Power Engineering

Battery Life Calculator Pro

This professional tool estimates battery runtime by analyzing Load Characteristics and Discharge Rate (C-Rate).

It features a Live Discharge Graph and a comprehensive safety analysis to ensure your configuration (Series/Parallel) matches the power demands of your application.

Battery Configuration

Input
Ah
V

Load Profile

A
%
%

Performance Analysis

Output
C-Rate

Safety Note

Runtime based on 50% DoD limit.
Low C-Rate (< 0.5C) recommended for longevity.

Live Discharge Characteristics

VOLTAGE (V) DISCHARGE CAPACITY (%) 0.2 C 2.0 C Your Load

Enter values above to see your load curve.

Key Parameters Explained

C-Rate (Discharge Rate)

A measure of how fast a battery is discharged relative to its maximum capacity. A 100Ah battery discharged at 100 Amps is 1C. At 200 Amps, it is 2C.

Tip: Keep Lead Acid below 0.2C and Lithium below 1.0C for long life.

DoD (Depth of Discharge)

The percentage of capacity removed from the battery. 100% DoD means the battery is completely empty.

Tip: Never drain Lead Acid below 50% DoD to avoid permanent damage. Lithium can safely go to 80-90%.

System Loss

Real-world inefficiencies. Inverters typically lose 10-15% of energy as heat during DC-to-AC conversion. Cables and connections also add resistance.

Tip: Use 15% loss for Inverters, or 5% for DC loads.

Discharge Stress

High current draws cause “Voltage Sag,” where voltage drops instantly under load. This tricks the system into thinking the battery is empty earlier than it really is.

Tip: If the calculator shows “High Stress” (Red), increase your battery bank size (Parallel).

How to Use This Calculator

Follow these steps to estimate accurate battery runtime.

1

Configure Battery Pack

Select your Chemistry (e.g., Lead Acid, LiFePO4). Enter the specs for a single cell, then specify how many are in Series (S) and Parallel (P).

2

Define Load

Toggle between Amps (DC current) or Watts (AC/Power load). If using Watts, you can adjust the Inverter Efficiency (typically 85%).

3

Analyze Safety

Review the Safe Runtime. Check the Discharge Stress (C-Rate) indicator—if it turns Orange or Red, your load is too high for the battery size.