The London-based oil major said it will work on the 49.9 megawatt Hawthorn Pit and 33 megawatt Wormald Green projects, which are set to come online in the first half of 2024.
It said the projects are intended to enable the storage of power from the grid during periods of low demand, which can then be deployed to ensure stability during high-demand periods.
The firm said the projects will be its first battery energy storage systems optimisation contract since its acquisition of real-time software developer Open Energi in 2021.
Hormoz Ala, senior manager in European Power, said: "This deal represents a significant opportunity to combine BP's established experience in power trading with Harmony's track record in battery development to help safeguard the stability of the GB power grid as we all work to transition to a Net Zero future.
"This project is also an example of how real-time decision-making, provided by BP's power trading team and the Open Energi platform, allows new ways for us to provide grid support optimization in the future. As BP looks to transform into an integrated energy company, it is vital that we continue to develop and diversify our own business to continue to perform for customers, investors and the energy market."
BP shares fell 0.4% to 525.20 pence each on Tuesday morning in London. Shares in Harmony rose 0.2% to 84.70 pence each.