DC to AC inverter

conntaxmanconntaxman Solar Expert Posts: 125 ✭✭✭✭✭
Im out to buy a new inverter,also will be buying batteries ,but not at once.Don't have that much money to get everything at once.Now I have 520 watts of panels [8-65watts each], i will be putting up another 520 watts in a few weeks.Each set of panels come in the house on 10gage wire 100feet.The 520 watts now give me No load 36/38 volts 2 panels are wired in series and then tied together.Have one mppt 40amp controller, and will be getting another same type of controller for the other set of panels,I could wire then together the company says.
I was looking at this inverter
http://www.aimscorp.net/5000_Watt_Power_Inverter_12_VoltNew_and_Improved_Design/
It only draws .6 amps on stand by. Why 5000 watts, in case i want to run a refridge on it if their is a power outage.
Question should I go to a 24volt sys,instead of a 12 volt?
I most likely to start with batteries from costco. Think their115 ah each but their cheap about 90.00 ea.
What I want to do is to take of one room in the house at a time off the grid.To see how this will work out.More fun then anything else. Noone really saves any money with solar yet for the amount they spend.
Don't have all the loads yet, but its an average house. 1st room will be the lcd tv, thats 225 watts,2 lamps= 30watts. Then the office,2 computers,fax,and shredder, Dinning room one chandlear with 6 bulbs ea 40 watts i think.
But like I said one room at a time,and batteries the same way.When i need more batteries then I'll buy them to do another room
So next would be the inverter.
tks
John

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: DC to AC inverter

    Do not buy that AIMS inverter. Trying to get 5 kW out of 12 VDC is insane. Their design (parallel wiring) is bad practice and should not be used. 5kW @ 12 Volts is over 400 Amps of current. That is completely nuts.

    You don't need 5kW to run a 'frige either.

    Before you spend any more money, make up a comprehensive plan. Figure out what you want to do with the solar power now and in the future. This means get numbers for total Watts and daily Watt hours for whatever you plan to run. Buy a Kill-A-Watt meter and get real numbers.

    Putting things together piecemeal is troublesome. Holding off on the batteries 'til last makes sense from a lifetime POV, but you need to know how many Amp hours of battery you're going to get. That is based on the daily Watt hours and system Voltage. The amount of battery you get determines how much panel you need.

    Right now you've got 520 Watts of panel. That would supply about 33 Amps @ 12 VDC and support up to about 330 Amp hours of battery. That's a pretty good size "small" system. You could get one of the Morningstar 300 Watt 12 Volt inverters and run lots of little things like lights and/or TV just as an experiment. You could expect about 1 kW hour of AC power per day from this.

    You say you will be adding another 520 Watts. That will double the figures above, either the Amp hours or the system Voltage. That would be 2 kW hours of AC power per day and would run a good (economical) refrigerator. You could use an Exeltech inverter for that: http://www.solar-electric.com/exxp12vol11w.html

    But don't waste your money on one of those horrible AIMS things. They shouldn't even be built. :grr
  • conntaxmanconntaxman Solar Expert Posts: 125 ✭✭✭✭✭
    Re: DC to AC inverter

    hi Carib. I have one of the kill a watt meters. and I have it hooked up to the living room,I know that I have to figure out the watts /ah that I'll be using. Guess I was wondering about that inverter. I know that all the things wont be turned on at once.
    Another question. running 24volt sys better?My charge controller will do both 12/24. My max input on the controller is 55vdc. wish it was higher. Oh here is a question ,when they say 55vdc max from the pv panels, is that under Load or not. Because when the battery is full I get about 36vdc,but as soon as it starts to charge the voltage will drop down 15-20vdc.I would like to wire up 3 panels in series to get more voltage to run the distance.But i could get above that 55vdc with no load.
    Ok so that inverter is OUT of here.
    I also think that I'll be looking at the modified sine wave.Reason they cost less , i know the pure sine is better. I will figure out about the total wattage of what I'll be useing like for a day, and then get a little larger inverter.I know it will be over 300 watts. Even if it is will say 1000 watt, you will only use what you need from it,and some times it is better to be a little bit over, it won't work as hard and get hot.
    But Tks for the heads up on the Aims.
    John
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: DC to AC inverter

    John;

    When you should consider upping the system Voltage:
    1). If your power needs will exceed about 1.2 - 2kW on a regular basis. You really don't want the Amps going over 150 on a regular basis.
    2). If the battery bank would needs to store a lot of Amp hours, making it larger than one charge controller could handle. This usually equates to around 2400 Watts hours for a 12 Volt system, 4800 Watt hours for 24 Volts.

    The maximum input Voltage on a charge controller is usually given as the Voc - Voltage open circuit - of the panels. 55 Volts is rather low, but it would handle "24 Volt" (nominal) panels which have a Vmp of around 35 and a Voc of about 44. Only with very cold temps causing a significant rise in Voc could you run into trouble (Voc might go above 55).

