Calculate UPS Battery Runtime | Backup Time in Hours, Minutes & Seconds
💡 Formula: Backup Time (hours) = (Battery Ah × Voltage × DOD) / Load (W)
Backup Time = (Ah × V × DOD) / Load
📖 Battery Backup Calculator
This tool calculates the battery backup time for UPS, inverter, and solar battery systems. Enter battery capacity (Ah), voltage, load (watts), and depth of discharge (DOD) to get the estimated runtime in hours, minutes, and seconds. Essential for UPS sizing and power backup planning.
📐 Battery Backup Formulas
Backup Time (hours): T = (Ah × V × DOD) / Load Energy (Wh): E = Ah × V Usable Energy: E_usable = Ah × V × DOD / 100
Where: Ah = Battery Capacity (Ampere-hour) V = Battery Voltage (V) Load = Connected Load (Watts) DOD = Depth of Discharge (%)
📊 Typical Battery Backup Times
Battery (Ah)
Voltage
Load (W)
Backup Time
Usable Energy
100Ah
12V
100W
9.6 hrs
960Wh
100Ah
12V
200W
4.8 hrs
960Wh
150Ah
12V
200W
7.2 hrs
1440Wh
200Ah
12V
150W
12.8 hrs
1920Wh
100Ah
24V
300W
6.4 hrs
1920Wh
50Ah
12V
50W
9.6 hrs
480Wh
📌 Battery Types & DOD Recommendations
Battery Type
Max DOD
Recommended DOD
Efficiency
Cycle Life
Lead Acid (C20)
50%
30-40%
80-85%
200-500
Tubular / Inverter
80%
50-70%
85-90%
500-1000
Lithium Ion (LFP)
95%
80-90%
95-98%
2000-5000
💡 Tips for Maximizing Battery Backup
Use energy-efficient appliances - LED lights, inverter ACs, energy star devices
Reduce load - Turn off unnecessary devices during power cuts
Choose the right battery - Tubular batteries last longer than flat plate
Use appropriate DOD - Deeper discharge reduces cycle life
Consider Lithium - Higher efficiency and deeper DOD, but higher cost
🔧 How to Use This Calculator
Enter battery capacity (Ah) - from battery label
Enter battery voltage (V) - 12V, 24V, 48V, etc.
Enter load (watts) - total power consumption of connected devices
Select battery type - Lead Acid, Lithium, or Tubular
Enter Depth of Discharge - recommended values shown in table
Results include backup time in hours, minutes, seconds, and energy details
❓ Frequently Asked Questions (FAQ)
❓ How to calculate battery backup time? ▼
Backup time (hours) = (Battery Ah × Voltage × DOD) / Load (Watts). This calculator does this automatically.
❓ What is Depth of Discharge (DOD)? ▼
DOD is the percentage of battery capacity that is used. For lead-acid, recommended DOD is 30-50%. For lithium, it can be 80-90%.
❓ How long will a 100Ah battery last? ▼
A 100Ah 12V battery with 80% DOD running 100W load will last about 9.6 hours. Formula: (100 × 12 × 0.8) / 100 = 9.6 hours.
❓ Which battery gives the best backup? ▼
Lithium-ion batteries give the best backup due to higher DOD (95%) and efficiency. Tubular batteries are a good cost-effective option for home inverters.
❓ What is the difference between C10 and C20 battery? ▼
C20 rating means the battery is rated for 20-hour discharge. C10 is rated for 10-hour discharge. C20 batteries are more common for home inverters.
❓ How many batteries do I need for my UPS? ▼
Calculate total Ah needed: Ah = (Load × Hours) / (Voltage × DOD). Then select batteries accordingly. This calculator helps you verify the backup time.