More sellable capacity and a longer life from battery storage

A grid scale battery energy storage system (BESS) is made up of racks or packs, which in turn consist of cells. It ranges from a few MW at a company’s own depot to hundreds of MW connected directly to the grid. It earns by storing power when it is cheap and releasing it when it is dear. It can also stand ready to help the grid operator keep the network stable.

The job is to deliver as much of the rated capacity as possible and to lose capacity no faster than the supplier guaranteed. The battery also has to stay available around 98% of the time.

Why the weakest cell decides how much of the asset can be sold

Cells drift out of balance over time, and the system then stops early to protect the weakest one. By some estimates, that leaves up to 10% of the energy unsold, even though it is physically still there. LFP, the cell chemistry in most large batteries, barely changes its voltage between 20 and 80% state of charge. A tiny reading error then becomes a 15% error in the estimated energy inside.

Batteries lose 2 to 3% a year, and contracts now accept a battery ending at 65 or even 60% instead of 70. If it drops faster than promised, the owner pays unless he can prove it.

The owner or investor of a BESS has a business case with a 10 to 20 year return. The optimiser is paid to earn as much as possible today, whatever that costs in capacity. BMB supports both, and the asset manager. The effect of today’s trading strategy on the long term health of the asset becomes visible to every party involved.

BMB reads capacity from how the battery actually behaves, instead of from the supplier’s BMS. It works out how much of the rated capacity each pack really delivers. Capacity unlock brings it back towards the limit, always inside what the manufacturer allows.

Anomaly detection flags cells running hot or drifting out of balance long before the yearly test. Peak shaving keeps the site’s draw from the grid low.