PV Battery Sizing Calculator

Technical Documentation and Calculation Methodology

The PV Battery Sizing Calculator implements battery capacity determination for stand-alone photovoltaic (PV) systems per IEEE Std 1013-2019. The calculator is designed to help system designers determine the appropriate energy capacity of lead-acid batteries to satisfy the energy requirements of electrical loads in stand-alone PV systems.

The calculator focuses on autonomy-based sizing, depth-of-discharge considerations, temperature effects, system voltage window determination, and iterative series cell selection. It implements the systematic approach outlined in IEEE 1013-2019 for both vented and valve-regulated lead-acid batteries:

• Load profile analysis with continuous and momentary loads
• Autonomy period definition (days of battery-only operation)
• Capacity corrections for depth of discharge (MDOD and MDDOD)
• End-of-life (EOL) capacity considerations
• Temperature correction factors for cold-weather operation
• Design margins for load uncertainty and system reliability
• Voltage window constraints from loads and charge controllers
• Iterative series cell determination per IEEE 1013 Clause 7.3
• Functional-hour rate calculation for appropriate discharge time

This calculator is specifically designed for stand-alone (off-grid) photovoltaic systems where the battery must supply all loads during periods without sufficient solar input. Key characteristics:

• Stand-alone PV systems: No grid connection; battery provides 100% backup
• Lead-acid batteries: Both vented (flooded) and valve-regulated (VRLA) types
• Low-voltage DC systems: Typically 12V, 24V, or 48V nominal
• Autonomy-based design: Battery sized for specified days without solar charging

The following system types require different sizing methodologies and are outside this calculator's scope:

• Grid-connected (grid-tied) PV systems: Use IEEE Std 1547 and utility requirements
• Hybrid systems with generators: Require modified autonomy calculations
• Lithium-ion batteries: Different depth-of-discharge and cycling characteristics
• UPS systems: Use IEEE Std 485 for short-duration backup applications
• Stationary float service: Different sizing approach per IEEE Std 485

IEEE 1013-2019 addresses lead-acid battery types commonly used in stand-alone PV applications:

Battery Type	Characteristics	Typical Applications
Vented (Flooded)	Liquid electrolyte, requires water addition, hydrogen venting	Large off-grid homes, telecom sites with maintenance access
Valve-Regulated (VRLA)	Sealed, limited water loss, oxygen recombination	Remote sites, minimal maintenance applications
AGM	Absorbed glass mat, VRLA subtype, better cycling	Mobile applications, high-discharge applications
Gel	Gelled electrolyte, VRLA subtype, deep discharge tolerance	High-temperature environments, deep-cycle applications

The IEEE 1013-2019 battery sizing process follows a systematic approach with iterative steps to ensure the battery can satisfy both capacity and voltage requirements. The methodology is illustrated in the flowchart below (conceptual):

1. Define Autonomy Period: Specify days of battery-only operation (Clause 4)
2. Analyze Loads: Calculate daily ampere-hours and peak currents (Clause 5)
3. Calculate Required Capacity: Apply corrections for DOD, temperature, EOL (Clause 6)
4. Determine Functional-Hour Rate: Calculate equivalent discharge time (Clause 6.4)
5. Establish Voltage Window: Define system Vmax and Vmin constraints (Clause 7.2)
6. Determine Series Cells: Iteratively select number of series cells (Clause 7.3)
7. Select Cell Size: Choose cell capacity at functional-hour rate (Clause 8.1)
8. Calculate Parallel Strings: Determine parallel strings if needed (Clause 8.2)
9. Perform Checks: Verify design against IEEE 1013 criteria (Clause 8.5)

Autonomy is defined as the number of days the PV system's fully charged battery can supply the load without any solar charging. This is a critical design parameter that balances system reliability, battery cost, and physical constraints.

