I never thought of a bike tube! I have the same gen setup right now. It gets hot after about 2hrs. I have been keeping it around 10amps. Didn't you have to work to get a tube over the cell? Did you cut the tube or use it whole? I tried splice tape, liquid tape, and I have seen what tool dip does. I almost broke down and ordered shrink tubing. I'll go try the bike tube. Thanks!