Guide for Test and Evaluation of Lead-Acid Batteries Used in Photovoltaic Hybrid Power Systems
IEEE 1661 is a guide published by the Institute of Electrical and Electronics Engineers (IEEE) that provides test methods and evaluation criteria for lead-acid batteries used in photovoltaic (PV) hybrid power systems. It addresses the unique charge/discharge characteristics of PV applications, where batteries experience irregular and partial-state-of-charge cycling that differs significantly from conventional utility or automotive duty cycles.
Published by: Institute of Electrical and Electronics Engineers (IEEE)
Current edition: IEEE 1661-2007
Related standards: IEEE 485 (lead-acid sizing), IEEE 1562 (stand-alone PV battery sizing)
Scope
IEEE 1661 applies to vented (flooded) and valve-regulated lead-acid (VRLA) batteries used in PV hybrid power systems. Hybrid systems combine PV generation with a diesel generator or other backup source alongside battery storage. The guide covers laboratory and field test procedures for characterising capacity, cycle life, and failure modes specific to these duty cycles.
Key Test Methods
Capacity Testing
Standard capacity tests at C/10 and C/20 discharge rates establish the rated capacity baseline. The guide defines test temperatures (25 °C reference), end-of-discharge voltage, and the number of conditioning cycles required before baseline measurement to ensure repeatable results.
Partial State-of-Charge (PSoC) Cycling
PV applications frequently operate batteries in partial state-of-charge, which accelerates sulphation in lead-acid cells. IEEE 1661 defines accelerated PSoC test profiles that replicate the irregular charge patterns of PV systems, allowing comparative evaluation of battery designs under realistic conditions.
Float and Recovery Testing
Testing protocols assess battery behaviour under float charging (low continuous charge) and recovery from deep discharge — both common in PV systems with extended low-insolation periods. Float charge current acceptance and recovery capacity are measured.
Failure Mode Analysis
The guide provides guidance on identifying and documenting failure modes including positive plate corrosion, negative plate sulphation, water loss, separator degradation, and grid growth. Post-test teardown analysis procedures are described.
Disclaimer: This is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.