The flooded lead-acid battery acceptance test is a comprehensive electrical performance evaluation conducted on new or reconditioned battery banks before they are first placed into service. The test suite includes identification of the battery manufacturer, model, type, and rated capacity in amp-hours (Ah), measurement of baseline voltage and cell-to-cell voltage balance at rest, and a load test in which the battery is discharged at a specified current draw (in amperes) for a defined duration while voltage is continuously monitored to confirm the battery maintains the minimum acceptable voltage throughout the discharge cycle. NETA ATS-2025 section 7.18.1.1 governs the acceptance test scope and acceptance criteria for flooded lead-acid systems installed for stationary or emergency power duty.
A lead-acid battery bank delivers reliable emergency or backup power only if every cell and string is in good electrical condition and balanced with its neighbors before service begins. Manufacturing defects, shipping damage, overcharge during transport, or improper installation can leave a cell with reduced capacity, or can produce voltage imbalance between cells or strings that is not obvious from an at-rest voltage check alone. A discharge-under-load reveals whether the battery can sustain the current and voltage a downstream inverter, charger, or load equipment actually demands; a battery that passes a static voltage check but fails to sustain voltage under load is a risk because it will drop off under the very conditions it was installed to handle. Running the test before the first energization allows corrective action (cell replacement, string rebalancing, or return of the unit) to occur before the battery is connected to critical systems.
The flooded lead-acid acceptance test is performed once, on a new or reconditioned battery bank before it is first connected to its charger, inverter, or load equipment and before the system is placed into service. Unlike some acceptance tests that may be repeated at multiple tap positions or test points, the flooded lead-acid battery acceptance test represents a single, comprehensive evaluation. The test captures the as-found condition of the battery as it arrives at the installation site, after any transit and staging, and before any operating cycles or charging events that might alter baseline parameters.
With the battery isolated from charging and load equipment and allowed to stabilize at ambient temperature, the technician records the manufacturer, model, battery type, and rated capacity in amp-hours from the nameplate or technical documentation, then measures the voltage at rest across the entire battery bank and across individual cells to confirm electrical continuity and cell-to-cell balance. The load test connects a calibrated load bank (or variable resistor) across the battery terminals, applies the specified test current (in amperes) according to the battery's rated capacity, and holds that current draw for the duration specified in NETA ATS-2025 section 7.18.1.1.D.7 while monitoring terminal voltage continuously. Test current, test duration, voltage readings at intervals throughout the discharge, and any anomalies such as cell temperature rise or electrolyte level changes are recorded along with ambient temperature and test equipment identification.
For each flooded lead-acid battery bank acceptance test: the manufacturer, model, battery type, and rated capacity in amp-hours; the at-rest terminal voltage and individual cell voltages; the specified load test current in amperes and the total duration of the test; the terminal voltage at the start of the load test and at each interval during discharge as defined in the standard; the minimum voltage observed during the load test; and the condition of each cell (temperature, electrolyte level, visual defects) before and after the test. Test date, ambient temperature, technician identification, test equipment make and model and calibration due date, and any notes on cell performance or concerns are captured alongside the readings for audit and future trend comparison.
The flooded lead-acid battery is accepted if it meets two criteria under NETA ATS-2025 section 7.18.1.1: first, all cells are present and show electrical continuity, with no cell voltage significantly lower than others, indicating no open circuits or failed cells; and second, when subjected to the specified load-test current for the time interval prescribed in ATS-2025 section 7.18.1.1.D.7, the terminal voltage does not drop below a minimum threshold during the discharge. The threshold voltage is set by the battery's nominal voltage rating (12 V, 24 V, 48 V, etc.) and capacity rating, and is provided in the standard or by the battery manufacturer's acceptance specification. A result that fails either criterion - such as a cell that is significantly lower in voltage than others, or a terminal voltage that falls below the minimum during load - must be investigated and remedied before the battery is returned to service. See the purchased NETA ATS-2025 standard for the complete acceptance table and voltage thresholds for different battery ratings.
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