text: I have a EP8 setup with the SC-EM800 display. Today, when riding in very cold weather (-15C), the bike worked flawless. But on the way back I could not turn the system on. When pressing the switch (EW-SW300) the display (SC-EM800) turned the backlight on and off a couple of times. Then died. When I got home, I got the bike inside and I managed to turn it on. Any ideas what could cause this? I know the older EP8000 power-button-units had a small battery that could prevent the system to start up in cold weather. But I cant find one on my setup..
  Indeed, it does light up without the battery in it. So it must have som internal battery. However, it does not seem to be replaceable in any way, so leaving this one to be just the temperature being the issue. Which is the same for the older versions.
  Continuing on this, I tried the alternative method of turning the bike on, via the bottle-holder-hole. Unfortunately they have not catered for that on the 2021 Canyon Spectraln. So the Size M frame has the hole about 1cm too low on the frame to hit the button.. Nice. See scratch-mark on battery:
  While this thread is a few years old it helped me troubleshoot my issue with the switch dying in the cold as well on my 2022 Norco Bigfoot VLT 1. I agree it is a design flaw - all the bike's systems should run off the main battery. I ride in temperatures as low as -40 C with this bike and as long as that switch has enough charge in it the bike will fire up and work well even though the components are not rated for temperatures that low. It would be nice if you could pop the switch and disconnect the cable at the switch to put the switch in your pocket to warm it up. The 900 Wh battery holds its own at -40 C, the weak point being the tiny switch battery. I had no idea you could power the bike by pressing the button on the 900 Wh battery. The location of mine is not easily accessible however with the creative ideas I've read here I am able to use a popsicle stick to reach the button on the main battery to turn the bike on when the switch isn't able to in the cold. Not ideal but definitely works!