I studied mechanical engineering in college, so electrical engineering isn't my strongest suit. Basically I have a 12V car battery that I need to discharge to 70%, how can I do this? I know that I can monitor the state of charge by determining the open circuit voltage after ~24 hours of non-use of the battery. So a fully charged battery would be 12.6V after 24 of no usage. Now, obviously a fully discharged battery will not read 0V or will it? If that is the case then I can just do 12.6V*(0.7) and that would give me the voltage I would need to have for a 70% charge state. However, I have read on numerous places online that a fully discharged battery is actually about 11V, but I don't know how or why... Any battery experts out there can you help me figure this one out? Thanks!