Absorbency testing is used to determine the percentage of ZnCl2 or NH4Cl solution absorbed by a hydroponics gel (HPG). It is found that the absorbency of ZnCl2 or NH4Cl solution decreases with increasing solution concentration. The conductivity of ZnCl2- and NH4Cl-HPG electrolytes is dependent on the solution concentration. A mixture of salt solution with HPG yields excellent gel polymer electrolytes with conductivities of 0.026 and 0.104 S cm(-1) at 3 M ZnCl2 and 7 M NH4Cl, respectively. These gel electrolytes are then used to produce zinc-carbon cells. The fabricated cells give capacities of 8.8 and 10.0 mAh, have an internal resistance of 25.4 and 19.8 Omega, a maximum power density of 12.7 and 12.2 mW cm(-2), and a short-circuit current density of 29.1 and 33.9 mA cm(-2) for ZnCl2- and NH4Cl-HPG electrolytes, respectively. (C) 2007 Elsevier B.V. All rights reserved.