Enter your battery capacity and add multiple loads to instantly calculate runtime for each. Supports LiFePO4, lead acid, AGM and all battery types with Peukert effect and DoD analysis.
🔋 LiFePO4 Ready✅ Multi-Load📈 Peukert Effect🌡 Temperature🔥 DoD Analysis
Ah
Capacity Input
DoD
Depth of Discharge
Multi
Load Scenarios
FREE
Always Free
① Select Battery Type
⚡
LiFePO4
Peukert ~1.05
🔋
Li-ion / 18650
Peukert ~1.08
⚖
Lead Acid
Peukert ~1.25
🔥
AGM / GEL
Peukert ~1.15
Ah
V
② Add Your Loads
③ Results
🔋 Usable Battery Capacity
0 Ah
📈 Runtime Per Load Scenario
📊 Runtime Comparison Chart
🔋 LiFePO4 vs Lead Acid — Runtime Difference
LiFePO4 batteries deliver rated capacity even at high discharge rates (low Peukert effect). Lead acid batteries lose up to 50% capacity at high loads. At the same Ah rating, LiFePO4 gives 2-3x more usable runtime in real-world conditions.
⚠ Peukert Effect Explained
At high discharge rates, batteries deliver less total energy. A 100Ah lead acid at 100A (1C) may only deliver 60Ah. This calculator applies the Peukert exponent automatically based on your selected battery type.
Battery Runtime Calculator — How Long Will Your Battery Last?
Whether you are building a solar power system, a camper van electrical setup, an e-bike battery pack or a DIY power station, one of the most important questions is always: how long will my battery last? The answer depends on much more than just dividing Ah by amps. Battery chemistry, temperature, depth of discharge, inverter efficiency and the Peukert effect all play important roles.
This Battery Runtime Calculator handles all those factors automatically. Add multiple load scenarios to compare — for example, see how long your system lasts running just essential lights versus running everything including an inverter and a fridge.
How to Calculate Battery Runtime
Find your battery capacity in Ah (printed on the battery label)
Multiply by your voltage to get Wh: 100Ah × 12V = 1200Wh
Apply depth of discharge: 1200Wh × 80% DoD = 960Wh usable
Apply temperature derating if cold: 960Wh × 0.90 at 10°C = 864Wh effective
Apply inverter efficiency for AC loads: 864Wh × 0.90 = 777Wh delivered
Depth of discharge is how much of your battery capacity you actually use before recharging. Going deeper increases total capacity used per cycle but drastically reduces total cycle life. LiFePO4 at 80% DoD can last 3000+ cycles. Lead acid at 80% DoD may only last 200 cycles. At 50% DoD, lead acid batteries commonly reach 500-700 cycles. This calculator lets you set your preferred DoD to get accurate real-world runtime figures.
Why Temperature Affects Battery Runtime
At 25°C: full rated capacity — this is the reference temperature
At 10°C: approximately 90% of rated capacity available
At 0°C: approximately 80% for LiFePO4, 70% for lead acid
At -20°C: LiFePO4 delivers about 60%, lead acid may deliver only 30%
Heat above 40°C also reduces capacity and accelerates degradation
❓ Frequently Asked Questions
How do I calculate how long my battery will last?+
Use this formula: Runtime (hours) = (Battery Ah × DoD%) ÷ Load Current (A). For more accuracy, also apply temperature and Peukert derating, which this calculator does automatically.
How long does a 100Ah battery last?+
It depends on your load. At 10A draw: ~10 hours. At 20A: ~5 hours. At 50A: ~2 hours. Add temperature, DoD and Peukert factors for real-world accuracy. Use this calculator for exact results.
What is the Peukert effect?+
Higher discharge rates reduce total energy delivered by a battery. A lead acid battery rated 100Ah at 20-hour rate may only deliver 60-70Ah at a 1-hour rate. LiFePO4 is much less affected with a Peukert exponent close to 1.0.
What DoD should I use for LiFePO4?+
80% DoD is the standard recommendation for LiFePO4 for maximum cycle life (3000+ cycles). You can safely use 90% DoD for occasional deep cycles. Avoid going below 10% state of charge regularly.
What is the difference between Ah and Wh?+
Ah (Ampere-hours) measures charge capacity at a specific voltage. Wh (Watt-hours) measures energy. Wh = Ah × Voltage. A 100Ah 12V battery = 1200Wh = 1.2kWh. Wh is more useful for comparing batteries at different voltages.
How does an inverter affect battery runtime?+
Inverters convert DC battery power to AC. They are typically 85-95% efficient, meaning 5-15% of your battery energy is lost as heat in the inverter. Always account for inverter efficiency when running AC loads from a battery.
Why does cold weather reduce battery runtime?+
Cold temperatures slow the chemical reactions inside batteries, reducing how much charge they can deliver. At 0°C, lead acid batteries lose about 30% capacity. LiFePO4 loses about 20% at 0°C but recovers fully when warmed up.
Can I add multiple loads with different wattages?+
Yes! This calculator lets you add multiple load scenarios. Each load gets its own runtime result. You can compare light usage versus heavy usage scenarios side by side in the results table and bar chart.
What is C-rate and how does it affect runtime?+
C-rate describes discharge speed relative to capacity. 1C = full discharge in 1 hour. 0.5C = 2 hours. High C-rates (above 1C) reduce total energy delivered, especially in lead acid batteries. This calculator accounts for C-rate via the Peukert exponent.
Is this calculator free?+
Yes, 100% free forever. No signup, no watermark, no account needed. ToolsCoops tools are always free for everyone worldwide.
