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25kWh daily output, but I only used to need 10kWh per day.

SenileOldGit

Solar Enthusiast
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Oct 15, 2022
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I have just set up my first solar system, 12kW using 20 x Canadian Solar 595W panels, two MPP Solar PIP5048MKX inverters in parallel, and two Pylontech US5000 batteries (10kWh in total). I have been using the system for three or four weeks. My girlfriend and I built a ground mount using ground screws and scaffolding poles, and Renusol mounting rails. I use MultiSIBControl to monitor the panels' output, the load and the battery SOC. My inverters came with a custom Pylontech cable, which I have inserted into the RS485 socket on the first battery, and the battery icon flashes on the inverter, to show it is communicating with the battery. My inverters are classed as 'off grid', they cannot export energy to the grid.
Here's my problem: before I got the solar system, I was using an average of 11kWh of electricity a day from the grid. I have several years of electricity bills, and they all show me that my average yearly use is 4,000kWh. But the solar system is bringing in from 22kWh per day, to 26kWh per day, and most days the batteries are fully charged by the solar panels before sundown, and during the night time hours, I normally use 70 - 80% of the power in the batteries. I don't understand how I am using more than twice as much electricity as before. Are there huge losses in the system that I am unaware of? I hired a very good electrician to do all of the electrical work, all cables, etc. were done by him, all I have done is physically mount the solar panels, he did all the connections, etc.
On sunny days I could easily fill six batteries (30kWh) but I am waiting to see how the two batteries I have already got, work out. On cloudy days, I get around 2kW coming in for most of the day, but I don't manage to charge the batteries completely, normally they get to four or five out of the six LEDs lit up.
Does it sound like something is wired wrong in my system? I have heard numerous reports from people with 4kW or 5kW systems, who say that their panels bring in more than enough to supply all the electricity they need, in houses similar in size to mine. I've heard that solar panels can work 'in reverse' and if power goes out to the panels by mistake, they will radiate it like giant LEDs (although you can't see the light due to its wavelength).
I've just turned off the circuit breakers on the panels for the last three days, and I have been taking meter readings from the electricity meter from the grid, and I'm using only 11kWh a day when I'm grid only. I've watched the graphs on MultiSIBControl when I turn on my 3kW immersion heater, and the load goes up correctly, by 3kW, and the same when I use an electric kettle, 2kW, the graph shifts up 2kW - so I think the data from the inverter is correct. (I also use WatchPower on my Android phone, the PIP5048MKX inverters have WiFi, and that shows me a daily total too, which has always been 22kWh to 26kWh).
I wonder if the batteries are actually communicating properly with the inverters - if I take the cable out of the battery's RS485 port, the inverter shows error 61 (battery communication not connected), but if I then plug the lead into the ACAN port on the battery, the error 61 goes away and the battery icon flashes again. This should be impossible, because ACAN and RS485 use different pins on the cable, and only two cables are actually in the connector (the RS485 ones). There is nothing in the MPP Solar manual to tell you which port on the battery to plug into, just a tiny diagram which isn't clear about which port to use.
Does anybody else here use MPP Solar inverters, and Pylontech batteries, and if so, what port are you using, and what information do you get from MultiSIBControl? I only get the battery voltage displayed, and the SOC, but I think the SOC may be estimated by the inverter, using the battery voltage, rather than direct communication from the battery.
I've attached a screenshot of MultiSIBControl from a few days ago - please note that I only turned the computer on 8:45am, and my system generates 1kW by 8am in October, so the daily total will have been over 21.7kWh. Note that the batteries have received 12.45kWh - and they were at least 10% full when the day started. The large power spike at around 3:30pm is when I was using a woodchipper and it jammed, please ignore it!
 

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Sorry you need to summarize...too many things going on in your post. People will use more than they are use to because you have the energy why not use it. I use about the same as you but I only have 5.8kw worth of panels. 15kw battery. I turn stuff on because I am making too much solar, so the usage will go up. Soon though the sun will be much lower and I will be screwed...
 
