The guys at Flow Battery Research Collective have been designing a Redox Flow Battery development kit that you can build yourself using a 3d printer and a few tools. It's a desktop size flow battery that you can use to either do your own research, e.g. on different electrolytes or just to replicate their experimental findings.
Redox Flow Batteries have the potential to become grid scale or home electric energy storage solutions that are way better for the environment than current lithium based batteries. They can often scale power and capacity independently and allow for repairs.
The FBRC project wants to spread the knowledge on RFBs and help kickstart a global community that develops sustainable energy storage technology in an ope source fashion.
Beware that the project is still in its infancy and sourcing the materials can be a bit of a challenge. Be sure to ask around in the forums for help!