The battery should lose very little to no charge when not in use and the fact that it is in only a short period of time does suggest that the battery is not good
Have you tried the Sony diagnostic tool
Another test that you can do is the PowerCfg utility, please see example below;
To use the PowerCfg utility, you'll need to open an Administrator Command Prompt. At the prompt, type the command powercfg -energy
After you press [Enter], the PowerCfg utility will begin analyzing your system's power-option settings. After a minute or so, you'll see a report brief and will be prompted to open the report titled energy_report.html for more details. The process is shown in Figure E.
When the PowerCfg utility is finished analyzing your system's power-option settings, you'll be prompted to open the report file for more details.
You can type energy-report.html at the prompt to launch Internet Explorer and open the HTML report file.
When the report opens, as shown in Figure F, you'll see a header with basic system information followed by color-coded sections that indicate the severity of the problems that were detected. Pink indicates errors, yellow indicates warnings, and white indicates general information. You can use this report to make adjustments to your power-plan settings.
The report is divided into three color-coded sections that provide details on the efficiency of your system's energy usage.
To delve even deeper into the power-management information contained in the report, you should download the "Using PowerCfg to Evaluate System Energy Efficiency" document from the Windows Hardware Developer Center. This document provides you with additional information on how to use the PowerCfg command as well as detailed explanations of how to understand and solve the reported energy-efficiency problems and warnings.