A storage device stores data in groups of memory cells using vectors corresponding to voltage code codewords, each codeword having k entries. Entries have values selected from a set of at least three entry values and 2n distinct inputs can be encoded into k-entry codewords for some n>k. A vector storage element comprising k cells can store an k electrical quantities (voltage, current, etc.) corresponding to a codeword. The voltage code is such that, for at least one position of a vector, there are at least three vectors having distinct entry values at that position and, for at least a subset of the possible codewords, the sum of the entry values over the positions of the each vector is constant from vector to vector in that subset. The storage device might be an integrated circuit device, a discrete memory device, or a device having embedded memory.