How Many Batteries For a 3000W Inverter?

Are you wondering how many batteries are needed for a 3000W inverter? In this video, I will provide you with surprising insights, especially since many guides often get this wrong. I'll explore two examples: one with a lithium battery and another with a lead-acid battery, to demonstrate the ideal setup for your needs.

Many people use a 3000W inverter with just a 12V 100Ah battery, leading to early battery failure. I'll show why this happens and what you should do instead.

In this detailed guide, I'll cover:

- The importance of limiting current to 100Amps in an off-grid solar power system, and how it leads to reduced wiring costs, cheaper charge controllers, and higher efficiency.
- The calculation for a 3000W inverter, demonstrates why a 48V system is more efficient and cost-effective.
- The concept of C-rate for both lead-acid and lithium (LiFePO4) batteries, and why it's crucial for battery longevity and performance.

I'll also provide a practical example using lithium batteries, showing the calculations for a 48V system and why it's a superior choice. Plus, I'll repeat the process for lead-acid batteries, highlighting the differences in size, weight, and efficiency.

Remember, always fully charge your batteries before connecting them and respect the C-rate to ensure maximum lifespan.

For those interested in lithium batteries:

[nicflanagan]

Your book was the 1st one I bought on the subject of Solar Power. I bought others, but kept referring back to yours for a simple clarification.
The content and ease to follow on the various subjects is excellent. Many Thanks 🙏🏼

[WalrusRiderEntertainment]

I worked in the battery industry for 10 years and you are teaching me new stuff in some of your videos. Well done

[OH-cjif]

This is really helpful, thanks for explaining it. I am just about to DIY a solar and battery system !

[damianbutterworth]

I ran my house off grid with 2 kilowatts of panels. 80 amp charge controller, 500 amp hour batteries(6 12 volt caravan batteries), 3500 watt sine wave off grid inverter. I never ran a heavy load at night. 24 volt system. This is in the UK. Worked great for at least 9 months of the year. I fitted a separate rings mains so I could switch to grid with a different socket in each room.

[wekapeka]

Very clearly explained with good graphics.

[twissted]

Very useful. I send it to my clients when dealing with what's needed in there RVs.

[frogsintheforest]

This is incredible! I can tell you, that I have visited all solar specialists along the Queensland coast, from the NSW border to Rockhampton, where they have no idea how to calculate the capacity of a 12 volt battery to produce 240 V. Using their own words, they had no idea how to calculate it and some said you just need to purchase additional 12V batteries to calculate it. Of course it has taken me until now to learn how to calculate it. Cheers

[blakeyscribner]

That’s the best video that I have ever understood on battery set up !

[Mag]

Great info for longer-term setups.

For short term, I use a 12v 100AH battery connected to a 3000 watt inverter. My total amp draw is about 12 amps per hour if I opt to run everything I need at the same time. This carry's the load for about 6 hours. I have a second battery that I charge on a propane generator while the other one is carrying the load, then switch them out. It takes about 1.5 hours to charge the battery, and I get about 14 hours of run-time on the generator for a 20# tank, which means I could get about 48 hours of power to the things I need. AC unit/ portable heater/etc as each is needed) - I normally do not run everything 100% of the time, for example the window AC unit draws about 800 watts/5 amps by itself, so I tend to only run that intermittently, and hunker down in just one room with it running about 20 minutes per hour on average. - Same for a space heater if it is cold, though it has an even higher current draw)

[theosalt]

A really well structured video, Thank you for being ome of the very few people who introduce your topic by outlining what you intend to demonstrate. ✴✴✴✴✴✴✴✴✴✴

[limey]

Thank you for the video and for the diagrams. I have been having trouble finding out and understanding this information, liked and subscribed!

[Qui-]

Yea, I agree it's best to size the inverter to a margin above the expected peak load. The total battery capacity would be determined by the expected average load, as would a solar array(plus a region/sunlight-based margin) and battery chargers.
Oversized inverters for a modest average expected power consumption has little effect, other than the idle current used to run the circuitry.

[WilliamRichardJames]

You actually sound like you know your subject ! Congratulations ! I have my doubts about many presenters on this platform as they often do not sound confident . Have a great year & life ! I will be buying your book, I bought Will Prowse book but when Amazon did not fulfill after payment was made, Will ignored

[joshm]

Concise & to the point. This really shows how far lithium batteries have come. Thanks!

[robertweekley]

Per your comments @ 1:21 & @ 1:49, it would seem a Lead Acid Battery Pack should also be given that "25% Buffer", meaning a 400 Ah x 48V pack, or 4S4P Pack is really safer!

But, most Lead Acid Batteries aren't rated at "0.2C" they are rated at a "20 Hour Discharge Rate". A 0.2C is actually a 5 Hour Discharge Rate (5 x 0.2 = 1.0). So a 20 Hour Rate, is 0.05C (20 x 0.05 = 1.00)

You can find "Some" Lead Acid Batteries, rated on a 10 Hour Discharge Rate, as well, if you get the Higher Priced And more Exotic ones.

However, this still doesn't count that Lead Acid Batteries shouldn't be discharged to "Dead" or "100%", but in normal use, should never be drawn down below "50%" of Rated Capacity! (If you want any meaningful Lifespan from them!) 😲

[Core-vumc]

You are oversimplifying a bit. Its not how big your inverter is but more what load you will put on it. Also you should have larger inverter than you need for starting motors unless you buy a coil based inverter. I'm running a 24v 960ah LiFePO4 system using a 3000 watt inverter. My daytime load (highest) is about 1000W. After a couple of days of cloudy skies, my batteries are empty. I could really use a larger battery however I don't have the solar capacity to support it (3.7kw) especially during the winter months.

[kevinward]

I did an experiment trying to make a system that was the cheapest possible that could run a 5000 BTU air conditioner. The single 12-volt 100 amp hour flooded lead acid battery it had lasted around 3 years. The cheap modified sine wave 1500 watt power inverter lasted almost that long. The system was also used to run a 500 watt heater in the winter. The goal was to use the power when it was available and not store it. The main drawback was that it would shut down on cloudy days often. Would be nice if there was an easy way of dialing in a cutoff voltage and having automatic restart with cheap inverters. Btw, I do only buy pure sine wave inverters now. They more than make up for the increased cost by how much longer they last, not to mention the increased efficiency, ... I've also moved up to sealed lead acid batteries.😂 My favorites are the 6 volt 200 amp hour Mighty Max sealed lead acid batteries. If you don't run them down too far they're supposed to last 10 years, completely maintenance free. You have to use 2 of course for a 12 volt system. You can get a pair for around $439 delivered from eBay. Seems to be the best bang for the buck concerning batteries I can find. They'll even build up your muscles, weighing around 64 lb each.😊

[TimeSurfer]

"Limit current to 100 Amps..."
This is why I shall do a 36V system.
And your explanation of the C-Rates of batteries explains why those Telephone Central Office Backup Banks I installed were so huge.
I'm a retired electrician, and, frankly, managed to miss that day in class.

[Derek_S]

I installed a 3KW pure sine wave inverter together with six 110 AH 12 volt leisure batteries wired in parallel on our boat six years ago. I didn't do any calculations. It was just my gut feeling of what was needed. We have a 230V fridge, a 230V 26" LCD TV, a 230V microwave, a 2KW 230V Electric kettle, a 17 inch Laptop PC run with a 230V charger and can go away from the mooring for a week at a time and run those things with no issue. We do have a diesel powered, 12 KVA generator installed too but rarely use it.

[adda]

This is by far the best explanation I have heard. New sub, thanks for your very informative vid!!