CREATE TABLE table_40109 ("Capacity" TEXT, "Volts" TEXT, "Temp." TEXT, "Energy-to-weight ratio" TEXT, "Power-to-weight ratio" TEXT)

How many volts has an energy-to-weight ratio of 54 kj/kg to 2.0v?
SELECT "Volts" FROM table_40109 WHERE "Energy-to-weight ratio" = '54 kj/kg to 2.0v'
SELECT "Volts" FROM "table_40109" WHERE "Energy-to-weight ratio" = '54 kj/kg to 2.0v'