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Thank you for the great forum, Safe Driving over the weekend. Sincerely Jason


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Coulomb last won the day on May 13

Coulomb had the most liked content!

About Coulomb

  • Birthday 05/11/1958

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    Brisbane, Australia
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    Solar energy systems with storage; firmware for inverters and chargers

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  1. I believe that they are the same thing, so they should be totally interchangeable.
  2. No, none of the solar charge controllers are isolated. The only isolation is between the battery and the DC bus. So for the 145 V max SCCs, they get isolation from the AC-out because they connect to the battery. But Axpert MKS IIs (as discussed in this topic) have a boost converter that connects directly to the DC bus. So you'll see chopped 230 V on the panel wires (with the high frequency component attenuated a little by a common mode choke). So you must be getting leakage from some panel wire / connector / inline fuse / panel junction box) to earth when it rains, causing the trip. Huh. Who said Axpert MKS IIs don't have insulation monitoring? Of course, if it was proper insulation monitoring, it presumably could just show a warning and disconnect the PV, rather than black out the whole house. Though I'm not certain that the MKS II SCCs have a relay that can disconnect their output from the DC bus. [ Edit: it looks like there isn't. Sigh. ]
  3. OK, but that doesn't mean that it's good for your particular battery. 50 A is C/4, which is generally too high for gel lead acid batteries. Only if you are utility charging during the day, which would be on rainy or cloudy days, and only if you enabled utility charging. Otherwise, you'll get 30 A of solar charging, if available, and if that won't exceed the absorb/CV or float battery settings (depending on what stage the charging is at). No, because you set the maximum utility charging to 20 A. So 20 A at night. Yes. The 30 A limit is to protect the battery. There is no need to limit the utility charging to a fraction of battery capacity. Setting 11 is there mainly for generators, so you can set a limit and hopefully not overload the generator (whether you actually overload the generator depends on your loads as well as charging power). The important one is setting 02, so definitely change that one. Presumably you're happy drawing 30 A from utility at night (around 750 W plus losses, just over 800 W), so you may as well increase setting 11 as well. Yes, it's a bit of a desperation measure, but saves outlay on another solar charge controller. But I believe it's fairly safe; once fully charged, the battery merely draws little current, and little harm is done (there is a little extra heating, which is not good for lifetime). If the battery gets hot (around 40°C), then 14 V per nominally 12 V module is a gassing voltage, so you might have to be careful in summer, and perhaps reduce the float voltage setting a little. In another topic, @plonkster has claimed that 14 V is a gassing voltage (even at 25°C I think), just with less volume of gas. My understanding is that it's a pretty much binary thing; at a certain voltage, the gassing starts, and at lower voltages, it's pretty much not happening, and a sealed battery (such as your gels) should cope with it happily. I'm no lead acid expert however, so do your research.
  4. Or maybe you could try @8321's idea: set the float voltage (setting 27) to 28.0 V. That's 14.0 VPC; enough to charge the battery, and yet under the 14.4 V per 12 V module required for gassing (except in extreme heat, perhaps). You don't want gassing for long in a gel battery, because most of the water can't be replaced; only a small amount of it can be replaced by recombination of 2H₂ and O₂. It might even get a little more life from your present battery.
  5. I guess that's one way of doing it. You have the chance of over-charging the battery, but since 56 V (14 V per 12 V module) is under the gassing voltage (14.4 V per 12 V module at 25°C), it should not be too damaging. Certainly better than chronically under-charging the battery.
  6. With the low panel voltage models, the output of the SCC (which in this case sounds like a PWM type, not MPPT) is the battery (directly after the fuse). So no need to open it up. Edit: so you're better off connecting the external solar charge controller directly to the battery, or as close as possible. It needs the best estimate of the battery voltage.
  7. It's really hard, because it depends on the battery type (gel in your case), temperature, and charge history. Most charts specify 25°C, and require the battery to be at no load for several hours, which is not practical for a home energy system. Do a search for lead acid voltage state of charge (images), and you will see many conflicting tables. They all quote 12V nominal batteries, so double or halve voltages as needed for 24V. Most agree however that at 25°C rested, 50% SOC is 12.06 or 12.05 V, and 0% SOC is 10.5 V. 11.5V varies from about 10 - 20%. So your settings (adding a little for the effects of load) are about 20% for back to utility, and say 5% for cutoff. Those SOC figures are very low, and will kill a battery in about a year. That's the hassle with lead acid, you should only use about 20% of capacity most of the time, and 50% rarely. You can use 80% in an emergency, but only once or twice in the battery's lifetime. So you can never use 20%, rarely the next 30%, and most of the time 80% is unused. The near impossibility of gauging SOC from voltage is why many users opt for a battery monitor like the Victron BMV. It also takes into account your the peukert factor, where large loads deplete a lead acid battery quicker than light loads. Yes, though 24.5V would be better for battery life. But you might find that runtime is too short with 24.5V. You should reduce it to 30A (15% of Ah capacity). If you find that premature float is badly affecting your system, it looks like you'll need an external solar charge controller. Sorry to be the bearer of bad news.
