Hello Fallingwater,
Let me see if I can clarify...
Both NiCd cells and NiMh cells prefer to be stored in a discharged state. You can also short out NiCd cells, after discharging them, and store them that way. You can not do that with NiMh cells.
A completely discharged NiMh cell will often have a open circuit voltage in the 1.0 - 1.2 volt range. If the load is heavy, they will show 1.2+ volts. If you leave the cell connected to a circuit, it will not only drain the battery, but also drop the voltage down. This very low voltage condition is one of the things that ruins NiMh cells. You end up with a "completely" discharged cell with a reading of 0 volts.
Self discharge is associated with capacity. Over the course of a year, a NiMh cell will loose nearly all of its initial capacity (healthy cells will loose 75 - 80% of their capacity), but it will still show a voltage of over 1 volt. When you purchase new NiMh cells, check their voltage. If they are below 1.0 volts, send them back. They have either been stored improperly, or they are old stock.
To properly store a NiMh cell, discharge it to 1.0 volts at 1 amp and store it that way. It is best to cycle the cell through a charge/discharge cycle every 30 days, but you can let it go for as long as 6 months in a discharged state before real damage starts to set in.
I just checked some cells that I had in storage for 4 months. The cells were stored at room temperature. I discharged them at 1 amp to 1.0 volts and after 4 months they still have no capacity left, but have voltages in the 1.15 - 1.18 volt range. I feel that 4 months is too long to go without cycling them, but in this case it was unavoidable. I am hopeful that a couple of charge/discharge cycles will restore them to their initial "vibrancy."
Tom