70-80% of your 9.6 kWh battery going out through a 90% efficient inverter is 6-7 kWh of usable AC electricity. 6-7 kWh used in 15-16 hours of evening/night/early morning seems consistent with 11 kWh used in a full 24 hour day.

But what's happening during the day? You produce 25 kWh and only use a few kWh directly. I don't fully understand that graph, but it seems to say the system fed ~18 kWh into the battery (2+ kW average for 8 hours). The battery should be full after 4-5 hours. It should stop charging at that point and your panel output should drop to match your load.

Is the system feeding the excess into the grid? The graph seems to say no, but I wonder. Or is it somehow self-consuming excess kWhs? Doubtful, that'd create a lot of heat. Is the reporting messed up, or (more likely) am I misunderstanding it?
 
Some standard electric meters will continue to count up even if current is flowing in opposite direction. Maybe you are feeding the grid and paying for the privilege?
 
My inverters came with a custom Pylontech cable, which I have inserted into the RS485 socket on the first battery, and the battery icon flashes on the inverter, to show it is communicating with the battery.en I was using a woodchipper and it jammed, please ignore it!
Are you sure your inverter & batteries are communicating ?
All the yellow Pylon * indicators have no value.
Maybe the blinking icon means the lack of communication ?
 
Thank you all for your replies. This morning I turned on the circuit breakers for the solar panels, as I have had three days without them, and MultiSIBControl tells me that the batteries' SOC was 11% at 9:30am, it is now 10:30am, the panels are at 1.8kW, and were at 1.3kW at 9:30am, charging the batteries with 700W at 9:30am, and now charging them at 1,300W at 10:30am, but MultiSIBControl still says the batteries' SOC is 11%. I've noticed this over the past few weeks too: if only around 1kW is going into the batteries, I never notice the SOC changing, but when I have 5kW or more of PV, and most of this is going into the batteries, then I can see the SOC increasing when I check MultiSIBControl every few minutes. At least 1kWh must have gone into the batteries since 9:30am, but the SOC hasn't changed. The voltage is 48.5V.
Re the meter: my electrician told me that the meter still moved even when there was no power on in the house, before he even connected the inverters to it - in other words, I have been being overcharged (only by a small amount) by the electricity company for years. I have a 70 year old meter, and I don't want to change to a smart meter, so I'll leave it as it is. The MPP Solar PIP5048MKX can't export, according to MPP Solar, I specifically asked for an inverter that wouldn't export anything.
Doggydogworld - It's very odd, the PV seems to be putting far more than 10kWh into the batteries every day, before it stops. I'm pretty sure that it isn't turning into excess heat, the inverters are in a Keter outdoor storage box, (the type that you put two wheelie bins into), and although I can feel it's warmer in there when the fans are working hard, it isn't particularly hot.
fromport - the blinking icon means the battery IS communicating, according to MPP Solar and their manual - if I remove the cable it stops blinking (I can't remember if it disappears or not) and I get error 61 on the inverter - which means 'Battery communication lost'. I didn't realise that the Pylontech LEDs have no value - is that what you meant? Currently there are two LEDs out of six lit up, so I would have thought I had 33% SOC.
Would I be better off changing the battery type in program 05 to 'USR' and then setting the battery charge voltage, and low DC cut off voltage, in programs 26, 27 and 29 manually?
I've attached another screenshot of MultiSIBControl on a different day, you can see that the batteries were given 14.95kWh before the inverters stopped charging them.
It's now 10:45am and there are 2,400W coming from the solar panels, charging the batteries at 1,858W - and finally the SOC has changed from 11% to 12%. The voltage is now 48.9V. I am really not convinced that the inverter is communicating properly with the batteries.
I have attached close up photos of the Pylontech communication cable that was supplied by MPP Solar with the inverters - the first photo is the end marked 'Pylon' which they said to put in the battery RS485 port. You can see that the wires go to different pins at each end. Does this look correct?
While I am looking at MultiSIBControl now, sometimes the 'Battery SOC' fields show '0%', (only on one inverter at a time), then it changes back to 13% after a few seconds.
 

