After the sudden, unexpected death of my 770, I got myself a used N800 - about one year old, good condition, not used very often AFAIK. (I know the person who sold it, I really think he didn't use it much... He wanted a simple video player and PIM, so he wasn't too happy with the N800.)

Although I have no exact figures yet, my impression is that battery life is really bad. I use the thing in the evening, activate offline mode while I sleep, browse a little again in the morning, activate offline mode again and find it dead when I come home from work. Sure, I play a lot with all the new Diablo features, but still... It's worse than I expected, even after reading that the N800's battery life in general isn't as good as the 770's.

What do you think? Is there a chance that the way the device was used (or left unused half-charged) ruined the battery? Is it reasonable to assume that a new battery would be worth the money? Or would you think that this is just what you get from an N800 and my expectations are too high?

My 1.5 year old N800 has a battery as good as new, as far as I can tell. But I'm careful of not discharging it too deeply - I generally charge it as soon as it drops one bar.

If the battery has been discharged a lot it could well be that it's been quite degraded after just a year. I'm still on OS2007 so I can't tell you much about what to expect of capacity from Diablo, but I only see battery suckage if I a) run the internet radio, or b) stay connected to a weak-signalled AP, or also APs with poor power savings management. With the signal at work I can stay on for a couple of days no problem. Oh, and c) metalayer-crawler could run amok now and then in OS2007 so I disabled that one, but that must surely have been fixed in Diablo.

If you've got all suspicious battery-sucking issues out of the way and still see bad capacity then it's probably a good idea to invest in a new battery.

I have an older N800 and leave it on and charging during the day at work. I use it each night for 3 hours on battery power useing wifi.

My original Nokia battery got weaker after 6-7 months frequent use. Now I have a cheap chinese battery from ebay and happy with it. If it fails, get a new one, costs almost nothing anyway.

at the moment it's almost as if battery life gets better the more I use the device. Of course this is highly subjective as the way I use it differs each time, but... I remember having read somewhere that these batteries need to be fully charged a few times at the beginning. Maybe the previous owner never did this but only half-charged it each time...?

These batteries (modern lithium-ion or lithium-polymer) aren't supposed to need initial charging cycles to reach their full capacity - although some say it got better after one initial charge cycle. That's not true in my experience though, my thinking is that if it gets any better it's due to _any_ initial charging, no deep-discharge necessary.

But note that (and here's where it's easy to get fooled) it doesn't take long to charge a lithium battery to apparent 100%. But it's not full then. It needs to stay at that point for quite a while (it could take 10 minutes to go to 100%, but 1.45 hours to _really_ get there). It's full when the device says its full (tick the battery icon), not before.