Nkunzi Posted July 1, 2023 Share Posted July 1, 2023 Thought I'd ask a new question here, specifically for @Logic because you have the same model and we've been talking about it in another thread. What I'm seeing is I'm often getting 0 apparent and active power reported by the inverter. I'm still testing it right now so it's on my desk and it's got a PC and few peripherals on it so not drawing a lot of power. I do sometimes get it showing some values, but mostly 0. Here's my rough Grafana chart of it. I'm speculating it's not registering anything under some value, maybe 100W? Curious if you see similar behaviour, do you ever use yours on fairly low power use and it's still reporting values? Many thanks. Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted July 1, 2023 Share Posted July 1, 2023 (edited) 6 hours ago, Nkunzi said: Thought I'd ask a new question here, specifically for @Logic because you have the same model and we've been talking about it in another thread. What I'm seeing is I'm often getting 0 apparent and active power reported by the inverter. I'm still testing it right now so it's on my desk and it's got a PC and few peripherals on it so not drawing a lot of power. I do sometimes get it showing some values, but mostly 0. Here's my rough Grafana chart of it. I'm speculating it's not registering anything under some value, maybe 100W? Curious if you see similar behaviour, do you ever use yours on fairly low power use and it's still reporting values? Many thanks. Yes you are right as far as not displaying low power use. Although I have a different inverter it does not shown below about 95W. Even my brick inverter (12V) with power meter does not show below about 35W. If you look at the battery discharge it does measure lower power than the AC power meter. Edited July 1, 2023 by Scorp007 Quote Link to comment Share on other sites More sharing options...
Logic Posted July 1, 2023 Share Posted July 1, 2023 (edited) On 2023/07/01 at 12:57 PM, Nkunzi said: Thought I'd ask a new question here, specifically for @Logic because you have the same model and we've been talking about it in another thread. What I'm seeing is I'm often getting 0 apparent and active power reported by the inverter. I'm still testing it right now so it's on my desk and it's got a PC and few peripherals on it so not drawing a lot of power. I do sometimes get it showing some values, but mostly 0. Here's my rough Grafana chart of it. I'm speculating it's not registering anything under some value, maybe 100W? Curious if you see similar behaviour, do you ever use yours on fairly low power use and it's still reporting values? Many thanks. Looking at your graph, you seem to have the same scenario as me, I'm away from home this weekend, but looking at my history graphs, it's only showing power usage while it's not on bypass, so mainly only during loadshedding for me. (Yesterday I ran off battery power for a while which is why it shows usage for a longer period. Edited July 3, 2023 by Logic Quote Link to comment Share on other sites More sharing options...
chrisc Posted July 1, 2023 Share Posted July 1, 2023 Using a Kodak 7.2KW inverter, if I switch off the circuit-breaker after the output (so no possible load) it still shows 22 watts They are all different Quote Link to comment Share on other sites More sharing options...
Logic Posted July 1, 2023 Share Posted July 1, 2023 Mine seems to report down to 11W, though the load might be around that, I can check to see how low it can report. Quote Link to comment Share on other sites More sharing options...
Nkunzi Posted July 2, 2023 Author Share Posted July 2, 2023 16 hours ago, Logic said: it's only showing power usage while it's not on bypass Seems to be something to that theory, I was on shedding last night 10 to 00. Don't know why I'm getting something in the day, maybe when usage is above a certain level even though I'm on bypass (should be on bypass all the time unless shedding). Doesn't seem to be the best inverter in the world, does it? Quote Link to comment Share on other sites More sharing options...
Logic Posted July 2, 2023 Share Posted July 2, 2023 (edited) 8 hours ago, Nkunzi said: Seems to be something to that theory, I was on shedding last night 10 to 00. Don't know why I'm getting something in the day, maybe when usage is above a certain level even though I'm on bypass (should be on bypass all the time unless shedding). Doesn't seem to be the best inverter in the world, does it? What does your grid voltage look like when you get the random readings on the graph? Maybe its during voltage dips or spikes, as the inverter will kick in when the grid volage goes outside a certain range. Edited July 2, 2023 by Logic Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 On 2023/07/02 at 4:56 AM, Logic said: [ maybe ] it's only showing power usage while it's not on bypass, That suggests that the sensor for AC-in power, the current transformer or associated components, is not working. If you're handy with electronics, the burden resistors are a common point of failure in this part of the circuit. zsde and Bobster. 2 Quote Link to comment Share on other sites More sharing options...
