Hi, Samad,
Please open the battery cell block and comment out the SOC, DOC, and T blocks. This will prevent the second error from happening, but will also prevent you from monitoring the SOC, DOC, and T. If you do want them displayed, you may want to replace those blocks by port blocks so as to have access to the signals from the top level.
Then, at the top level, you should be able to connect the cells in series like in the attached example.
Javier
