youd want to get them to a 40% charge (or as close as you can to 40%), and store them in a cool dry place. ego-c to be best of my memory is an unregulated battery, which ends up playing to your advantage. if it were regulated, youd have a difficult time determining remaining voltage. but with the ego-c, all youll need is a multimeter or a voltage tester. deplete the battery to 40% (3.6 volts), then safely store the
batteries for up to several months or more.