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Coulomb

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Coulomb last won the day on April 11

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About Coulomb

  • Birthday January 5

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    Male
  • Location
    Brisbane, Australia
  • Interests
    Solar energy systems with storage; firmware for inverters and chargers

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  1. We're not sure what's going on either, and are throwing around theories to be shot down by evidence, or not, as the case may be. Your dips seem to be short duration; by the next set of data (30 seconds afterwards), it's all back to normal. So I'd guess what is happening is that the inverter is in the float stage, and your PV input is just barely able to cover your geyser load on a good day. Remember that there are other loads, there is a ~7% loss through the inverter, perhaps 10% from PV to load, and some 70 W (wild guess for a 7200 W model) of self consumption. So a sudden load, such as
  2. I would try a cable as per MPPSolar's recommendation, which uses BMS pins 1 and 2 instead of 7 and 8 (not necessarily respectively). Youda posted it here: https://powerforum.co.za/topic/2322-youdas-off-grid-lab/page/2/?tab=comments#comment-55761 Edit: use the bottom part of the diagram, the one meant for Axpert Kings. They would have the same removable display as your Kodak OG-7.2, I believe, and therefore the same RS-485 connector pinout. Actually, they do use different firmware, so I suppose it's possible that the hardware is different. But where to find the right answer? Edit
  3. I happened to notice a dip myself today. It was an unusually sharp decrease in sunlight, while the car was charged in pulling 6 A (so around 1.5 kW load, quite modest). When the battery is nearly full (it was at about 98.5%), the battery voltage does jerk around a fair bit. Especially if the charge current happens to change sign, from charging to discharging. I'm thinking that the 1.2 V drop threshold for going from float back to bulk (via a dip) is perhaps too low. The battery readings involved are also not load compensated. We had the threshold at 1.0 V for a while, and increased i
  4. Yes. This model has no removable display, so you can't get use a cable between the inverter and the battery BMS. You could however use a different cable from the BMS to a Raspberry Pi running ICC. That will enable ICC to control switching to and from utility at precise SOC values. It would also be helpful to update the firmware to the appropriate LFP patched firmware for your model. Unfortunately, that's in the date range where it could still be a PF0.8 model (4kW), or a PF1 model (5kW). Check your U1 data page to find your current firmware version, that will determine what patch
  5. As it says in the manual (near the end, not with the other warning and fault codes), warning 61 means no communications. It takes 3 minutes for the warning to come up, presumably became some battery BMSs can be slow to talk. After 10 minutes, it will stop charging or discharging the battery. So actually you haven't yet successfully connected the inverter and BMS. What cable are you using?
  6. A thought: perhaps the BMS hasn't reset its coulomb counter in a long time, for whatever reason. Then it's possible that the BMS is giving unreliable SOC estimates, and the voltage based estimates from the inverter are actually more sensible That could happen if the battery isn't getting fully charged lately. Check the battery voltages against reported SOC to see if the BMS reported SOC makes sense. Or perhaps one of your battery modules isn't connecting (thrown an error, cable loose), so the battery capacity is less than what the master thinks it is. Actually, if a module is in an erro
  7. Ok, so perhaps your voltage settings are too high. Here are the manufacturer's recommended settings, with corrections and brief explanations. Setting 26 might be what is causing the battery to disconnect.
  8. That should be plenty, unless they are really rubbish. It only matters if you have a relatively small capacity battery. They can somehow add or subtract secret sauces to make the battery store more energy in a given volume, or put out more power without sagging. A123 cells are usually power cells, for example. What you'd find in a bus is probably an energy cell; they need as much range as possible, and make enough peak power available by having many strings of cells in parallel. I'm out of ideas for now.
  9. I don't use ICC, but my understanding is that it can only override the settings in the Axpert as long as various settings are "out of the way". So setting 12 needs to be a very low value; otherwise it can take effect before the SOC threshold is reached. The subtle setting is setting 29, battery low DC cutoff voltage. If it's not also quite low, then there can be an "effective" back-to-grid voltage setting (the inverter firmware only deals with voltage) of 2.0 V higher than the cutoff voltage. I explain it in FAQ #2.
  10. Is this with the cable between the inverter and the battery's BMS, and the battery type set to PyL? Do you have more than one module installed? If they have different ages, it may take a while for the state of charge of the modules to equalise, and some may be disconnecting until it all evens out.
  11. Well, yes. Soft starters are intended to reduce starting current surges. By ramping up the voltage relatively slowly (over a second or few), there is never a huge difference between back-emf and applied voltage, so there isn't ever a huge current drawn. I imagine that the current might still be 20-50% higher than steady state, but that's much easier to handle than a 700% increase.
  12. Oops! I forgot to mention that with fully patched LFP flavour firmware, that 4.0 V becomes 1.2 V. I forget who is running what model inverter and what firmware. Right. But 1.2 V could happen, so if you were running fully patched firmware, you could get back to bulk charging when needed. Nothing so elegant. It makes about 500 measurements in that 10 seconds, and if even one of them has the battery voltage above the threshold, the counter resets to zero and it needs to see another 500 measurements after the last one that was above the threshold. That's what I mean about "no excep
  13. Oh. Unless your BMS is misbehaving badly, I can't see how this fits with the theory. Your absorb voltage setting is nowhere near the point where the BMS should be disconnecting due to overcharging. What is the capacity of your cells? Are they "energy" or "power" cells? Thanks for the graphs, but I really would prefer a graph of battery voltage, rather than battery power, if that's possible.
  14. I'm starting to like @ThatGuy's theory (see another of today's posts; sorry, it's way past my bedtime). Or perhaps a version of it. It looks to me that your battery is getting quite full by 13:00, and the sudden drop in load caused the solar charge controller to over-voltage the battery. Do you have a Pylontech or similar battery? Is your absorb voltage up around 53.2 V, or are you perhaps using the direct cable (so that the BMS itself will be using 53.2 V)? What might be happening is that the temporary over-voltage of the battery is causing the BMS to shut off, which may cause the inverter to
  15. Hi. We're going to need some more details; what battery model do you have?
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