Tesla also have spent millions of dollars and had teams of expert engineers design their manufacturing process, test procedures and quality control. For example they will have dialed their spot welding down perfectly so the cells won't be heat damaged but still have a low resistance connection, can you really say you can hand solder hundreds cells with no I'll effect to the cells? I could go on about batteries and UPS's all day, is a real iceberg of a subject.

Good on you for going all electric and have an interest in renewable energy. Save yourself some pain and start at the start, work out your requirements using leisure or marine batteries, design and assemble your own charge system using available parts and research DC power systems and batteries as you go. Starting simple will help you develop the skills and techniques to go on to more ambitious projects in future.