This article is highly important for individuals who want to understand the backup duration of their normal acid or lead-acid battery. In this post, we will provide detailed information on how to calculate the backup time of a battery. We’ll also explain the real capacity of the ampere-hours (Ah) written on a battery. For example, if you have a 100Ah battery, can you fully utilize its 100Ah capacity? Or how much of it can actually be used?
Battery Ampere and Capacity
On a battery, the ampere rating is usually written. For instance, in the image, you can see that the model is TX 1800, and a small label shows 185Ah, which represents the ampere rating. Each battery model has a different ampere rating. For example:
- TX 1800: 185Ah
- TX 2500: 230Ah
- TX 3500: 280Ah
This information pertains to Phoenix batteries. Similarly, Osaka, AGS, Exide, and Inverex also offer models like 1800, 2500, and 3500.
Tubular Batteries
Currently, tubular batteries are widely used. Models like 1800, 2500, and 3500 are available in the market. For example:
- The 1800 model typically has a 185Ah capacity.
Can We Fully Utilize the Battery Capacity?
The answer is No. Utilizing the full 185Ah would damage the acid battery. This is because a battery should not be discharged below 10.5 volts. Discharging beyond this limit can cause problems in recharging or reduce backup and charging efficiency.
Usable Capacity Formula
You can use a simple formula to determine the usable capacity of a battery: divide the ampere rating by 2. This means only 50% of the ampere capacity is usable.
For example:
- 185Ah ÷ 2 = 92.5Ah
This is a straightforward formula to calculate the usable capacity for any battery.
Converting Amperes to Watts
To calculate watts from ampere-hours, use the following method:
- Battery Voltage: 12V (when fully charged at 100%)
When the battery is charging, the voltage may show between 14.2 to 15 volts. During backup, the fully charged battery shows 12.8 volts.
For example:
- If a battery has 12.8V and 92Ah is usable: 12.8V × 92Ah = ~1200 Watts
Here are the approximate wattages for different models:
- TX 1800: ~1200W
- TX 2500: ~1500W
- TX 3500: ~1850W
These watts can be used all at once or spread over several hours depending on your load.
Power Consumption of Appliances
Different appliances consume varying amounts of power. For example:
- Normal 1-ton AC: 1500W per hour
- Inverter 1-ton AC: 900W per hour
- Normal 1.5-ton AC: 2000W per hour
- Inverter 1.5-ton AC: 1200W per hour
- Washing Machine: 500-900W per hour (depending on size)
- Iron: 1000W per hour
Backup Time Calculation
The backup time depends on your battery bank. Let’s calculate backup time for different scenarios:
Scenario 1: Four Ceiling Fans and Four Lights
- TX 1800 (185Ah): ~2 to 3 hours
- TX 2500 (230Ah): ~3.25 hours
- TX 3500 (280Ah): ~4 hours
Scenario 2: Four DC Fans and Four Lights
- TX 1800 (185Ah): ~5.25 hours
- TX 2500 (230Ah): ~6.5 hours
Key Considerations
- The above calculations are for new batteries. As the battery ages, its backup time will decrease.
- You can refer to the power consumption table for various appliances provided earlier.
Conclusion
These calculations can help anyone determine the backup time of their battery. Whether it’s a 5Ah or 200Ah battery, you can now easily calculate how long your battery will last and for how many hours your appliances can run. This information is especially helpful in determining whether your current battery bank is sufficient for your household load.
