Unexplained Morningstar TS60 PWM daily log reading

Ako · February 2022

Looking at the Daily report summary that shows several preset parameters i sometimes see a sudden Minimum Voltage thats a volt lower than normal but defies explanation and cant be seen through constant monitoring . My batterie bank is small at 400 amp/hours so i assumed a large load for a second or two could produce such a drop however i am yet to see where or know how as we dont have anything on during the night that would draw so much power .

My Minimum Voltage is always logged at around 24.5 in a 24 hour period but every now and then it displays a much lower voltage and going through the daily log i can never identify it to see when it was ., the lowest voltages are always early morning before we start to see any charge coming in . Yesterday was a perfect example , my voltage as always was around 24.8 when we went to bed with only 65 Watts constantly being drawn by small pieces of equipment like Internet , router , clock radio and the laptop that records the data from the Charge Controller and over the course of 8 hours the voltage can be seen to slowly and consistently reduce to around 24.5 volts , this is the pattern i am seeing most days . Friday when i did a daily report it shows my actual minimum for Thursday night was 23.38 . no idea why and i do not think the Charge controller can be faulty as i have two of them and having swapped them over i am still seeing the same results on both . The other parameters , Maximum Voltage , batterie Temperature , time in absorption etc are easy to check and all correct

I have tried doing a running log of every 20 seconds but even then i can not see the sudden drop that's been recorded .

Batteries are new AGMs and performing as they should

Has anyone else noticed the same or have an explanation for it .

BB. · February 2022

Check DC cables that the connections are clean and tight? Any new loads (quick surge to start a motor, etc.)?

-Bill

Ako · February 2022

Had a look and everything as it should be connection wise . Theres no loads once the days charging has finished and while its charging the voltage is 29+ volts so i am assuming whatever is taking the voltage down is doing so when its at its lowest , 25 volts or less , the maximum load in the evenings up to the time we retire is 250 Watts ( TV , fan , lights etc , none are inductive ) which only has the effect of reducing the Battery voltage down to the high 24 volts over 6 hours . Checked the Inverters Peak load and it shows 1750 watt/hours , the Inverter is only 1500 watts but would support that load for up to 6 minutes so it would be long enough time to see it on the 2 minute log i can only think that peak which i don't often see would be an inductive load kicking in while toaster or something similar was already drawing a reasonable load .

I did question once if connecting the Charge controller to the Bus bar with Inverter and battery was a good or bad thing ,opinions varied but none came down hard either way although someone did mention that if i had a Shunt which i dont that the inverter could draw from the busbar without it passing through the Shunt if the Charge Controller was inputting at the same time . Im wondering if that could explain the momentary drop in voltage as im sure if power was going from controller the batteries then to inverter the batteries it would be a buffer and not immediately pass on any extreme draw ,unfortunately i dont have the experience to know so its only a theory ..

BB. · February 2022

You have verified that the Vbatt terminals on the charge controller read the same voltage with a DMM (verify controller readings vs DMM)?

The DC Battery Bus should be the "ideal place" to connect charging sources and loads (lowest resistance connections to battery bank)--Good/short/heavy connections to battery bank. Each + connection from DC Bus through a fuse/circuit breaker (to protect wiring against shorts), then to their respective end point/loads/sources.

http://www.smartgauge.co.uk/batt_con.html (parallel battery strings and DC Bus connections)

Only other physical issue I can think of--+ and - wiring should be bundled together... to keep electrical noise from pumps and motors (and nearby lightning energy) from entering the wiring. Running + and - wires separately (and/or in loops) can act like an antenna and "receive" electrical interference (don't think it is a an issue in your case--Just discussing "possibilities").

Last suggestion I can think of (other than replacing controller) is to do a "controller reset to factory defaults" and reprogram (if their is a data base error).

Otherwise, if you don't see anything in the logs--Just let the system run and wait to see if anything ever "goes wrong" (if ever).

-Bill

Ako · February 2022

Thanks BB , I follow al of that , batterie terminals read same as busbar and terminals on Charge Controller , cables short and plenty large enough .

Just looked back at the daily logs from 2017 to 2021 and i see exactly the same pattern , odd days when Minimum voltage is registered at low 23 volts while majority of other days its mid to high 24 volts . A couple of days its explained by bad weather and extremely little input so to be expected but the other times no logical explanation . The batteries were different ones back then but the Charge Controller i was using was also a Morningstar TS60 so im wondering if these Controllers are so sensitive they record a drop in voltage on the daily log but not on the running log as it happens to fast to happen just at the fraction of a second the log is being recorded which is why i cant see it by going through it 20 seconds at a time .