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Re the attached screenshots: the first one shows that the battery SOC has stayed at 11% since I rebooted the inverters this morning and there was about 750W going into the batteries from 9:45 to 10:15am, but the SOC didn't change at all.
At relatively low PV output, the second screenshot, the Load W plus the Battery W add up to only 7W short of the PV W, so the losses are very low - but when I was using grid power over the last three days, the Load W was only about 75% of the Grid W, at low wattages (my house normally uses 400-500W when I am not using any high energy appliances).
The third screenshot shows something odd is happening: the sun was out and I couldn't understand why the solar panels were only giving out just under 2.5kW, as normally they would be giving out at least 5kW at this time of the day, in the sunshine, so I turned on the immersion heater (3kW) and saw the PV output shoot up to match it, at over 5kW - then I turned off the immersion heater and the PV output stayed at over 5kW.
The batteries were only at about 50% SOC at this point, so I expected the inverter to be charging them with as much power as was available from the PV.
 

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Here's my problem: before I got the solar system, I was using an average of 11kWh of electricity a day from the grid. I have several years of electricity bills, and they all show me that my average yearly use is 4,000kWh. But the solar system is bringing in from 22kWh per day, to 26kWh per day, and most days the batteries are fully charged by ths solar panels before sundown, and during the night time hours, I normally use 70 - 80% of the power in the batteries. I don't understand how I am using more than twice as much electricity as before. ...
Is it really a problem? Or is it a case of misleading information from your monitoring programs.

First thing to be concerned with is that your grid usage should be next to nothing since you are running on solar and batteries.
The next thing is that your batteries are being properly charged from your solar panels.
 
I'm fairly certain that the monitoring programs are showing the correct data, because when I turn on a 2kW heater, I see a 2kW increase in the graph of the PV, and I've had multiple loads on at the same time - a kettle, (2kW), a bathroom heater (2kW) and an immersion heater (3kW), and the PV graph rose by 7kW to match it.
My grid usage is next to nothing, but it seems that the inverter is trying to charge the batteries from the grid in the early morning (i.e. maybe the two hours before sunrise when the batteries have run down to under 20% (this normally only happens if they weren't 100% charged the day before) and I don't think it should be doing this until the batteries are down to 5% - is that correct?
 
These are some weird results, especially the panel output jumping to 5 kW when you turned on that heater. I agree you might be getting some misleading info. Things I'd want to measure directly, if possible.

1. Utility meter turning with no power on in the house. Is it a bad meter, or is there some "leak" in your wiring? Replicate the situation if possible and measure current in front of and behind the meter.

2. Battery inflow/outflow. Use a shunt and meter to measure flows at/near the battery itself. Does it match up with MultiSIBControl reporting? I'd also want to figure out how MultiSIB estimates SOC, and if that SOC makes sense vs. what you measure with the shunt & meter.

3. Measure PV array output, voltage and current directly, compare to MultiSIBControl readings. Measure while running the heater experiment, if you're able to replicate that behavior. Sometimes the MPPT will get stuck on a "local maximum power point" that's not the real MPP. Maybe turning the heater either "unsticks" the MPPT algorithm. Or your unit may be intentionally throttling the panels to limit power sent to the battery, and the higher power levels with the heater on resets the logic that decides battery charging rate. Or maybe something else entirely is going on. Understand what part of the unit is causing this to happen and maybe you can figure out what settings to change.
 
My grid usage is next to nothing, but it seems that the inverter is trying to charge the batteries from the grid in the early morning (i.e. maybe the two hours before sunrise when the batteries have run down to under 20% (this normally only happens if they weren't 100% charged the day before) and I don't think it should be doing this until the batteries are down to 5% - is that correct?
Grid usage next to nothing or nothing is the goal. To accomplish that you need to adequately charge your batteries from your solar array, supply house loads and all the loads when solar power is not available. There indeed could be days that the need to charge the batteries as well as carry your normal loads will cause days where your average generated solar power will be much higher than if you were running from the grid. That is because the previous days you did not reach full charge.

What are your settings to charge from the grid?
 
