Help choosing an inverter please

jrcent · June 2019

Hello

I'm new to site but great information and kept realistic.

Problem is that store I have been talking to wants to sell me an aims 6000 watt inverter which sounds great to have it all! Lol I'm afraid I'll end up constantly upgrading which I don't want.

I have a midnight classic 150
6 x 300 watt 24v solar panels
8 x 100ah agm 12v batteries
A 3200 watt generator for backup and battery charge

We are in a RV with 30 amp service while building a cabin. The solar will be connected to RV from the house. I was originally thinking about multiple smaller inverters that can feed different loads as needed. Such as one big enough for RV frig 24/7 and off grid internet (35-40 watts load with kill-a-watt meter). RV service would cover lights (led) and occasional appliances like coffee and toaster oven etc... Not much else all the time

I think one big inverter would take too much idle to run constantly. Aims has too many reviews that cover the spectrum.

Please any recommendations for brand and size to get. Everything I try to find is more sales pitch than really what's good. Thanks for any help.

Tecnodave · June 2019

AIMS has a horrible track record, skip that one and keep looking.....they have a horrible standby draw that in most cases draw more power through the day than your load is using. If you are 12 volt then that thing is AWFUL,!!!
Cheap Chinese junk that does not even make a decent boat anchor!!

Inverter advise, do not buy bigger than you need, keep it small and simple KISS!!!

So so do post a bit more on your usage, what voltage system and what loads do you expect.

Decent American inverter manufacturers do not recommend more than 2000 watts on a "12 volt" system. MagnaSine makes good sine wave inverter/chargers for the RV market

Tiawan based Cotek also makes quality inverters and inverter/chargers that are quality.

I do own Classic's, a MagnaSine MS4024AE, (I'm 24 volt) and a Cotek inverter, I am not a sales shill....I like good quality gear, am retired engineer!

PNW_Steve · June 2019

If you have a conventional RV refrigerator you probably don't want to run that from your inverter. When running on 110v they are power hogs. Off grid you should consider running it on propane. I have switched to residential refrigerators and have been very happy with them. Much more efficient when running on 110v.

I agree 6kw is a monster inverter. Idle power consumption will definitely be on the high side.

Consider running your generator to support loads like your coffee maker and toaster oven.

When I was on the road full time we settled into a routine. Get up, start the generator, make coffee and let SWMBO run her hair dryer then shut the generator down. That also gave our batteries a head start on charging. It worked out well for us. 45-60 minutes of generator run in the morning and then battery for the rest of the day.

jrcent · June 2019

I have been running generator for mostly anything bigger. Trying not to run as much.

Up to now have been using a single 300w 24v solar panel hooked up to the 8 batteries in 2 x 24v legs. On a sunny day it will charge ok but it's tight. Biggest issues are that I've been using cheap ebay 2000 watt inverter (5 or 6 so far) and am tired of buying them every few months.m

Been planning on 24v still but after reading here thinking about 48v. Now would be a good time to switch.

I like the xantrek, samlax, or cotek in 3000 to 4000 watts.

"When I was on the road full time we settled into a routine. Get up, start the generator, make coffee and let SWMBO run her hair dryer then shut the generator down. That also gave our batteries a head start on charging. It worked out well for us. 45-60 minutes of generator run in the morning and then battery for the rest of the day. "

Almost exactly what we have been doing lol. Especially during the winter when lots of snow and little sunshine.

jrcent · June 2019

Using RV frig mostly on gas but would like to eventually get off grid model

Not much bigger stuff. A 115v well pump ( 9amp) to fill a tank couple days a month .

Propane on demand hot water.

Not much else little stuff I can add a second smaller inverter that hopefully can switch off when not in use.

Would like to keep under $1500 for now and around $1000 even better but that might be hard. More just something reliable that won't constantly shut down . Would going to $2000 magna make that much difference in reliability.

PNW_Steve · June 2019

I picked up a pair of Xantrex 1800/24's on eBay at a great price.

I bought a new Xantrex 1000watt PSW and installed it in my travel trailer 3-1/2 years ago. It has seen regular service without a hitch.

