Easy Small cabin Question: inverter

[OffGridForGood]

I have a cabin that I go to a few times a year for a day or two at most. It has lights, a 120VAC 1/3Hp jet pump, a few small corded tools. In the past I brought a 3000W honda (120VAC only no 240) with me and some gas to run 'stuff' while I am there for a day or two max. It has always been a pita to start and stop the Honda when I needed power for something.
Now that I have an operational PV system at home, I am thinking it would be easy enough to bring a 280Ahr rack battery with me instead of the Honda and gas. I would just need a suitable DC-AC transformer that can remain at the cabin, to connect the battery to the cabin system. The cabin has a small load centre that I plugged the honda into using a 30A plug in the exterior wall.
So What is a suitable Inverter that will give me 120VAC from 48VDC and will maybe start up my jet pump without tripping on overload? Hopefully not too pricy.
I don't run a TV or any electronics at the cabin (kinda the whole point of going there) so perhaps the modified sine wave options are not off the table to run a pump, lights and some corded tools like a drill, or jigsaw kind of stuff?
Anyone have suggestions?

 

[FilterGuy]

run a pump, lights and some corded tools like a drill, or jigsaw kind of stuff?

Those sound like high start-surge devices, so I would recommend looking at a low-frequency inverter.
Since you do not have DC loads, I would say a 24V system at a minimum.... but you should seriously consider a 48V system

I can't really tell what size you should get without knowing more about the tools you would use. Have you considered doing an energy audit?

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

Even if you ignore the system sizing in the spreadsheet, the effort of listing all your loads, wattage and watt-hours is extremely valuable in understanding your needs

The above spreadsheet is probably going to recommend a higher wattage system than you need. It assumes all of the loads will be on at once but in the list you described it sounds like you will most likely have the pump and one power tool as the worst case.

Note: If you are like most people, once you have a system, you will start adding 'a few more things' and before long you have exceeded what your system can do. Consequently, I recommend erroring on too big and not trying to cut it too close to what you think you will need.

 

[Rednecktek]

Because of the pump you'll probably want a LF inverter. Not as energy efficient as more modern HF inverters but they don't whine about the startup surges as badly.

Since you're working with 48v your options are pretty open. You're going to want to look at about 3kw for your inverter and that'll pretty much duplicate what your generator was capable of.

Aims has always been a popular choice, they make good reliable inverters. If you're not sure if it's a High or Low frequency inverter, look at the shipping weight. If it's only about 10 pounds, it's HF. A good LF will be in the 30lb or more range due to the honkin huge torids inside.

 

[Bluedog225]

There’s a lot to be said for a 12 volt system for a lot of your needs.

Lights, radio, small ice chest, dozens of ryobi tools that have a 12 volt charger. Even if you pursue a 48 volt system and inverter for your heavier loads as needed.

 

[MichaelK]

All the loads you mention are running electric motors, so you do NOT want to buy a modified SW inverter. They will overheat and fail prematurely. Most likely the jet pump is going to be the single biggest load and that's what you need to plan for. Rather than guessing what it's starting surge might be, you should be determining it directly. Get a clamp meter that can read "inrush current". Currently (pun) I'm using a UniT 216C. You can find it on Ebay for <100$

Put the clamp around either the hot or neutral leading to the pump (NOT both), press the "inrush" button, and start the pump. The meter will read off the starting surge in amps. Multiply the amps by 120V and you get the wattage needed. You may also use the same meter to determine the running amps.

Let's make up some pretend numbers to illustrate planning. Let's say your clamp meter shows 20.0A at startup, and 5.0A while running. That means your pump needs 2400W to start, and 600W to keep running. A good rule of thumb I always apply is the 2X rule. That is, if you want to supply 2400W to a unit, you better have an inverter that can supply 4800W. Not carved in stone, but it has worked for me.

I would second the idea of the low-frequency inverter, but pay attention to two parameters for your inverter besides just the running watts. Also look at both the surge wattage, and the surge TIME. Serious inverters will be able to surge to 200% their rated wattage for between 5 and 60 seconds. Lesser inverters may claim to surge to 200%, but only for 8-16 milliseconds. If the brand does not tell you how LONG the inverter can surge, take that as a warning sign.

