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plonkster

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Everything posted by plonkster

  1. Water harvesting and use, same logic as solar systems.

    I can see how it can be done potentially. First, I suspect the free education will eventually cost as that much, but will have to be phased on, and as I have said repeatedly: You will still have entry requirements. You still have to qualify to actually go to university, and with the state of our education system I half suspect the number of takers will be relatively low in the beginning. In other words, we have a bit of time to find the funds for this. Second, by some sources the amount of money lost to corruption annually is in the order of 20 billion. I don't think we should make the mistake of assuming we'll be able to stamp corruption out completely, but even if you just half that, you're 20% towards that first 50 billion. Then there is the hugely inflated salary bill. This won't be popular. But every new administration tends to kick out the bad seeds of the previous one, so I suspect a lot can be gained here, and it will sommer double up in helping with the recovery of the aforementioned 20 billion. So I have a feeling, with some hand waving and postulating, that half the money we need we already have. It was being stolen and wasted up to now. It's a feeling, but I think it is a good one.
  2. Battery Spikes

    And yet more... for this intrigued me... My pictures are not as nice as @Weasel's, but at least somewhat informative. This is a 100/50 charger. I also see 400mV peak to peak at the battery, but note the scale. That's at a 50ns scale, so we're up in the megahertz's here. I really doubt that matters much. The other picture is more in the 100khz range, and that shows about 100mV peak to peak.
  3. Water harvesting and use, same logic as solar systems.

    Dude, Return of the Jedi has significance towards the other side. The bad guy comes back into the light, he reforms. I can work with someone like that :-)
  4. Water harvesting and use, same logic as solar systems.

    Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to use it in a fruit salad.
  5. Huawei SUN2000L Inverters

    That might in fact be due to them being "smaller". Small engineering lesson coming up... :-P A modern inverter works like this: First it takes your low DC voltage, and converts it into high-frequency AC. Then it pushes that AC through a transformer to turn it into a higher voltage AC. The reason for using a high frequency is it allows you to be more efficient and use smaller transformers. Then it turns the high-voltage AC back into DC. At this point it typically generates around 400VDC. This first phase of the inverter is called the "boost stage". The second phase then turns this 400VDC into 230VAC. You may wonder why does the DC have to be so much higher? Because the 230VAC figure is an RMS value. The peak voltage is over 300V. Now you get some inverters that use a high voltage DC input. Those inverters don't need a boost stage. Usually they are PV inverters (SMA makes some nice ones), but the same thing can be done with batteries. In addition, the boost stage of an inverter is the more stressed part of it. A high voltage input unit will be less stressed and less likely to fail. So this "smaller" unit likely relies on the high input voltage for exactly that reason. And it may well require a special battery. The Tesla battery is a high-voltage battery as far as I know. Perhaps that is what they are aiming for.
  6. Mecer 5kVa settings and monitoring

    To be fair, if you pay a lot for something, the firmware had better be sorted! If you get it cheap, you can cut the device some slack. I think what you see here is that old thing about the pain of something lasting much longer than the sweetness of the bargain or something like that, I forgot the exact saying. The pain of the high cost is now almost 5 years in the past... long forgotten.
  7. Geyserworx PV geyser unit

    Technically it doesn't need to be a very good inverter. It can make a square wave and the element won't care. It could even be a boost converter that makes 300VDC and it will work fine. There are some people making little car "inverters" for charging phones, cheap nasty boost converters that actually make something like 150VDC, which is good enough for the average laptop/phone SMPS to work. So something like that, might be cheap enough to be cost effective even. :-)
  8. Mecer 5kVa settings and monitoring

    The hunt for good firmware continues to amuse me. I'm sorry... it shouldn't, but it does.
  9. Battery Spikes

    Okay, a bit more info on this. Not all the BlueSolar models are interleaved, only the larger ones. I'm not sure if the 150/35 is considered a larger one but I suspect it is. The 100/50 definitely is. This knock-off illustrates this quite clearly. So if your testing a 100/15 perhaps the results will be slightly different to the larger ones. I don't have quite as nice an oscilloscope as you do (I have a fairly nice 100Mhz analog scope), but I do have a couple of diverse blue chargers, a 100/15, a 150/35, a 100/50, a 80Ah lead acid battery that is practically new, and I have access to a few nice power supplies to simulate some PV with, so I could possibly contribute some results if I have some spare time. Rare these days :-) Alternatively, if you lug that nice scope up here to Cape Town you can always do some measurements here :-)
  10. Victron BMV 702 - No Power?

