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plonkster last won the day on June 20

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About plonkster

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  1. I hate this term. They still have a transformer, they can just get away with a much smaller component and use a different material (eg Ferrite, so no eddy current issues in the core) because of the higher frequency. Basically, if you study the various conversion topologies, there are a few low-power designs that use only capacitors (also called charge pumps), but they are generally good for generating a high voltage supply to drive FETs at most. For anything that can do any level of power, you'll want to use some kind of magnetic component, some kind of inductor. Now there are numerous such converters, buck, boost, sepic, cuk, and they all use some kind of magnetic component, and almost always there is an equivalent isolated version that essentially uses a secondary winding on the inductor: aka a Transformer. So anyone talking about it being "transformerless" must be in marketing. They are also the idiots who think the inverters with bigger transformers (MLT, Victron) are old tech... the truth is these inverters use toroidal transformers for better efficiency. Zero problems. Designed in in fact. It has a bonding relay. When the power goes out, it bonds the neutral to the case of the inverter. All you have to do is ground the inverter case to a suitable earth. For example, on a boat/barge/yacht it would be grounded to the hull while in inverter mode, but it would use the shore earth when on the grid. When you install it in the city, you simply earth the case of the inverter and you're done.
  2. plonkster

    Infinisolar not reading PylonTech SOC

    35 is fine if each inverter has it's own pair to the busbars. 4kw at 48V is less than 100A. You can get away with 25mm^2 in a pinch. Of course if any part of the current path is shared, then you got to beef that bit up.
  3. It's 3.5KW for single phase, so I'd expect it to be around 10 for 3-phase. You are allowed to fit a larger array or a larger inverter as long as the inverter is configured to not feed in more than the legal limit. It helps if it is on the list, and many installers won't touch it if it isn't on the list, but the list is more of a guideline, a resource that helps you select something that will sign off. The Victron inverters for example (the older ones, before the MultiGrid came along) has NRS097-2-1 compliance if they are paired with a Ziehl anti-islanding device, and the Ziehl is on the list on its own too, so you generally can get it signed off, though it takes more work: It is not on the list so some won't touch it. I'm also told that it isn't really policed, so there are people who fit one unit and later upgrade to something else. Of course I'm supposed to tell you not to do that.
  4. It depends entirely on the topology used, and whether the designer thought it best to reference all things to a common place. The long and short of it is don't make assumptions :-)
  5. plonkster

    digital thermometer placing

    I'm not always sure if they do as well on surfaces other than human skin. The one we have (which is notoriously inaccurate even for its intended purpose!) has two settings, one for human skin and another for other objects. This alone leads me to believe your results with this rather expensive meter is going to be disappointing. In fact, I'm thinking of getting a nice industrial one for maybe double the money shown here... and using it on my kids too. 50 bucks says it will do better that way round than the cheap pharmacy model.
  6. It depends on the make, literally. Some can be bonded safely. Most cheap modified sine-wave things cannot. Whether you can ground the battery and/or PV input also depends. With some MPPTs the current sensor is in the negative line, so grounding both negatives bypasses the current sensor and can potentially damage the MPPT. In general you should not ground the negative of anything (except maybe in a vehicle, and then only the battery). Inverters with a fully isolated boost stage can be grounded both battery and AC neutral side. But why would you want to find out? :-)
  7. plonkster

    digital thermometer placing

    It's customary to mount the temperature prove to the negative probe of the battery. Not sure why that one precisely, but it seems that the lead probably conducts the heat better than the plastic/rubber/polyurethane/whatever casing of the battery.
  8. Yes, apparently they try to push you into replacing even your prepaid meter with a BMI unit that costs around 8.5k. That's the info I've got, but of course you cannot google for it because BMI is also body mass index.
  9. plonkster

    midpoint panic

    I may have been wrong to tell you not to change anything on the BMV. You had a false positive there. The voltage was high enough and the charge current low enough for long enough to reset even though you're at 85%. Two things to do about that. Either move the charged voltage setting on the BMV up as well (set it 0.3V below the current absorption voltage). Or... alternatively... for the next few days, don't rely too much on the SoC measurement.
  10. plonkster

    midpoint panic

    Indeed... since I made that argument I am now so aware of using this term. Of course in this context it is not fallacious: There has been somewhat of a technological progression towards things being less simple. My gripe with it would be akin to using it in a moral context, such as "slavery!? in this day and age!?", as if the concept is unthinkable merely because ostensibly humankind has grown up :-)
  11. plonkster

    midpoint panic

    Off Topic: Speaking of that. I saw a really ingenious use of such a device recently: To diagnose a non-firing spark issue on an engine. The outlet manifold is colder at the non-firing one. Of course you might tell me to just pull the plug wires one by one... that really doesn't work as well anymore in this "day and age" of coilpacks and ECUs. :-)
  12. plonkster

    midpoint panic

    But further to this: For the next few days, or at least today, I would use the grid for my loads and use everything to charge the batteries. Don't run them in normal cyclical use until you get to the bottom of this. Charge them fully (with no discharge blips in the middle), then discharge to a lower SoC once (early morning or late night) and repeat for the next few days. If all goes well your midpoint deviation will become lower every day. I must say though, that low battery warning (it most likely hit your configured low voltage limit), that might point to a bad cell. If you have a bad cell... none of this is going to help. Two things to do about that. Either what TTT said (test using a battery tester), or while charging view them with an IR temperature camera thing (those really expensive ones), a bad cell should show up as warmer as the rest.
  13. plonkster

    midpoint panic

    Recalling something @Coulomb wrote, after a low battery event the Axpert will remain on grid for a certain time period. Also, ICC changes the priority setting (as I recall) but the inverter may decide to override that anyway. It is often the case, even with my own equipment, that what you give the inverter is more of a wish than an order, and the inverter does the best that it can. For example, in our own little universe, we might tell the inverter to discharge at 5kw, and it might well give us only half because of a variety of reasons including what the BMS limits are, what the temperature is, if there is a large DC ripple, and so on and so forth. Often the reasons for whatever the inverter is doing isn't communicated to the outside world all that well... (so most of our job sheets these days have an item at the bottom that says "communicate clearly to the user what is going on")
  14. plonkster

    Axpert VM III

    The fight is real. At least within Victron circles: 1. We talk of Solar Chargers rather than MPPTs (the company also has other kinds of chargers). 2. We talk of PV-inverters rather than Grid Tied Inverters. I prefer grid-interactive. All PV-inverters are grid-interactive. Not all Grid-interactive inverters are PV-inverters (eg SMA SunnyIsland). Also, not all of them can operate without batteries. The Infini can, the Multi and the Quattro cannot.
  15. plonkster

    midpoint panic