 

[ArtDeco]

Notice how "easy" and "small" often appear in the questions but never in the answers. Grin I am following this thread

 

[OffGridForGood]

Thanks for all the comments guys, and the joke from ArtDeco LOL.
Since I will be 'stealing' one 280Ahr rack from my main system, I will stick with the 48 Volt. It would be easy enough to add a step down DC-DC buck transformer to give me 12VDC for some small lights and avoid inverting to AC for such small loads.
The pump has always run from the 3000W Honda without any hic-ups but next trip to the cabin I will bring the amp clamp meter with me. I was able to find the in-rush on my big motors in the shop and well pump with it when I was working on the main off-grid set up for my work-shop and home (two MPP 6048's , 2 100Ahr racks and now 2-280Ahr racks, and a third on order)
For the cabin, if I am able to have everything set up, and just slid in the 280Ahr rack from my truck, then this would let me do a few things out there without having the lug out the Honda and gas cans, and will keep it peaceful too! The Aims inverter I have seen on a few youtube vid before, and i see it has super high online ratings. Not as many options at 48-volts though, and the price is at a point where maybe I should consider a 3048 or 4048 MPP and be able to add solar PV one day in the future, for not a lot more money now.
So much for small and easy decision.

 

[OffGridForGood]

Doing some online searching:
Option one. Looking for a 3-5kw LF inverter starting with the Aims - It is heavy (so RedNeckTech will be smiling) but I see the price delivered to tim-buck-three (we're a bit father out than Timbukto) takes a few more bucks to get here - in USD the 5kW 48VDC Aims shipped to my door is $671.16
It checks all the boxes on low THD, 3x overload for 20-seconds, pure sine wave, highly rated online by other purchasers.
Some cheap copies of the Aims are half the cost, but do not check the boxes either, reading the post by 73Powerstroke I am not keen to rely on cheap equipment.

Option two. If I consider at this price, what AIO MPP would I be able to get, and one day add solar PV to the cabin, maybe one day pair the MPP with a second one. MPP solar 3048 (120VAC output) shipped to my door is $769.56 USD but this is not a low freqency inverter, I could be in trouble to start the water pump even at only 1/3Hp -could be disapointed and need a second MPP to be able to start the pump, or be looking as down-sizing the pump to suit the inverter. The LVX6048 is a low frequency inverter, but it's also 6kW and would be about $1500USD shipped to me. Maybe more capacity than I really need for the cabin, although like the other AIO it would be available to connect PV in the future and would certainly be able to run other big loads in the future.

Third option? Get the Aims now, and use it to do what I need for under $700, and later on in the future if I want some PV just add a charge controller for not a lot more money really, a Victron MPPT100/30 would only be another $100 or so, and still be less total cost than one MPP 3048.
I will think about it, but am leaning to the Aims 5kW-48VDC and later be able to add PV if I want.
Thanks for all the good suggestions everyone.

 

[MelBayer]

OffGrid, are you sure about that price of $671 for the Aims inverter the size you want? If so, do you have a link? I can't find that price but I'm a noob so I could very well be misinformed.

 

[OffGridForGood]

OffGrid, are you sure about that price of $671 for the Aims inverter the size you want? If so, do you have a link? I can't find that price but I'm a noob so I could very well be misinformed.

Check it on Ebay - 'AIMS 5000W 48V Power Inverter'
base price is 632 US$ plus shipping
The seller is listed as Virventures

 

[wiseacre]

Check it on Ebay - 'AIMS 5000W 48V Power Inverter'
base price is 632 US$ plus shipping

More than likely the inverter is a Modified Sine Wave at that price point
An Aims Pure Sine Wave will run about $1300

 

[MichaelK]

Aims inverters in general have the highest distortion levels in the inverter industry, I believe around 10%. I consider that awful and would never even consider Aims. Sorry I didn't mention this in my previous post. Research total harmonic distortion, or THD for whatever you want to buy.

Honestly, if all you are focusing your attention on is the price, I'm afraid you are going to find yourself with a burnt-out pump. You'll end up spending more money in the end, both buying better components, and also replacing the appliances you've destroyed.

You'll remember the quality long after the price is forgotten. Sister-in-law taught me that.