I would definitely stick with a "name brand". I would go along with the above mentioned: Xantrex, Cotek or Samlex.

I have installed Samlex at remote communication sites. I installed them 2007-2008 and as of a few months ago they are all still in service.

jrcent · June 2019

Xantrex and samla x were the 2 brands that I liked the most. Low idle amps.

So a 2000 would be big enough? With 1800 watts of solar (PNW maybe half that) and 8 100ah batteries at 48v. I know a 2000 watt Chung ho is about useless lol

mike95490 · June 2019

8 AGM batteries in parallel is going to be an expensive nightmare when they start failing. And fail soon they will. I say min-december, you will have walked them down to less than 50% ( I'm assuming you are running this all as a 12v system )

My suggestion - build a battery /power/ generator shed and park that gear in it. Firewall between generator and batteries.

Configure it to 48V with only 2 parallel banks. return the inverters and such and get quality gear. Plug your RV into it, and feed the fridge propane.

When house is complete, wire it to the shed too.

Estragon · June 2019

Just to throw it out there, there's a lot to be said for using a quality inverter (Outback, Schneider, etc) which includes onboard battery charging and transfer switch. It simplifies things, and by the time you buy quality individual components (eg properly sized, multistage PFC charger), it might be cheaper.

Tecnodave · June 2019

A lot of Samlex America inverters are built by Cotek, look close at them, it is the identical unit, Samlex America has a lot of rebranded product. Cotek builds their inverters with a variety of names on them, including Vanner, an ambulance and fire truck outfit....these are standard Cotek models, not special builds.

jrcent · June 2019

mike95490 said:

8 AGM batteries in parallel is going to be an expensive nightmare when they start failing. And fail soon they will. I say min-december, you will have walked them down to less than 50% ( I'm assuming you are running this all as a 12v system )

My suggestion - build a battery /power/ generator shed and park that gear in it. Firewall between generator and batteries.
Configure it to 48V with only 2 parallel banks. return the inverters and such and get quality gear. Plug your RV into it, and feed the fridge propane.

When house is complete, wire it to the shed too.

Have been running these batteries for 2 years in a 24v configuration. I like the idea of a separate room but it's hard to get a place that is not below freezing where we're at. The cold weather really effects the power. Thinking about a utility room in the house that is heated. Could also make an insulated box for batteries to keep them from freezing. That way have a separate shed.

I haven't purchased an inverter yet (not a real one yet anyway) and would really rather have something reliable and undersized than overkill and constant maintenance.

Last winter with a woodstove going we only ran generator every 3 days or so and frig was on propane. Solar power ran lights and internet with 600w cheap $30 inverter that didn't last but worked but constantly swapping

jrcent · June 2019

I have been reading lots of back posts and looking for a 48v inverter to upgrade to. I really like the Magnum 4448 or 4048 but I don't think I have enough solar panels and batteries for them yet. I think a 2k to 3k inverter would be better for now for only 1800 watts and 8 agm 100ah batteries but only one I have been able to find is the Cotek in that size and 48v. Classic 150 will handle any upgrades as my system grows? Am I missing some different models? I'm trying to stay with the better name brands if possible. Thanks for the help

petertearai · June 2019

Consider an outback , if you need more power in the future you can get another and stack them .

Estragon · June 2019

+1 on OB. I'd also put Midnite's "coming soon" b-17 inverter on the short list if I wasn't in a rush. It's apparently modular 2kw chunks. No idea when "soon" might be though.

wellbuilt · June 2019

I really like my out back , the 36 48 inverter , it just works .
The outback inverters all use 34watts when on , the smaller units use the same power , I looked at Less expensive inverters
But buy the time I figured out how much all the equipment cost , I just bought a outback Flex power one system and bolted it to the wall .
I had ac power and battery’s charging in a few hours .
I started out with 200 AH of battery power and 900watts of solar .
With a generator for extra charging .
I didn’t want to have to buy the equipment twice , my place runs on 200watts day and night .
The built in charger runs on a Honda 2800 watt generator .
You won’t be disappointed

jrcent · June 2019

I'm guessing the Outback is reliable as magnum? They're easily repairable? Guess I have some more research to do lol

Probably will just get a interim 2k and plan for the future. Maybe a couple years from now who knows what will be available. Estragon said:

+1 on OB. I'd also put Midnite's "coming soon" b-17 inverter on the short list if I wasn't in a rush. It's apparently modular 2kw chunks. No idea when "soon" might be though.

