actually you are right...
there is an exception to non-oem batt's
yup...the polarcell would be the only other option I would safely use.
forgot all about them...
they tend to be pretty consistent with their batteries.
I have one as one of my backup batts for my n900...
not used it much...
I haven't tried the bp-5l polarcell ...but imagine it would work just as good.

Wouldn't trust my device with this bestbatt alternative.
let alone any other ...
sans the polarcell which was mentioned ...
that would be the only non-oem batt I would try.
Even proper oem used bp-5l batteries that have been rejuv'd and rejuiced will get you 94.5% capacity when fully charged (they lose a bit of the top capacity when rejuv'd )....still at the 7 hr in use/ 10 day stand-by ...I've bought a few rejuv'd batts..for the n810....under $10 each with the shipping...work great...no complaints.

Nokia Phones have good battery backup.

That's a tad cryptic....

http://www.youtube.com/watch?v=-08OyPwwFR8

WUT!
Naw...

I was wondering what you were asking for, since I run my N800 from the wall wart most of the time. Then I had a crazy thought and popped the battery out of my running device - and surprise! It went dead. All these years I had no idea it only worked off the charger with battery installed.

Yup...
Old Bessy is great...greater still would be making her battery self-reliant...sooner or later batteries will stop being made for her...and I know I'm not the only one who will be upset when that happens.
Her days will truly be numbered then.
I'd like to see (if possible) even a dummy pass-through battery that is just a "form" (so-to-speak) to take voltage fluctuations and surges ...like a "breaker switch"...and as well to fool the internal protocols ....and so continue using my lovely n800... possibly even the n810..if such a thing can be done for the n800 it can be done for the n810....hell they have "pass-throughs" for electronic cigarettes ...they're common enough...(they plug the pass through into the battery and into a usb port (computer or wall socket port) and puff away without really utilizing the battery charge)....the thing is whether it is do-able for the n8x0....

Oh come on, OF COURSE it is doable. It's just a battery, FFS. It has just two contacts, (+) and (-). Connect a simple 4V regulator to those two contacts and you are set.

I recall someone attempting/ doing just that...
can't remem. the thread(s) ..
There was something else though...some difficulty....it wasn't exactly just that simple ...can't remember what it was though...

When all else fails, use something like this



(Pic courtesy to cheesburger.com)