i just rebooted, before I did the built-in battery expectation was 1day idle or 2 hours use, has now dropped to 1day/1 hour. The estimation of a reboot = 4 hours idle seems reasonable. We all have different configurations and applications, and no common language or tool-set to measure battery use. I am sure mine is worse because of my wireless router, and plan to reinstate my old WRT54G. I re-flashed, installed no software, took out my memory cards and by far, the biggest influence is connection to my SMC barricade, apparently a crappy router. What routers do other people have?

Incidentally, another piece of research says a cell-phone battery has a life of charge/drain cycles (or absolute total current of discharge), and since the N800 runs off the battery, even when charging, leaving it in standby WiFi-connected (looking for e-mail, updating RSS) and charging overnight, is wasting battery life.

I never ever shut it down, but because of a different reason. I have burned myself (several ) times by not having enough juice to boot up the unit, which in turn sent it into a nasty boot loop. I'm pretty certain there was enough ENERGY in the battery but am not really sure how the Power Management section reacts to the high-draw case of a boot with a far-less-than-full battery.

For example, I had 20% battery power, and the power on did not manage to go through. If there really WAS 20% in the (2 months old) battery, that would have been also a quited heated event. So why risk, just leave the thing on, it's <10% through the night anyway.

SD cards seems to be the problem for my battery drain in idle/standby (offline) mode. I removed all of my user installed programs. This had no affect on saving battery power. Nokia N800 would only last 2 days in idle/standby (offline) mode, even with no user programs installed. I then removed both of my SD cards and there was basically NO battery drain for 7 days. Battery lasted 16 days and probably could have gone another day for 17 days in idle/standby (offline) mode. Using two Kingston Elite Pro 2GB 50X SD Cards. I've seen other threads that say Kingston are good cards for battery usage.

http://talk.maemo.org/showthread.php?t=29146

There are only three or four companies in the world that actually manufacture SD cards: Panasonic, SanDisk, Toshiba, and possibly one more. Kingston--and everyone else--is just applying stickers to what they buy in bulk from one of the real manufacturers.

So, Kingston almost certainly switches up manufacturers for different models of card depending upon available deals from the manufacturers and what quality/speed/price point Kingston wants to hit with a given model. In fact, I'd not be surprised if the manufacturer of one particular model of Kingston card changes over time.

Also, the latest, fastest card from a given manufacturer is almost certainly going to draw more power than a slower card of the same capacity from an older line from the same manufacturer.

In the end, it's impossible to say that all cards from a given company have a given trait such as sipping power.

Don't want to get off topic. My only point is SD cards can affect battery life in a major way. The other threads indicated that cheap unknown SD brands may have problems related to battery life. (Why is the real question and what if anything can be done about it.) They were saying Kingston has high quality and tests and checks everything they sell. They also were saying it had to do with software on the SD card related to sleep mode. Not sure if this could be true or not. Kingston has a Co-Logo program where they design and apply labels with your brand name to bulk purchases. So if Kingston is good these would be good also.

Kingston Technology Company, Inc. is the world’s largest independent manufacturer of memory products. Kingston designs, manufactures and distributes memory products and Flash memory products. Kingston has established five manufacturing facilities around the world to meet the needs of the memory market on a global scale. These manufacturing facilities are strategically located in the U.S., Taiwan, Malaysia and in China (Shanghai +Shenzhen ). Each facility serves the memory needs for Kingston and the top tier system manufacturers that employ Kingston to make their system memory. Kingston has more than 50 state-of-the-art Surface Mount Technology (SMT) lines that build more than eighteen million customized modules each month for servers, desktops, notebooks, workstations, printers, personal digital assistants (PDAs), hand-held PCs, graphic cards, digital cameras and cell phones. Kingston has the world's largest memory module manufacturing facility in Shanghai, China.

iSuppli ranks Kingston as world's number-one memory module manufacturer for the third-party memory market for the fifth consecutive year. Kingston receives Intels Outstanding Supplier Award for Exceptional Support, Quality and Timely Delivery of FB-DIMM Products. Kingston released the world's first 128GB USB Flash drive. The 128GB drive is build-to-order only.

I set up the Linksys WRT54G v2 yesterday and had the N800 online, in standby for more than 8 hours with negligible impact on the battery, then able to download and play TWIT podcast this morning. Connected through the SMC7904WBRA2 would see the battery drain in four hours. (The Linksys provides the wireless access point; it is connected to the SMC which still supplies DHCP and Internet gateway routing etc).

No, it's not that easy. What a light bulb does is mostly convert energy into heat. You can make electronic devices which consume 150W and don't convert that much energy onto heat, but in something else.

Actually, no. Energy can never disappear or be created, only converted to some other form of energy. Doing that it might do some work for you, but work by itself (i.e. calculations) is not energy. Electronic devices only have limited options here, so almost everything is converted to heat energy. A little bit may be converted to chemical energy (charging the battery), an even tinier bit may be stored in capacitors on the board, but then you're out of options.

A proportion will be RF EM energy...

Indeed, that's true. Still tiny though.. the wi-fi transmitter transmits up to 100mW, and some of that will be heat too. The BT transmitter even less. The N900 can transmit some power through its GSM radio. Some photons escape via the LCD screen and won't become heat until they're absorbed by a wall or something.