Nkunzi Posted July 3, 2023 Author Share Posted July 3, 2023 9 hours ago, Logic said: What does your grid voltage look like when you get the random readings on the graph? Maybe its during voltage dips or spikes, as the inverter will kick in when the grid volage goes outside a certain range. Hmm good thought, I don't see anything that jumps out though, looks more like below a certain use. It started showing again a little bit while I'm working on the PC, guess I'm using the physical hard drive so it jumps up a bit. 5 hours ago, Coulomb said: That suggests that the sensor for AC-in power, the current transformer or associated components, is not working. If you're handy with electronics, the burden resistors are a common point of failure in this part of the circuit. Thanks bud, I do know how to use a soldering iron kind of thing but I'll first try my luck with my vendor, hopefully still in warranty. While I've got you, what do you make of this charging current? Lead acid x2 12v, supposedly 120AH each. I got the feeling it's not giving enough amps for long enough, I bumped up bulk to 30V and float to 29 to try and get more amps for longer, but doesn't look like enough to my untrained eye at least. I've got the unpatched 00043.05 I can try your patch see if it's any better. Muchos gracias Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 6 hours ago, Coulomb said: That suggests that the sensor for AC-in power, the current transformer or associated components, is not working. If you're handy with electronics, the burden resistors are a common point of failure in this part of the circuit. Thanks, I'll have a look to see if I can spot a burnt resistor. It would be nice to have those stats as well. Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 1 hour ago, Nkunzi said: Lead acid x2 12v, supposedly 120AH each. I got the feeling it's not giving enough amps for long enough, I bumped up bulk to 30V and float to 29 to try and get more amps for longer, but doesn't look like enough to my untrained eye at least. Did the inverter's built in bulk charging work there or did you use a workaround for bulk charging to work? Looking at how the inverter would handle bulk and absorption, I'd assume absorption would start once the charge current starts to reduce, your time spent charging at 25A seems rather short, so I'd guess your battery was close to full when you started bulk charging, which would result in a short absorption time. Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 @Nkunzi I see mine inverter randomly started reporting bypass power draw again. It might be because my "idle" power draw is too low to be reported. I'll continue to monitor and let you know how it goes. But so far, I'd guess the inverter can measure smaller currents (power draw) while supplying compared to when it's on bypass. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 2 hours ago, Nkunzi said: what do you make of this charging current? Lead acid x2 12v, supposedly 120AH each. It depends on how depleted the battery was. It's getting 25 A of charge current, which then decays in a beautiful exponential fashion like a capacitor charging up. The utility charger is doing what it's told: hold the battery voltage at 30 V until the current drops to ⅕ of that, i.e. 5 A, then go to float voltage. So the battery is getting an average of roughly 12 A for 20 minutes before going to float stage; that's about 4 Ah. If it was at 4/120 = 3.3% depth of discharge or say 5% DoD to take charge efficiency into account, then that's fine. If it was discharged to 50% (it should never be discharged more than 50% for longevity), then sadly it's toast. The patched firmware won't change this; the premature float bug is when you have a good battery and the charging stops, and goes to float voltage a minute later, well before the battery current drops to a fifth of maximum. It usually happens when solar charging and there is a passing cloud. Usually the premature float bug does not affect utility charging, since utility charging doesn't get interrupted by clouds or anything else. By the way, that fraction of one fifth is good for lead acid batteries, but about a twelfth is more appropriate for LFP. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 1 hour ago, Logic said: As an aside, the text below T1 on these diagrams is pure fiction. Well, a copy and paste error; they've been using that diagram since their first UPS systems well over ten years ago. You'll likely find this diagram in the manuals for the latest inverter models. On paper, it's very hard to read; congratulations on reproducing the fiction in all its glory Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 1 hour ago, Logic said: I see mine inverter randomly started reporting bypass power draw again. It might be because my "idle" power draw is too low to be reported. It might be reporting noise, because the circuit is fried. That data does look particularly noisy (mind you, load power does tend to look fairly noisy, but usually not that noisy). Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 2 minutes ago, Coulomb said: It might be reporting noise, because the circuit is fried. That data does look particularly noisy (mind you, load power does tend to look fairly noisy, but usually not that noisy). I think it just looks noisy because the default view is for 24 hours. Does the zoomed in look fine to you or still too noisy? To me the overall reported power draw does seem accurate but not precise. Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 17 minutes ago, Coulomb said: By the way, that fraction of one fifth is good for lead acid batteries, but about a twelfth is more appropriate for LFP. The 1/12th for LFP, is that 1/12th of your charging current or 1/12th of the battery's max rated charging current? If say you have a 100Ah LFP battery, at what current would that be for ending bulk? From my understanding around 4A would be ideal for this. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 11 minutes ago, Logic said: Does the zoomed in look fine to you or still too noisy? Ah, it's just dawned on me that my 8h power graph only gets values every several minutes (lest it overwhelms the browser, or actually more likely the Pi-like server). That would remove a lot of the noise. So I really don't know, sorry. Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 21 minutes ago, Coulomb said: As an aside, the text below T1 on these diagrams is pure fiction. Well, a copy and paste error; they've been using that diagram since their first UPS systems well over ten years ago. You'll likely find this diagram in the manuals for the latest inverter models. On paper, it's very hard to read; congratulations on reproducing the fiction in all its glory Thanks for pointing this out. I guess with these inverters, you can't trust anything you haven't tested. