When the power goes out, the one thing you instantly rely on is your inverter battery. But the most common question that comes to mind is —
“How long will my 150Ah battery last?”
Well, don’t worry — in this post, you’ll not only learn how to calculate your battery backup time but also understand the factors that affect it and how to increase it for better performance.
Step-by-Step: How to Calculate 150Ah Battery Backup Time
The formula to calculate the backup time of any inverter battery is quite simple:
Backup Time (in hours) = Battery Capacity (Ah) × Battery Voltage (V) × Battery Efficiency / Total Load (W)
Let’s break it down for a 150Ah battery (which is the most common choice for homes and small offices).
Example:
Battery Capacity = 150 Ah
Battery Voltage = 12 V
Battery Efficiency = 0.85 (i.e. 85%)
Total Load = 300 Watts (Suppose you are running lights, fans, and a TV)
Backup Time = 150 × 12 × 0.85 / 300
= 5.1 hours (approx)
So, if your load is 300 watts, your 150Ah battery can run for around 5 hours continuously.
Want to Quickly Estimate? Here’s a Simple Table
| Load (Watts) | Backup Time (Approx.) | Usage Example |
|---|---|---|
| 100 W | 15 hours | 3 LED bulbs + 1 fan |
| 200 W | 7.5 hours | 3 fans + 3 LED bulbs |
| 300 W | 5 hours | 2 fans + 1 TV + 3 lights |
| 400 W | 3.8 hours | 1 fridge + 2 lights |
| 500 W | 3 hours | 1 TV + 1 fridge + 2 fans |
(Backup time may vary depending on battery age, inverter efficiency, and temperature.)
Factors That Affect Battery Backup Time
Even if you have the same 150Ah battery, two people may get different results. Here’s why:
Battery Efficiency – Older batteries lose efficiency, which means shorter backup.
Load Consumption – The more appliances you run, the faster the power drains.
Battery Type – Tubular batteries usually last longer and deliver better performance than flat plate or local batteries.
Charging Condition – Undercharging or overcharging can reduce battery life and backup capacity.
Temperature – Extreme heat or cold can affect the chemical reaction inside the battery.
How to Improve Your 150Ah Battery Backup
You can easily extend your inverter’s backup time with a few smart tips:
Use energy-efficient appliances (LEDs, BLDC fans).
Keep your battery terminals clean to ensure smooth power flow.
Make sure your battery is fully charged before a long power cut.
Prefer tubular batteries — they offer deeper discharge cycles and better life.
Do regular maintenance and water topping if it’s not a sealed battery.
Free 150Ah Battery Backup Time Calculator (Quick Formula)
You can calculate backup for any load with this quick formula:
Backup Time (hours) = (150 × 12 × 0.85) / Your Load in Watts
Example:
If your load is 250W
= (150 × 12 × 0.85) / 250
= 6.12 hours
So, your 150Ah battery will run about 6 hours for a 250W load.
Why Tubular Batteries Are the Best for Long Backup
If you live in an area with frequent or long power cuts, choosing a tubular battery is the smartest option.
Here’s why:
Longer life span (up to 5–8 years)
Deep discharge recovery
Low maintenance
Ideal for high-temperature conditions
Consistent backup performance
That’s why brands like Myoko India Pvt. Ltd. design advanced tubular batteries that deliver maximum efficiency, durability, and stable backup — making them ideal for home, office, and industrial use.
Final Words
Your 150Ah inverter battery can provide 3 to 15 hours of backup depending on your power load. By using the above battery backup calculator, you can easily predict and plan your usage during outages.
And if you’re looking for a long-lasting, high-performance tubular battery,
Myoko India Pvt. Ltd. is one of the best battery manufacturers and suppliers, serving countries like Nepal, Sudan, Nigeria, Syria, Afghanistan, and Uganda — offering reliable power solutions built for tough conditions.
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