    That sounds likely.
  11. Battery Spikes

    Current- and voltage ripple on buck converters is a design parameter. Lower is better, but it depends on the load. I am not too surprised that lower-end controllers will cheap out on this. The BlueSolar is interleaved as far as I know. In other words, it has two inductors that it drives anti-phase. That will always significantly improve the output ripple. It is something to take into account when you compare apples with prickly-pears.
  12. Mecer 5kVa settings and monitoring

    I agree with Silver. You want at least a fuse in the DC line. Sometimes the inverter might have one. The fuse inside the inverter is actually there for reverse polarity protection. Diodes lose too much power and they get hot. So what they do is stick a FET across it that conducts if you hook it up in reverse and blows the fuse. But I still prefer an extra fuse, preferably on the battery side, because if I screw up somewhere downstream from that (who owns a proper insulated spanner and who just uses the 13mm from the main Gedore set?) I don't melt cables. Regarding earthing. Well, the case of the inverter itself should be grounded for obvious reasons. Now I don't know the Voltronics, how they do it. On the inverters I know, there is a bonding relay that bonds the neutral of the inverter output to the case of the inverter, so as long as the case is earthed, you get a full safe bonded setup. The early Voltronics didn't have the ability to bond earth and neutral. Later ones can. I don't know how it works, but it is important to get this right. You want earth and neutral bonded when it's disconnected from the grid and the inverter is running. You want the bond to go away while it's in passthru. We have this discussion at least once a month. Well I do... :-)
  13. Voltronic, Axpert, Gride Tie, Red Tape

    Newer models/firmware closes a bonding relay when the inverter is running. I bet you can use that.
  14. Water harvesting and use, same logic as solar systems.

    Again, I am so tired at people quoting this "we knew" story. Yes, we did, and we still do. The question is WHAT it was that we knew. We knew that on average, rainfall would come down. That was the prediction, and that is still the prediction. This year however, the last three in fact, is completely OFF the average, they are outliers. We didn't know that in 2011. No model could predict that, that is precisely the trouble with stats: It cannot predict outliers. It can only tell you that they are outliers. If the past few years followed the model that we KNEW about, we'd be at significantly less stringent water restrictions. Instead it threw an outlier we didn't know about.
  15. New Infini Super

    I think this is where the Pylontechs are coming in. We're at the point where a good set of Trojans cost the same as a comparable (mostly) Pylontech rack.
  16. Which batteries should I buy (rhetorical question)

    I was led to believe that the BMS uses the same (CAN) protocol as the BYD battery, which is also used by LG-Resu, and also used by Pylontech. Though it seems there are tiny differences between them. But their website seems to suggest they are using ODB2 (aka SAE J1939). It probably does not matter. These things all work the same way, they stuff all the data end to end into 8-byte packets with either the 11-bit ID in front or the extended 29-bit one, and chuck it onto the can bus. All you have to do is read them, chop it up in the right spots, potentially swap for endianness, and you're done :-)
  17. Anyone use Solarus panels before?

    Agreed, but I'm willing to bet money on it that those people telling you that this is "4 times more efficient" was looking at the overall output, ie hot water (reverse-calculated at 1.16Wh/liter/Kelvin) plus the PV output. Then 4x is not that surprising. Looking at PV output only... even a 50% improvement sounds too good to be true.
  18. Grid tie without battery backup question

    You mean SunnyIsland. Let's get technical. I think what those SMA inverters do (most likely) is include really big capacitors that act like small batteries, so you have a kind of self-consumption setup: The PV panels charge the capacitors, and a small inverter draws from it. Control electronics shut things off really quickly if they go out of bounds. And the PV array has to be 4x oversized. So the question is if this recipe can be scaled to 7kw. I suspect it can... but at what cost? Might be cheaper to put in a small lithium bank then and do a proper self-consumption setup. Of which Victron remains the best... (also, could not resist :-) ).
  19. Grid tie without battery backup question

    You sound as muddled as I do :-) Just read the SMA link I posted. It is simple enough. The inverter only provides a portion of the power so that even if there is some cloud cover it can still drive smaller loads. If you attempt to draw more power than it can handle, it switches off. If the cloud cover is really heavy, it switches off. Easy as that. Subtext: Don't be a dumbass and try to run your house off this feature :-) But.... never ever seen an actual model with this feature. Even in the US... that feature costs extra money so it's rare.
  20. Just got this from an Australian reseller :-) --- snip --- I just had a call from a customer with a Victron System. He was caught in Cyclone Debbie in North Queensland, Australia. His MPPT was inside a temporary building that was caught in a flood and filled up with water. When the flood level went down, he looked through the window and could see the blinking blue light of his Victron regulator UNDER WATER! System is still working to this day nearly a year later.
  21. Grid tie without battery backup question

    The secure power feature, at least on the SMA, is meant for small loads. It's sized no more than 25% of the nominal capacity. It's for charging of phones, non critical things. I've never seen it on a South African model. It's on some of the US models, presumably for areas that get bad weather where the power might be off for a few days. Then you can at least run some essentials. This case with the Goodwe was the first time I ever heard of it happening with another brand. So what I am saying is that it is at least possible in principle, and before you assume that it is a mistake, check the documentation. It might be a feature :-)
  22. Anyone use Solarus panels before?

    We all know that solar water heaters are significantly more efficient than PV panels. So it sounds about right, if you combine a single panel, generate some electricity and absorb the heat into water, you'll make at least 3 times the energy.
  23. Grid tie without battery backup question

    Yes. @Chris Hobson called me the other day about that. He had a Goodwe powering loads even though the grid was down. Keep in mind though that the Goodwe has an input and an output, and this was on the output, so no feedback rules are being broken here. I am also aware that some SMA models have a secure power feature that can power some loads when the power is out. It's meant to power smaller loads.
  24. 5kva Axpert MKS model - faulty

    Oh yes! I think the mypower24/solarmd people have the ability to repair as well.
  25. Water harvesting and use, same logic as solar systems.

    Schmutzdecke. Got to love the German language.
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