IEEE 1013 Section 4 identifies several considerations for selecting the autonomy period:

Factor	Consideration	Impact on Autonomy
System Criticality	Importance of continuous power availability	Critical loads (telecom, medical) → longer autonomy (7-10+ days)
Solar Resource Variability	Frequency and duration of cloudy periods	High variability (monsoon regions) → longer autonomy
Site Accessibility	Time required to reach site and repair	Remote locations → longer autonomy to allow intervention time
Load Predictability	Certainty of load patterns and ability to shed loads	Unpredictable loads → longer autonomy; shed-able loads → shorter OK
Economic Constraints	Budget limitations and physical space	Higher cost/space requirements for longer autonomy

Common autonomy periods for various applications:

• 3-5 days: Residential off-grid systems with accessible locations
• 5-7 days: Remote cabins, small commercial installations
• 7-10 days: Telecommunications sites, critical monitoring stations
• 10-15 days: Remote navigation aids, weather stations
• 15+ days: Critical applications in extreme climates (Arctic research stations)

Accurate load analysis is fundamental to battery sizing. IEEE 1013 Clause 5 provides a systematic approach to characterizing loads and calculating the battery's duty cycle.

Loads are categorized by their operating characteristics:

Loads that operate for extended periods (minutes to hours) at relatively constant current. Examples: lighting, refrigeration compressors, communication equipment.

Loads lasting 1 minute or less. Examples: motor starting currents, compressor inrush, inverter surge. IEEE 1013 treats these separately because their ampere-hour contribution is small, but their impact on battery terminal voltage can be significant.

For each load device, the following information is required (IEEE 1013 Worksheet 1):

• Running current (I_run): Steady-state current draw in amperes
• Momentary current (I_mom): Inrush or peak current (if applicable)
• Duration: Hours of operation per occurrence
• Occurrences: Number of times load operates per day
• Load timing: When loads occur (for coincident current analysis)
• Voltage limits: Maximum and minimum acceptable voltages at load terminals

The daily ampere-hour load is calculated for each device:

Where:

• I_run = running current (A)
• t_run = duration per occurrence (hours)
• n_occurrences = number of occurrences per day

For momentary loads, if the exact duration is unknown, IEEE 1013 recommends assuming 1 minute (1/60 hour).

The maximum current draw determines the functional-hour rate and affects voltage drop during discharge. IEEE 1013 Section 5.3 distinguishes between:

• Coincident currents: Loads that can operate simultaneously (sum the currents)
• Non-coincident currents: Loads that never overlap (take the maximum single value)

The maximum running current is:

The starting point is the unadjusted autonomy capacity, which is simply the autonomy period multiplied by the average daily load:

This represents the ideal capacity needed if the battery could be discharged to 0% SOC, operated at 25°C, and maintained at 100% of rated capacity throughout its life. In reality, multiple correction factors must be applied.

IEEE 1013 Section 6.3.1 requires three separate depth-of-discharge checks, with the battery sized to satisfy the most restrictive:

MDOD is the deepest discharge the battery should experience during the autonomy period. Typical values for PV applications:

• Shallow-cycle batteries: 20-30% MDOD for longer autonomy periods (>5 days)
• Deep-cycle batteries: 50-80% MDOD for shorter autonomy or daily cycling

The capacity adjustment is:

Example: If MDOD = 80%, the battery must be 1.25× larger than the unadjusted capacity.

MDDOD limits the discharge depth on any single day, which is critical for battery life even if the overall autonomy discharge is acceptable. This prevents excessive cycling during normal operation:

Typical MDDOD values:

• Shallow-cycle systems: 15-25% MDDOD
• Deep-cycle systems: 20-30% MDDOD

Batteries lose capacity over their lifetime due to sulfation, grid corrosion, and active material degradation. The battery must be sized so that even at end-of-life, it can still provide the required autonomy:

IEEE 1013 notes that while 80% EOL is common in stationary float applications (IEEE 485), PV systems may use 50-80% depending on the application and acceptable performance degradation.

