A bit late in reply, but there was a guy that had stuff on the wiki page on the battery life
http://garminoregon.wikispaces.com/Back ... ttery+Life although the original data over at GPSfix has gone since the domain wasn't renewed.
But other tips including ones already mentioned are:
- Minimize backlight strength and set it to turn off automatically (Setup>Display>Backlight Timeout>30 Seconds)
- Disable the electronic compass (Setup>Heading>Compass>Off)
- Disable WAAS/EGNOS (Setup>System>GPS>Normal)
- Set tracklog to auto or off (Setup>Tracks>Track Log>Do Not Record)
- Use the odometer or compass page instead of the map page or 3D View
- Set your orientation to North Up instead of Track Up or Automotive if you do use the map page
- Set the battery type set for the right type of battery (NiMH, Alkaline, Lithium)
- Remove the SD card if you are not using it
- Make sure you are running the latest Software
- Don't use brand new NiMH batteries (or cycle new batteries a few times before using them)
For myself I am still using an Etrex 30, and an Oregon 600. I have only used lithium batteries once in the Etrex 30 before switching over to Eneloop low self discharge NiMH batteries. The Etrex 30 and Oregon 600 have different power usage profiles your 550 but as a guide, for a month last year in Nepal I took 8 spare 2400mAH NiMH batteries in addition to the 2 in the Etrex 30 (total of 10). That worked out nicely for 12 days without reliable recharge as the Etrex would do about 18-20 hrs logging before quitting. I also carried a 7W foldable solar panel (Goal Zero) and USB AA charger.
The Oregon 600 has a great wiki page where someone has worked out the power consumption of various features, so you can decide for yourself which ones to turn on/off
http://garminoregon6xx.wikispaces.com/Power+SourcesBut from my recent experience, the battery life of the Oregon 600 was between 10-12 hrs on 2400mAH NiMH Eneloops. So for hiking in Iceland, with the longest stretch off grid about 6 days I carried 12 rechargeable AAs in addition to the 2 already in the unit. Going with lithiums might have been a lighter option given they would have doubled the lifetime, but I've already invested in Eneloops.