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Cheapo Inverters vs. Expensive Ones

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  • #31
    Originally posted by LETitROLL View Post
    The basic simple answer is that inverters for large loads need to be very heavy duty, and the parts and manufacturing methods to achieve that are not cheap. So in most/all cases cheap inverters are a mix of not putting out as much as they say, and almost always put out dirtier power than quality more expensive versions, which shortens the life of the loads you plug into them, some people that run reasonable loads of products that are not sensitive to low quality power do fine with cheapo inverters, but all in all those are the type of inverters that earned the nickname "smoke in a can". The best bet is to define a inverter budget then get the best (new or used) quality inverter for that price, it will run as many or more loads than a higher rated cheapo inverter. The cheapo inverters are real and they do work (sometimes) but the ratings are a mirage, so you dont end up getting the great deal you thought you got, especially after you factor in the price you ended up paying for the new TV and Refrigerator 3 months later.
    More good feedback, thanks. Unfortunately, for me the choice is between a cheap off-grid solar solution or none at all. The budget for a quality system just isn't there. If the grid goes dark, I think I'd rather have a potentially flaky system than nothing. It seems like my only option is to research the crap out of anything I buy and try to verify its quality and durability as best I can, then roll the dice and hope for the best. Surely I am not the only one in this boat?

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    • #32
      Originally posted by eric@psmnv View Post
      More good feedback, thanks. Unfortunately, for me the choice is between a cheap off-grid solar solution or none at all. The budget for a quality system just isn't there. If the grid goes dark, I think I'd rather have a potentially flaky system than nothing.
      If you need short term backup for power outages, there are plenty of VERY cheap UPSes out there that will provide basic power for small loads for a while. You can usually add batteries to these if you want to extend run times. They run around $200 for a 1200 watt UPS.

      If you need long term backup then a generator is going to be cheaper than almost anything else out there. You can get a 3000 watt generator for about $300.

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      • #33
        Originally posted by eric@psmnv View Post
        More good feedback, thanks. Unfortunately, for me the choice is between a cheap off-grid solar solution or none at all. The budget for a quality system just isn't there. If the grid goes dark, I think I'd rather have a potentially flaky system than nothing. It seems like my only option is to research the crap out of anything I buy and try to verify its quality and durability as best I can, then roll the dice and hope for the best. Surely I am not the only one in this boat?
        Have you calculated what loads you want to run if the grid loses power? I would imagine it is nowhere near 5000w. You can get a pretty good inverter for the money you are willing to spend on one or two of those "cheap" inverters. The way to size the system is to start with:

        0) Conserve as much as possible. Get LED lights. Low wattage appliances.

        1) Measure your loads and estimate how much you need to run in case of a failure. Calculate the number of hours you would want to run the necessary loads and then get the average kWh / day as well as the peak watts at one time.

        2) Multiply the daily kWh by your days autonomy (eg 5) and then by 1.5 or 2 for inefficiency.

        3) Size your batteries with #2.

        4) Size your inverter with #1

        5) Size solar panels from #1 and #3

        Do you need a 5000w inverter? If you scale the rest of your system from that, you will need a large battery bank, larger AWG wires to prevent fire, and lots of solar panels and CC to charge all that equipment.

        For example, since your inverter can draw 5000w, so you don't go over C/8 you need at least a 48v 833AH battery bank with 8 batteries. 6v Surrettes at 820AH for 8 will cost over 11K. (Check my calcs!)

        Do you need a system that big? It will cost.

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        • #34
          high voltage battery cutout

          An issue I had with a previous cheap inverter is that the high voltage battery cutoff activated when I did a battery equalization. I could not EQ my batteries at the manufacturer specified voltage (31V) without tripping out the inverter. So I had to either lower the EQ voltage setting on the charge controller or not have an operating inverter while the EQ was in progress. The inverter you listed specs the over voltage protection at 31V +/- 1V, so there is a good chance it would trip out during an EQ. It also specs the over voltage recovery at 31.8V, which make no sense since the over voltage recovery should be lower than the over voltage ??? Maybe its a typo. The 24V Magnum inverter has a high battery cutout of 33.2V, which can handle EQ's no problem. Its issues like this that make all the difference when you buy a quality inverter.

