How Many Batteries For a 3000W Inverter | Battery Sizing Calculator
Solar batteries are one of the most misunderstood components of a solar system, since they really are not anything “solar” by themselves. Instead, a solar battery is used to hold any excess energy that has been generated, and becomes available for use when solar energy is not being produced.
The most important thing to remember about the solar batteries is that the need to be deep cycle. Deep cycle batteries are designed to be discharged then recharged hundreds if not thousands of times.
A deep cycle battery is designed to discharged to nearly empty, but not completely and then be slowly recharged over time.
How many batteries do you need for a 3000 watt inverter?
The size of the battery needed will depend greatly on the total amount of watts your appliances uses, as well as climate conditions and exposure to sunlight. Because a battery is also used as a backup plan for sunless days, it is important to purchase a battery large enough to store enough electricity.
The 3000w inverter battery sizing must be done according to the type of batteries (Chemistry) and a required runtime.
To keep your batteries operating safely and reliably, it is always recommended to go for a somewhat larger battery bank- generally, for lead-acid batteries 6 x 100Ah 24V battery Or 12 x 100Ah 12V battery is the smallest battery bank recommended for the 24V 3000W inverter.
For lithium (LiFePO4) batteries a 24V 100Ah battery Or 2 x 100Ah 12V battery is the smallest battery bank recommended for the 24V 3000W power inverter.
Let me to explain how these values are calculated, for that, we'll divide this section into two parts: one for lithium batteries (LiFePO4) and one for lead-acid batteries.
What size lithium battery for 3000w inverter?
For a 12V 3000 watt inverter: 3000 watts / 12 volts = 250 amps.
This means that when fully loaded (3000 watts), it will draw 250 amps from the batteries (ignoring things like efficiency). So, you would need batteries with a capacity to meet a discharge rate (C-Rate) that allows the inverter to draw 250 amps safely.
Since the recommended C-Rate for lithium batteries is 0.5C, you would need at least batteries with a capacity of (250A ÷ 0.5 =) 500Ah 12V or 6 kWh.
For a 3000 watt inverter at 24 volts: 3000 watts / 24 volts = 125 amps. You would need batteries with a capacity that allows the inverter to draw 125 amps safely. So, you would need at least batteries with a capacity of (125A ÷ 0.5 =) 250 Ah 24V.
For a 3000 watt inverter at 48 volts: 3000 watts / 48 volts = 62.5 amps. You would need batteries with a capacity that allows the inverter to draw 62.5 amps safely. So, you would need at least batteries with a capacity of (62.5A ÷ 0.5 =) 125 Ah 48V.
Notes:- These calculations were done ignoring the inverter efficiency (inverter efficiency = 100%). For example, if the inverter efficiency is 95%, the inverter will actually consume 3157 watts to produce 3000 watts.
This calculation was based on the assumption that the inverter would be fully loaded (actually consuming 3000 watts). If the maximum load that will be connected to the inverter is less than the inverter's maximum capacity (3000 watts), which is the typical practical use, you can use the same calculations but replace 3000 watts with the total load to determine the battery requirements.
What size lead-acid battery for 3000w inverter?
According to the same calculations we did for lithium batteries, we can calculate the minimum number of lead-acid batteries recommended for the 3000W inverter by changing the discharge rate of the batteries to a safe range from 0.5C to 0.2C.
For a 12V 3000W inverter: You will need at least batteries with a total capacity of 1250 Ah 12V, or 15 kWh.
For a 24V 3000W inverter: You will need at least batteries with a total capacity of 625 Ah 24V.
For a 48V 3000W inverter: You will need at least batteries with a total capacity of 313 Ah 48V.
Here is a calculator that can perform all of these calculations for you.
Inverter Battery Sizing Calculator
We have provided a list of common appliance and their power consumption at the bottom of the page. This can then be entered into Total load above.
Understanding C-Rate of discharge
The important factor to consider when calculating the number of batteries needed for the inverter is the type of batteries you will use because it determines their maximum discharge rate (C-Rate).For example, the C-Rate of lithium battery is 1C, which means for a 100 Ah battery we can draw (100Ah x 1C =) 100 A, but the recommended C-Rate is 0.5C or less.
For lead-acid batteries, the C-Rate is 0.2C (C20 or C/5), which means a 100 Ah battery we can draw (100Ah x 0.2C =) 20 A, but the recommended C-Rate is 0.05C.
Therefore, battery with higher recommended C-Rates can provide a higher discharge current, reducing the number of batteries needed to meet the inverter's requirements.
Note that though a battery is rated as 100Ah @ 0.05C (20 hour rate), it does not mean that you cannot draw more than 5A. You can still draw more current like 40A but remember that if you keep on doing this you will have capacity loss due to high discharge current and you will shorten the battery’s lifespan.
Inverter Battery Sizing
The time a battery will last when powering a 3000-watt inverter depends on the battery bank's capacity and the load connected to the inverter. For example, if you use a single 12V 100Ah lead-acid battery to power a 2000W load, the battery will be depleted in about 15 minutes. However, using 10 of these batteries with the inverter will extend the runtime to approximately 5 hours.
- Capacity loss due to high discharge current: 166A @12V is a current of 1.7C, so you will only get about 41% of the battery's capacity due to internal heat generation.
This means the inverter will draw (2000 W / 12 V =) 166 Amps from the battery to supply 2000 watts. For example, based on the datasheet of a 12V100 Ah lead-acid battery below, discharging the battery at a rate of 166 A will last for approximately 15 minute.
When connecting 10 x 12V 100 Ah battery in parallel, each battery can discharge up to 16A, giving us a total of 160A available for discharge. Based on the battery's characteristics, if we discharging it at 16A it will last for 5 hours.
Similarly, we will only need 18 batteries (18 x 9.20 A = 165 amps) to power the load (2000W) continuously for 10 hours.
Tricks for using the inverter battery sizing Calculator Above without knowing the Watts of an Appliance
There are times that you don't know the consumption of a hypothetical situation. To get you closer, you can start by selecting the appliances from this drop down menus below. To the right will appear typical wattage values for the appliance you selected.
Remember, for the most accurate information look on your appliance to find its wattage rating (or it amperage rating and then multiply that by its voltage to approximate its wattage).
= Watts
Mohamed Bellamine
I'm the blogger behind Goo SolarPower. As a solar engineer, and a strong supporter of renewable energy. I've always been interested in Solar devices. I loves to write articles, guides, and tutorials about solar PV technology. Through goosolarpower.com I want to help people build and understand how solar power systems work.