I am getting a morningstar 300w suresine to run essentials 24/7 so the bigger inverter will be more for daytime use so no big rush. Plus cabin is still in progress. Would like to keep a small system of +/-3k at the most when finished.

Estragon · June 2019

I had one of my OBs die early in its life - my guess is a bad run of boards. OB was good about getting replacement boards to me, and swapping them was pretty straightforward. Bad boards can happen to anyone, but not everyone will be there for you if it does.

I like my little Morningstar as well. It can run pretty much everthing I need except big pumps, tools, and the AC fridge. It even runs the on-demand water heater and circ pumps for in-floor heating system.

jrcent · June 2019

wellbuilt said:

I really like my out back , the 36 48 inverter , it just works .
The outback inverters all use 34watts when on , the smaller units use the same power , I looked at Less expensive inverters
But buy the time I figured out how much all the equipment cost , I just bought a outback Flex power one system and bolted it to the wall .
I had ac power and battery’s charging in a few hours .
I started out with 200 AH of battery power and 900watts of solar .
With a generator for extra charging .
I didn’t want to have to buy the equipment twice , my place runs on 200watts day and night .
The built in charger runs on a Honda 2800 watt generator .
You won’t be disappointed

Isn't that overkill for 200 watts day and night with 4400 solar with 3500w inverter? Even in the winter it will still run everything year round? I was thinking or a larger system and running everything but then after reading posts here I was leaning more towards a smaller 2-3k system and supplemental generator and propane. I really need to sit down and research more about what I want to be able to do. Being in an area where not much sun in the winter the propane and generator work great but require a constant gas and propane supply.

BB. · June 2019

Have you actually sat down with a Kill-a-Watt or similar power meter and measure you loads?

It is "easy" to put a large AC inverter out there and run just about anything. The bigger issue is usually sizing the battery banks.

Battery banks have to store enough energy (our typical recommendation is 2 days of stored energy for bad weather, and 50% maximum discharge for longer battery life). Batteries are big and heavy (especially lead acid)... And they only last 5-7 years or so (less in hot climates--Longer if Forklift/Industrial batteries--10-20 years is doable). It is very easy to kill a battery bank with over discharging, under charging, and maintenance issues.

The battery bank is the "heart" of your system... Figure out your energy needs (average watts, peak watts, Watt*Hours per day by season, etc.).

Just to give you an idea what a "balanced" system design may look like... I suggest a 3,300 WH per day system as a "near normal" electrical life--Fridge, LED lighting, "solar friendly" well/water pump, clothes washer, LED TV, laptop computer, etc. (lots of conservation--It is almost always cheaper to conserve than to generate power).

If you have a propane fridge, a 1,000 WH per day system is not bad with a 300-600 Watt AC inverter (depending on what your heavy loads maybe).

Sizing the battery bank:

3,300 WH per day * 1/0.85 AC inverter eff * 1/24 volts * 2 days storage * 1/0.50 max discharge = 647 AH @ 24 volt battery bank

Suggest a minimum of 1,200 to 1,500 Watt AC inverter (to run full size energy star refrigerator), and a maximum of ~3,200 Watt inverter (500 Watt AC inverter per 100 AH @ 24 volt FLA battery bank).

Note that I suggested a minimum of 24 VDC battery bank... For many reasons, I highly suggest to avoid going over an 800 AH battery bank if possible. I.e., 800 AH @ 12 volts vs 400 AH @ 24 volts is the same amount of energy storage, but 1/2 the amount of current in the DC battery cables/connections.

Next, you want to size the solar array to 1) keep the battery bank "happy", and 2) to keep up with your loads... First "happy". Generally 5% to 13% rate of charge for solar, with 5% barely enough for weekend/sunny season usage, and 10%+ highly recommended for full time off grid (9+ months a year).

