Battery Life Calculator: Runtime & Discharge Estimator
Electrical & HVACCalculate exactly how long a battery will last based on capacity (Ah) and current draw (Amps). Features advanced settings for Peukert's Law, C-Ratings, and Depth of Discharge (DoD) for accurate engineering estimates.
How to Use Battery Life Calculator: Runtime & Discharge Estimator
Frequently Asked Questions
How do I calculate how long a battery will last?
The basic formula is Time = Capacity (Ah) / Current (A). However, this calculator uses a modified Peukert's Law formula to account for efficiency losses at high discharge rates, providing a much more realistic estimate than simple division.
What is Depth of Discharge (DoD)?
DoD indicates the percentage of the battery that has been discharged. Using 100% of a battery's capacity often damages it. To extend battery life, we recommend setting the DoD slider to 50% for Lead Acid batteries and 80% for Lithium-ion (Li-ion) or LiFePO4 batteries.
Why does the runtime decrease faster at high amps?
Batteries become less efficient as you draw power faster. This is known as the Peukert Effect. Internal resistance generates heat, wasting energy that would otherwise power your device. Our calculator adjusts for this "shrinkage" of capacity automatically.
What is a C-Rating?
The C Rating specified on a battery is defined by the rate of time it takes to safely charge or discharge a battery. A 1C rating means the battery will empty in 1 hour. A 10C rating means it can empty in 6 minutes (1/10th of an hour). Knowing the C-rating ensures you don't draw more current than the battery can safely handle.