Battery capacity decreases at low temperatures. IEEE 1013 Section 6.3.2 requires sizing at the minimum expected operating temperature using manufacturer-provided correction factors:

Where C_discharge is the maximum of C_MDOD, C_MDDOD, and C_EOL.

Typical temperature correction factors (K_temp) for lead-acid batteries:

Temperature	Correction Factor (Ktemp)	Capacity Relative to 25°C
25°C (77°F)	1.00	100%
15°C (59°F)	1.08-1.12	90-93%
0°C (32°F)	1.25-1.35	74-80%
-10°C (14°F)	1.50-1.65	61-67%
-20°C (-4°F)	1.80-2.00	50-56%

IEEE 1013 Section 6.3.3 recommends adding 10-25% design margin to account for:

• Load estimation uncertainties
• Unanticipated load growth
• Sub-optimal charge controller performance
• Array production variations
• Actual vs. rated battery capacity

Where K_margin = 1.10 for 10% margin, 1.25 for 25% margin, etc.

The functional-hour rate is an effective discharge time used to select the appropriate battery capacity from manufacturer data. It accounts for varying discharge rates during the duty cycle:

This represents the number of hours the battery would last if discharged continuously at the maximum running current. The functional-hour rate may be greater than the autonomy period in hours (Days_autonomy × 24) because:

• Loads may not operate continuously
• Maximum current may be higher than average current
• Correction factors increase required capacity

One of the most critical and iterative steps in IEEE 1013 sizing is determining the correct number of series-connected cells. This must satisfy both charging voltage limits and end-of-discharge voltage requirements simultaneously.

The voltage window is the range of acceptable system voltages, bounded by:

This window is determined by the most restrictive requirements from:

• Load voltage limits: Each load has minimum and maximum operating voltages
• Charge controller setpoints: Low-voltage disconnect (LVD) and regulation voltage
• Inverter specifications: Shutdown voltage and maximum input voltage

The system V_max is the minimum of all maximum voltage limits:

The system V_min is the maximum of all minimum voltage limits:

IEEE 1013 Clause 7.3.1 starts by calculating the maximum number of series cells allowed by the charging voltage constraint:

Where V_cell,charge is the manufacturer's recommended charging voltage per cell. Typical values:

Battery Type	Float Voltage (V/cell)	Equalize/Absorb Voltage (V/cell)
Flooded Lead-Acid	2.25-2.30	2.35-2.50
AGM (VRLA)	2.25-2.30	2.35-2.40
Gel (VRLA)	2.25-2.30	2.30-2.35

IEEE 1013 Clause 7.3.2 requires verifying that the calculated EOD voltage per cell is not below the manufacturer's recommended minimum:

This calculated EOD voltage must satisfy:

Where V_cell,EOD,rec is the manufacturer's recommended minimum cell voltage at the functional-hour discharge rate. Typical values:

• Fast discharge (1-5h rate): 1.75-1.80 V/cell
• Moderate discharge (10-20h rate): 1.80-1.85 V/cell
• Slow discharge (50-100h rate): 1.85-1.90 V/cell

If the EOD voltage check fails (V_{cell,EOD,calc} < V_cell,EOD,rec), IEEE 1013 Clause 7.3.3 provides two options:

Increase V_min by adjusting the charge controller's low-voltage disconnect setpoint or by accepting tighter load voltage constraints. This is the preferred approach because it maintains the optimal number of series cells for charging.

Decrease N_series by 1 and recalculate. This is not normal practice per IEEE 1013 but is allowed if adjusting the voltage window is not feasible. The iterative process is:

1. N_series = N_series - 1
2. Calculate V_{cell,charge,calc} = V_max / N_series
3. Verify V_{cell,charge,calc} ≤ V_{cell,charge,max} (with reasonable tolerance)
4. Calculate V_{cell,EOD,calc} = V_min / N_series
5. Check if V_{cell,EOD,calc} ≥ V_cell,EOD,rec
6. If not satisfied, return to step 1

If no solution is found (too few cells for proper charging or too many cells for adequate EOD voltage), the system design must be revised.

