Overview
To support TWAICE’s Asset Performance Analysis, we recommend running specific test profiles designed to key performance metrics such as energy capacity, round-trip efficiency (RTE), and DC resistance (DCR). These metrics establish a quantitative baseline for the system prior to the start of commercial operation.
In most cases, each test profile is executed while TWAICE maintains a continuous data connection to your BESS. This enables rapid processing of the test results in the TWAICE platform, where any anomalies, inhomogeneities, or signs of underperformance are flagged.
📘 For information on how these profiles fit into the commissioning workflow, refer to the Asset Performance Analysis Process article.
Charge-Discharge Cycle
This profile is used to evaluate several key performance metrics:
Energy Capacity: Determined using the discharge portion of the cycle
DC-DC Round-Trip Efficiency (RTE): Calculated over one complete discharge–charge cycle
Voltage Spreads: Calculated during the entire cycle
Temperature Spreads: Calculated during the entire cycle
To ensure reliable results, the cycle should be performed only after the manufacturer’s initial checks have been completed.
Prerequisites
Before executing this test profile, please ensure:
The BESS is in a balanced and stable initial state
The ambient temperature is around 23 °C ± 5 °C.
Test Profile Description
Since capacity and RTE depend on the charge and discharge rates, the ideal test setup mirrors your storage’s typical operating regimes. For most energy storage applications, a constant power (CP)-phase profile is most appropriate:
For a 4-hour system, use a CP-rate of 0.25
For a 2-hour system, use a CP-rate of 0.5.
Other CP-rates can also be used, as long as the same rate is applied to both the charge and discharge steps to ensure an accurate RTE calculation.
Procedure
Charge the system to full SoC before performing the discharge part of the test.
Rest for 15 minutes.
Fully discharge the battery at constant power.
In some systems, this is limited by a cutoff voltage, in others the BMS SoC limits discharge. Where possible, aim for the largest possible depth of discharge-ideally close to 100%, though CP-phase testing may prevent reaching 100%.
Rest for 15 minutes.
Fully charge the battery at constant power. The goal is to reach the maximum achievable SoC.
Rest for 15 minutes.
Example test procedure for a 0.5 CP system. For systems with a different power ratings, the charging and discharging times can be proportionally increased or decreased to ensure the cycle reaches the maximum and minimum SoC levels.
Data Requirements
TWAICE Asset Performance Analysis can be performed for any data resolution and quality. However, the accuracy and comparability of the calculated results may vary depending on the sampling rate and data resolution provided, as well as the test profile that was run.
📘 For details regarding BESS data model components, expected sensor requirements, sensor data resolution, data logging methods, please refer to the TWAICE Help Center article: BESS Sensor Requirements & Model Components.
To support proper interpretation and benchmarking, the following additional meta information is needed:
Date of first operation
System topology and/or electrical hierarchy
Battery specifications, including cell chemistry, including nominal capacity (Ah) and energy (Wh), format, and manufacturer
👉🏻 Reach out to us for any question or further details: support@twaice.com.