Getting batteries/inverters into generator input.

[jwrezz]

I have a generator interlock on the side of my house. L14-30. I use a gasoline predator inverter generator with it, but I don't have the need too often. Was wondering if as a start if I could get some batteries, and I already have one and access to a second whistler 3kw modified sinewave inverters. Could I attach batteries to inverters and use a y adapter with dual 120v plugs to LM14-30 like this:

y-adapter

Then just flip my generator interlock and it'd work? Of course I'd love to gradually expand the system with LiFePO4 racks, and real inverters, but would this work?

 

[jwrezz]

Didn't get any response so figured I'd elaborate.
I have one of these interlocked into my main panel with a dual 30amp breaker:

https://a.co/d/gULunBM\

Found this "combiner" plug:

https://a.co/d/ajeV3g9

Wondering if two of these could plug into the combiner and into my generator input:

https://www.harborfreight.com/3000-watt-continuous6000-watt-peak-pure-sine-wave-power-inverter-57274.html

 

[BentleyJ]

Yes, but you would only get 120V on both bus bars in your main panel, NO 240V. Best practice would be to turn off any 240V breakers and all unnecessary 120V breakers since the inverter is really only large enough to run a few items like refrigerator, lights and computer-router. Maybe a coffee maker, toaster oven or microwave but only one at a time.

 

[Lane]

Yes, but you would only get 120V on both bus bars in your main panel, NO 240V. Best practice would be to turn off any 240V breakers and all unnecessary 120V breakers since the inverter is really only large enough to run a few items like refrigerator, lights and computer-router. Maybe a coffee maker, toaster oven or microwave but only one at a time.

Perhaps I'm reading your reply wrong but, isn't 240v simply 120v on one bus bar and 120v on the other?? When you measure bus bar to bus bar you will read 240v... Yes, singly measured to ground or neutral they are indeed only 120v. That Y adaptor is a good trick.

 

[jwrezz]

Perhaps I'm reading your reply wrong but, isn't 240v simply 120v on one bus bar and 120v on the other?? When you measure bus bar to bus bar you will read 240v... Yes, singly measured to ground or neutral they are indeed only 120v. That Y adaptor is a good trick.

Exactly what I was thinking. BentleyJ had me worried for a minute. Just to be clear, I'd use two inverters with separate batteries. As the y-cable works, one plug will feed one leg of the split phase, and the other plug will feed the other leg. If I have any 240volt things in my main panel (AC, compressor outlet, and a 240v sub panel for the upstairs addition to the house) it should feed them, but not necessarily be enough to power them. My other concern is the y-adapter's standard 120v male plugs. They likely couldn't deliver the full 3000 watts that the inverter says it's capable of. Looking at the inverters though, they same to have terminals for L, N, and G. Actually both AC input and output. Wonder if it has a built in charge controller? But the inverter's output I could hard wire the connections to my generator input from those terminals...Hopefully.

I'm an absolute beginner, but would love to try a simple DIY build, and begin learning. Already have plenty of grid tied solar that I'd love to be able to use to charge my batteries during an outage.

 

[jwrezz]

Just found the manual for the inverter. The AC input is for pass-through only. Not charging the batteries.

 

[jwrezz]

https://manuals.harborfreight.com/manuals/57000-57999/57274-792363572743.pdf

 

[Browse]

No, you can't use a 120V generator or inverter to power 240V equipment. You need two phases of 120V which are 180 degrees out of phase with each other. If you connect a 120V generator to both sides of your breaker panel, you need to turn all of the 240V 2-pole breakers off. All of the 120V outlets, lights and appliances should work fine.

 

[Browse]

I'm doing something similar with my generator interlock, but on a larger scale. I have a 240V Nema L14-30P input box on the side of the house for the generator connection which is connected in parallel ("Y") to another 240V L14-30P input panel and power display on the inside of the house. The output of this feeds the 240V 30A 2-pole interlock breaker. I will have a 240V Growatt 12k inverter mounted near the load center that will connect to the inside input box and running on four 48V rack mount batteries (20kWh total). When we lose power, we will turn on the interlock breaker and turn on the inverter to power the house. When batteries get low, we will turn off the inverter and connect the generator to power the house, while recharging the batteries after turning the inverter back on (with it's output off and disconnected). We expect to use the generator during the day and the batteries/inverter at night.