647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,218 Watt array minimum
647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,437 Watt array nominal
647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,168 Watt array "cost effective" maximum

Then sizing the array based on your daily loads and hours of sun per day... Fixed array facing south Bonner's Ferry ID tilted to 49 degrees from horizontal:
https://pvwatts.nrel.gov/pvwatts.php

Month	Solar Radiation ( kWh / m2 / day )
January	2.09
February	3.26
March	4.27
April	5.46
May	5.67
June	5.49
July	6.60
August	6.13
September	5.69
October	3.69
November	2.49
December	2.03
Annual	4.41

Solar panels are relatively cheap, and batteries+genset fuel is expensive... Say you toss the bottom three months out as needed a genset, and that makes February at 3.26 hours per day as the "break even" month (may or may not need genset depending on weather):

3,300 WH per day * 1/0.52 off grid AC system * 1/3.26 hours of sun per day (Feb) = 1,947 Watt array (Feb break even)

So, a full time off grid system I would suggest a minimum array of 1,947 to 3,168 Watts, and really a 10% minimum rate of charge at 2,437 Watt array minimum.

There are lots of different ways to do things... For example, being in far north with few hours of sunlight in the winter, a larger array split in 1/2... 1/2 the array facing south easterly, and the other 1/2 facing south westerly... You get most of the advantages of a tracking array without the cost and maintenance of a tracker--Lead Acid batteries need something like 6-8+ hours a day just "on charge" -- Absorb of 2-6 hours a day) to fully recharge. The split array gives you those more hours of sun with (usually) only a slight loss of harvest (panels are cheap, make the "virtual tracking" array that 10-20% larger if needed).

Anyway--Just a quick starting point for your system design (and a whole bunch of guess work on my side). Measuring your loads (and conservation) will be critical here to ensure you have a successful install.

https://www.amazon.com/s?k=kill+a+watt+meter&ref=nb_sb_noss (kill-a-watt meters)

And any issue your site may have (trees, nearby structures, north side of a valley, etc.--Anything that reduces light on the array) that you may have to address (clearing trees, moving array 100's of feet from your home, etc.).

-Bill

Estragon · June 2019

Winter just plain ain't good for solar at higher latitudes. The east/west azimuth is really narrow, so virtual tracking would be of limited help IMHO. With the low sun, shadows from trees etc get really long, so unless you're on open prairie or a mountain top, it might even be worse than a straight south array.

wellbuilt · June 2019

Over kill ?
I have a 5 bed room cabin with 3 baths .
If the frig turns on it uses another 100 plus watts .
The thing is the 2 /3000 watt inverters cost about the same and the out back inverters use 34 watts no matter what the size ?
The 3600watt inverter also charges at a higher rate then a smaller units. Big plus it snows here day and night all winter .
I have a second 4500 watt solar bank in storage so I can ground mount and sweep the snow off .
I was looking at a samlex inverter charger system EVO2224 2200WATS , It cost 1300 bucks , the out back was $1600
The out back has support which I need , alot of the guys here on the forum run out back systems and help tremendously .
You can buy all outback equipment that plugs together (big plus’s )
The only down side is it cost 300 bucks more .
The 4500 watts of solar is a lot but in my area my Engineer told me it would take to days of Average sun to charge my battery bank from 50% to full , so I added a Additional string of three 295 panels .
In a snow storm I get 3to 500 watts so I can run 5 /6 days with out running the generator , if the sun pops out my battery charge up fast.
Solar panels are cheep now buy them locally mine where 165 bucks and I loaded them in my truck 30 units
The larger inverter will be nice to run a well pump
I bought my system from our host , I emailed them with my needs and they sent me a quote with a complete system in the same day.
I wanted the EVO INVERTER the engineer that designed the system for me told me out back has been building inverters for ever and I will love it . If I ever have any question I can call the store and any one can help me .
They know the out back systems inside and out.
I can see how any one sells the AIM inverters you should find a new store John

jrcent · June 2019

Estragon said:

Winter just plain ain't good for solar at higher latitudes. The east/west azimuth is really narrow, so virtual tracking would be of limited help IMHO. With the low sun, shadows from trees etc get really long, so unless you're on open prairie or a mountain top, it might even be worse than a straight south array.

