Why state of charge is key to BESS success with Blake Rector (Principal, Markets & Optimization @ Powin)

May 6, 2025

Blake Rector, Director of Markets and Optimization at Powin, leads initiatives to maximize battery energy storage performance. He discusses the critical role of state of charge (SOC) in revenue generation, revealing that even a 1% error can significantly impact profits. The conversation delves into the differences between operational and theoretical capacities, forecasting, and SOC management strategies. Listeners gain insights into algorithmic improvements and the importance of precise SOC estimation, underscoring the nuances of battery technology in the evolving energy sector.

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ANECDOTE

Battery State of Charge History

Blake Rector shares how state of charge estimation has been a long-standing challenge, even in consumer electronics like cell phones.
Older phones often showed inaccurate battery percentages, illustrating the complexity of this problem.

INSIGHT

Complexity of Battery State of Charge Estimation

State of charge estimation is complex because utility-scale batteries contain up to millions of individual cells.
Aggregation and balancing issues make the problem much harder than measuring a single cell.

INSIGHT

LFP vs NMC Charge Estimation

LFP batteries have a very flat voltage curve between about 20% and 90% charge, making voltage a poor indicator of actual state of charge.
NMC batteries have more distinguishable voltage changes, making state of charge easier to estimate.

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From arbitraging volatility and unlocking grid stability, battery energy storage is playing an increasingly central role in power markets. But even the most well optimized units can fall short of their potential if one key metric is off: state of charge (SOC). Get it wrong, even slightly, and the revenue losses can be staggering.

State of charge is hard to measure accurately - errors can compound over time, and what operators do to improve performance can make huge differences in profitability. Whether you're an asset owner, optimiser, or just want to understand the real-world constraints behind battery revenue models, this conversation is packed with detail and lessons that could change how you think about storage strategy.

In this episode of Transmission, Quentin sits down with Blake Rector, Director of Markets and Optimization at Powin explore the nuances of SOC. Over the course of the conversation, you’ll hear about:

Why state of charge matters: How even a 1% error in SOC estimation can significantly reduce revenue from energy trading and grid services.
Operational vs. theoretical capacity: The difference between nameplate and usable capacity, and why operators often leave value on the table.
Forecasting and dispatch constraints: Why better SOC management means more flexibility and higher earnings in volatile markets.
Hardware vs. software approaches to SOC: What Powin has learned about algorithmic improvements, calibration strategies, and real-time feedback loops.
Powin’s scale and strategy: With 17 GWh online or under construction, what’s next for one of America’s fastest-growing battery OEMs?

About our guest

Blake Rector is Director of Markets and Optimization at Powin, where he leads the company’s efforts to maximise the performance and revenue of battery energy storage systems across multiple markets. With a background in energy markets, analytics, and operational strategy, Blake focuses on the interface between algorithmic control, asset health, and market opportunity.

Powin is a U.S. based global energy storage platform provider specializing in fully integrated, utility-scale battery energy storage systems. With over 17 GWh of systems deployed or under construction worldwide, Powin delivers scalable solutions that enable the transition to clean, reliable, and affordable energy. For more information, head to their website.

About Modo Energy

Modo Energy helps the owners, operators, builders, and financiers of battery energy storage solutions understand the market - and make the most out of their assets.

All of our podcasts are available to watch or listen to on the Modo Energy site. To keep up with all of our latest updates, research, analysis, videos, podcasts, data visualizations, live events, and more, follow us on LinkedIn or Twitter. Check out The Energy Academy, our bite-sized video series breaking down how power markets work.