 

[jwrezz]

No, you can't use a 120V generator or inverter to power 240V equipment. You need two phases of 120V which are 180 degrees out of phase with each other. If you connect a 120V generator to both sides of your breaker panel, you need to turn all of the 240V 2-pole breakers off. All of the 120V outlets, lights and appliances should work fine.

But two separate inverters each powering one phase (one 120v leg) of the panel?

 

[jwrezz]

I'm doing something similar with my generator interlock, but on a larger scale. I have a 240V Nema L14-30P input box on the side of the house for the generator connection which is connected in parallel ("Y") to another 240V L14-30P input panel and power display on the inside of the house. The output of this feeds the 240V 30A 2-pole interlock breaker. I will have a 240V Growatt 12k inverter mounted near the load center that will connect to the inside input box and running on four 48V rack mount batteries (20kWh total). When we lose power, we will turn on the interlock breaker and turn on the inverter to power the house. When batteries get low, we will turn off the inverter and connect the generator to power the house, while recharging the batteries after turning the inverter back on (with it's output off and disconnected). We expect to use the generator during the day and the batteries/inverter at night.

Reading and learning I think a 48v system is more what I should be leaning towards. I have found a few 240v split phase inverters. Many not costing much more than 2 if the 12v 3000 watt inverters.

 

[Browse]

Reading and learning I think a 48v system is more what I should be leaning towards. I have found a few 240v split phase inverters. Many not costing much more than 2 if the 12v 3000 watt inverters.

This is my setup I'm working on. It's for emergency backup purposes only atm.

 

[jwrezz]

This is my setup I'm working on. It's for emergency backup purposes only atm.

That is pretty much my exact idea. The AC input to the inverter would be turned off when the grid is down, I assume? Do you have 2 generator inlet boxes or just one and you decide weather to plug in the generator or inverter? If you have 2, I would think you'd only have the generator running (inverter off) or inverter on (generator off). Could you charge the batteries by running the generator and having the breaker from the main load center to back to the inverter switched back on? I was looking at the Sungold Power units:

6000W 48V Hybrid Solar Inverter Split Phase 120/240VAC (Grid Feedback & Batteryless)

Hightlight: ★ Solar Inverter Charger: 6000W DC 48V Split Phase Low Frequency Inverter, AC input 240V AC, AC Output 120V/240V, MPPT Max 120A solar charger and 120A AC charger 100A ★ Parallel Kit: This grid tie solar inverter parallel supports up to 9 units (54KW Max), 120V/240V split phase output...

sungoldpower.com

or

6000W 48V Split Phase Pure Sine Wave Solar Inverter Charger

Sungoldpower 6000W 48V Split Phase Pure Sine Wave Solar Inverter Charger. Pure Sine Wave Solar Inverter charger is a combination of an inverter, AC charger, Mppt solar charger and Auto-transfer switch into one complete system.It is packed with unique features and it is one of the most advanced...

sungoldpower.com

 

[Browse]

That is pretty much my exact idea. The AC input to the inverter would be turned off when the grid is down, I assume? Do you have 2 generator inlet boxes or just one and you decide weather to plug in the generator or inverter? If you have 2, I would think you'd only have the generator running (inverter off) or inverter on (generator off). Could you charge the batteries by running the generator and having the breaker from the main load center to back to the inverter switched back on? I was looking at the Sungold Power units:

Yes, the input to the inverter is disconnected when it's powering the house. When the generator is hooked up and powering the house, the output of the inverter is disconnected and batteries can charge up via the inverter after the 240V input cord is plugged back in.

