about 3000 mAh Q10 capacity).

My storage method is to charge them to max, then ASAP discharge to 3.8V (stop discharging when it "touches" 3.8V at Q10 discharge current [Q10 = current equal to 1/10 battery capacity/h), which means it have ~80% capacity. I leave it in this state in room temperature, repeating operation every half year or so.
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I know that theory seems to suggest otherwise, but my practical experiences seems to prove otherwise, so I'm sticking with it.

Also, there are other practical examples of this "tactic" working great for prolonging Li-Ion's life - even during usage. AFAIK, Li-Ions used in hi-tech trains are never charged above 80% capacity, and never discharged below 20%. This gives them extraordinary service life, around 5x longer than for batteries charged to full (i.e. they tend to lose max capacity and increase internal resistance ~5 times slower, than if you "abuse" them to full, 4.2V charging).

/Estel

Hi, sorry for bothering, but is it an error or were the PolarCell's downgraded from 1520 to 1400?

This is a good point the table and the comments at the top of the OP do not match.
One can only guess this was a earlier test?

that's the old test, polarcell looked at the size that could be used after i had them checked to SCUDs, after that polarcell made a new thicker version to match the SCUDs

Got a warranty claim going through right now with a lightly used Polarcell. Failed cell will not hold a charge

Quick message...
I have just bought PolarCell and Battery charger, because it looks like my N900's port is too loose to be used for charging-or-any-data-transfer. However, the battery will not arrive for another week (sigh). Will it be charged at factory, at least? Because this charger will arrive even later, and the genuine-original Nokia's battery is currently discharged (less than 10%; N900 is switched off).
And this is surely a scam, right?.. Too high capacity, too fancy package...
So, what do you think about it? Are the battery and charger reliable? How should I find the best way to repair the loose USB port of Nokia N900? At the very least, I will get a new USB cable with the charger... Next month, when it arrives.
Best wishes.
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Per aspera ad astra...

@Wikiwide you should hold a hot air gun over the usb port and make it damm hot while pressing it down lightly after it cools reniforce it with solder alloy if you cant go to a technecian

what is the average battery life of n900 on heavey usage ?? I get no more than 30 minuts how to find curlpit easy way ? I do have extras devel and lotta huge list of repos. How to check battery consumption ? Btw my battery heates like hell on charging also considerably on usage why ( is it a hardware issue) on the other hand when it try a 800mah it dosent heat that much and usage time is same about 30 minuts on 2000 mah battery i gen get barely an hour whats the problem

You can expect it to be at ~60% of charge, maybe less. Level of charge may indicate how long it was in storage, as "from factory" it have around 80% of charge.

Yes, it is scam, and discussed just few posts ago, on the same page Fancy package shouldn't be considered a sign of fake battery (once, "best" scuds have some most extreme over-packaging for a batteries - a box for single battery, that could hold 10 cells or more...), but capacity *is* such a sign.

Again, using current technology, you can't expect a battery of this size to hold more than 1600 mAh. When new technology will arrive, you won't have chance to "buy" it by accident - price will be 20x or 30x higher, at the beginning.

Charger should work OK, but don't expect it to charge battery quickly. Those things are damn slow (low current). Some tends to heat a lot, too (due to poor implementation of" constant voltage" charging scheme), but the latter improved in "cheap external chargers" market, lately.

As for repairing uSB port, you definitely *should NOT*:

...unless you want to fry other elements, due to heat dissipation through ground plane and via tracks (if not by heat from hot air, itself). To properly repair it, you should use a needle-thin tip for regular soldering iron, a good soldering flux/paste. Apply flux or paste via (another) needle to contact pads and USB port pins, heating your soldering iron in the meantime. You need to have it *very* hot, to do quick job on pins - you don't want to heat them for prolonged time, due to mentioned heat transfer through tracks (which may, and often *will*, damage adjacent components).

re-solder every pin (magnifying glass can help, too), then, you should reinforce port to the ground itself, using normal n(not needle-like) soldering tip. Keep in mind to not overheat ground plane - you need decently heated soldering iron to job quickly, without heating ground for too long.
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Generally, everything you need to know was wirtten dozens of times in appropriate threads, like "fixing USB port, before and after it's too late").

/Estel