Well, there is a grain of truth in what's been said, in that older Li batteries didn't mind charges that were < 3% or so, as they never counted as a cycle. Note that topping 3% is NOT trickle charging.

Newer chemistries do get bothered by small charges so Nokia has to choose between protecting the battery and letting you leave home with a low battery. They chose 80% and frankly it's fine. Could be 90, but in time battery will lose capacity and when "top" is 92%, it will destroy it cycling it 4 times a night. Also, if you leave it charging and doing something, it could cycle like 20 times overnight.

80 is good, leave it be. If you want to make sure it's full, leave it charging until LED is green. It's full then.

Also, battery charges faster from low to medium than from medium to full, as above some 70% or so the rate drops (Assuming Nokia can charge a battery right, and they do). So top charge at 40% while at work rather than overfilling it to 99.9 at home. 20 minutes in a charger will do wonders. Use a wall wart.

Last but not least, a little rant. Please, before starting a hints and tips page, make sure you check your facts. Ask around. Battery university has a must read.

One note - I leave my N900 charging overnight and I know that it has MORE battery juice than I charge it at night and disconnect before going to sleep. N900 actually uses a charger power overnight.

So, dropping capacity to 80% overnight on charger is strange for me.

The logic behind the first is based on some reports of some devices (Blackberry to name one) that when battery reads 100% it's not really at 100%, it's actually closer to 95%. Which would make sense in this case.

N900 never uses charger power, like other phones, because charger power is too unstable. It always runs off the battery.

ETA: You have a drainer if it drops at 80% overnight. Mine tops at 97 and in the morning it's 86%, but I know why. It used to be 95-92, but with daemons and daemons it started to drain.

IIRC, ESpeakcaller, shortcutd, phone speaker switcher, recaller, battery eye, that where am i thing, all have daemons running. More probably do as well. Also, encrypted wifi. And mail. And IM. And update check.

my theory:
staying connected to the internet is much better than permanently connecting/disconnecting. at least as far as wlan is concerned.
i think the whole process of connecting requires a lot of energy (just like starting your cars engine) so it pays out to keep an idle connection.

not sure if that counts for gsm-internet (especially on 3g), though.

right now i'm connected to my homes wlan for aroud 10 hours nonstop and there is no difference in batterydrain.

Is there some kind of application available that will make a (loud) sound when the battery is finished charging? Believe it or not, but when I'm asleep I can't tell if the little green light has come on to let me know I should take it off the charger.

In fact doing that may be harmful to your battery.

Modern Lithium Ion batteries like those used in Nokia phones such as our beloved N900 don't have memory and don't need to be primed or "trained" like old-fashioned Nickel or Lead-based batteries. It should work to its full potential right away and your N900's battery life during the first cycle should be no different than in the 10th or 20th cycle. You can charge whenever is convenient, no need to periodically discharge, trickle charge, etc. That's battery management of the previous era.

The "smart" chip on the battery tries to regulate voltage for charging and discharging, preventing the battery from discharging when voltage gets low. Sometimes this can be a problem when charging requires the battery to power on (like N900), if the battery is "too dead" it won't have enough power to go into the charging state, but the charger should still be able to s-l-o-w-l-y add charge to this battery until it finally has enough to enter low voltage mode and charge like normal. During this situation the N900 probably wouldn't even indicate that it is charging. So you should really avoid ever running out of battery completely if you can help it.

You should try to always keep the battery full whenever possible, or at leat keep it "not almost empty". Especially if you're turning off the phone overnight or removing the battery for a spare. (Charge the dead battery as soon as you can, don't leave it around for weeks.) Battery percentage remaining is really a guess, voltage is what it's really all about. The battery usually outputs a consitent amount of voltage until it gets close to dead and then it starts to weaken. That's why it may sometimes seem like your battery is on "full" all day and then suddenly declines rapidly. The decline is not linear. There is logic in smart battery systems to try to estimate based on experience that "X minutes at Y voltage means Z energy was used" but from one device to another this varies.

The smart chip also prevents it from overcharging, so there should be no harm in leaving the phone plugged into the charger even when the battery is full. It knows better than to overcharge it. (beware of generic aftermarket battery chargers that might not honor this "smart charging")

Personally, I leave my N900 plugged into charger whenever I'm sitting at my desk, or as soon as the battery indicator is not "full" I will put it on a charger my earliest convenience. I have chargers at work (USB), car, home (wall, USB) so I'm usually near a charging source.

If you have an extra battery you should keep it fully charged and store it in your refrigerator or other cool place. Warm temperature will reduce the effectiveness and lifetime of the battery.

It's also better to avoid rapid charging or discharging, and ideally the rate of charging should not exceed the maximum rate of discharging (but nobody really wants to wait all day for a charge, do they?). So using your USB charger is better than using the wall charger, since the wall charger pumps energy into the battery more quickly. It does of course take longer, but if you charge frequently there won't be as much charging needed, so time is not as important.

At least, that's AFAIK. IANABE (I am not a battery expert)

Since this morning I now leave wifi on ALL the time. I tell you guys I'm now VERY VERY happy with the n900!

Also, you will NOT have to keep charging and unpluging and charge again everytime. Once you have done this 3-4 times the phone will charge to FULL and it will be correct. You can test it by simply pluging again and the phone WILL say FULL.

The phone just needs calibrating with the battery, end of story.

No need, the Nokia charger is smart enough not to keep charging when it is fully charged. When your N900 has a green light, that's because the battery told it that it is full. It also tells the charger, and in this state the charger is using virtually no electricity.

A simple way to illustrate this is to touch the wall plug after your phone has been charging for a few minutes (yellow light), it will be warm. Now touch it after the charging has been done for a few minutes (green light), it will be cool.

Hmm, then I don't get it. Why all the scary warnings that leaving it charging overnight will kill the battery? I was really worried for a second. So I can just plug it in at night, forget about it, wake up in the morning, unplug, no harm done to battery, no electricity wasted?