@Katrina
It seems you intend to run a very long timelapse. I doubt anyone has tested this with a DSLR. Note that cameras are not designed to run for months on end, so it is probable, or almost certain, that it will fail after some days or weeks. And since it is possible to damage a DSLR programmatically, you may not want to try. It may be possible to use a trick long since known for P&S Canons in the CHDK community: if the power switch is set to "on" and power is applied, the camera will go "on". Thus, with a programmable power supply, the camera can be switched on for only the duration required to take a couple of shots or a short video. This works on 550D, but I have no idea if it works on the others. And I have a gut feeling that it a dangerous practice with a DSLR.
May I suggest you consider another, far cheaper alternative: rather than use a Canon DSLR with ML, think of a Canon P&S with CHDK, where long timelapses is a proven and well tested concept. For the price of a DSLR you can get half a dozen of decent P&S. Video quality will probably be not as good, unless you pick one of the high-end models, which are expensive though. But then, are you sure you need video, 20s every day? Why not a still shot, or a few of them, which can then be combined into a nice hi-res timelapse video? If you need further advice on this, ask nicely at the CHDK forum, explaining your project and needs, and a few nice people out there will surely be more than happy to provide you with any general or practical advice.
It seems you intend to run a very long timelapse. I doubt anyone has tested this with a DSLR. Note that cameras are not designed to run for months on end, so it is probable, or almost certain, that it will fail after some days or weeks. And since it is possible to damage a DSLR programmatically, you may not want to try. It may be possible to use a trick long since known for P&S Canons in the CHDK community: if the power switch is set to "on" and power is applied, the camera will go "on". Thus, with a programmable power supply, the camera can be switched on for only the duration required to take a couple of shots or a short video. This works on 550D, but I have no idea if it works on the others. And I have a gut feeling that it a dangerous practice with a DSLR.
May I suggest you consider another, far cheaper alternative: rather than use a Canon DSLR with ML, think of a Canon P&S with CHDK, where long timelapses is a proven and well tested concept. For the price of a DSLR you can get half a dozen of decent P&S. Video quality will probably be not as good, unless you pick one of the high-end models, which are expensive though. But then, are you sure you need video, 20s every day? Why not a still shot, or a few of them, which can then be combined into a nice hi-res timelapse video? If you need further advice on this, ask nicely at the CHDK forum, explaining your project and needs, and a few nice people out there will surely be more than happy to provide you with any general or practical advice.