  8. Welcome. Actually, that looks like a genuine Axpert MKS to me. It might or might not be a 64 V model. Yes. Nearly 2 kW of panels, x 0.8 for heating and orientation, is about 1600 W, or about 32 A at 50 V. I wonder if it's the premature float bug. Check the charge LED; if it goes solid before the battery is full, then the inverter is in the float stage prematurely. That could be coincidental, but it's sounding more like there is something strange going on with your battery. Can you interrogate the battery about its state of health, or if it has error codes, or is balancing? Yes, that's the Solar Charge Controller firmware version. As a point of interest, what's the main (U1) firmware version? Yes. As above, that sounds like the battery needs to get to a lower state of charge, or just rest, to get into a state where it can take more charge. But I'd like to rule out premature charging first.
  9. Sadly, it sounds like your battery is shot. When you switch to utility power at sunset, there should be little load on the battery, something like 25W. The SOC display on the inverter is probably inaccurate like an Axpert's, but not too bad for a lead acid battery. It certainly should not plummet to 25% in half an hour, and 23 V by morning is pretty much dead flat. My guess is that you have a weak cell, so you lose about 2V soon after charging. But the other cells are probably not far behind. You might get some extra months from it by carefully charging one of the battery modules with a good 12V charger, but I think you need to invest in a new set. The Growatt firmware is similar to but not identical to Axpert firmware. I don't know if the Growatt firmware has fixed the premature float bugs that they would have inherited. If so, you need some workaround to not murder the next battery. Does your firmware have timed absorb or equalisation settings? When your battery is sorted, you can change your output source priority to the equivalent of SBU on an Axpert, and use stored solar energy to power loads in the evening and perhaps the night. Consider raising your back to utility voltage to preserve battery life. If you can't get a new battery for a while, your present settings are about all you can do.
  10. Perhaps I should have added that the reason for this is that when switching from battery to utility or back again, there would always be a 120° phase shift, which is very hard on the relays, and you'd end up with a single phase output. Axpert Kings might be different, as they have double conversion. Even in line mode, they should handle it, though I don't know if they would allow it. Even then, if they overload, they would switch to bypass mode (line and bypass modes are different for Kings only), so there would be the same problem. Maybe Kings would allow connection to out of phase AC input if bypass on overload was disabled.
  11. There are EMI capacitors, usually around 1 nF, from active and neutral to earth. One or more of these may have gone leaky or shorted. The other possibility are components across the line (active to neutral). There are MOVs that degrade a little every time they absorb a transient and thereby protect the inverter; see this AEVA post about them in 5 kVA models, and part numbers a few posts down from there. See if you can find the service manual that best fits your model; there are several in the files section of this forum.
  12. Since you are running Watchpower, you presumably have an Axpert or clone. It sounds like you are using the SOL output source priority (setting 01). That's best for load shedding readiness, but not for minimising Eksom use. Try SBU if you have that option. The other thing is to check that the battery is getting fully charged. Watch the battery voltage, and make sure it stays around 56 V or so for at least an hour on a good solar day, and doesn't head for around 54 V (float voltage, charge LED on solid) before that solid hour or more of 56+ V. Chronic undercharging of a lead acid battery will quickly ruin it, and of course you won't save much Eksom usage.
  13. It depends on the software monitoring them. Usually that software knows how to send commands that refer to the other inverters. I would think that it would not let you make these settings different to the master. If it does, I'd assume that it would ignore those settings.
  14. Welcome. Thanks for the pictures; they save a lot of time. Your inverter appears to be a clone. So it's hard to say what its exact behaviour is going to be. I note that they don't appear to be connected properly; the set in the foreground will not work as hard as the set at the back. You should move one of the cables to the inverter to the front set, for a diagonal connection. That will let your back battery modules last longer. Yes. It means that even on the best days, your battery is not getting fully charged. The battery State Of Charge display on these inverters (presuming a faithful copy of the Axperts) is not great, but also not terrible for lead-acid batteries like yours. It seems that with the battery at 53.2 V (an average of just over 13 V per 12 V module), the battery is not charging. You could well be suffering from the premature float bugs. Your clone seems to be an early one; Axperts exceeded this specification in about 2015. That means it's less likely to be able to have its firmware updated. If you are suffering from one of the premature float bugs but can't update firmware, you'll need to try one of the workarounds. The trouble is, both of the work-arounds require reasonable modern firmware, with facilities for timed absorbtion, or equalisation. You should watch the middle CHG LED and report when it stops flashing on a good solar day. That will tell us when the charger has gone to the float stage. You are also a bit low on panel power, you could do with another pair of panels (I assume that your panels are connected 2S4P). It looks like you have room for 2 more. That will bring you to 10% over 3 kW of panels, which is its rated power (shown as rated "current"). If you don't correct these problems, your battery life will be cut short, perhaps to a few months or a year at best.
  15. I note that the Infinisolar V II series are higher PV voltage. So they are like Axpert MKS II. The lower MPPT voltage range of the non-II series means you have to use more strings of fewer panels: 3S of 60-cel panels, or 2S of 72-cell (or 144 half-cell) panels. In practice, this means more flexibility in the number of panels (you can start with 2-3 and expand to more in sets of 2 or 3), but more wiring, fuses, and space for a combiner box. It also means more wire, which is a little more expensive, and you may need thicker wire. I don't know much about the internals of the Infinisolars, V or otherwise. The Infinisolar non-Vs seemed to have too much hardware to me; I suspect that the V series are more Axpert-like, with just enough hardware to get by.


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