It's no secret that at iFixit we're pretty excited about Apple-related news. So when a pair of Apple's top iPod engineers left the company to follow their product development dreams, our interest was slightly piqued. When they released a refined, second-generation Nest thermostat, we couldn't resist—it had to be torn down. Opening the Nest revealed a clutch of pleasant surprises. First moment of joy: the thermostat is held together with Phillips screws, handily removed with the included driver. Next, the rechargeable battery is easy to access and replace, with convenient directions printed inside the device. The icing on the cake: all of this great design is nested in a tough steel case, making for a long-lasting product that's both repairable and durable. With these considerations in mind, we happily assigned the Nest Learning Thermostat a 9 out of 10 on our repairability scale.

Teardown highlights:

• The Nest is made up of two primary components: a wall-mounted base that connects to the signal lines from your HVAC system(s), and the snap-on display unit that houses the LCD and controls.

• The base unit is home to ten spring-loaded connectors that let you easily route signal lines from your HVAC system to the Nest: Rc, Rh, W1, W2/AUX, Y1, Y2, G, O/B, Common “C”, and Nest star.

• Noteworthy ICs on the base motherboard:

  • ST Microelectronics STM32L151VB ultra-low-power 32 MHz ARM Cortex-M3 MCU
  • Sensirion SHT20 humidity and temperature sensor
  • Texas Instruments LW051A 8-channel CMOS analog multiplexer/demultiplexer

• Nothing makes us happier than a device with an easily replaceable battery. We feel the engineers at Nest Labs must have been thinking of us when they added numbered flags showing three easy steps for battery removal.

• The Nest receives a constant source of power from your home's thermostat lines, a low-power connection that can't provide enough juice for big operations like Wi-Fi broadcasts and powering the LCD. Hence the 568 mAh lithium-ion battery, which trickle charges during downtime and gives the Nest reserve power to spare.

• The Nest features an auto-away function that can detect when you've left your home and then automatically switch to an "away temperature" to avoid heating or cooling an empty house. This feature is controlled by two motion sensors (long and short range), capable of detecting movement within a 150° field of vision.

• It may look like the folks at Nest cut a couple of corners on the six-sided LCD, but in fact it's a rather remarkable round display, with only the visible portion populated with pixels.

• A quick look at the last component hanging off the side of the motherboard reveals an Avago ADBM-A350 optical finger navigation module, responsible for detecting the position of the outer steel ring. This component works similarly to an optical mouse's sensor, by snapping images of the inside of the ring and comparing sequential pictures to determine position as it spins.

• With all of the I/O connections on the back, the main motherboard houses all of its important ICs on the front:

  • Texas Instruments AM3703CUS Sitara ARM Cortex A8 microprocessor
  • Texas Instruments TPS65921B power management and USB single chip
  • Samsung K4X51163PK 512 Mb mobile DRAM
  • Ember EM357 integrated ZigBee/802.15.4 system-on-chip
  • Micron MT29F2G16ABBEAH4 2 Gb NAND flash memory
  • Skyworks 2436L high power 2.4 GHz 802.15.4 front-end module
  • Texas Instruments WL1270B 802.11 b/g/n Wi-Fi solution

But hey, you don't have to settle for just the highlights. Check out the full teardown.