LI battery tuning

JRHill
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LI battery tuning

Post by JRHill »

It's time to move from the previous threads. It would be good to have a spot to ask specific questions that aren't deeply buried in other threads. So I'll start it out:

I don't want the FNDC SOC relay limits. I want to work from the voltage. So how does one disable the FNDC relay for SOC? The manuals don't help. Set both hi and low to to zero?
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Re: LI battery tuning

Post by raysun »

From SimpliPhi install manual (for their Access battery)
Screenshot_20201126-105227_Drive.jpg
They advocate disregarding SoC, and 0/0 seems to do that.
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Re: LI battery tuning

Post by JRHill »

Here is another: we have to leave for a while and will get back later. I fired the generator manually with the PHI batteries at 52.5v. The generator came on line and is only charging at 1.4kw at the connection. Hmmm, AAC is 20. Could/should be 2.5kw on the Mate3. I am trying to figure these batteries. Everything is different.
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Re: LI battery tuning

Post by JRHill »

The EQ. Since I can't disable it why not use it to reset the FNDC? xx.x volts at xx.x time?

BTW, I wish y'all wonderful time giving thanks. For us it is newlyweds and baby people.
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Re: LI battery tuning

Post by raysun »

JRHill wrote: Thu Nov 26, 2020 1:10 pm Here is another: we have to leave for a while and will get back later. I fired the generator manually with the PHI batteries at 52.5v. The generator came on line and is only charging at 1.4kw at the connection. Hmmm, AAC is 20. Could/should be 2.5kw on the Mate3. I am trying to figure these batteries. Everything is different.
Charger AAC = 20? What's the AC IN current limit? What's the load?

I'd see 1.4kW charge from my FX3048 with 14AAC charger limit. With my dual FXR is see 2X that.

I don't think its a battery limit they can accept far more than one would want to put in (37.5A X 3 is safe). I've seen 60ADC going in @ 56V with it dropping through 15A in 2 minutes, so even at full charge, they are charge sponges.

20201126_115733.jpg
Screenshot_20201126-134542_Office.jpg
Last edited by raysun on Thu Nov 26, 2020 3:51 pm, edited 3 times in total.
raysun
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Re: LI battery tuning

Post by raysun »

JRHill wrote: Thu Nov 26, 2020 1:23 pm The EQ. Since I can't disable it why not use it to reset the FNDC? xx.x volts at xx.x time?

BTW, I wish y'all wonderful time giving thanks. For us it is newlyweds and baby people.
Not sure I'd want to get into the habit of thinking EQ even exists.

If choosing the "Absorb" of 54.8V @ 1H, 100% is going to be reached.


Screenshot_20201126-120608_Office.jpg
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Re: LI battery tuning

Post by sodamo »

I know we are very different environments...
I agree, disregard EQ
I don’t use FNDC relay, inverter AUX.

I’m very hesitant to use generator for a full charge any more. Had long talk with my installer and he agreed. Even if multiple runs goal is to make it to point of PV doing the majority. So I don’t do long absorb on gene, only .5 hours. When I see the charge voltage drop like you did, I stop the generator as not very cost effective at that point.
David
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Re: LI battery tuning

Post by JRHill »

raysun wrote: Thu Nov 26, 2020 1:53 pm
JRHill wrote: Thu Nov 26, 2020 1:10 pm Here is another: we have to leave for a while and will get back later. I fired the generator manually with the PHI batteries at 52.5v. The generator came on line and is only charging at 1.4kw at the connection. Hmmm, AAC is 20. Could/should be 2.5kw on the Mate3. I am trying to figure these batteries. Everything is different.
Charger AAC = 20? What's the AC IN current limit? What's the load?

I'd see 1.4kW charge from my FX3048 with 14AAC charger limit. With my dual FXR is see 2X that.

I don't think its a battery limit they can accept far more than one would want to put in (37.5A X 3 is safe). I've seen 60ADC going in @ 56V with it dropping through 15A in 2 minutes, so even at full charge, they are charge sponges.


20201126_115733.jpg


Screenshot_20201126-134542_Office.jpg
Sorry - legitimate question. The CHARGER was 20aac, the AC in limit is 30. We rarely draw more than .5Kw unless I'm in the shop or using shop tools and that was not the case. All these behaviors are new to me.
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Re: LI battery tuning

Post by JRHill »

raysun wrote: Thu Nov 26, 2020 1:53 pm
JRHill wrote: Thu Nov 26, 2020 1:10 pm Here is another: we have to leave for a while and will get back later. I fired the generator manually with the PHI batteries at 52.5v. The generator came on line and is only charging at 1.4kw at the connection. Hmmm, AAC is 20. Could/should be 2.5kw on the Mate3. I am trying to figure these batteries. Everything is different.
Charger AAC = 20? What's the AC IN current limit? What's the load?

I'd see 1.4kW charge from my FX3048 with 14AAC charger limit. With my dual FXR is see 2X that.

I don't think its a battery limit they can accept far more than one would want to put in (37.5A X 3 is safe). I've seen 60ADC going in @ 56V with it dropping through 15A in 2 minutes, so even at full charge, they are charge sponges.