 

[OffGridForGood]

I suppose we all watch our money, I only go to the cabin a few times a year, for a few days each time, so spending is normally 'in scale' with the time I spend there. I am noticing there are two types of AIMS units, the blue ones and light grey ones, is there a difference ?- are the grey ones 'entry level equipment' with different spec?
If you're recommending less than the <10% THD of the AIMS what level would you suggest is 'acceptable'

 

[Rednecktek]

Again, this is where the shipping weight will be a good indicator to differentiate HF and LF inverters.

Personally, a 3kw LF inverter sounds fishy. I'll look that up and get back when I have a real screen and internet.

Option 3 is going to be the best bang for the buck until you're ready to grow. Even then since you're already modular it's much easier to add parts rather than throwing out an AIO for a new larger model since you can't parallel a 3kw and a 6kw as far as I know.

 

[OffGridForGood]

More than likely the inverter is a Modified Sine Wave at that price point
An Aims Pure Sine Wave will run about $1300

YOU ARE CORRECT - although the unit I found yesterday is an AIMS unit it is not pure sine wave it is modified sine wave. It appears the grey units are all modified sine, and the blue units are pure sine wave. I see these are as you say quite a bit more money. Actually it seems I need to start over now: The comparison between a dedicated inverter and an AIO unit has changed. With the AIMS coming in at 1300-ish plus delivery to Tim-buck-3, I am in the same price range as the LVX 6048 which would be 6000W, and also be able to handle solar PV inputs at 500VDC
Then again, the LVX has pretty high standby current, and it may be better for me to use the 4048 or 5048, and be able to parallel two some day in the future. Hum. more to ponder again.

 

[Rednecktek]

Just to throw it out there...

The LVX series have really been impressive in their sure capacity whereas the 3048's are straight HF and don't do so well.

As for the standby draw, one of the downsides of the LF inverters is their lower efficiency and higher standby draw. It's worth it to look at the standby draws between the LVX and the Aims, it might be a wash.

 

[OffGridForGood]

Again, this is where the shipping weight will be a good indicator to differentiate HF and LF inverters.

YES you are right there, the cheaper AIMS (grey 5000W unit) was only 16 pounds!
While the Blue 2000W AIMS is 53 pounds.
Micheal K is recommending against the AIMS, even the pricier one, as he suggests the <10% THD is still too high. Okay, but what mfr has a better THD, and does it actally just push the price point to where I get a third MPP 6048 (I have two MPP 6048's in my permanent set up).

 

[Rednecktek]

Wait, you already have a pair of 6048's up there? Are they configured to run together? That should be plenty of power to feed your pump!

A pair of those should give you 240v @60a before working into the "surge rating" areas.

 

[OffGridForGood]

The LVX series have really been impressive in their sure capacity whereas the 3048's are straight HF and don't do so well.

You are right, a 3048 can not parallel to anything but another 3048, and is not Low Frequency, It could struggle to start the jet pump. The LVX will not have any problem to start the pump I am sure, but will draw a lot of stand-by power, and I will be tempted to shut it down while I go do stuff out and about, and then restart it when I am in the cabin doing stuff. Ditto shut it off at bed time perhaps.
After Michaels' comment on the AIMS, I wonder what the THD is for the MPP 3048, LVX do they list this information in the manual?

Wait, you already have a pair of 6048's up there? Are they configured to run together? That should be plenty of power to feed your pump!

A pair of those should give you 240v @60a before working into the "surge rating" areas.

Some confusion here: I have a pair of MPP 6048's at my home, but not at the cabin.
I started this thread off with thinking, perhaps, If I make one of the 280Ah rack batteries (from my home) 'mobile' then I could set up the Cabin with just an inverter to plug into with the 280Ahr and I would be set for 2-3 days even without PV panels at the cabin, take the 280 back home when i leave the cabin and recharge it at home for next time. but then we got into what inverter i should get for the cabin, and would it run a 1/3hp 120VAC pump motor, or would a cheap inverter burn my pump due to poor THD etc etc.

 

[Rednecktek]

Aaahhhh, that makes sense. If you're considering an AIO you might want to consider the EG3500 as it'll give you a bit more power than your Honda and it seems to handle startup surges better than the 3048. It also leaves you primed to add more panels to the system so you could get some charging going on while you're up there.

A cheap inverter would most likely die before your pump does if it's pure sine. Modified sine could go either way.