Batterijopslag (BESS) en slim laden

What does Stekker do with your battery?

Stekker integrates your Battery Energy Storage System (BESS) into the same energy management platform that controls your EV charge points. Instead of operating your battery in isolation, Stekker optimises it as part of your entire site — charge points, solar panels, other loads, and the grid connection all taken into account.

Stekker manages your battery across four key dimensions:

• Price arbitrage — charge the battery when energy prices are low, discharge when prices are high. Stekker uses real-time wholesale market prices (day-ahead and imbalance) to maximise the financial return from every charge cycle.
• Peak shaving — your grid connection has a maximum capacity (the fuse limit). When EV charging or other loads push demand towards that limit, the battery can discharge to keep total site power within bounds. This prevents expensive capacity overruns.
• Solar self-consumption — when your solar panels produce more than your site consumes, Stekker stores the surplus in the battery for later use. This reduces grid export and increases the value of your solar investment.
• Coordinated optimisation — the battery and all charge points are scheduled together. The system does not optimise the battery first and then fit in charging sessions — it finds the best combined solution for all assets simultaneously.

Optimisation strategies

Stekker offers three distinct planning strategies for your BESS. The right choice depends on your site configuration and goals.

Cash optimised

Maximises financial return by trading on energy price differences. The planner uses a linear programming solver (GLPK) to find the optimal charge and discharge schedule across a rolling 24-hour window. It considers:

• Day-ahead market prices per quarter hour
• Round-trip efficiency losses — only trades when the price spread exceeds the energy lost in a charge-discharge cycle
• State of charge limits — never charges beyond the configured maximum or discharges below the minimum
• Grid connection capacity — respects your fuse limit when scheduling battery power
• Continuation bias — avoids unnecessary switching between charging and discharging when the financial benefit is marginal

This strategy works best for sites with a significant battery capacity relative to their base load, and a grid connection on a dynamic energy contract.

Solar optimised

Maximises self-consumption of your own solar production. Stekker uses solar production forecasts from your site sensor to determine the optimal charging window. The planner:

• Identifies production periods (when the site exports to the grid) and consumption periods (when the site imports)
• Concentrates charging around the peak production hours for maximum capture
• Schedules discharging during consumption periods to reduce grid import
• Accounts for one-way efficiency — the energy stored is less than the energy absorbed, so the planner factors in conversion losses

Ideal for sites with significant solar capacity where feed-in tariffs are low or where maximising self-sufficiency is the goal.

Winter optimised

A seasonal strategy designed for periods with limited solar production. Rather than relying on forecasts (which may be unreliable in winter), this planner uses a deterministic approach based on solar noon:

• Calculates true solar noon for your location using longitude correction and the equation of time
• Schedules a 4-hour charging window centred around solar noon — the period most likely to have any solar production
• Discharges during morning and evening peak consumption hours
• Includes idle buffer periods (25 minutes before and 55 minutes after charging) to avoid unnecessary power direction switches

This strategy ensures the battery contributes even when accurate solar forecasts are unavailable.

Technical specifications

To integrate your BESS, Stekker needs the following parameters from your battery system. These are configured once during onboarding and can be updated when your system changes.

The effective usable range of your battery is determined by the minimum and maximum SoC settings. For example, a 100 kWh battery with SoC limits of 10% and 90% has an effective usable capacity of 80 kWh.

Integration with EV charging

The battery is registered as a topology node in the same site network as your charge points, solar arrays, and other loads. This means the energy management system sees the battery as a first-class participant when optimising your site.

In practice, this enables several powerful scenarios:

• Load balancing — when multiple EVs are charging simultaneously and approaching the grid connection limit, the battery can discharge to provide additional headroom. This allows more vehicles to charge at higher power without exceeding your contracted capacity.
• Solar-to-EV — solar surplus flows into the battery, which later discharges to charge EVs during evening hours. The entire chain is optimised together, not sequentially.
• Price-aware coordination — the planner considers both EV charging needs (departure times, energy requirements) and battery trading opportunities. It will not sacrifice an EV charging deadline for marginal battery revenue.

The tree-based planner (Engine v4) solves this multi-asset optimisation problem using constraint programming. It models the full site topology — from grid connection through junctions to individual charge points and batteries — and finds a globally optimal schedule that respects all physical constraints.

S2 protocol

Battery systems can communicate with Stekker via the S2 protocol (EN 50491-12-2), an open European standard for energy flexibility management. In this architecture:

• Stekker is the Customer Energy Manager (CEM) — it receives flexibility information from the battery and sends control signals back
• The battery is the Resource Manager (RM) — it reports its capabilities (capacity, power limits, current state of charge) and executes the instructions from the CEM

The S2 protocol ensures vendor-neutral communication. Any BESS that implements S2 can integrate with Stekker without custom development. The protocol supports real-time state updates, so Stekker always has an accurate picture of your battery state for planning.

For battery systems that do not support S2, Stekker can also integrate via manufacturer-specific APIs. Contact us to discuss your specific system.