Thank you for your advice, Doggydogworld, I will see if I can get my electrician to come out and have a look at it, and test what you have suggested.
Re point 3 - I think the inverter isn't communicating properly with the batteries, and it sometimes doesn't send as large an amount of power as it can to them, or it thinks they are less full than they are.
I am still wondering about changing the program 5 setting from 'PYL' to 'USR', and then I can adjust programs 26, 27 and 29. Program 29 is fixed at 45V when I set program 5 to 'PYL', but the manual says 'PIP5048MKX default setting: 42.0V', so I wonder why the Pylon setting is so much higher. The manual says "Low DC cut-off voltage: If PV energy, battery power and utility are all available, inverter will transfer to line mode and provie output power to loads." I think 45V is too high a value for my Pylontech US5000 batteries, and I think that's why, in the morning sometimes, I have an 04 error message on the inverters, and they are no longer using the batteries to supply power, even though the batteries appear to be a third full (two LEDS lit up, out of six).
 
Grid usage next to nothing or nothing is the goal. To accomplish that you need to adequately charge your batteries from your solar array, supply house loads and all the loads when solar power is not available. There indeed could be days that the need to charge the batteries as well as carry your normal loads will cause days where your average generated solar power will be much higher than if you were running from the grid. That is because the previous days you did not reach full charge.

What are your settings to charge from the grid?
My setting for program 11 (Maximum utility charging current) is 2A. But see my previous post which I made while you were typing yours - I think the 45V 'Low DC cut-off voltage' is too high. I will have a look at what the voltage is tomorrow morning, I should have thought of this before, especially when the '04' error is flashing on the inverter.
 
45v sounds low to me. But I do not like to run batteries lower than 20%. The low voltage fault that you get overnight seems to indicate that your batteries do not have the capacity to carry the loads through the night until solar becomes available next day.

You might need to watch the loading on the battery during times that no solar is available so that you know what is drawing the batteries down.
 
45V sounds low to me, too. That's 2.8V per cell (I assume Pylontech is 16S, like most 48V LiFePO4 systems). The Best Charger Settings.... thread recommends 3.1V per cell!

LiFePO4 charts usually say 3V is roughly 10% SOC, and you're well down the "knee" at that point. I'd set the cutoff at 3V per cell. It's much better to burn a few grid Watts than burn the batteries.
 
45V sounds low to me, too. That's 2.8V per cell (I assume Pylontech is 16S, like most 48V LiFePO4 systems). The Best Charger Settings.... thread recommends 3.1V per cell!

LiFePO4 charts usually say 3V is roughly 10% SOC, and you're well down the "knee" at that point. I'd set the cutoff at 3V per cell. It's much better to burn a few grid Watts than burn the batteries.
So I'll have to change Program 5 to 'USR' in order to change Program 29 to 48V or maybe higher? I wonder why MPP Solar have set Program 29 to 45V is you select 'PYL' in Program 5? Thanks to both of you for telling me about this, I'm still learning. I would like to buy a couple more US5000 batteries, that way I won't have to worry about getting through the night.
 
MultiSIBControl is telling me, at 21:30, that the batteries are at 49V, and the SOC is 59%. I will see what it says in the morning when the battery SOC is at its lowest, and post those two values here.
 
I'd leave it for now. 45V will protect your battery. A higher setting like 48V might extend longevity, but that's more of a fine-tuning thing. You have to consider other things, e.g. voltage sag under load and the fact that voltage the MPP sees is not exactly the same as voltage at the battery terminals. All stuff that can wait for later.

Let us know how battery voltage holds up overnight. It'd also be good to directly measure voltage at the battery terminals and compare it to the reading from the MPP. Maybe take that reading both under normal house loads then with your heater turned on. You can do that tonight while the battery is well-charged. A slightly bad connection can wreak havoc with your MPP's control logic.
 
As an added thought about your grid average use. Averages might conceal periods of high daily use since they lump them in with low daily use. There is also the possibility that your grid reported usage is less than you are actually using. You stated your meter is old. 70 years old!. A new calibrated Smart meter might give you different results.

What you care about is peak daily loading. The reason being your solar system and battery capacity has to meet peak daily loading if it is not going to draw from the grid. Just like your inverter must be able to handle starting surge even if running current is less.
 
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