We are about 4000 ft elevation but good southern exposure although lots of trees. December has only a few hours of daylight. Doesn't get light till 8 or 9 in the morning and is dark by 3. Not much wind for windmills to make it worthwhile.

jrcent · June 2019

BB. said:

Have you actually sat down with a Kill-a-Watt or similar power meter and measure you loads?

It is "easy" to put a large AC inverter out there and run just about anything. The bigger issue is usually sizing the battery banks.

Battery banks have to store enough energy (our typical recommendation is 2 days of stored energy for bad weather, and 50% maximum discharge for longer battery life). Batteries are big and heavy (especially lead acid)... And they only last 5-7 years or so (less in hot climates--Longer if Forklift/Industrial batteries--10-20 years is doable). It is very easy to kill a battery bank with over discharging, under charging, and maintenance issues.

The battery bank is the "heart" of your system... Figure out your energy needs (average watts, peak watts, Watt*Hours per day by season, etc.).

Just to give you an idea what a "balanced" system design may look like... I suggest a 3,300 WH per day system as a "near normal" electrical life--Fridge, LED lighting, "solar friendly" well/water pump, clothes washer, LED TV, laptop computer, etc. (lots of conservation--It is almost always cheaper to conserve than to generate power).

If you have a propane fridge, a 1,000 WH per day system is not bad with a 300-600 Watt AC inverter (depending on what your heavy loads maybe).

Sizing the battery bank:
3,300 WH per day * 1/0.85 AC inverter eff * 1/24 volts * 2 days storage * 1/0.50 max discharge = 647 AH @ 24 volt battery bank
Suggest a minimum of 1,200 to 1,500 Watt AC inverter (to run full size energy star refrigerator), and a maximum of ~3,200 Watt inverter (500 Watt AC inverter per 100 AH @ 24 volt FLA battery bank).

Note that I suggested a minimum of 24 VDC battery bank... For many reasons, I highly suggest to avoid going over an 800 AH battery bank if possible. I.e., 800 AH @ 12 volts vs 400 AH @ 24 volts is the same amount of energy storage, but 1/2 the amount of current in the DC battery cables/connections.

Next, you want to size the solar array to 1) keep the battery bank "happy", and 2) to keep up with your loads... First "happy". Generally 5% to 13% rate of charge for solar, with 5% bearly enough for weekend/sunny season usage, and 10%+ highly recommended for full time off grid (9+ months a year).
647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,218 Watt array minimum
647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,437 Watt array nominal
647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,168 Watt array "cost effective" maximum
Then sizing the array based on your daily loads and hours of sun per day... Fixed array facing south Bonner's Ferry ID tilted to 49 degrees from horizontal:
https://pvwatts.nrel.gov/pvwatts.php
Month Solar Radiation
( kWh / m2 / day )

January 2.09

February 3.26

March 4.27

April 5.46

May 5.67

June 5.49

July 6.60

August 6.13

September 5.69

October 3.69

November 2.49

December 2.03

Annual 4.41

Solar panels are relatively cheap, and batteries+genset fuel is expensive... Say you toss the bottom three months out as needed a genset, and that makes February at 3.26 hours per day as the "break even" month (may or may not need genset depending on weather):
3,300 WH per day * 1/0.52 off grid AC system * 1/3.26 hours of sun per day (Feb) = 1,947 Watt array (Feb break even)
So, a full time off grid system I would suggest a minimum array of 1,947 to 3,168 Watts, and really a 10% minimum rate of charge at 2,437 Watt array minimum.

There are lots of different ways to do things... For example, being in far north with few hours of sunlight in the winter, a larger array split in 1/2... 1/2 the array facing south easterly, and the other 1/2 facing south westerly... You get most of the advantages of a tracking array without the cost and maintenance of a tracker--Lead Acid batteries need something like 6-8+ hours a day just "on charge" -- Absorb of 2-6 hours a day) to fully recharge. The split array gives you those more hours of sun with (usually) only a slight loss of harvest (panels are cheap, make the "virtual tracking" array that 10-20% larger if needed).

