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Everything posted by Calvin

  1. Another key issue: Even when batteries use the same chemistry they can have different cell counts. For instance the Pylons are 15S while most other LiFePO4 batteries are 16S - they can most definitely not be paralleled.
  2. The article below is aimed at electric vehicles but most of it applies pretty well to the Li-on home ESSs that many of us use. One point not clarified: does the replacement cost include trading in your old batteries, or are you at liberty to keep them and re-purpose the cells? Given the low usage of electric vehicles in SA, and that the article is written about the Australian market, any thoughts @Coulomb? How much does it cost to replace the batteries in electric vehicles? (thedriven.io)
  3. Are you sure that you are not confusing generators with inverters? (Unless you are talking about inverter generators?) I have never heard of modified sine-wave other than as inverter output. A quick Google search confirms that.
  4. You may be able to do better than that: if you run the pwrsys command, the field "System RC" is the system remaining capacity and the field "System FCC" is the Full Charge Capacity. The more accurate SOC is ((double)SystemRC * 100 / SystemFCC). The reported SOC is that number, truncated to the integer. This applies to the whole stack irrespective of the number of batteries in it. Have you found a good source of load-shedding schedules, ideally via an API rather than scraping? I am aware of https://loadshedding.eskom.co.za/LoadShedding/GetStatus but am looking for actual schedules. Nice system BTW. And there I thought that I was a control freak...
  5. Yes, remember that in mid winter the sun rises NE (60°) and sets NW(300°) (at CPT latitude anyway), so East or West facing panels are never pointing straight at the sun. In summer the sun rises SE and sets SW, so at mid-morning the East panels at least face directly towards the sun. For most people the size of the PV array is determined by the requirements in winter, and in winter it is really important that they should face as close to North as possible.
  6. It is because this panel is in series with the rest of the panels in the string. There is a relatively easy way to test this. Take a picture of the shade when the power is low. Now take a piece of cardboard (or similar) and cut it to roughly the same size. Wait until the shade is gone, and put the cutout on the panel in the same place as the shade was. If the power is low again, shade was your problem. If not, look elsewhere.
  7. Correct. The box in the top left of each graph has the configuration. 1 @ 315/30 means 1 panel facing NW tilted 30 degrees.
  8. Combination 50/50% Just NE: Just NW: For reference: Directly North
  9. No problem at all - what is the tilt on the panels?
  10. See graph below for output of panels facing East at 30 degrees tilt in Cape Town. Peak is about 50% of nominal.
  11. Everything points to shading - the chimney is terribly placed. I am not surprised that it sometimes causes a 50% drop in the lower string. The problem with this diagnosis is: "Last year and the year before I never had this issue but the shading was exactly the same." What time of day was this picture taken?
  12. Is each array a single string? If yes, it is almost certainly shading. All panels in a string are affected by shade on one. The effect is more pronounced if the shade is across the short side of a panel. Shading a long row will normally lose you at most 1/3rd of the power - shading a short row can lose you most of the whole string. You can find a lot of information online - search for "pv panel shading effect"
  13. My 72 cell 365W Canadian Solar panels are 47.2V VOC and I had to rewire to 2S. These fact that these 365W JA modules are 60 cell panels makes all the difference. What has changed (I think) is that 60 cell panels were not available with such high power until recently.
  14. One thing that you may not be aware of: I was also a 3 phase Landrate (rural) user, paying about R2000 for connection before any usage charges. There are prepaid options "LandLight 20A" and "Landlight 60A" that provide single phase power with no fixed monthly charge. The rate per kWh is much higher (about R5) but that is still a lot less than diesel, with the advantage of not having to start / maintain your generator. One caveat: with the new ESKOM proposals that there should be a connection charge for all customers, perhaps this will no longer be true. As for your original question: I sent them an email and eventually (about 6 months) got a response. Then they sent a bunch of jokers round to change the meter - they changed the 3 phase x 40A meter to a single phase (60A) pre-paid, but left the 3 phase transformer on the pole, with 40A breakers. That is the bad news. The good news is that they installed a prepaid meter with urban tariffs (R1.80/kWh) rather than rural (R5.50) so I have stopped complaining...