The only concern i have is longevity of the new expensive AGM batteries as im aiming for a maximum SOD of 50% ( 24.45 v ) other than these odd occurrences its ben easily achievable .

BB. · February 2022

As long as there are no "serious loads/load surges" on your system... I would just go with the log's voltage readings. It does not sound like you are doing anything horrible with/to your AGM batteries.

Besides the Logged "low voltage readings" (i.e., less than 24.2 volts resting, or 23.0 volts under "heavy loads"), check and make sure you are not "over charging them" either (typically for AGM, around 28.4 to 28.8 volts @ 25C).

From others here--They generally see batteries (including AGM) failing more often from under charging/over discharging. Over charging failures are not very common.

-Bill

Ako · February 2022

Set the charging voltage at 28.8 @ 25c as also stated by Trojan and they are charging at 29+ at the moment as its winter and temperatures are around 14c so the temperature probe is adjusting the temperature to the required settings but Trojan has confirmed that to be correct so im happy with that . I cant say what the load would have been when the daily log registered 23.36 but the bare minimum load would have been 65 Watts so its not possible for them to have been at rest so i guess thats a good thing .

I have now had chance view the last 24 hours and again its showing 23.45 but for once the event has ben captured on the 2 minute log and i can actually see the time they voltage went that low . The time was 10am and was caused by the electric toaster , voltage prior to the drop was 25.7 and charging but when the 1200 Watt @ 220 volt AC toaster was on it dropped to around 23.45 for 5 minute then once the toaster went off the voltage went back up to 25.7 within 5 minutes . Possibly if my battery bank had been larger then the effect would not have been so extreme .

BB. · February 2022

With that load--Below ~23.0 volts (aka 11.5 volts @ 12 volt reference)--That is a starting point for 50% SoC with some sort of loads... AGM usually support higher surge current vs flooded cell lead acid. And that 23.0 volts is at the battery terminals (such as >5 minutes under load)--Vs on a bus bar (some voltage drop in wiring to bus bars)... And, lower temperatures, Lead Acid batteries have less capacity (14C is not "that cold").

http://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf (general Trojan battery manual)

Just monitoring Lead Acid / AGM battery voltage itself is only a very rough estimate of state of charge. Once you have a "base" of how your bank normally runs--Then look for difference years down the road to indicated if maintenance is needed, charging issues, failing cell/battery, etc...

At this point--If the batteries are stable (not getting worse)--And they last 7 years (?--What are your expectations)--That is not bad.

And just do a voltage test across each battery in the string (charging/discharging/resting)--"Good" batteries should all be pretty close to each other in voltage (for a 12 volt battery, each battery ideally would be within ~0.18 volts of its bank-mates)... If you see one battery with higher or lower voltage than the rest--That can be an issue (wiring, battery cell issue, etc.).

The other check--Monitor the charging current ~28.8 volts (temperature corrected)--A "full AGM battery" will have a final current at 0.005 or 0.5% final current (self discharge). 400 AH * 0.005 final charging current = 2 amps... The battery bank should be pretty near full when charging current falls below ~1% rate of charge (400 AH * 0.01 rate of charge = 4 amps).

If you see higher charging currents at the "charging tail current"--Then the batteries are not yet full, or they are old and beginning to fail (more or less, suggest a "failing bank bank is >=2% final/float steady state charging current--At that current if for hours/day at a time steady current from AC mains or genset--Batteries can overheat).

-Bill

Ako · February 2022

Thank you for bearing with me BB and providing explanations for what i was finding unexplainable .I do feel a lot more confident now from various comments you made . I have tried to apply your statements to my batteries and the results are encouraging .

Final current you mention 5% which to be precise on my bank is 1.85 volts according to Trojan Data sheet . I have set a log to record every 20 seconds near the end of charging while still in absorption and without fail its always been between 5 and 6 amps , once it goes into Bulk its pointless monitoring it . It occurred to me that the small 65 amp load thats always on would distort the figures so I experimented a few times , as the charging periods are very predictable i turned off my Inverter approximately 30 mins before i knew the charging period would end so there was absolutely no draw from the batteries , the moment i turned the Inverter off the input current dropped to around 3 amps and over the following 30 mins down to between 1.85 and 2.10 amps , from what you said im content knowing that although i dont always reach .05% i am always well below 1% , 3.7 volts .

