Hi all,
I just wana inform all the people who are building the series cell like bob or tero.
I did try so many different materials and all failed one way or another.
I did now find the "weather resistent EPDM Rubber sheet Plain, 60A durometer " this withstand teperature up to 250 degree and did not deform or be damaged by KOH.
I use this in my series double cell and did drive it realy hard and it is perfect.
It can be ordered from McMaster carr in different thickness I used the 3/16 a sheet of 12 X 24 inches cost $ 16.38. the order # for the 3/16 is 8610k765.
I thoughd it may help
greetings
walt