Electronics Calculators
Battery Life Calculator
Estimate battery runtime from capacity (mAh / Ah), load current, and chemistry type. Includes depth-of-discharge correction, temperature derating, multi-load scenarios, and cycle life estimation.
Battery Life Calculator
Runtime, energy, cycle life — real-time analysis
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Battery Chemistry
Parameters
mAh
mA
V
%
%
%/mo
°C
Estimated Battery Life
—hrs
Enter values above to calculate
Usable Capacity—
Effective Capacity—
Energy Stored—
Temp Derating—
Runtime
—
hours : minutes
Runtime
—
days (continuous)
Energy Used
—
Watt-hours (Wh)
Power Draw
—
Watts (W)
Depth of Discharge (DoD)
0%80%100%
Circuit Efficiency
0%90%100%
Temperature Capacity Factor
0%100%100%
Configure a multi-cell battery pack by specifying how many cells are connected in series (raises voltage) and parallel (raises capacity). The calculator shows pack-level voltage, capacity, energy, and runtime.
Single Cell Specifications
mAh
V
mΩ
C rate
Pack Configuration
cells
cells
mA
%
Pack Runtime
—hrs
Configure cells above
Pack Voltage (S x V_cell)—
Pack Capacity (P x C_cell)—
Total Energy—
Total Cells—
Pack Voltage
—
Volts (V)
Pack Capacity
—
mAh
Pack Energy
—
Watt-hours (Wh)
Pack Int. Resistance
—
mΩ
Max Discharge Current
—
Amperes (A)
C-Rate at Load
—
C (load / capacity)
Pack Diagram
Series-Parallel Cell Layout
Cell (S=series, P=parallel index)
Series connection (voltage adds)
Series Connection
Voltage multiplies by number of cells. Capacity stays the same as a single cell. Use to reach higher system voltages (e.g. 3S Li-Ion = 11.1 V).
Parallel Connection
Capacity multiplies by number of cells. Voltage stays the same as a single cell. Internal resistance divides. Use to extend runtime or increase current output.
Add multiple loads to calculate combined discharge current and total battery runtime for your system.
Battery Parameters
mAh
V
%
Load Devices
| Device / Component | Current (mA) | Duty Cycle (%) | Avg Draw (mA) | Runtime |
|---|
Total Avg Current
— mA
System Runtime
— hrs
Total Power
— W
Cycle Life Inputs
%
cyc/d
%
Rated Cycle Life (100% DoD)—
Adjusted Cycle Life (at selected DoD)—
Estimated Service Life—
Total Energy Throughput—
End-of-Life Capacity (80% point)—
Cycle Life Rating—
DoD Impact: Reducing depth of discharge dramatically increases cycle life. A Li-Ion at 50% DoD may achieve 1,500+ cycles vs 300–500 at 100% DoD. LiFePO4 is the most DoD-tolerant chemistry.
Basic Runtime
T = C / I
T = Runtime (hours), C = Capacity (mAh), I = Current (mA). Simple ratio — the foundation of all battery calculations.
With DoD
T = (C x DoD%) / I
Usable capacity is limited by Depth of Discharge. Li-Ion: 80%. LiFePO4: 90%. Lead-Acid: 50%. Protects battery cycle life.
With Efficiency
T = (C x DoD x n) / I
n = circuit efficiency (0 to 1). Accounts for converter losses, regulator losses, and wiring resistance. Typical n = 0.85 to 0.95.
Energy Stored
E = C(Ah) x V
Energy in Watt-hours (Wh). E.g., 2000 mAh at 3.7 V = 7.4 Wh. Essential for comparing batteries of different voltages.
Temperature Derating
C_T = C x f(T)
Capacity reduces at low temperatures. At 0 C, Li-Ion loses approx 20% capacity. f(T) is approx 1 – 0.005 x (25 – T) for T below 25 C.
DoD vs Cycle Life
Cycles_adj = Rated x (1/DoD)^1.5
Approximate relationship. Lower DoD exponentially extends cycle life. Exact factor varies by chemistry and manufacturer.
How to Calculate Battery Life
The fundamental battery life formula is: Runtime (hours) = Battery Capacity (mAh) divided by Load Current (mA). For example, a 3000 mAh battery powering a device that draws 300 mA will last approximately 10 hours under ideal conditions.
Real-world battery life is always lower than this theoretical maximum. Three key correction factors apply: Depth of Discharge (DoD) limits how much capacity you should use to protect cycle life, circuit efficiency accounts for power converter losses, and temperature derating reduces effective capacity in cold environments.
Rule of thumb: Multiply your theoretical runtime by 0.70 to 0.85 for a realistic real-world estimate. This accounts for efficiency losses, self-discharge, and aging effects combined.
Battery Chemistry Comparison
Li-Ion is the most common choice for portable electronics — high energy density, 80% recommended DoD, and 300–500 cycle life. LiFePO4 (Lithium Iron Phosphate) offers superior cycle life (2000+ cycles) and safety, ideal for solar storage and EVs. Lead-Acid is cost-effective for large stationary applications but must not be discharged below 50% DoD to preserve cycle life. NiMH is a reliable middle ground with moderate energy density and no memory effect.
Frequently Asked Questions
How do I calculate battery life from mAh?
Divide the battery capacity in mAh by the load current in mA. A 2000 mAh battery powering a 200 mA load lasts approximately 10 hours theoretically. Multiply by an efficiency factor of 0.80 to 0.90 for real-world estimates. Use the calculator above for a complete analysis including DoD and temperature correction.
What is Depth of Discharge (DoD) and why does it matter?
Depth of Discharge is the percentage of battery capacity used before recharging. Discharging a Li-Ion battery to 100% DoD may yield 300 cycles, while limiting to 80% DoD can extend life to 500+ cycles. LiFePO4 batteries are most tolerant — they can sustain 80–90% DoD with 2000+ cycles. Lead-acid batteries should never exceed 50% DoD to avoid sulfation damage.
Why does cold temperature reduce battery life?
Low temperatures slow the electrochemical reactions inside batteries, reducing the speed at which charge carriers can move. Li-Ion batteries lose approximately 20% capacity at 0°C and up to 40% at -20°C compared to their rated capacity at 25°C. This is temporary — capacity largely recovers when the battery returns to room temperature.
What is the difference between mAh and Wh?
mAh (milliamp-hours) measures charge capacity at a specific voltage. Wh (watt-hours) measures actual energy stored and is voltage-independent, making it more useful for comparing batteries with different voltages. Convert using: Wh = mAh x V divided by 1000. A 2000 mAh Li-Ion at 3.7 V stores 7.4 Wh of energy.
Calculated values are estimates for ideal conditions. Actual battery life varies with temperature, age, discharge rate, and manufacturer specifications. Always refer to battery datasheets for critical applications.
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