Abstract: Multiterminal, high voltage D.C. power networks in which the sub-terminals are electrically isolated from each other comprise D.C. transformers, as the terminals. Each transformer comprises a large number of efficient, high energy batteries, connected as two separate groups: one group made up of paralleled long strings of series connected batteries and the other group made up of paralleled short strings of one or more batteries each. Each transformer also comprises automatic monitoring, control and switching means for periodically exchanging charged and discharged strings between the two groups, one of which--the "primary"--is connected across the supply lines from the power source(s) for the network and the other of which--the "secondary"--is connected across the service lines providing power to users thereof.

Abstract: If one of a series string of battery cells fails on open circuit, the circuit through all of the cells is broken. An automatic means for by-passing the failed cell maintains the circuit and allows operation of the string to continue (at a lower no-lead voltage). The potential difference across the failed cell is utilized to heat a body of a conductive liquid so that it expands, ruptures the ampoule containing it and fills the gap between two conductors, thereby completing a shunt circuit.