An emergency system for power failures includes a single-cell or multiple-cell rechargeable battery selected from the group consisting of NiMH, NiCd, NiZn, Ag2O/Zn or lithium-ion, and a charging electronics system that charges the battery, wherein the charging electronics system provides a charging voltage at which the battery does not overcharge at a temperature of up to 80° C., and wherein the charging electronics system supplies a charging voltage at which the battery is transferred into a charging state and/or is kept in a charging state, in which the battery is charged to 5% to 30%.