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

May 6, 2025

Blake Rector, Principal of Markets & Optimization at Powin, digs into the critical nuances of state of charge (SOC) in battery energy storage systems. He explains how even a 1% error in SOC can lead to staggering revenue losses. Discover the difference between operational and theoretical capacity, and why many operators leave value on the table. Blake also discusses the role of hardware versus software in improving SOC accuracy and shares insights on how better SOC management can enhance flexibility and profitability in volatile markets.

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INSIGHT

Understanding State of Charge (SOC)

State of Charge (SOC) measures the energy available for discharge in a battery, not just a simple percentage.
Using energy estimates instead of percentages yields more accurate and useful SOC information for optimization.

INSIGHT

Complexity in SOC Measurement

Measuring SOC for large battery systems is complex due to millions of cells aggregated together.
Cell imbalances and system temperature affect SOC accuracy, unlike single simple batteries.

INSIGHT

LFP Battery SOC Estimation Challenge

LFP battery chemistry voltage curves are flat from ~20% to 90% SOC, making SOC estimation very challenging.
This flat region causes large errors in SOC when relying on voltage-based estimation methods.

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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.