BFL13 wrote:
#1 Misses the whole point IMO. It is this variety that makes it so difficult to match the converter "size" to the generator "size" needed to run it for battery charging while camping.
#2 My test approach is to do it in real life. As seen, you get different answers from using the converter as "supply" (less VA needed) from "battery charging" (more VA needed) Also true that it varies by battery type.
#3 If you use a scientific fixed load to see what the gen can do, you miss the problem of just how much load your chosen converter will be when faced with your particular battery bank (type of battery, condition, wiring set-up, etc) at different SOCs.
#4 Some converter makers also seem to rate their converters using an artificial fixed load, and publish misleading "specs" as a result, which understate the VA needed on a real battery bank.
#5 In my case, I started with the actual VA this 75 amp converter required from my previous Honda 3000 on my actual battery bank (just under 1700) and matched that with the generator spec of 1700w continuous for my new generator.
#6 I also thought being a "2200" it would have some margin above 1700. My Honda 3000 could do more than its rating without overloading.
#7 Of course I don't like the word "flawed" there, but take comfort in seeing how closely Mr Wiz's results match mine with totally different set-ups except having the same model of converter. IMO this shows the measurements are valid.
#8 You want the test to be what will happen when you are actually out there off grid with your batteries at 50% and you will be using your converter from your generator. Can it do it or not? Know before you go!
#9 There still doesn't seem to be a reliable way to shop for a gen and converter to know exactly how they will match to get the most DC charging amps from the published gen ratings and converter ratings. It is expensive to get it wrong if they don't take "returns" on those.
You have to be lucky enough to be on this forum before you go shopping to get at least some notion about that. :)
Cleaned up and added item numbers to make my comments vs your comments easy to follow..
#1 Splitting hairs by trying to micro size your gen when camping. It is well known that 1Kw-2kw gens are on pretty shaky ground concerning trying to recharge your RV batteries let alone try to do anything else on top of that. There is very little headroom to work with on smaller gens and you have nothing to gain or save by micro sizing your gen.
#2 Your "test" does not fully reflect "real life" since you have too many "variables" which are skewing your initial base test to see if it works with that gen. Remove the variables, THEN ONE BY ONE ADD THE VARIABLES BACK IN UNTIL IT FAILS. This IS a valid "scientific approach".
#3 Starting with a "KNOWN" fixed load (non variable) you find out IF your generator CAN handle the converter load of say 75A on the 12V side. If the generator passes this test, THEN you ADD say the battery back in to the test and ADD say a 75A non variable load to the battery AND THE CONVERTER. By doing this you are methodically going one by one through all of your "scenarios".
#4 You don't really "know" what the manufactures have used to "rate" their specifications. You ARE "assuming" that they are using a "static" load.. What I can tell you is there IS some "slop" allowed in their "specifications" due to tolerance stacking in the components.
Tolerance stacking means that the sum of all the tolerances of all the components within a device must not exceed the manufacturers final specifications.
In a nutshell, due to component tolerances there is an "acceptable range" that the manufacturer will allow to go out the door. So, when they say a converter can do 75A at say 14V that supply MUST be able to at least supply that current at that voltage.. The input voltage and current will also have a tolerance range.
#5 As I mentioned before, comparing a "non inverter gen that IS larger to a SMALLER Inverter gen is "Apples and oranges" type of comparison. In reality, you NEED to take say a 2Kw NON INVERTER gen and a 2Kw Honda INVERTER gen and see if those pass your test..
I PERSONALLY THINK THEY WILL WORK BETTER THAN THE B&S INVERTER GEN.
#6 Not sure what gives you this "idea" that a CHEAP UNDERSIZED B&S inverter gen will work as good as a 3Kw name brand gen. That B&S gen IS a Chinese gen and I highly doubt that it is capable of handling the reactive load you giving it.. Better gens most likely will have a better chance of dealing with a reactive load.
#7 "Flawed" definition..
HERE"Flaw..
1. An imperfection, often concealed, that impairs soundness: a flaw in the crystal that caused it to shatter. See Synonyms at blemish.
2. A defect or shortcoming in something intangible: The two leaders share the flaw of arrogance.
tr.v. flawed, flaw·ing, flaws
To cause a flaw in; make defective: an argument that was flawed by specious reasoning.
Flawed..
characterized by a defect or imperfection: The scheme is fundamentally flawed.. "Seems to fit when you have too many "variables" in your tests..
#8 Which IS why you start with a KNOWN "load" to start with then add in your variables. This way you KNOW where the problem lies. Right now, you simply know that it won't work the way you want or need it to.
Also known as "Process of elimination", one of the very FIRST basic lessens that I learned 30+ years ago in Tech school for troubleshooting electronics..
#9 Working with AC voltages it is much more complex than working with DC voltages. It is a very complex relationship due to something called IMPEDANCE (Impedance is a combination of resistance, inductance and capacitance which a switching power supply does present to the AC load..
Impedance plays havoc with your tests and is difficult to quantify.. You would have to really get done to the nuts and bolts of the circuit at hand to determine what is happening, pretty much an Electrical engineering job.
Honestly, way over thinking this, much simpler sometimes to simply move up a notch in your generator size or buying a BETTER "BRAND" to get the results you are requiring..