With the required capacity (C_required), functional-hour rate (H_func), and series cells (N_series) determined, select the cell size from manufacturer data.

Key considerations per IEEE 1013 Clause 8.1:

• Use the functional-hour rate (H_func) to find capacity in manufacturer tables
• Use the calculated EOD voltage (V_{cell,EOD,calc}) or the recommended EOD, whichever is higher
• If V_{cell,EOD,calc} > V_cell,EOD,rec, the battery delivers less capacity (shallower discharge), requiring a larger cell
• Select the next available cell size that meets or exceeds C_required

If a single string of series cells cannot provide the required capacity, multiple strings are connected in parallel:

Parallel string considerations (IEEE 1013 Clause 8.2):

• Keep parallel strings as equal in capacity as practical
• Use matched cells (same type, age, manufacturer, capacity)
• Balance charging between strings using individual string fusing
• Consider using a single large cell rather than many parallel strings
• Limit paralleling to 2-4 strings when possible for reliability

The final battery configuration is expressed as:

Example: A 12S2P configuration has 12 cells in series (e.g., 24V nominal) with 2 parallel strings.

Total cells:

Final battery capacity at the functional-hour rate:

IEEE 1013 Clause 8.5 requires several verification checks after battery sizing. These ensure the design is practical and will perform as expected.

Verify that the maximum available charging current from the PV array does not exceed the battery manufacturer's recommended maximum charge rate during bulk charging:

Typical maximum charge rates:

• Flooded batteries: C/5 to C/8 (0.20C to 0.125C)
• AGM batteries: C/4 to C/5 (0.25C to 0.20C)
• Gel batteries: C/10 to C/20 (0.10C to 0.05C)

After the battery reaches the regulation (absorb) voltage, verify that the float/finishing charge current is within the manufacturer's recommendations to prevent excessive overcharge:

This is particularly critical for VRLA batteries, which are sensitive to overcharging and can experience thermal runaway if overcharged at high rates.

The PV array must be sized to both supply daily loads and recharge the battery. IEEE 1013 recommends verifying the array-to-load ratio for the minimum design month (typically December in northern hemisphere):

A ratio ≥ 1.3 is typically required to account for:

• Charging losses (85-95% efficiency)
• Self-discharge (1-5% per month for lead-acid)
• Array soiling and degradation
• Controller losses
• Occasional above-average load days

If the maximum current results in a discharge rate faster than 20h, or if large momentary loads can occur near the end of the autonomy period, the battery voltage may drop below V_min even though the capacity is adequate.

Check the discharge rate:

If this is less than 20h, consider using the detailed voltage profile analysis method described in IEEE Std 485 to verify adequate voltage throughout the discharge.

At low states of charge, the electrolyte specific gravity decreases, raising the freezing point. Verify that the freezing point at MDOD is below the minimum operating temperature:

State of Charge	Specific Gravity	Freezing Point
100%	1.265	-71°C (-96°F)
75%	1.225	-40°C (-40°F)
50%	1.190	-24°C (-11°F)
25%	1.155	-16°C (3°F)
0%	1.120	-9°C (16°F)

If freezing is possible, consider:

• Thermal insulation for the battery enclosure
• Heating elements (though this increases load)
• Reducing MDOD to keep specific gravity higher
• Using higher-density electrolyte (consult manufacturer)

All lead-acid batteries experience self-discharge, which increases with temperature and battery age. If self-discharge amounts to more than 5% of the capacity per day of autonomy, it should be included as a parasitic load in the original sizing calculation.

Typical self-discharge rates at 25°C:

• Flooded batteries: 3-5% per month
• AGM batteries: 1-3% per month
• Gel batteries: 1-3% per month

Self-discharge doubles approximately every 10°C increase in temperature.

