How Many 12V Batteries for 3000W Inverter

UPDATE: at 14:30 I used the wrong formula. It should be Capacity=Current/C-rate or 250A/0.2C=1,250Ah.
UPDATE 2: at 6:40 you should fuse every cable with a 200A fuse instead of one 350A fuse.

In this video, I'm tackling a question that some of you have asked: How many 12V batteries do you need to power a 3000W inverter? While I typically recommend using a 48V system for efficiency and simplicity, I understand that some of you already have a 12V inverter and need to make it work. That's why in this video, I'll break down everything you need to know to get your 12V system up and running effectively.

We’ll start with the basics: understanding your inverter's efficiency and how it impacts the power your batteries need to supply. A 3000W inverter can deliver up to 3000 watts of power to your appliances, but it’s important to note that inverters aren’t 100% efficient. In fact, most operate at around 90% efficiency. This means that your batteries need to supply more than 3000W to account for the energy lost during the conversion process. I’ll walk you through the math and explain how this affects your battery requirements.

Next, we'll dive into battery selection. For those using lithium batteries, I'll explain why these are generally the best choice for off-grid systems. I’ll calculate exactly how many 12V lithium batteries you need, depending on their capacity, to reliably power your 3000W inverter. For instance, if you're using 12V 100Ah lithium batteries, you’ll need three of them in parallel to meet your power needs. If you have larger 12V 200Ah lithium batteries, two in parallel will suffice. I’ll break down the calculations step-by-step to make it easy to follow.

After covering the batteries, we'll move on to wiring and fusing. This is a critical part of your setup, especially with a 12V system where high currents are involved. I’ll explain how to size your wires and fuses correctly to prevent overheating and other issues. You’ll learn why it’s sometimes necessary to use thicker cables or even multiple cables in parallel to handle the current safely. I’ll also show you a diagram that outlines the wire and fuse sizes needed for different setups, including how to split the current across multiple wires to make your installation easier and safer.

And for those of you considering a 48V or 24V system, I’ll explain why I typically recommend a 48V system for a 3000W inverter. With a 48V system, you can reduce the current, simplify your wiring, and even save on costs in the long run. I’ll show you the wire and fuse sizes needed for a 48V setup and compare it to what you’d need for a 24V system, so you can see the advantages for yourself.

I’ll provide some tips on how to connect your batteries to a busbar, why fusing each battery individually is a good safety practice, and how to choose the right busbar for your high-current system.

But what if you’re using lead-acid batteries? Lead-acid batteries have different characteristics and limitations compared to lithium. I'll discuss the concept of C-rate, which is crucial for understanding how much current you can safely draw from lead-acid batteries without drastically reducing their lifespan. To power a 3000W inverter with lead-acid batteries, you’d need a whopping 13 batteries in parallel! I'll explain why this setup is much less efficient and more cumbersome compared to a lithium setup, and why you might want to consider upgrading to lithium if you haven’t already.

[cleversolarpower]

UPDATE 1 : at 14:30 I used the wrong formula. It should be Capacity=Current/C-rate -> 250A/0.2C=1, 250Ah.
UPDATE 2: at 6:40 you should fuse every cable with a 200A fuse instead of one 350A fuse.

[marines]

One of the best instructional videos with clear and detailed steps.

[wilty]

As a beginner, I appreciate your your thorough and detailed explanation of the solar system setup. Thanks

[SoundzAlive]

Thank you, you have explained things much clearer than most other channels. All you explanations and designs translate perfectly for boats where it is critical to get it right. André in Sydney

[peterhepburn]

This is the best ever explanation of this subject. I’ve already sent it to my friends who are building camper power systems.
Thanks for this.

[billweber]

Nice job. You made things pretty simple on why higher voltage systems are more efficient, cheaper and easier to setup. Thanks again.

[VicariousAir]

Wow... That was the best explanation you could get. Answered why my RV keeps dying and why the RV mechanics that "fixed" the system may have just set me up to die in a fire.