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 (edited) 9 minutes ago, Logic said: The 1/12th for LFP, is that 1/12th of your charging current or 1/12th of the battery's max rated charging current? 1/12th of the maximum charging current setting in the inverter. The inverter unfortunately doesn't know the actual maximum charging current for the battery, so the inverter current is used as a rough proxy. 9 minutes ago, Logic said: If say you have a 100Ah LFP battery, at what current would that be for ending bulk? From my understanding around 4A would be ideal for this. Generally for lead acid, you would use a maximum charge current of 0.15C, or 15 A for a 100 Ah battery. So that would be 15/5 = 3 A "tail" current. LFP is often about 0.5C, so 50 A max current setting. One twelfth of this is about 4.2 A, so yes, 4 A is close to what Weber and I came up with. We started with 1/15th, but found that was a little too small. Edit: But some LFP batteries specify 1C maximum charging; that makes it hard to have a firmware that is ideal for all batteries. Edited July 3, 2023 by Coulomb Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 2 minutes ago, Coulomb said: Ah, it's just dawned on me that my 8h power graph only gets values every several minutes (lest it overwhelms the browser, or actually more likely the Pi-like server). That would remove a lot of the noise. So I really don't know, sorry. No problem, that would make sense. Mine updates every 2 seconds, and the readings tend to go up and down within an average range of up to about 40W. The load is also not perfectly consistent, and I seem to get similar fluctuations with other power meters. Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 1 minute ago, Coulomb said: 1/12th of the maximum charging current setting in the inverter. The inverter unfortunately doesn't know the actual maximum charging current for the battery, so the inverter current is used as a rough proxy. Generally for lead acid, you would use a maximum charge current of 0.15C, or 15 A for a 100 Ah battery. LFP is often about 0.5C, so 50 A max current setting. One twelfth of this is about 4.2 A, so yes, 4 A is close to what Weber and I came up with. We started with 1/15th, but found that was a little too small. Cool, thanks, that makes perfect sense. As I don't need fast charging speeds, I tend to limit my charging speed to about 20A. But with automating to float voltage for mimicking bulk charging, the current at which I reduce the charge voltage back to float seemed like 3-5A would be the ideal range, I still want to test +-5A to avoid fully charging the battery to keep it at a slightly lower voltage to increase the lifespan. Just out of curiosity, did you disable the absorption in your LFP optimised patched firmware? Or does part of the absorption time fiction mean that there's no absorption stage? Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 3, 2023 Share Posted July 3, 2023 (edited) 4 hours ago, Logic said: did you disable the absorption in your LFP optimised patched firmware? Not at all, LFP needs that charge even though more current would lead to dangerous voltages. LFP has the strange quirk of a highish internal resistance (highish rate of change of voltage with respect to current) when nearing full charge. But even well before that, the start of absorb stage, perhaps better called the constant voltage stage, just means you've finally gotten to the voltage you want to be to charge the battery, without exceeding the current that both the battery and the charger can withstand safely. So as I see it, there is no fiction about the absorb stage for LFP. Edited July 3, 2023 by Coulomb Quote Link to comment Share on other sites More sharing options...
Logic Posted July 3, 2023 Share Posted July 3, 2023 21 minutes ago, Coulomb said: Not at all, LFP needs that charge even though more current would lead to dangerous voltages. LFP has the strange quirk of a highish internal resistance (highish rate of change of voltage with respect to current) when nearing full charge. But even well before that, the start of absorb stage, perhaps better called the constant voltage stage, just means you've finally gotten to the voltage you want to be to charge the battery, without exceeding the current that both the battery and the charger can withstand safely. So as I see it, there is no fiction about the absorb stage for LFP. Thanks for the explanation, though I'm not sure if I understand you correctly. Is the reason that the additional charge is needed on LFP for the cells to balance? From what I can see online regarding absorption time for LFP batteries, some people refer to the time it takes for the tail current to fall below +- 4% of the battery's Ah rating, while others say 2 hours, and others say no more than 30 minutes. The information feels very conflicting. My batteries don't have any BMS communication, so I have no idea what the optimal absorption time would be for my batteries (the manual doesn't mention anything regarding absorption either). My plan is to use a lower tail current before switching to float. I have 2x 200Ah batteries in series (each battery is 4s2p), so I'm thinking that 4A as the tail should ensure enough time for balancing. Do you think this will be somewhat ideal for absorption in my case, or am I perhaps missing something? Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 4, 2023 Share Posted July 4, 2023 12 hours ago, Logic said: Is the reason that the additional charge is needed on LFP for the cells to balance? No, just to fully charge. In my case, balancing occurs with bypass resistors when a certain voltage is reached. Perhaps unfortunately, at absorb voltage, they are all bypassing, so there is no net balancing effect in the absorb stage. I occasionally raise the float voltage for a day or two now and then, so as to better balance the cells. 12 hours ago, Logic said: My plan is to use a lower tail current before switching to float. I have 2x 200Ah batteries in series (each battery is 4s2p), so I'm thinking that 4A as the tail should ensure enough time for balancing. So: 200 Ah @ 24 V made up of 100 Ah cells? So your 4 A termination condition would be 0.02C. It's impossible to say without knowing more about the BMS. It seems like a reasonable place to start, and if it becomes impossible to transition to float, or it takes more than about 1-2 hours, increase the value. The longer the cells stay at absorb voltage, the lower the lifespan. Quote Link to comment Share on other sites More sharing options...
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