Battery Life Calculator
Calculate accurate battery runtime and discharge time
Battery Life Calculator
Professional Battery Runtime Analysis
Results:
Runtime (Hours): 0.00
Runtime (Days): 0.00
Power Consumption (W): 0.00
Energy Consumed (Wh): 0.00
How to Use the Calculator
Basic Calculation
- Enter battery capacity in Amp-hours (Ah)
- Input the load current in Amps
- Specify battery voltage
- Set discharge efficiency (typically 80%)
- Enter cutoff voltage if known
Understanding Results
- Runtime shows how long battery will last
- Power consumption indicates load power
- Energy consumed shows total Wh used
- Results account for discharge efficiency
- Cutoff voltage affects actual runtime
Optimization Tips
- Higher capacity = longer runtime
- Lower load current = extended life
- Temperature affects battery performance
- Deep discharge reduces battery life
- Regular maintenance improves efficiency
Battery Life Fundamentals
Battery Capacity
Battery capacity determines runtime:
- Measured in amp-hours (Ah)
- Higher Ah equals longer runtime
- Temperature affects available capacity
Discharge Rate
- Higher current drains the battery faster
- Peukert's law affects available capacity
- Efficiency shifts with different loads
Key Formulas:
Basic Runtime: Hours = (Capacity × Efficiency) ÷ Load Current
Power Consumption: Watts = Voltage × Current
Energy: Wh = Watts × Hours
Calculation Formulas
Runtime (Hours):
Hours = (Capacity × Efficiency) ÷ Load Current
Power Consumption:
Watts = Voltage × Current
Energy Consumed:
Wh = Watts × Runtime Hours
Example Calculation
12V Battery System:
Capacity: 100Ah
Load Current: 5A
Efficiency: 80%
Runtime = (100 × 0.8) ÷ 5 = 16 hours
Power = 12V × 5A = 60W
Energy = 60W × 16h = 960Wh
How to Calculate Battery Life
1. Gather System Inputs
- Identify battery chemistry, nominal voltage, and rated capacity (Ah)
- Measure the continuous or average load current in amps
- Look up discharge efficiency or Peukert adjustments for your battery
- Confirm cutoff voltage or depth-of-discharge limits from the manufacturer
2. Run the Core Math
- Convert efficiency to decimal (e.g., 80% → 0.8)
- Usable capacity = Battery Ah × Efficiency
- Runtime (hours) = Usable capacity ÷ Load current
- Runtime (days) = Runtime hours ÷ 24
3. Adjust for Reality
- Reduce time if the cutoff voltage is higher than nominal
- Factor inverter or conversion losses into the load current
- Apply temperature or aging derates to heavy-use batteries
- Validate with discharge testing when uptime is critical
Compare how capacity, load current, and efficiency change the total runtime. Use these samples as a baseline before entering your exact scenario.
| Battery | Load Current | Efficiency | Estimated Runtime |
|---|---|---|---|
| 12V 12Ah | 1 A | 80% | ≈ 9.6 hours |
| 12V 40Ah | 2 A | 85% | ≈ 17 hours |
| 12V 100Ah | 5 A | 80% | ≈ 16 hours |
| 12V 200Ah | 10 A | 85% | ≈ 17 hours |
| 48V 5.12kWh LiFePO4 | 20 A | 95% | ≈ 12 hours |
| 12V 100Ah (200W load) | ≈ 16.7 A | 80% | ≈ 4.8 hours |
Battery Life FAQs
How do you calculate the life of a battery?
Multiply the battery capacity by efficiency to get usable amp-hours, then divide by the load current. Example: (100 Ah × 0.8) ÷ 5 A ≈ 16 hours before reaching the cutoff voltage.
How long does 40% battery life last?
Take the full-runtime estimate and multiply by 0.4. If your pack can run a load for 10 hours when full, 40% remaining gives about 4 hours assuming the same current draw.
How long will a 200Ah battery last calculator 12V?
Enter 200 Ah, your load current, and efficiency (often 70–90%). With an 8 A load and 85% efficiency, runtime ≈ (200 × 0.85) ÷ 8 ≈ 21 hours on a 12 V system.
How long will a 5.12 kWh battery last?
Convert 5.12 kWh to watt-hours (5,120 Wh) and divide by the load power. A steady 1,000 W load would run for roughly 5 hours at 95% efficiency, while lighter loads extend runtime proportionally.
How long will a 5000mAh battery last in hours?
5,000 mAh equals 5 Ah. Divide by the device draw in amps—at 0.5 A you get about 10 hours ideally, or closer to 8–9 hours after accounting for converter losses.
How long will a 12V 12Ah battery last?
Assuming 80% efficiency you have 9.6 usable amp-hours. At 1 A load the battery lasts about 9.6 hours, while a 3 A draw shortens runtime to roughly 3.2 hours.
How long will a 100Ah battery last with a 200W load?
A 200 W load on 12 V draws about 16.7 A. Using 80% efficiency, runtime ≈ (100 × 0.8) ÷ 16.7 ≈ 4.8 hours before reaching the recommended depth of discharge.
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