Abstract: There is disclosed a method for preparing enveloped plates for batteries which comprises introducing an active material composition into the porous envelope of an enveloped plate when the envelope is assembled on the current conducting element of the plate characterized in that the active material composition is introduced into the envelope as an aqueous slurry, which has a degree of sulphation in excess of 50% and a rotating vane viscometer torque value (as herein defined) of not more than 0.2 lbs ft. at 20.degree. C, the said aqueous slurry being introduced into the envelope at a pressure of less than 5 psi until the envelope is filled with the composition, liquids issuing through the walls of the envelope, the pressure then being allowed to rise to a value above 5 psi but not in excess of 70 psi, the pressure there after being released. A variety of suitable active material compositions are described together with apparatus for carrying out the method.