With a total lit length of 5 meters, you can connect additional sets using 4 different power options depending on the additional length you require.
The AA size battery box is perfect for just a single string.
The D size batter box or Solar panel is ideal for 2 strings with a total length of 10meters.
For up to 30 meters the Plug-in transformer will give you all the power you need.
I found these on the lights4fun website :