Sorry about the stupid question: why hasn't any company developed a power source that would permanently replace BP-5L batteries for my Nokia N800? Is that technically difficult or too costly? I would gladly pay $ 50 for the freedom of not needing to buy the replacement batteries once every year or so.

Besides, these N800 seem to last for ages, don't they.

Once a year? Really? I bought my first N900 second-hand in June 2012 and I still use it with the same battery it came with. I find it hard to believe the N800 would be so much worse on the batteries.

I´m still on my first battery for my n900 pre-ordered from nstore and delivered first day 2009. The battery time isn´t the best now but its working.

count me too. Bought my N900 in late 2011 and still using it with the battery it came with and it was also a used N900.

Just because this story seems to be inconsistent with other's experiences I am interested to know if those are Nokia batteries or coming from some OEM like this:

http://www.bestbatt.com/Nokia-BP-5L-.../bbnokbp5l.htm

it was 3 month, since i replace my original battery. still function but not perform good. i replace with battery "flash power" i don't know where is nation that producing it china maybe. ( not be mention in package )

first time i use it, it show only 1150mAH. albeit on the package said 2800mAH. then i try calibrating it using "estelle battery calibration guide" then it show real capacity 1596 mAH. not bad

For the n800 ...I think in all my years I had to delegate 1 battery to "always plugged in " state for the studio...since it finally got to a fully charged level of only under 2 hours. Other than that one battery (which was the original I got +7yrs ago and used every day since)...all the rest of my bp-5l batts are perfectly fine...had them more than 5 years and all show 7 hours.
I do heartily suggest if you have batt consumption issues with the n800 .
1- get proper OFFICIAL OEM bp-5l batts.
2- install cssu, asui, and diablo turbo
3- tweak your power settings
there is no reason you can't have 7hours active/ 10days standby.

As a side note....
I sure wouldn't mind (and I'm sure others as well) having permanent power by wiring and bypass the need for a battery.
Perhaps a cash bounty $$$ would be good incentive to seeing movement and getting it done.(If it can be done... that is...some serious wizardry will be involved for sure....power fluctuation, surges etc...will be an issue for a start...the device wasn't really built for direct wiring ....)

@supergaban, a LiIon battery of BP-5L size claiming to be anything over 1500 mAh is a dead giveaway. It is just physically not possible to squeeze that kind of capacity into something of that size without inventing a completely new technology. It is a fake and you are lucky its real capacity is what it is.

Yup.......veeerrrry lucky. coulda' "boinked" your device.
I steer clear of nxx0 batts. that don't state the proper specs....
let alone "look" different than the proper batts.

I bought some n810 "wannabe" batteries once...they even "almost" looked like proper ones...
but there were visual discrepancies...
the batts. were garbage power-wise.
They can do serious harm to your device too.
Stick to official OEM's my best suggestion.
Or let's find a hardware wizard shovel some coin at him/her to come up with permanent wired solution ...wouldn't mind that (again...hint-hint! )

From the n900 battery thread (one of the gems on the boards), many of us had good experiences with Polarcells. They advertised a high but plausible capacity, and testing showed they delivered.

They make BP-5l batteries.