Water electrolyzer stacks are a key component of regenerative fuel cells, designed to replace batteries as a means of storing electric energy on the lunar surface. The delivery of a 2,000 psi balanced pressure, lightweight prototype electrolyzer is proposed. The cell design will be significantly smaller and lighter, and capable of higher pressure operation than previous aerospace electrolyzers designed and built by Giner Electrochemical Systems, LLC. The successful completion of Phase I yielded test data, trade studies, a thin frame design, and model enhancements that would provide the basis of stack sizing. In a Phase II program, an enhanced, 2,000 psi test stand will be created by upgrading the existing 1,200 psi stand. It will then be used to demonstrate thin frame designs, the robustness of internal components, and the innovative prototypical compression hardware at realistic conditions. Further advances in thin frame technology will be investigated, and additional analyses of a new thermoplastic material will be conducted with the prospect of using them in the deliverable if these technologies are ready.