I actually was making contacts on 40 meters, and as I have noted before, I am using my Yaesu FT-897D that normally I would be running on the internal batteries with 20 watts out max.
In this photo, I have the 897 connected to the 30 caliber power-can sitting just to the left of the radio on the tail-gate.
When connected to the 30 caliber power-can, the radio is capable of 100 watts out.
With the temperature sitting at -16 Celsius, the batteries would be struggling to rise to their full potential.
In fact I found with the band conditions such as they were on this day, I was able to make a number of contacts while running the 897 on the 30 caliber power can with 100 watts out, where as when I was set up to run on the internal batteries and 20 watts out, I struggled to make contacts on this day.
Click on the photo for a closer look.....