If you used a stainless box or tube connected to negative. Inside have positive plates isolated from the box with more negative plates separating them. have a external automotive fuel pump(about 7psi) connected to a outlet on the bottom. have that t out into 2 automotive transmission coolers then piped back into cell at say just below the water lvl. Using a thermoswitch in cell, use it to operate a fan to blow over the rads (note: must be taking outside air to pass through, not engine compartment air). Using a stainless container you have now eliminated the use of a negative lead as mounting locatoin will take care of that. As long as the positive lead is fused there should be no worries for a continuing short if something should happen inside cell. Any thoughts to this design?