    As for MSW, remember that some of the things you may want to run might not like the non-sine waveform.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: DC to AC inverter

    "conntaxman", the first thing to learn is that Cariboocot knows what he's talking about and is NOT, WILL NOT, point you in the wrong direction. He, as well as a lot of us on this sight have been there, done that, Many of us have gone down the same road you're now on, and have learned the hard way, thus know what we're talking about. So think before asking more questions. Do I really want the answer that will prevent me wasting my money, throwing more money after bad, and then living with regret - - -
    The next thing to learn is Conserve, conserve, conserve. But more on that later - - if you wish.
  • conntaxmanconntaxman Solar Expert Posts: 125 ✭✭✭✭✭
    Re: DC to AC inverter

    hi Carib.As i was running around the net reading I figured that I will get a pure sine wave.Fax machines laser printers computers,ya better safe then sorry.
    How's sunforce,I know outback and morring star, but they are over priced I think so their out.lol . Just thinking what I might run,I think a 1000 watt. Thats not big big. I think a frig, draws 700. I wouldn't hook that up all the time.Just if we had a storm and them plug it in a couple of times to keep the food cold. So i think that I should be able to find one around 250.00
    John
  • WilisWilis Solar Expert Posts: 84 ✭✭✭✭
    Re: DC to AC inverter

    The exeltech 1100 will run a LG LFC25776 25 Cubic Feet ref, small freezer and 32" TV 24/7 if your batteries has enough power. I know I have been doing it for months. The TV is only on about 2 hours a day. I did have a 24v system and now I have changed to 48v. I have liked my Exeltech very much.
  • conntaxmanconntaxman Solar Expert Posts: 125 ✭✭✭✭✭
    Re: DC to AC inverter

    wilis, thats about the size i think that I'll end up getting .why did you go from 24 to 48. was that because of the panel voltage?
    My refrig, will most likely be on the grid all the time.Just the nor. lighting and stuff. Solar isn't that good yet.And by the time it gets real good I'll be dead.Lol
  • petertearaipetertearai Solar Expert Posts: 404 ✭✭✭✭
    Re: DC to AC inverter

    Dont go 12 volts . Get a sine wave inverter.
    700 watts on fridge? is that the start watts? I have a cheep samsung fridge frezer 339kw per year, run watts around 100.
    All the best with your solar adventure.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • conntaxmanconntaxman Solar Expert Posts: 125 ✭✭✭✭✭
    Re: DC to AC inverter

    hi Pete. I just went to check our refrig, and it has 11.6amps x120 and that =1392 watts.But like I said, i will only plug that in if we have an outtage of power, like a storm.So i would need an inverter at least 1500 I think.
    Now about going to 24 volt VS 12. in the end you still use the same amount of power from the batteries. [I think]. I have my 10ga lines ran into the house already 2 sets,1 set for each set of 520 watt panels.I looked up the resistance on a chart for the wire size to come out with that.
    Back to 12 vs 24. It looks like the inveters are alittle cheaper.
    I'll let those that did it explain it to me, seeing that they went through this already. Learn from others!
    tks
    John
    " I always try to buy" American".But if the price is crazy I won't. ;)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: DC to AC inverter

    There's nothing wrong with 12 Volt inverters, providing you don't need the higher power requirements as described before. There are many off-grid applications using 12 Volt systems that work just fine, including running refrigerators. You do have to think about future expansion; 12 Volt is not good for high power stuff like water pumps or air conditioners. If you go with 24 or 48 you may find you're spending money for capacity you don't need.

    Which brings us to how much a refrigerator uses. Forget the info provided by the manufacturer, it's wrong. Running it will be under 200 Watts. The big problems are the start surge which can be over 1 kW and the defrost cycle (if you can't disable it) which will use around 500 Watts. The K-A-W meter will not capture the start surge. Without an expensive Ammeter you won't be able to measure this, so you take your chances. It can be 3 to 5 times the running current usually.

    Some refrigerator tests: http://forum.solar-electric.com/showthread.php?t=12272
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: DC to AC inverter

    First step in designing a system is to conserve. You'll get more bang for your bucks upgrading high-wattage equipment than buying a larger PV system to run it. In this case your fridge is using way too much and buying a more efficient unit will pay for itself in lower utility bills. Then your PV system can be smaller, too.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • WilisWilis Solar Expert Posts: 84 ✭✭✭✭
    Re: DC to AC inverter

    ConnTaxMan,
    The reason I went to 48 was I had 16 T105 batteries and at 24v that made 4 parallel strings. Now I only have 2 at 48v. Also some of my wire was just marginal for 24v so with higher voltage and low amp that is helping.
  • petertearaipetertearai Solar Expert Posts: 404 ✭✭✭✭
    Re: DC to AC inverter

    Hi Defrost watts on my fridge is 140 watts, that's on the label and verified on a watt meter.Maybe your amps relates to start current.
    My system is 12 volts and works well , I too started an the smallest of budgets,I only had enough in the budget for a single 12 volt panel. But if starting again from scratch would do 24 or 48 volts, Reasons same as other posters,wire size and eliminating parallel battery strings.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: DC to AC inverter
    Hi Defrost watts on my fridge is 140 watts, that's on the label and verified on a watt meter.Maybe your amps relates to start current.
    My system is 12 volts and works well , I too started an the smallest of budgets,I only had enough in the budget for a single 12 volt panel. But if starting again from scratch would do 24 or 48 volts, Reasons same as other posters,wire size and eliminating parallel battery strings.

    Defrost currents depend on model. I had a GE that defrost heater was 1000 watts. During defrost cycle which lasted for 20 minutes the kW heater would cycle on for a 10-15 seconds then cut off for a few minutes. I think the theory was this dislodged ice buildup without having to totally melt it which would use more power and dropped off ice would absorb heat in refrig again saving power.

    The automatic ice tray had a 200 watt heater to cause ice to release from tray when it was turned upside down.

    I have told the story a couple of times, during 2005 hurricane when we were without power for a week I rigged a bypass switch on defrost heater to save battery power (defrost cycle occurred every 16 hours). It turned out to be a bad idea. Within a day and half in the high humidity without air cond. the ice built up so much on evaporator that compressor run time went way up. Net, net used more power then just letting defroster do its thing.

    You should have a sinewave inverter with at least a 2kW surge capability to be 100% sure you can make startup surge on compressor.
Sign In or Register to comment.