I also looked at Sungold and AIMs, but decided on Growatt since they can communicate with the Lifepower4 batteries via the BMS port. I looked at the 6k units, but saw that a bunch of people had issues starting larger motor loads, so I went with the 12k even though I likely won't use all the power at this time. I like to have headroom so everything runs cooler. I put a webcam over the power input & display box so I can see and manage the loads on each leg from my phone.

 

[jwrezz]

Love that simple setup! Is the power meter something you put together yourself? I'd love to see inside, but pretty much understand how it's working. Two inputs, one output, only you have to be in control of which input and not both at the same time. Thanks again!

 

[Browse]

Love that simple setup! Is the power meter something you put together yourself? I'd love to see inside, but pretty much understand how it's working. Two inputs, one output, only you have to be in control of which input and not both at the same time. Thanks again!

Yeah, I just used WAGO connectors for all the 10 AWG wires, with the current sensors for the meters on the L1 and L2 wires going to the interlock breaker.

https://www.amazon.com/gp/product/B085Z8KVBT/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

You can use smaller gauge wires to feed the meters since they draw very little power. I used a jigsaw and a Dremel cutting blade for the the meter holes.

This is the box I used:

https://www.amazon.com/dp/B005UP9M3G?ref=ppx_yo2ov_dt_b_product_details&th=1

Input plug for the box:

https://www.amazon.com/dp/B074KMRNHV?ref=ppx_yo2ov_dt_b_product_details&th=1

Meters:

https://www.amazon.com/gp/product/B07YC1XHKQ/?th=1

Had to buy a 2-1/4" hole saw for the input plug:

https://www.amazon.com/57mm%EF%BC%88-inch%EF%BC%89-Metal-Cutter-Stainless/dp/B0B31BSKPV/ref=sr_1_6?crid=F1SKSANVO4B8&keywords=57mm%2Bhole%2Bsaw&qid=1675089060&s=industrial&sprefix=57mm%2Bhole%2Bsaw%2Cindustrial%2C63&sr=1-6&th=1

It was a fun project!

 

[Browse]

I have since updated the wiring from the generator input box to the power display box to allow for complete separation of the two inputs (gen and inverter). This allows me to feed the generator directly into the inverter for charging while the inverter is powering the load center. It also alleviates any possibility of having both powering the load center at the same time. When I want to run the house on the generator, I just connect the jumper cord as shown:

 

[jwrezz]

I have since updated the wiring from the generator input box to the power display box to allow for complete separation of the two inputs (gen and inverter). This allows me to feed the generator directly into the inverter for charging while the inverter is powering the load center. It also alleviates any possibility of having both powering the load center at the same time. When I want to run the house on the generator, I just connect the jumper cord as shown:

View attachment 132220

Thank you! That was my next question, do you charge batteries while using the generator. Question answered! Thanks again!

 

[Hedges]

I have a generator interlock on the side of my house. L14-30. I use a gasoline predator inverter generator with it, but I don't have the need too often. Was wondering if as a start if I could get some batteries, and I already have one and access to a second whistler 3kw modified sinewave inverters. Could I attach batteries to inverters and use a y adapter with dual 120v plugs to LM14-30 like this:

y-adapter

Then just flip my generator interlock and it'd work? Of course I'd love to gradually expand the system with LiFePO4 racks, and real inverters, but would this work?

(other than the issue of using two unsynchronized generators)

Be careful with that adapter, it is a "Suicide Cord".
With one male plug connected and a 240V load on the female socket, the second male plug is electrically hot.

 

[Browse]

(other than the issue of using two unsynchronized generators)

Be careful with that adapter, it is a "Suicide Cord".
With one male plug connected and a 240V load on the female socket, the second male plug is electrically hot.

It's hard to know from the product description if the adapter is splitting the inputs into two separate legs of the NEMA L14-30R receptacle. If so, then the other male plug wouldn't be energized. If the hot wires from both male plugs are feeding just the X spade of the female receptacle, then the two hot wires are joined and the other male plug would be energized. You'd have to verify with a multi-meter or continuity tester. Most of these types of adapters split the male hot wires to X and Y. See some of the similar Parkworld adapter descriptions and Q&As...