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Solar Battery Calculator

Calculate battery bank size from load (W) & run hours
Selecting a model will auto-fill the battery nominal voltage & Ah fields. These are common models found in the Philippines (Motolite, Crown, Trojan, CALB, Sinopoly, BYD). Prices and availability vary — always confirm with local suppliers.
Calculated energy

Required AC energy: - Wh

Required DC energy (battery side): - Wh

Required battery capacity at system V: - Ah

Battery bank

Series per string: -

Parallel strings (exact): -

Parallel strings (round up): -

Total batteries (rounded): -

Wiring diagram notes & protection recommendations
General wiring & layout:
  • Wire each battery string in series to reach the system voltage (e.g., four 12V in series = 48V system).
  • Parallel multiple identical strings only (same age, model, Ah rating). Balance and matching improves life.
  • Place battery negative and positive busbars near the inverter/charge controller to minimize DC cable runs.
Protection (fuses / breakers / isolators):
  • Use DC-rated circuit breakers or slow-blow fuses close to the battery positive for each parallel string — this protects against short-circuits at the string level.
  • Size the breaker/fuse at approximately 125% of the maximum expected continuous current (see example below). Do not exceed the ampacity of the chosen cable.
  • Install a battery disconnect / master switch accessible and clearly labeled for emergency isolation.
Cable sizing & practical tip:
  • Estimate DC current: I = load (W) / system voltage (V). Use the inverter continuous rating if that's higher than the steady load.
  • Choose cable ampacity greater than the calculated current and compliant with local wiring codes. As a rough guideline (country codes vary): up to ~30 A use 4 mm² copper, ~30–60 A use 6–10 mm², ~60–120 A use 16 mm² — but confirm with local code and voltage drop limits.
  • Keep DC cable runs short to limit voltage drop; use larger gauge for longer runs. Tighten terminals to manufacturer torque specs and use proper battery lugs & heat-shrink.
Short-circuit / fault considerations:
  • Batteries can supply very high short-circuit currents. Use properly rated DC breakers/fuses and fuses close to the battery terminal to limit fault energy.
  • Never rely solely on AC-side protection for DC faults — DC faults must be controlled at the battery side.
  • Consider using busbars and terminal covers and keep battery area ventilated (for flooded lead-acid) and away from combustible materials.
This guidance is for estimation and planning only. Electrical installations are hazardous — always have a licensed electrician / solar installer verify wiring, conductor sizing, protective devices, and local code compliance before installation.
Wiring Diagram (live preview)
Diagram reflects series per string and parallel strings. Fuses shown on each string positive lead.
Tip: toggle Show wiring diagram above to hide/show the diagram.
Notes & recommendations
  • Round up parallel strings to nearest whole number — batteries must be whole strings.
  • Consider battery temperature, aging and reserve margin (add 10–20% if uncertain).
  • This tool gives an estimate only. Use manufacturer specs and a licensed electrician for final system design.