Can I replace one battery string without taking the site out of service?

This is now an explicit requirement in the better specifications and it is worth insisting on. NZTA requires that “replacement of any string shall not require removal of the complete UPS or other strings”, with plug-and-socket DC connections and Anderson-type connectors. TMR requires multiple parallel strings, rack mounted, which supports the same outcome. For a network of hundreds of intersections, string-level replaceability is the difference between a routine maintenance visit and a site shutdown with traffic management.