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Everything posted by Coulomb

  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?
  16. Coulomb


    Can you isolate each panel conveniently, say by popping fuses out of their holders? (Best not to do that under load; opening DC rated breakers is fine). If so, do you see about equal contribution from each string? Is that testing each panel in isolation? If that's an open circuit voltage, that sounds like they are 60-cell panels, which sounds OK for a PWM solar charge controller. What brand of solar charge controller is it? Maybe it's a cheap brand that is actually only capable of 11 amps output. Or it's prematurely PWMing. Can you temporarily connect PV-in to battery ou
  17. Be aware that this is probably not a 30 minute operation, so it could be costly. Extra wires and fuses have to be installed, possibly more conduit, possibly a second combining cabinet, and more. So perhaps hold off while we see how well @ThatGuy's theory works out.
  18. As mentioned above, ambient temperature doesn't have to be particularly high for the internal temperature to reach a level where the solar charge controller may throttle back maximum current, possibly to zero. But thinking about this, I would expect more of a gentle slope towards zero power, not necessarily reaching zero every time, and not plummeting quickly to zero and back again just as quickly as we seem to see.
  19. Brilliant! Now that you put it like that, I can't see why I didn't think of this before. Perhaps I did and dismissed it for some reason. For reasons that are beyond me, when an Axpert goes from absorb stage to float stage, it does so via "zero charge" stage, which means that the charge current is zero for about 15 seconds. This would be a "dip". Someone mentioned today (and I think others too) that their dips only tend to happen in the afternoon. While that means it might be internal temperature related (it doesn't have to be a hot day, just hot inside the inverter case), it could also be
  20. I responded to the same post on AEVA here.
  21. That suggests, but by no means proves, that the cause may be temperature.
  22. Actually, on re-reading your second last post (assuming that was you), I'm wondering if perhaps you have panels wired to more than one inverter's PV inputs. The PV inputs on some models are not isolated from the mains, and current might be diverting via the panels. This would not be doing any good for the panels, the wiring, or the inverter electronics. Each inverter must have its own panels, and there must be no connection between the PV inputs. Regardless of the cause, it sounds that one inverter has had something burn out now.
  23. Thanks, Calvin. Always happy to learn. Though in this case, I should have remembered that I posted about the "KP" model designator in a post long ago. Sigh.
  24. Ah. So far, not a single factory firmware, even the very latest, has fixed the premature float bug. That was the impetus for the patched firmware, and we assumed it would only be needed temporarily. But not so. I'll check in a moment, I vaguely recall doing a light patch on a 24V firmware. Maybe it was this one. [ Edit: It was not. 18.22a forced 24 V mode. It may not even have fixed the premature float bug. ]
  25. No, the capacitor adds very little current, and since it's running on AC, the current drawn is continuous; I believe that there is very little surge at start-up that is solely due to the capacitor. [ Edit: the starting capacitor is usually only a few microfarads, compared with a few hundred microfarads you would see in a power supply. So the current is proportionally much smaller. ] Most of the surge current is from the motor starting speed at 0 rpm, so there is no back EMF to counter the supply voltage. So initially, the only thing limiting the current is the reactance (inductance and re
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