The calculator implements automated checks based on IEEE 1013-2019 Clause 8.5 and displays warnings when design issues are detected. Understanding these warnings is essential for creating a safe and reliable battery system.

This error indicates that no valid number of series cells can satisfy both the charging voltage and end-of-discharge voltage requirements within the specified system voltage window. This is a critical design issue that must be resolved before proceeding.

What This Means:

The calculator attempts to find a number of series cells where:

• Charge voltage constraint: V_max / N_cells ≤ V_cell,charge
• EOD voltage constraint: V_min / N_cells ≥ V_cell,EOD

Per IEEE 1013 Section 7.3, the calculator starts with the maximum number of cells allowed by the charge voltage (Equation 1), then verifies the EOD voltage per cell (Equation 2). If the calculated EOD voltage is below the manufacturer's recommended limit, it decrements the number of cells and rechecks. The error occurs when this iterative process cannot find a valid solution.

Common Causes:

• Voltage window too narrow: The difference between V_max and V_min is insufficient for the selected cell voltages
• V_min too high: Minimum voltage doesn't allow cells to discharge to their rated EOD voltage (typically 1.75V per cell)
• V_max too low: Maximum voltage doesn't allow cells to reach proper charge voltage (typically 2.40-2.45V per cell)
• Incompatible nominal voltage: System voltage (12V, 24V, 48V) incompatible with load voltage requirements

Resolution Steps:

1. Widen the voltage window:
   • Increase V_max (if loads can tolerate higher voltage)
   • Decrease V_min (if loads can tolerate lower voltage)
   • Check load device specifications for actual voltage tolerances
2. Adjust charge controller settings:
   • Verify controller voltage set points are appropriate for battery type
   • For temperature-compensated controllers, check voltage at battery's coldest temperature
   • Ensure controller regulation voltage matches battery manufacturer recommendations
3. Review system voltage selection:
   • Consider changing nominal system voltage (e.g., 12V to 24V or 24V to 48V)
   • Higher voltage systems typically have wider voltage windows
   • May require different loads or DC-DC converters
4. Verify cell voltage parameters:
   • Check that Full Charge Voltage per Cell matches manufacturer data (typically 2.40-2.45V)
   • Verify EOD Voltage per Cell is appropriate for application (typically 1.75-1.80V)
   • Some battery types may use different voltages

Example Scenario:

System: 12V nominal, V_max = 29V, V_min = 20V, Cell charge = 2.40V, Cell EOD = 1.75V

• Maximum cells: 29V / 2.40V = 12.08 → 12 cells
• Check EOD: 20V / 12 cells = 1.67V per cell
• Problem: 1.67V < 1.75V required ❌
• Try 11 cells: 20V / 11 = 1.82V per cell ✓ (meets EOD)
• Check charge: 29V / 11 = 2.64V per cell
• Problem: 2.64V > 2.40V × 1.1 = 2.64V (at tolerance limit, may trigger error)

Solution: Increase V_max to 30V or increase V_min to 21V to provide adequate margin.

The calculator displays warnings in the Results panel when potential design issues are detected. These warnings do not prevent calculation but indicate conditions that require engineering review.

Trigger Condition:

Displayed when (Final Capacity / Maximum Current) < 20 hours, indicating high discharge rates that may cause voltage depression below V_min even when capacity is adequate.

What to Check:

• Review peak load timing - does it occur near end of autonomy period?
• Consider detailed voltage profile analysis per IEEE Std 485
• May need larger capacity battery to maintain voltage under peak loads
• Verify momentary loads (motor starting, inverter surge) are properly specified

Trigger Condition:

Displayed when the electrolyte freezing temperature at MDOD is higher than the minimum operating temperature entered.