Anyway--Just a quick starting point for your system design (and a whole bunch of guess work on my side). Measuring your loads (and conservation) will be critical here to ensure you have a successful install.

https://www.amazon.com/s?k=kill+a+watt+meter&ref=nb_sb_noss (kill-a-watt meters)

And any issue your site may have (trees, nearby structures, north side of a valley, etc.--Anything that reduces light on the array) that you may have to address (clearing trees, moving array 100's of feet from your home, etc.).

-Bill

Wow! Thank you. This gives me a great place to really get an understanding of what I can shoot for. So much better than a 6000 watt aims and a few solar panels lol but the secret is happy batteries 😊

I have a kiil-a-watt and have gone through everything for the most part. I figured I need about 3100 watts per day if I had everything I wanted / needed. We have a location for panels even though we are surrounded by trees. Full sun from 8 till 5 in the summer.

We spent last winter off grid with a woodstove and enough solar and a generator to keep the lights going. I didn't mind but we're wanting a little bit more "comfort " lol.

mike95490 · June 2019

jrcent said:.......We are about 4000 ft elevation but good southern exposure although lots of trees........

If any branches of the trees cast any shadow on your panels, your harvest will be severely reduced. If the panels are in the clear and no shade, great

jrcent · June 2019

mike95490 said:

jrcent said:.......We are about 4000 ft elevation but good southern exposure although lots of trees........

If any branches of the trees cast any shadow on your panels, your harvest will be severely reduced. If the panels are in the clear and no shade, great

We got the panels placed wher sun is on the from 8 or 9 AM till 5 in the afternoon.

paulcheung · June 2019

jrcent said:

I have been reading lots of back posts and looking for a 48v inverter to upgrade to. I really like the Magnum 4448 or 4048 but I don't think I have enough solar panels and batteries for them yet. I think a 2k to 3k inverter would be better for now for only 1800 watts and 8 agm 100ah batteries but only one I have been able to find is the Cotek in that size and 48v. Classic 150 will handle any upgrades as my system grows? Am I missing some different models? I'm trying to stay with the better name brands if possible. Thanks for the help

The Magnum 4448PAE do has an issue. When use the inverter at near capacity for a period of time, the internal fan stop work and the inverter get hot then turn off, I had that problem and have to use an external fan to cool down the inverter. because the fan is on out side. it can't cool the inverter properly, I only can use a little more than half of the rated power especially use it to charge the battery bank. my load is not more than half of the rated capacity so I don't have much problem during the daily use. I recently bought a Schneider XW6848+. I couldn't be happier on this purchase and can't believe how can I never get it at the beginning.
PS, because the fan issue the dealer I bought the XW6848+ stop sell the Magnum 4448 few year back. too many return for repair for the same issue. My Magnum was bought 7 years ago. hope they fix that problem now.
Hope this help.

jrcent · June 2019

I guess they all have their issues. Both outback and magnum have lots of good history also. I have a little time before I actually get one either way so that gives me more time to research. Leaning toward outback even though I was liking magnum.

Local shop says he only carries the magnum because they are so good. I just want something that works good and lasts a long time!

Estragon · June 2019

There's a lot to be said for local support if it's good. Sometimes it's just that they get better margins being exclusive, and/or they're too lazy to understand and deal with options. Sometimes they really do believe in the product though, and can be a real help if things go sideways.

jrcent · June 2019

Local shop seems really sincere about selling and offering the best service but buying something I don't really need is too expensive for me. Overall I like buying local and keeping local money in the community is sometimes worth more than saving a few dollars plus good service is really nice .

mcgivor · June 2019

For what it's worth, I purchased a 2KW inverter locally, a store branded unit with a 1 year gaurentee, almost 3 years ago, it's a "pure sinewave" but dose have its limitations, radio interface along with it's inability to support a microwave, neither of which are a personal concern for me, but for the >$300 spent as a stop gap solution, it has performed flawlessly for my needs. Sometimes you get lucky, other times not, death and taxes not withstanding.

littleharbor2 · June 2019

I've found it to be a crapshoot as to whether the small low priced inverters have fans that run 100% of the time or only under a heavy load. For my homebuilt travel trailer I got lucky and actually never heard the thing run, if it ever has.

Help choosing an inverter please

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