This is more complex than you think.
I had charged my phone up full capacity to take out with me for the weekend. I turned power saving mode ON at this point. To allow maximum standby time. Around 10 hours later, after less than an hours use it was flashing low battery. I though that's well strange so I turned the phone off to save it for later use. So I carry on regardless and then turn the phone back on a few hours later. Power saving was disabled at this point. What's interesting is that my battery was full.

Ok, maybe a it was a misreading by the phone ? I don't think so, when I switched back to Power Saving it immediately flashed low battery. When switched back to normal mode, again full battery. So I left the power saving mode OFF and the phone lasted me a further 20+ hours. Until I was back home and charged it. So the power saving feature must hold a "reserve" tank in the battery to use when it's activated. So using the normal power first is great, you then switch to power saving mode when it's low. And it uses the reserve tank of power
Very clever if you ask me, and highly impressive..

when is the next upgrade?? maybe like add turbo already...

N85 Firmware v11.047 Released Available on NSU. Change log:

Quote: New features and applications:
- DVB-H accessory support (SU-33W)
- Nokia software checker application
- Support forNokia MU-44 16GB microSD memory card

Changes/improvements:
- Bad sound quality using BT headsets (CAP 97705)
- Cannot display the video under edit menu (CAP 99698)
- Keypad no response after make call with slide close (CAP 99169)
- Problems with finding contacts starting by "CH" (CAP 97026)
- Music player keep searching new songs when activated (CAP 97082)
- Message type changed to multimedia message (CAP 99880)
- Video recording quality improvement
- Imaging quality improvements, better colours saturation and flash
- Defaul setting change: Closing slide doesn’t disconnect call
- Short slide key illumination applied for Java application compatibility
- "Video call" is shown in Options when highlighting a contact in Space UI.
- Not detecting always wall charger -> Not charging
- 2G cannot connect to GPRS service in some cities in China
- Non stop Music Player "Library update"
- FMTX: The audio is routed to DUT speaker after receiving a message when FM transmitter is transmitting audio.
- Predefined contacts does not support Chinese characters
- APN setting for Vodafone Mobile connect "Promt Password is set to Yes"
- Audio >> downlink quality
- Some of the S60 key presses are not registered by device
- Google Maps application not working with "Vodafone live!" access point
- Network level icon is not shown during VT call
- ITU is not responding when MO is done where slide is closed and opened when call is established
- Long press of Media keys prev/next not working correctly for local videos
- DTMF tones sent from prepaid line to *600 (or *400) are not received by NW
- OFR_pop-up at boot about positioning
- Orange enterprises APN is used by default in the email Wizard
- Pod cast: messed up characters
- All key presses are not registered by device
- E-mail address limiting to max 30 characters
- SMS converting to MMS if more than 20 recipients