Comment by driverdan

Except this is exactly what you want to happen. The reason electricity prices range is because of supply and demand. Batteries help smooth out the supply curve.

In the short term adding more batteries may allow someone to generate income using this strategy but long term what it will do is push electricity prices down and prevent power generation from being overwhelmed. As the battery "market" gets crowded profit margins will fall and everything will reach an equilibrium.

This is a great demonstration of how capitalism works and why it's beneficial.