What to Check:

• Verify minimum operating temperature is realistic for site location
• Consider battery enclosure insulation or heating
• Review MDOD setting - reducing depth of discharge raises specific gravity
• Consult manufacturer about higher-density electrolyte for cold climates
• Note: A frozen battery can suffer permanent damage

Trigger Condition:

Displayed when battery self-discharge exceeds 5% of the daily capacity requirement, indicating it should be included as a parasitic load in the calculations.

What to Check:

• Particularly relevant for systems with long autonomy periods (>10 days)
• Self-discharge increases significantly at high temperatures
• May need to add self-discharge as a continuous parasitic load
• Consider VRLA (AGM/Gel) batteries which have lower self-discharge

The calculator also provides informational messages to guide proper system design:

Capacity Adjustment Messages:

• "Capacity adjusted for MDOD" - Shows sizing for maximum depth of discharge limit
• "Capacity adjusted for MDDOD" - Shows sizing for daily cycling limit
• "Capacity adjusted for EOL" - Shows sizing to account for aging
• "Largest of three capacities selected" - Indicates which constraint controls sizing

Series Cell Selection Messages:

• "Calculated EOD voltage acceptable" - Series cell count meets voltage requirements
• "Series cells decremented to meet EOD constraint" - Iterative correction was needed
• "Final series cells: X" - Shows selected configuration

Temperature Correction Messages:

• "No temperature correction applied (>25°C)" - Standard temperature assumption
• "Temperature correction factor: X" - Shows capacity increase for cold weather

The calculator validates inputs and prevents calculation with invalid data:

• "Load table cannot be empty" - At least one load must be defined
• "Days of autonomy must be positive" - Cannot be zero or negative
• "Voltages must be positive" - All voltage fields require valid positive numbers
• "MDOD/MDDOD must be between 0-100%" - Depth of discharge as percentage
• "Design margin must be ≥ 1.0" - Cannot reduce capacity below calculated value

Warnings should be treated as opportunities to optimize the design:

1. Document all warnings - Include in design calculations for review
2. Evaluate trade-offs - Larger battery vs. modified voltage window vs. different loads
3. Consult manufacturer data - Verify assumptions against actual battery specifications
4. Consider system architecture - May indicate need for different nominal voltage
5. Plan for worst case - Size for coldest temperature and end-of-life capacity
6. Review with IEEE 1013 - Standard provides detailed guidance on resolving issues

IEEE 1013 Annex A provides guidance on selecting between different lead-acid battery types for PV applications. The selection involves trade-offs between performance, maintenance, cost, and environmental factors.

Advantages:

• Lower cost per kWh of storage
• Proven technology with long track record
• Can be maintained (water can be added)
• Good performance in hot environments
• Tolerant of occasional overcharge
• Can accept high charge rates

Disadvantages:

• Requires periodic water addition (every 1-6 months depending on conditions)
• Hydrogen gas evolution requires ventilation
• Acid spill risk during maintenance or seismic events
• Must be kept upright
• Heavier per unit capacity than AGM

Best suited for: Large off-grid residential systems, agricultural installations, telecom sites with regular maintenance access.

Advantages:

• No water addition required
• Can be oriented in any position (some models)
• Lower hydrogen evolution
• Better high-rate discharge capability
• Better vibration resistance
• Lower self-discharge than flooded

Disadvantages:

• Higher cost per kWh (typically 150-200% of flooded)
• More sensitive to overcharge (risk of thermal runaway)
• Cannot be repaired if water is lost
• Shorter life in high-temperature environments
• Requires more precise charge control

Best suited for: Remote sites without maintenance access, mobile/RV applications, systems with sophisticated charge control.

Advantages:

• No water addition required
• Best deep-discharge tolerance among lead-acid types
• Good performance in high-temperature environments
• Low self-discharge
• Very low hydrogen evolution
• Long cycle life at moderate DOD

Disadvantages:

• Highest cost per kWh (typically 200-300% of flooded)
• Lower charge acceptance rate (longer recharge time)
• Very sensitive to overcharge
• Requires strict voltage regulation
• Not suitable for high-current applications

Best suited for: Hot climates, applications requiring deep cycling, systems with high-quality charge controllers, premium off-grid installations.

