Several chargers like this built by the author of this article thus far used miniature Siemens mobile phone charging adapters (switching power supplies) able to output 5-10V of unregulated DC voltage while producing up to 0.4A of output current. Older AC/DC adapters containing 50Hz transformers (standalone AC/DC adapter “cubes”) should work equally well with this circuit. As has been noted, using stabilised power supplies such as 5.0V USB power or ever more popular standalone 5.0V AC/DC adapters that mimic a USB port (cunningly used for recharging various handy devices) will prevent red LED from turning on after the charging phase is finished, but there are ways to enable this as well. We hope that creative readers will find this a challenge and devise new and better circuits.