Here is a site from another fourm I belong to.
http://www.fireflyenergy.com/images/stories/pdfs/FFE-27Grp31BatteryBro10[1].25.07_FINAL.pdf
http://www.fireflyenergy.com/images/stories/pdfs/White%20Paper%2010.30.06.pdf
I wonder what the allowed dod is before it starts causing major damage.