Watt-hours (Wh) is a measure of energy. 1 Wh = 1 Watt for 1 hour.
Watts (W) is the rate at which energy is consumed by your device(s).
Account for energy lost during discharge and conversion (e.g., inverter). Enter 10 for 10% loss.
Estimated Battery Run Time:
–:–:–
Understanding Battery Run Time and Calculations
The run time of a battery is the total duration for which it can supply power to a device or system before depleting its stored energy. This is a critical metric for everything from portable electronics and electric vehicles to backup power systems and renewable energy storage. Several factors influence this run time, primarily the battery's total energy capacity and the power consumption of the connected load.
The Basic Formula
The fundamental calculation for battery run time assumes ideal conditions (no energy loss). It's derived from the definition of Watt-hours (Wh) and Watts (W):
Run Time (hours) = Battery Capacity (Wh) / Average Load (W)
For instance, if a battery has a capacity of 50,000 Wh and it's powering a device that consumes an average of 100 W, the theoretical run time would be:
50,000 Wh / 100 W = 500 hours
Accounting for Real-World Losses
In reality, batteries are not perfectly efficient. Energy is lost due to:
Internal Resistance: Batteries generate heat as current flows through them.
Discharge Rate: Higher discharge rates can sometimes reduce the usable capacity of a battery.
Inverter Efficiency (if applicable): If you're converting DC battery power to AC for devices, inverters are not 100% efficient and lose energy as heat.
Temperature: Extreme temperatures can affect battery performance and capacity.
Battery Age/Health: Older batteries have reduced capacity.
To account for these losses, we introduce an Efficiency Loss factor. If a system is 90% efficient, it means 10% of the battery's energy is lost. Therefore, the available energy is effectively reduced. The formula becomes:
First, calculate the effective capacity considering the loss:
Solar Power Systems: Estimating how long battery banks can power a home during outages or at night.
Electric Vehicles: Though EV ranges are typically miles, the underlying principle relates to battery capacity and energy consumption.
Portable Power Stations: Determining run time for camping, job sites, or emergency backup.
UPS Systems: Calculating how long a Uninterruptible Power Supply can keep critical equipment running.
Electronics Design: Estimating battery life for battery-powered devices.
By understanding and accurately calculating battery run time, users can make informed decisions about power management, system sizing, and energy storage solutions.
function calculateRunTime() {
var batteryCapacity = parseFloat(document.getElementById("batteryCapacity").value);
var averageLoad = parseFloat(document.getElementById("averageLoad").value);
var efficiencyLoss = parseFloat(document.getElementById("efficiencyLoss").value);
var calculatedRunTimeSpan = document.getElementById("calculatedRunTime");
// Clear previous results
calculatedRunTimeSpan.textContent = "–:–:–";
// Input validation
if (isNaN(batteryCapacity) || batteryCapacity <= 0) {
alert("Please enter a valid Battery Capacity (must be a positive number).");
return;
}
if (isNaN(averageLoad) || averageLoad <= 0) {
alert("Please enter a valid Average Load (must be a positive number).");
return;
}
if (isNaN(efficiencyLoss) || efficiencyLoss 100) {
alert("Please enter a valid Efficiency Loss percentage (between 0 and 100).");
return;
}
// Calculate effective capacity
var effectiveCapacity = batteryCapacity * (1 – (efficiencyLoss / 100));
// Calculate raw run time in hours
var rawRunTimeHours = effectiveCapacity / averageLoad;
if (rawRunTimeHours = 60) {
hours += 1;
minutes = 0;
if (hours >= 24) {
days += 1;
hours = 0;
}
}
// Format the output string
var formattedRunTime = "";
if (days > 0) {
formattedRunTime += days + (days === 1 ? " day" : " days") + ", ";
}
formattedRunTime += hours + (hours === 1 ? " hr" : " hrs");
formattedRunTime += ", " + minutes + (minutes === 1 ? " min" : " mins");
calculatedRunTimeSpan.textContent = formattedRunTime;
}