Live Demo — Battery Runtime Calculator
Enter battery capacity, system voltage and load power to find how many hours the fully charged battery keeps the light on.
Battery Runtime Calculator
Free professional battery runtime calculator for solar lighting systems. Input battery capacity, system voltage, depth of discharge, battery and wiring efficiencies, then total load power and nightly lighting hours to determine exactly how long a fully charged battery can continuously power the luminaire during an outage or no-sunshine period.
Key Features
Battery Parameters
Set battery capacity in Ah, system voltage (12V / 24V / 48V), depth of discharge and battery charge/discharge efficiency.
System Efficiency
Include system wiring and controller losses as a separate efficiency so runtime reflects real-world power delivery.
Load Parameters
Enter total luminaire, controller and device power plus nightly lighting hours to define the load being served.
Runtime Result
Get the continuous runtime in hours, plus how many typical lighting nights that corresponds to.
Chemistry Reference
Built-in table compares lead-acid, gel, LiFePO4 and NMC batteries by DoD, efficiency and cycle life.
Rate Discharge Awareness
Understand the Peukert effect: higher discharge current reduces effective capacity, so runtime at 1C is only 70-80% of rated Ah.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | T = C × V × DOD × η_bat × η_sys / P |
| Battery Capacity | 1 - 1000 Ah |
| System Voltage | 12V / 24V / 48V |
| Depth of Discharge | 10% - 100% (lead-acid 50-70%, LiFePO4 80-90%) |
| Battery & System Efficiency | 50% - 100% each |
| Total Load Power | 1 W and above |
| Nightly Lighting Hours | 1 - 24 h/night |
| Industry Standards | IEEE 485, IEC 61427-1 |
| Output | Continuous runtime (h) + equivalent number of lighting nights |
Frequently Asked Questions
How is battery runtime calculated?
Runtime divides effective stored energy by load power: T = C × V × DOD × η_bat × η_sys / P. For a 12V 100Ah LiFePO4 battery at 90% DoD, 95% battery efficiency and 90% system efficiency feeding a 60W light, the runtime is 100 × 12 × 0.9 × 0.95 × 0.9 / 60 = 15.4 hours.
Why do the efficiencies matter so much?
No battery delivers its full rated capacity. Battery charge/discharge losses (lead-acid ~85%, lithium ~95%) plus wiring and controller losses (~90%) multiply together and directly reduce usable energy. Ignoring them overstates runtime by 20% or more on a typical system.
What is the Peukert effect and why should I care?
The Peukert effect describes how effective battery capacity falls as discharge current rises (C_eff = C × k(I)). A lead-acid battery delivers about 100% capacity at a low 0.1C rate but only 70-80% at a 1C rate. For precise results, use the manufacturer's discharge curves per IEC 61427-1.
How do I convert runtime hours into lighting nights?
Divide the runtime by the nightly lighting hours. For example, 15.4 hours of runtime with a 10-hour nightly schedule supports about 1.5 nights. This tells you how many consecutive nights of lighting the battery guarantees before the solar panel needs to recharge it.
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