Calculate How Long Will a 24V Battery Last

When setting up a solar power system, one crucial aspect is understanding how long your battery will last before needing to recharge. For systems that operate at 24V, whether you’re running a small backup system or powering larger loads, calculating the runtime of a battery is essential for planning and efficiency.

In this blog, we'll explore the factors that influence 24v battery running time and provide you with easy-to-follow formulas to estimate how long a 24V battery will last with different capacity ratings (e.g., 100Ah or 200Ah) and with an inverter.

 

 

How to calculate running time of 24v battery

To calculate how long a 24V battery will last, we can use the follow formula:

 

In this formula:

• Battery Capacity (Ah) refers to the amp-hour rating of the battery, indicating how much current it can supply over time.
• Battery Voltage (V) refers to the fixed voltage level of the battery, such as 12V, 24V, or 48V. In this case, it’s 24 volts.
• Power Consumption (Watts) is the total power drawn by the devices or appliances you are running.
• Inverter efficiency measures how effectively an inverter converts DC power from batteries or solar panels into usable AC power.
• Depth of Discharge (DoD) refers to the percentage of a battery's capacity that has been used.

LiFePO4 batteries, like those used in solar systems, are designed to withstand deep discharges better than other types of batteries, such as lead-acid. They can typically handle 3,000 to 5,000 cycles at an 80% DoD.

This means that regularly discharging the battery to below 80% of its capacity can help extend its lifespan as much as possible.

To protect battery life, it’s recommended to use a 50-80% DoD to maintain a balance between maximizing available power and preserving battery health over the years.

 

For example, PowMr 24V LiFePO4 battery's recommended DoD is 80%, you would multiply the battery's capacity by 0.80 to estimate how much usable energy you have available.

 

How Long Will a 24V Battery Last with an Inverter?

Inverters convert the DC power stored in batteries into AC power, which is essential for most household appliances. We can assume that when the inverter operates at full power, its rated power equals the power consumption, simplifying calculations.

For instance, let's take the PowMr 1000W inverter, which boasts an efficiency of 94% in converting DC current from a 24V battery.

Now, let’s explore some practical examples using two common battery capacities: 100Ah and 200Ah.

 

How Long Will a 24V 100Ah Battery Last?

Let’s assume we are using a PowMr 24V LiFePO4 battery with a capacity of 100Ah and a PowMr inverter rated at 1000W, with an efficiency of 94%. The recommended Depth of Discharge (DoD) for this battery is 80%, meaning we will use 80% of the battery’s total capacity to prolong its lifespan.

Applying these values to the formula mentioned earlier:

• Battery Runtime = 100Ah * 24V * 0.94 * 0.80 / 1000W

So, a 24V 100Ah battery will last 1.8hours powering a 1000W load through a 94% efficient inverter. This runtime can change based on the actual power consumption of your devices and the efficiency of the inverter.

 

How Long Will a 24V 200Ah Battery Last?

Using the same approach, we can calculate the runtime for a larger 24V 200Ah battery. Again, we will assume the same PowMr 1000W inverter with an efficiency of 94% and a Depth of Discharge (DoD) of 80%.

• Battery Runtime = 200Ah * 24V * 0.94 * 0.80 / 1000W ≈ 3.6 hours

Thus, a 24V 200Ah battery will last around 3.6 hours with a 1000w inverter.

 

Other factors affecting battery running time

While the above calculations provide a solid estimate of battery runtime, several other factors can influence actual performance:

Battery Type:
Different battery chemistries (such as lead-acid, AGM, or LiFePO4) have different discharge characteristics and tolerances. Lithium batteries, for example, can often be discharged deeper than lead-acid without damage, which affects runtime.

Battery Age:
Over time, all batteries lose capacity due to natural degradation. A brand-new battery will perform better than one that has been cycled hundreds of times.

Temperature:
Extreme temperatures (both hot and cold) can reduce a battery’s effective capacity and affect how long it can provide power.

Load Variability:
The runtime estimates above assume a constant load. In real-life applications, loads may vary throughout the day, affecting overall battery performance.

 

Conclusion

Calculating how long a 24V battery will last comes down to understanding your power consumption and the battery's capacity.

Keep in mind that real-world performance can vary based on factors such as battery type, age, and environmental conditions.

Understanding your battery's capabilities allows you to better plan your solar power system or backup solution, ensuring you have enough stored energy to meet your needs.