  15. Update: I have recently upgraded the firmware in my US3000Bs to 2.8, and this issue has been resolved. They seem to have taken a different approach to deciding that the SOC is 100% - it now needs a higher voltage to get there (52.9V vs 52.5V previously). There is also no longer a "buffer" above 100 - as soon as you start discharging the SOC (which is rounded down to the next integer value) drops to 99%. Sadly the ridiculous "feature" of the reported SOC being stuck at 89% during charging is still there. It is a ratchet effect: it will not go up but it will come down. Once this offset between real and reported SOC is present it can only be reset by charging to 100% SOC.
  16. The 3 address switches are only set to values other that 0 on the Master in each group. If you have only 1 group (8 or fewer batteries) all the switches should be off. The system assigns slave addresses in sequence starting with the one connected to the master.
  17. That is completely dependent on the tilt in your panels. Flat mounted panels produce much more power in summer than in winter - tilt them at 40 degrees and the picture changes hugely. Below is a graph comparing panels tilted at 0, 10, 25 and 40 degrees in July. You will see that the panel at 40 degrees produce double what the flat one does. The picture is of course very different in summer: So you can see that for flat mounted panels the drop is 8.2 to 2.6, or 68%! For panels tilted at 40% the drop is 6.4 to 5.1, or 20%. These figures are for panels pointing North, in Cape Town. It will vary a bit for other locations.
  18. The main problem is that a shaded panel affects all the panels in the same string. In your case, you will lose a big part of the 6 panels in the 2 left hand strings. You can kill 2 birds with one stone if you re-wire to 2S6P with the 2 offending panels in the same string. It will eliminate most of your shading losses and remove the risk of overvoltage damaging you inverter (I am assuming 145V max VOC inverter) .
  19. Not only ambient: all batteries have internal resistance, which generate heat proportional to the square of the current. So, charging at 1C for 1 hour will heat the battery up 10 times more than charging it at 0.1C for 10 hours. I suspect that this is a big part of the reason why Pylon do not want you to charge/discharge at 1C.
  20. Google "solar power diverter hot water" and you will find lots of information. A system like this is quite complex: you need to identify how much excess PV is available (clipped) and you need a way of controlling the power to the geyser. The first bit is the most difficult - most MPPT controllers do not "publish" the amount of PV that they are clipping. The second is normally done with a microcontroller that does zero-crossing detection to fire the triac at the right moment. I use something similar - loosely based on the design featured here Learn | OpenEnergyMonitor. I agree with @P1000 - use a triac based solution rather than a thyristor chopped one. Most solid state relays will also work. The topic is quite controversial - many people believe that it is bad for you inverter. I can only speak from my own experience : my Axpert Kings do not seem to mind - it works very well. I might of course change my mind if all my inverters die in a few years....
  21. Sounds about right. A lot of fuss is made about the fact that the Pylon is not a "1C" battery, but it actually is: the specs are very clear "Maximum discharge 74A" with a 15s peak of 100A. I suspect that you are right and that the recommended discharge rate of 37A is for the 6000 cycles. Anyway, in practice the ability to completely discharge your batteries in 1 hour seems more relevant in an application like an EV than a domestic ESS.
  22. I upgraded my Pylons, hoping (in vain as it turned out) that the "stuck at 89%" bug will be gone. The main change that I have seen is in the voltage that is required to reach 100% SOC. Previously my batteries easily reached 100% with a charge voltage of 52.6V, and would even go beyond 100%. After the upgrade they need 53.0V to (barely) get to 100%, and I have never seen them go beyond 100%. Whether this is an improvement or not is open to debate. It does however mean that you may have a problem where only some of the batteries in a stack are on the version 2.8 firmware.
  23. On my paralleled Kings each inverter will always switch on or off according to the its switch position (as long as there is a battery connected). If the master is turned off any online slave will take over as master. If there are no slaves online the ac output will be interrupted.
  24. The slave inverter is acting like it is switched off. This can be caused by: It IS switched off? The switch is faulty. The inverter is faulty. 1 seems very unlikely, but easily rectified. 2 is easily checked by swopping the 2 Remote Display Units. The switch is a purely mechanical pushbutton - if that is faulty it is easily replaced. 3 seems unlikely given that there are no error codes. Perhaps @Coulomb may have some insights?
  25. The issue is with the battery's BMS - nothing to do with Inverters. The BMS reports SOC correctly when discharging. When charging however it "sticks" at 89% until the battery is in reality at about 99%, then it quickly catches up and goes to 100%. It has been much discussed, including on this post: Pylontech SOC jump while charging - Batteries - Power Forum - Renewable Energy Discussion
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