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          • #35
            Originally posted by eric@psmnv View Post
            More good feedback, thanks. Unfortunately, for me the choice is between a cheap off-grid solar solution or none at all. The budget for a quality system just isn't there. If the grid goes dark, I think I'd rather have a potentially flaky system than nothing. It seems like my only option is to research the crap out of anything I buy and try to verify its quality and durability as best I can, then roll the dice and hope for the best. Surely I am not the only one in this boat?
            I had a small budget for an inverter also and got lucky and got a very nice major brand ($600 retail) slightly used 1000/2000 pure sine (for real, not kinda maybe pure sine) for $100. It is not just a matter of quality and durability, read reviews on amazon and other sights you will see that many cheap inverters will not even start up large appliances the very first try, and a smaller output high quality one will. If you expect to actually run more than 1000-2000 watts worth of loads, regardless of what inverter you buy be advised it takes much more in the battery department and you will ruin batteries quickly by undercharging so even more solar will be required and those 2 items will skyrocket a budget.

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            • #36
              Originally posted by eric@psmnv View Post
              Did you scroll down to the certifications section? There's a lot of information on the page. Overall, it looks pretty legitimate. Is UL listing the only way that you check a product's worthiness or safety? That said, suppose for the sake of my original question that I eventually find one that has the UL mark in the same price range. The real question is, is there any reason to think that a $700 inverter would not do the same job as a $2200 Magnum inverter?
              The Magnum Inverters are also battery chargers, they can charge the battery bank with Grid power or generator, It also can do preventive equalization, they have programable settings such as LVD to any voltage in the range and can program to charge your battery in the night or day at any time, also can limit the current to charge the battery to fit any size battery bank in it's range. They are heavy duty, proven long lasting product that is UL listed. They also come with battery temperature senser too.

              On the other hand, the cheap inverters are Not UL listed, when a fire in the house and the insurance investigrator fund an electrical appliance is NOT UL listed, they found the best reason and excuse not to pay out any insurance, that won't be cheap to the house owner at all. The cheap inverter usually come with pre-set low voltage cut off at 10.5 volts for 12 volts system or 21 volts for 24 volt and 42 volts for 48 volts system, by that time when your battery bank reach the voltage to cut off, they are dead! need new battery bank, so it will cost more then. Also if you see those DC connectors in the unit, you know that they can't be possible safely deliver the amount of DC current they claim if you know about electricity.

              Hope this answer some of your questions. Just think like a cheap Car without any safty features and compare to a well designed expensive comfortable Car with all the air bag and safty features.

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              • #37
                Originally posted by paulcheung View Post
                The Magnum Inverters are also battery chargers, they can charge the battery bank with Grid power or generator, It also can do preventive equalization, they have programable settings such as LVD to any voltage in the range and can program to charge your battery in the night or day at any time, also can limit the current to charge the battery to fit any size battery bank in it's range. They are heavy duty, proven long lasting product that is UL listed. They also come with battery temperature senser too.

                On the other hand, the cheap inverters are Not UL listed, when a fire in the house and the insurance investigrator fund an electrical appliance is NOT UL listed, they found the best reason and excuse not to pay out any insurance, that won't be cheap to the house owner at all. The cheap inverter usually come with pre-set low voltage cut off at 10.5 volts for 12 volts system or 21 volts for 24 volt and 42 volts for 48 volts system, by that time when your battery bank reach the voltage to cut off, they are dead! need new battery bank, so it will cost more then. Also if you see those DC connectors in the unit, you know that they can't be possible safely deliver the amount of DC current they claim if you know about electricity.

                Hope this answer some of your questions. Just think like a cheap Car without any safty features and compare to a well designed expensive comfortable Car with all the air bag and safty features.
                Good point! An Inverter/Charger is three pieces of equipment, not one! It is also a transfer switch. A better cost comparison to the cheap inverter would be the Cotek 3000w 48v for about $1000 -> http://www.wholesalesolar.com/291531...0-148-inverter

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