Battery cycle life is highly dependent on depth of discharge and operating temperature. Typical cycle life expectations at 25°C:

Battery Type	50% DOD	80% DOD	100% DOD
Flooded Deep-Cycle	1200-1500	600-800	300-400
AGM Deep-Cycle	800-1000	400-600	200-300
Gel Deep-Cycle	1000-1200	600-700	300-400

Temperature effects on cycle life:

• Every 10°C increase above 25°C reduces cycle life by approximately 50%
• Operation at 35°C may reduce life to 50% of rated cycles
• Operation at 45°C may reduce life to 25% of rated cycles
• Low temperatures increase cycle life but reduce available capacity

While charge controller design is outside the scope of IEEE 1013, the battery sizing process requires consideration of charge controller setpoints and capabilities.

Lower cost, direct connection between array and battery. Array voltage must match battery voltage. Suitable for small systems (typically <1kW). Limited charge efficiency at low battery SOC.

Higher efficiency, DC-DC conversion allows array voltage optimization. Suitable for all system sizes. Can provide 20-30% more charging energy than PWM, especially in cold weather or when battery is discharged.

Setpoint	Purpose	Typical Value (12V nominal)
Bulk Voltage	Maximum voltage during main charging	14.4-14.6V (flooded), 14.2-14.4V (AGM), 14.0-14.2V (gel)
Absorption Time	Duration at bulk voltage to complete charge	1-4 hours depending on battery size and discharge depth
Float Voltage	Maintenance voltage after full charge	13.2-13.8V depending on battery type
Equalization Voltage	Periodic high voltage for flooded batteries	14.8-15.5V (flooded only, not VRLA)
LVD (Low Voltage Disconnect)	Load disconnect to prevent over-discharge	11.0-11.5V (adjustable based on load criticality)
LVR (Low Voltage Reconnect)	Voltage at which loads are reconnected	12.5-13.0V (must allow sufficient recharge)

This calculator implements IEEE Std 1013-2019 methodology for preliminary battery sizing. It is intended for:

• Initial system design and feasibility studies
• Educational purposes and learning IEEE 1013 methodology
• Comparative analysis of different design scenarios
• Understanding the relationships between autonomy, load, and battery size

• PV Array Sizing: Array sizing requires solar resource data, system losses, and seasonal analysis (see IEEE Std 1562)
• Detailed Load Profiles: Does not model complex duty cycles or time-series load data
• Battery Model Selection: Cannot recommend specific battery manufacturers or models
• Economic Analysis: Does not perform life-cycle cost or payback calculations
• System Optimization: Does not iterate to find optimal autonomy or battery size
• Charge Controller Sizing: Assumes user has selected appropriate controller

For critical applications, consider adding extra capacity margin (15-25%) beyond the calculated IEEE 1013 requirement to account for these variations.

1. IEEE Std 1013-2019, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stand-Alone Photovoltaic (PV) Systems
   

2. IEEE Std 485-2020, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications
   Reference for detailed voltage profile analysis and duty cycle calculations
3. IEEE Std 1562-2023, IEEE Guide for Array and Battery Sizing in Stand-Alone Photovoltaic (PV) Systems
   Comprehensive guide including PV array sizing integrated with battery sizing
4. IEEE Std 1361-2024, IEEE Guide for Selection, Charging, Test and Evaluation of Lead-Acid Batteries Used in Stand-Alone Photovoltaic (PV) Systems
   Guidance on battery selection, testing, and maintenance for PV applications
5. IEEE Std 937-2023, IEEE Recommended Practice for Installation and Maintenance of Lead-Acid Batteries for Photovoltaic (PV) Systems
   Installation and maintenance procedures specific to PV applications