[nobody]

Sailboat life (15 yrs) - my 329w hi output panel outperforms 500+ watt regular panels. I use 4 6v golf cart bats for total of 450 amp hrs. I often see the panel output 63+ volts and 20amp input from the Victron 30amp controller. I run a Victron inverter, and as a photographer I use calibrated monitor, computers, external drives, battery charging for many devices, etc.
Add the frig, lights, 8 fans, a real hifi stereo, blender, water pumps, shower sump pumps and the batteries are usually floated back down by noon. Next time I'm going lithium, maybe add another panel. Maybe not. It's the high output panels that make it possible. Otherwise there would be many solar panels needed.
If my sailing grounds weren't in FL, Bahamas, I would definitely need more panels, no doubt.

[daves]

Thank you for the reminder that we can use multiple smaller gauge wires to carry the high current loads from each battery!!! Much easier than working with 4/0 wiring.
On why 12v batteries, I started with a system to supply my RV with DC power first, and used 12V a Lithium battery systems because 24 or 48v system would need a DC-DC converter to supply ALL 12v DC needed by the RV for lights, propane heater, fans, water pump, 12v refrigerator and all of the DC controls for other appliances. Most DC converters have poor efficiency so there is a lot of heat/energy loss to power all the DC devices in the RV.
Then ….. we decide we want to expand our system to add an inverter for occasional use of AC appliances like a microwave oven or charging laptops/tablets/phones/etc and don’t want to replace our 12v battery bank.

[toddstanley]

Overall this is a great video and very informative. Understanding types of batteries is important. Lead acid standard car batteries are not the same as lead acid deep cycle. Deep cycle batteries are used in heavy equipment, commercial diesel trucks, and marine applications.
13 lead acid batteries is standard car batteries. If using marine or big truck 12 volt deep cycle the 4 is minimum 6 is good, 8 is best when talking about stored power. Deep cycle like LiPo discharges at a slower rate over time. Standard car batteries discharge quickly.

[jbreezy]

You just saved me from making a costly mistake looks like I need to get some Lipo batteries now thanks very clear informative video

[owolabiadeteye]

Thanks for time taken to prepare and deliver this insightful lecture. Great one boss

[kabandajamir]

The world's best teacher thanks sir

[nordic]

I have one of these in my camping car, plus 2x 120AH Kings 12V LFP batteries in parallel. Works great. I upgraded my alternator, and charge these LFP batteries @ 90A. Works great, too easy.
This inverter has a very quiet fan that is rarely even audible. I can recommend it hightly.
It also has a UPS function. The relay will switch from mains to inverter power in 30ms.
Buy it.

[Detourit]

You know your science, and your videos are detailed and a great help.👍

[bnsfamchannel]

great job sir...As a beginner, I appreciate your thorough and detailed explanation. Gbu.

[j.b.]

Nice job with your presentation! I am a power plant operator, and have these formulas on the brain, and had the calculations in place almost instantly when you asked your various questions on how to set up this system (safely).... As I say, great job! Thanks for the important service to others which you've provided here! Most house fires are electrical (malfunctions and failures) fires...so presenting good info, as you do, completely, (after amending the calculations in subsequent updates), will definitely save lives!
God bless you, brother! Happy new year!

[uupyerkilt]

Thank you so much as this is exactly the system I have been looking to install in our small travel trailer.

[angrydutchman]

Really awesome instructional videos . . . thank you! As a newbie to solar generated power, the 48v system you diagrammed in the video is very appealing. However, I am wondering if you might either, 1: add an addendum video on how to calculate needed solar panels to charge the EG4 battery, or 2: simply respond with the number needed and the calculation used to arrive at the required number.

Thanks and keep up the great work!

[UmpTSquat]

Nick, I am late watching this. I learned quite a bit from you in this video. Thank You. You explained things in a very easy to understand video. I have watched hundreds of hours of videos. I don't remember seeing it explained in this manner. Thank You again. I have subscribed. I'll go back and watch your other videos.