Well it has been a while, and a few have been built from France to Queensland and every where in between from the looks of it, and this is too little too late really.
All the info is in the previous posts in several sites... it is all out there now... so this is different to what I would have done months ago... it is just a simple... this is how I built this one kind of thing, and nothing new will be here I suspect..... thats the problem with lassitude or lack of time.. or both.
So we will start with the boards you can buy off the shelf, with a brief explanation.
These are not the best in the world by any means, but they are the cheapest very good cards you can get hold of easily, and cobble together a world class system
Much has been written about power jack crap, and a good amount of it is true.... but just as every compulsive lair can tell the truth sometimes, there are a few jems in their inventory that deserve credit where credit is due.... and total stuff ups too.
They managed to stumble upon a generic board that seems to be in China in a lot of unheard of brands. They are the same basically as the W7 power star cards in nearly all aspects.... except the reporting to the outside world stuff..... lots of colored leds for the W7 style units, and a large digital interface on the later power jacks... which seem to be fairly useless... but I guess they tried. It reports incorrectly, and half of it is useless information..... better without it really...
The odd thing about these boards, is that coupled with a decent transformer, they are capable of showing off against the best in the world as far as just being a solid powerful inverter is concerned. They are amazingly powerful, and tough, and will drive any load thrown at them if your transformer and battery regime can handle it.... truly remarkable performance, and second to none that I have witnessed.
Just about everywhere they can mess it up, they have done so. They supply transformers capable of reasonable performance, but rate them astronomically high.... just sad.... at least halve or more to get a real idea of their power....... I say more, as they never build the same inverter twice... they change transformers willy nilly, use one or two for the same specs, then supply from one to three fans to paper over the transformer swindles.... it is just sad.
Their QC is very marginal.... if it exists at all, and the first thing you do is go over their product very carefully, to find loose connections, and foreign matter left in the box... screws etc. You have no idea what will be in the box either. I have seen at least 4 versions of 8kw units turn up on the island... all different. The common thing seems to be trying to be cheap... and using as small a transformer as they dare, and then try to cool it as best they can to get some performance out of it...... in a lot of instances for particularly 12v units, this is probably good enough, as folks with them probably don't have the battery to bother it for long anyway, but in the 24v and particularly 48v range most folks can drive them hard for extended periods,..... and they will fall down from over heat.
The programming is woeful for the battery charger inter change.... not from inverter to grid sync, that is good and smooth transition, but from grid cut off to inverter stand alone .... it will blow up the fets from reactance if you have decent transformers in it... so if you roll your own transformer.... you MUST MUST MUST turn off unit before turning off grid power to it... or you will kill it spectacularly...... just a matter of time when the cross over is near zero in the cycle. The original W7 styles had lossy transformers, and so could stand the inrush currents.... but not with big low leakage torroids
The inrush current to the caps in the 15kw power boards will blow up 190 amp overloads just turning it on... so beware when you hook batteries to it, it will blow off chunks of the terminal.... so touch the nuts, not the threads with the lugs. ( I use a 15 ohm resistor for a few seconds, then there are no sparks.)
So with that in mind, we move on and build inverters that so far have been faultless for over a year over several sites ( there are a few of them about the place over here). They all drive large loads during the days including hot water services of 3.6kw while running the houses with water pumps, kettles, washing machines and anything else at the time.. so going into the 5-7kw range during the daylight hours is normal.
They also reverse grid tie very nicely, and up to 6kw has been seen going into them for short periods...... battery banks are far and few between that can absorb in the 200 amp range for long @50-60v , so if you want to drive them that hard you will need to have big AC loads, as the grid tie does NOT repeat NOT care what happens to the batteries, and will not regulate. More likely, it will push the battery hard until it goes up in voltage, and this will in turn absorb less power, so the excess will drive up the AC voltage, and at about 258v it will shut down the grid tie unit from over voltage... unless you interfere first with some other way to regulate the grid tie.
So thats what we have to work with. We can make a very useful inverter that will run a decent sized household without costing much more than $500 ( even in France.... buying the cores from England). Other comparable units capable of the same performance with the same idle characteristics are very much more than that.... probably 10-20 times in fact...... The W7 powerstar and copies...... inverters are well built, and have almost no bad habits except for the 5kwh/day idle losses... so if you have solar to spare, that may be a better way to go too.... but they will use up 5kwh/day, and the fans runs full time. There are some units like that here as well, and have performed flawlessly for over three years in their native state.... they were only $700 for 6kw and 18kw surge... very good units too.
So this is what we want to end up with:
And this is what we start with. A set of 15kw 48vdc 220v boards. They can be found on ebay, and are very much more expensive than when I first started out with these kritters... there are an awful lot sold since I asked them to put them up for sale. They have also since read some stuff on the net and improved their idle currents significantly..... so we have changed some of their poor behavior.
The newer boards have a black wire coming out from nowhere as seen here..... it goes to neg terminal, along with all the other black wires coming from the power card.... and no, I have not bothered to find out what t does.... my originals do not have it.
Here is a pic of the black neg leads, and a side on of the pins in the 20 pin header. If you buy the set, it comes complete with the start board that uses 12 of those pins. We can also see the later model replaceable fet boards... neat idea too.
Here is the front of the board, showing the driver sub board, and the CT and the transformer output interface to the control board.