Yet another long term time lapse post. Well, I recently saw a design for a gizmo having nothing to do with photography, and it used a Texas Instruments MSP430 microcontroller. These chips are ultra low power, to the point that the guy didn't bother to include an ON/OFF switch.
An MSP430 chip in real time clock mode operates at about 1 microamp, at a voltage as low as 1.8 VDC. So it seems you could set up a long term time lapse, perhaps at a construction project, and the 430 would wake itself up every hour during the day, weekdays, then it would power up the camera, which would auto-run a CHDK script that takes a picture. Then the camera power would be turned off again and the 430 would go to sleep until it's time for the next picture.
On my A590, if I hold down the power button, then open and close the battery door, every time I close that door, the lens retracts back into the camera, then immediately extends again. There doesn't appear to be a way to make it stay extended through power cycles.
The problem is that a lot of power is used up running that extension/retraction motor, plus it would tend to wear out quickly if it has to cycle for every picture. So I wondered if there is a Powershot that doesn't have zoom, and perhaps doesn't use such a motor. Or if there's another solution, please post it.
By the way, these TI MSP430 processors are quite remarkable, particularly at a cost of $2-3 each.