I am shooting a nightlapse (RAW frames, Noise Reduction off) using my 6D with a few images every minute (I use Magic Lantern's intervalometer). My battery was in good condition and was close to full (yet not 100% full) and it took just over a 1000 pictures before dying in a few hours. I know my camera can take more images, and I'm suspicious about the high ISO (10000) being a battery drainer too in addition to 8 seconds of exposure on each frame.
Now, I know that it's mainly the exposure time that drains the battery, but how much does, if any, using high ISO (therefore higher gain on sensor) impact battery life compared to the exposure?
I was using Canon EF 17-40 f/4L @ f/4 and f/4 is not the best choice for nightlapses. I've also got a Samyang 24mm f/1.4 and I know that I can get 8x more light with that lens (though color quality is not the same) but would it be worth it? How much would it affect the battery life if I lowered down the ISO to 1250 with the same exposure time? (I'd like to reduce noise so I'm planning on lowering the ISO instead of lowering the exposure to 1s) Or would it not matter at all and not worth sacrificing the color quality and sharpness of my 17-40 f/4L?