Battery operating time
Calculation of autonomy at different loads and capacities
to calculate battery life
Battery discharge time
🔋 How do you know how long your battery will last?
Our tool will help you accurately plan your backup power system. No more guessing when your inverter will shut down or your car battery will die. The calculator operates in two modes:
If you have an ammeter or know the exact current consumption of the load.
Convenient for household appliances. For example, you know that a boiler consumes 100 W and a light bulb consumes 15 W.
Where is this used in practice?
- 🚗Car audio and camping:Calculate how long the radio or refrigerator will last from the car battery on a picnic.
- 💻 UPS (Uninterruptible Power Supply): Find out the real time of a computer or server during a power outage.
- ☀️ Solar systems:Helps you choose the right battery bank capacity for an off-grid home.
How to get an accurate calculation?
- Select mode (Amperes or Watts).
- Enter the battery capacity (usually written on the case, for example, 60 Ah or 190 Ah).
- Specify the load.
- Important: Don't forget about the discharge factor. For lead batteries it is not recommended to discharge to zero; set the coefficient to 0.5–0.7. For Li-ion you can set 0.8–0.9.
Use this calculator before buying a battery so as not to overpay for extra capacity.
Frequently asked questions (FAQ)
❓ What coefficient (efficiency) should I indicate for the inverter?
If you connect 220V devices through an inverter to a 12V battery, part of the energy is spent on heating the inverter. Typically, the efficiency of a good inverter is 0.85 - 0.90. Please take this field into account for accurate results.
❓ Why is the actual operating time less than the estimated one?
Real time is influenced by three factors: temperature (capacity drops in cold weather), battery wear (old batteries hold up worse) and high starting currents of devices.
❓ Is it possible to completely discharge a car battery?
Ordinary (starter) lead-acid batteries are afraid of deep discharge. If you drain it to 100%, it may lose capacity forever. We recommend leaving at least 30-40% charge (coefficient 0.6).