IEEE 1661:2019 pdf free download – IEEE Guide for Test andEvaluation of Lead-Acid Batteries Used in Photovoltaic (PV)Hybrid Power Systems
5.4.1 General
The battery test consists of an initial battery charge, followed by battery discharge, and then a recharge.The testresults include the battery capacity with temperature measurements, cell voltages on charge and on discharge,and cell specific gravity (ventcd cclls). lf the performance is not acceptablc. a review of charging paramctersand discussions with the battery manufacturer may be necessary.
5.4.2 Test equipment and data acquisition
The battery test requires a dispatchable resource,e.g., an engine generator and a constant-current or constant-power load that is capable of discharging at the required rate (see 5.4.4).The load can be a dc connecteddirectly to the battery or ac through an inverter with a load appropriate for the discharge rate. lf the ac loadis selected, the inverter must function at voltage levels below the battery end voltage because of lR(voltage)losses in the cabling.
Data acquisition requires measurement of battery voltage, current, and temperature to obtain a capacity inampere-hours.The associated test durations (time) should be measured and recorded as well.The batteryampere-hours should be calculated during the discharge and recharge of the battery. Accurately determiningthe ampere-hour data requires sampling the current at regular intervals and integrating this current data overtime.The data sampling and integration interval should be frequent enough to account for current changes thatoccur as a result of the power supply or charge taper when the battery reaches regulation voltage.The ampere-hour measurement also provides a capacity status or SOC that can be used to predict time left to discharge orcharge the battery. Data acquisition is usually accomplished using a computer-based data acquisition system.
5.4.3 Initial battery charge
The main objective is to measure operational battery capacity of a charged battery using the system ‘s standardoperating conditions. Therefore, prior to performing the capacity test, the standard system absorption chargeshould be performed.Charging is complete when the current required to maintain the absorption voltagesetpoint decreases to 2% to 3% of the battery nominal rated capacity. If charging information is unavailable,Table 1 provides suggested values.Acurrent-limited, constant voltage method should be used for the charging.
The end voltage is usually 1.95 V/cell to 1.75 V/cell for lead-acid batteries. The discharged ampere-hoursshould be determined and recorded at the end-of-discharge voltage.New batteries may not be fully formedand may only supply an initial capacity at slightly below the rated value. Initial capacities as low as 90% ofthe rated capacity are not uncommon.But, even lower initial capacities may be encountered, e.g., for somedeep cycle batteries. The battery manufacturer should be contacted to determine the acceptable range in initialcapacity.
The battery temperature should be monitored during the capacity test.Most battery manufacturers specifycapacity at 25 ℃. Therefore, if the battery is above or below 25 C at the beginning of the test, then thedischarge time should be temperature-compensated by adjusting the discharge time according to IEEE Std 450for vented cells and IEEE Sid 1188 for VRLA cells. The test should be conducted at the adjusted time.Forexample, if a vented cell is at 35 C, the discharge time should be increased by multiplying the discharge time At a minimum, measure and record cell/unit voltages on discharge at the beginning of the test, measurevoltage again at a nominal voltage of about 2.00 V/cell, and again approaching the end-of-dischargevoltage. If some of the initial cell voltages are well below the other cell voltages, then monitor them asrequired for potential termination of the test.