Stationary energy installation (2; 102; 102a; 102b) for powering a load or a grid and/or for storing energy from a load or a grid, comprising: - a battery system for power supply and/or energy storage, comprising at least a first set of automotive traction batteries (6a, 6a') and a second set of automotive traction batteries (6b, 6b'), each set comprising at least a first automotive traction battery (6a, 6b) and a second automotive traction battery (6a'; 6b'), - electric means connected between the battery system and the load or the grid, to adapt the power issued from the battery system to the load and/or the grid power characteristics or to adapt the power issued from the load or the grid to the battery system characteristics, wherein the electric means comprises at least a galvanic insulated component chosen between a DC/DC converter, a DC/AC converter or a transformer, said at least galvanic insulated component being at least a part of a batteries insulation means, and - each automotive traction battery (6a, 6a', 6b, 6b') comprising a ground fault monitoring unit (8a, 8a', 8b, 8b') and a disconnect switch (20a, 20b; 120a, 120a', 120b, 120b') having an operational position wherein the automotive traction battery (6a, 6a', 6b, 6b') is able to supply power and/or to store energy and a ground fault detection position wherein the automotive traction battery (6a, 6a', 6b, 6b') does not supply power and/or store energy, characterized in that the stationary energy installation (2, 102, 102a, 102b) comprises battery insulation means to electrically isolate the sets of automotive traction batteries (6a, 6a', 6b, 6b') from each other and/or against ground, wherein said at least galvanic insulated component being at least a part of the battery insulation means; and the stationary energy installation (2, 102, 102a, 102b) further comprises at least one switching device (14a, 14b) to connect the first automotive traction battery or the second automotive traction battery of the first set of batteries and/or the first automotive traction battery or the second automotive traction battery of the second set of batteries to the electric means. - a battery system for power supply and/or energy storage, comprising at least a first set of automotive traction batteries (6a, 6a') and a second set of automotive traction batteries (6b, 6b'), each set comprising at least a first automotive traction battery (6a, 6b) and a second automotive traction battery (6a'; 6b'), - electric means connected between the battery system and the load or the grid, to adapt the power issued from the battery system to the load and/or the grid power characteristics or to adapt the power issued from the load or the grid to the battery system characteristics, wherein the electric means comprises at least a galvanic insulated component chosen between a DC/DC converter, a DC/AC converter or a transformer, said at least galvanic insulated component being at least a part of a batteries insulation means, and - each automotive traction battery (6a, 6a', 6b, 6b') comprising a ground fault monitoring unit (8a, 8a', 8b, 8b') and a disconnect switch (20a, 20b; 120a, 120a', 120b, 120b') having an operational position wherein the automotive traction battery (6a, 6a', 6b, 6b') is able to supply power and/or to store energy and a ground fault detection position wherein the automotive traction battery (6a, 6a', 6b, 6b') does not supply power and/or store energy,