BGE reviews several alternatives for a battery open-circuit monitoring device to protect from a dc supply single point of failure. The Federal Energy Regulatory Commission issued Order 867 on Jan. 23, ...

The ct.qmat team have employed the PT symmetry to still make the open circuit system with gain and loss share a large amount of features with an isolated system.

Qucs is a GPL circuit simulator. And if you want the GUI option, you might want to try out QucsStudio, which uses Qucs under the hood, and is free to use, but binary-only.