I have done voltage tests between the 4 x 6volt batteries several times under different conditions , charging , nigh time etc , they are all within 0.03 , another good indication but as the batteries are only 6 weeks old i would be surprised if there was a greater discrepancy .

If i get 5 years out of the batteries i will be content , electricity here is very expensive , highest in Europe and not always that reliable so at 5 years i will be happy .

Many thanks for everything Bill

BB. · February 2022

You are very welcome Ako,

Note: For our "rules of thumbs" around here... We use the 20 hour discharge rate (100% to 0% state of charge over 20 hour discharge cycle):

https://www.dcbattery.com/rollssurrette_s605.pdf

468 AH / 20 hours = 23.4 Amps (for 20 hours) average current

Just to be clear... 0.5% or below is AGM "Full" current:

468 AH (at 24 volts and 20 hour discharge rate) * 0.005 tail of charging curve = 2.34 amps or less @ 28.8 volts is AGM "full"

Also typed about small DC load current of 65 Amps... Missing "." somewhere (6.5, 0.65, or what?).

Anyway--It does sound like your system is running OK. At this time, you are running into increasing amounts of sun into summer--You want to get the system stable before you hit the declining sun in fall and winter (guessing):

http://www.solarelectricityhandbook.com/solar-irradiance.html

Madrid Spain
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 50° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.43	4.19	5.27	5.25	5.46	6.15
Jul	Aug	Sep	Oct	Nov	Dec
6.40	6.26	5.59	4.22	3.35	2.98

As you hit Nov/Dec/Jan -- Managing your loads and battery bank will become much more work.

Yea--I am in California--Our power is now in the range of $0.20 to $0.40 USD per kWH. And our natural gas pricing has almost doubled in the last months. I don't know how much more we can survive "renewable/green energy programs" around here.

People are not trusting the "utility grid" for power now--And nobody seems to be working to make it better/more reliable:

https://www.forbes.com/sites/robertbryce/2022/02/10/whats-good-for-generac-is-bad-for-america/

Over the past few months, while doing speaking engagements, I have been asking the people in the audience to raise their hands if they have a home generator. Usually, a handful, or perhaps a dozen hands, go up. Then I ask, “now raise your hand if you are planning to buy a generator or have already ordered one.” Invariably, most of the remaining people in the audience raise their hands.

One of the people aiming to get a new generator for their home is my friend, K., who lives near Houston. (K. asked me not to use her full name.) She and her husband are spending $11,600 on a new 24-kilowatt Generac generator. (She sent me the receipt.) They put half of the money down last December, but don’t expect to get the machine delivered and hooked up to their home until the end of this year. They recently got an email update telling them that more than 2,500 people are in line ahead of them.

The reason why K. and so many other people in Texas and across the country are buying generators is obvious: the reliability of the electric grid is declining. According to data from the Department of Energy, between 2000 and 2020, the number of what the agency calls “major electric disturbances and unusual occurrences” (read: blackouts) on the U.S. electric grid jumped about 13-fold.

-Bill

Ako · February 2022

Should have typed constant load is 65 Watts not Amps . I just bought a Honda EU2200i and it runs for 200 mins on 2 ltrs at half load so very pleased with it , that is enough to power what we need in the house and puts 45 amps into the batteries when needed which gets us through the rest of the night .

Although in a couple of months the days will be longer and brighter i wont see any benefit as batteries already go from Bulk to Absorption in a couple of hours at around 40-50 amps , after that its just a diminishing Absorption for the rest of the charging period and from everything i have now learnt the timing seems to be just long enough now and if i do use more power in the day then im still replacing it in time so i guess the summer months will just give m more to spare if i need it .

BB. · February 2022

Yep--Off grid solar in summer--System is "over designed". In winter, solar is limping through (in most locations).

In summer--That unused power can be used for other things--Such as irrigation your spring/summer garden. Some folks even use for water heating (a bit much for a "small" solar system).

And small loads that run 24x7 can be a real hit against solar power systems:

65 Watts * 24 hours per day = 1,560 WH per day
1,560 Watts*Hours / 12 = 130 AH (at 12 hours per day)

-Bill

Unexplained Morningstar TS60 PWM daily log reading

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Madrid Spain
Average Solar Insolation figures

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Unexplained Morningstar TS60 PWM daily log reading

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Madrid SpainAverage Solar Insolation figures

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Madrid Spain
Average Solar Insolation figures