My camera's is about 2% less efficient (power input wise) at 2.4 V than it is at 3.15 V. You seem to have a way bigger difference there (1.38 W vs. 1.2 W)... are you measuring the current you're supplying to the camera or the camera's input voltage (cable and current sense losses removed)?
Measuring V and I at power supply regulator end of 25cm or 80cm cable to camera.
That's why I'm taking a break, cam is running a timelapse script test for some hours yet. Ended up with too many variables and my mental model needs some forgetting
I've got the current sense in series with the cam 3V, so there's 50mV/A to account for there. Now I have two cam 3V cables, one is 25cm, other is 80cm, so there's a V drop for that. From memory about 1mV/cm at cam record active mode in chdk, assuming the cam Batt mV readout is accurate.
I now have the DPO calculating output voltage - shunt loss (no differential input), but I need to take a cable resistance measurement as well, tell the cam to show Batt mV in play mode.
While using the lower current shunt resistor and shorter cable stopped the cam shutting down when switching to record mode from play mode, it did not change the cam's refusal to ''load firmware'' at low voltage -- hence my conjecture on the firmware Batt mV safety factor.
So I need to take more care in measurements -- that's why I like taking the screenshots, others can then spot an interpretation boo-boo as long as I accurately describe how the measurements were taken.
Yesterday I also failed to create a bootable SD
I think cardtricks-144 is broken on Win7rc, as I had trouble getting a580 dump recently too. But there seems more to making SD bootable than writing 'BOOTDISK' to 0x40 in MBR (from linux), as all I got was 'Card Locked!' Maybe it has to be 'BOOTDISK',0x0? Yet to try that. So I was unable to check power up into CHDK mode. But my recording of power up in play and load firmware showed no great increase in power consumption loading the CHDK and rebooting -- nowhere more than half record active mode power.
And yes, there's no appreciable difference powering up in record mode or switching to record mode from play mode.
could very well explain why more than a few people think CHDK makes their cameras consume more current
CHDK does not obviously draw more current, but there are things people could do to extend battery life. Using the CHDK menu from play mode will consume about a third of the power compared to being in the menu from record mode. It's not the LCD or backlight consuming the power, rather, it seems the cam's 'live view' accounts for two-thirds of the power in record mode (Edit: supported by temperature increase in CCD indicating power consumption). Play mode power is not very different from record mode idle (within 25-30%). This too is supported by the long play time battery life seen in the camera's specification.
So yes, there will be a followup, maybe later today or tomorrow, I have the DPO on extended loan, lots of time to play