20201126_115733.jpg


Screenshot_20201126-134542_Office.jpg
Since I can't disable EQ from the Mate3 and it cant be set lower than Absorb I thought this would be a good single keypress to calibrate the FNDC to a fully charged status. If mistakenly pressed it is no less damaging than an intended way to satisfy parameters met to reset the FNDC. This was my idea anyway to protect the batteries and still make the button useful.

Next, my install manual shows a 1hr Absorb soak at whatever DOD. I think you do less than that. Maybe I am mistaken?

You have an Absorb End Amp value. My install instructions have zero End Amps (on the FM. The FX doesn't have a suggestion). Whether an absorb timer or end amps probably depends mainly on where the charge is coming from, the FX or FM. As I try to minimize generator run time with virtually no input I am leaning to short on the FX and recommended on the FM with sunlight to finish it. I think this is yet more confusion to the FNDC that is a reason for pressing the EQ button to do a full recharge and reset the FNDC as I was thinking.

So I only have one full day of service and I have a lot to learn. So far one on the things immediately evident is the efficiency in vs power used. My gosh I was wasting a lot of potential with the old batteries. But even if I had gone with FLA batteries again I wouldn't be seeing what is apparent - I was wasting a lot of incoming power regardless of the source.
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Re: LI battery tuning

Post by JRHill »

sodamo wrote: Fri Nov 27, 2020 12:31 pm I know we are very different environments...
I agree, disregard EQ
I don’t use FNDC relay, inverter AUX.

I’m very hesitant to use generator for a full charge any more. Had long talk with my installer and he agreed. Even if multiple runs goal is to make it to point of PV doing the majority. So I don’t do long absorb on gene, only .5 hours. When I see the charge voltage drop like you did, I stop the generator as not very cost effective at that point.
Yup. As I see it. But I'm watching a real knock down between Nebr and IA so I'm distracted.
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Re: LI battery tuning

Post by raysun »

"Next, my install manual shows a 1hr Absorb soak at whatever DOD. I think you do less than that."

SimpliPhi specifies two charging profiles:
#1
Constant current (Bulk) to 54.8V (FM)
Constant voltage (Absorb) for 1H.
#2
Constant Current to 56.4V (FM)
Constant voltage for 0.1H

#1 is aligned with "traditional" LA two-stage charging.
#2 (which I use) is actually a single stage charge. The very abbreviated "absorb" time is the minimum the outback chargers support.

In both profiles (FM) End Amps = 0

In either profile, charge termination can be executed by the FNDC with the appropriate parameters set. For the profile I use:
Charged Voltage = 56
Charged Time = 1 minute
Charged Return Amps = 15

The Charged Return Amps (CRA) specified by SimpliPhi is lower - 1.5 to 2% of AH capacity, or 6.75 to 9A for my 450AH battery. I did not care for the lower CRA because of battery behavior at End of Charge. Set to 9A, and held for 1 minute at 56.4V causes the current acceptance to drop very rapidly, past 9A to 0A within the minute. I saw no need for reaching that absolute termination point, and "fudged" the CRA to 15A. The "absorb" phase terminates 2 minutes from its start, with charging current in the 12 to 9A region.

Screenshot_20201127-134026_Chrome.jpg
Illustration of the "Bulk only" charge cycle option. Charging just completed. Note the steady rise in SoC. When battery voltage reaches 56.4, an "Absorb" phase is started, then terminated by the FNDC in 2 minutes. The 0 PV harvest is due to the Charge Controllers sleeping until the battery voltage falls to 53.1, the selected Float voltage.
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Re: LI battery tuning

Post by JRHill »

raysun wrote: Fri Nov 27, 2020 1:45 pm "Next, my install manual shows a 1hr Absorb soak at whatever DOD. I think you do less than that."

SimpliPhi specifies two charging profiles:
#1
Constant current (Bulk) to 54.8V (FM)
Constant voltage (Absorb) for 1H.
#2
Constant Current to 56.4V (FM)
Constant voltage for 0.1H

#1 is aligned with "traditional" LA two-stage charging.
#2 (which I use) is actually a single stage charge. The very abbreviated "absorb" time is the minimum the outback chargers support.

In both profiles (FM) End Amps = 0

In either profile, charge termination can be executed by the FNDC with the appropriate parameters set. For the profile I use:
Charged Voltage = 56
Charged Time = 1 minute
Charged Return Amps = 15

The Charged Return Amps (CRA) specified by SimpliPhi is lower - 1.5 to 2% of AH capacity, or 6.75 to 9A for my 450AH battery. I did not care for the lower CRA because of battery behavior at End of Charge. Set to 9A, and held for 1 minute at 56.4V causes the current acceptance to drop very rapidly, past 9A to 0A within the minute. I saw no need for reaching that absolute termination point, and "fudged" the CRA to 15A. The "absorb" phase terminates 2 minutes from its start, with charging current in the 12 to 9A region.


Screenshot_20201127-134026_Chrome.jpg
Illustration of the "Bulk only" charge cycle option. Charging just completed. Note the steady rise in SoC. When battery voltage reaches 56.4, an "Absorb" phase is started, then terminated by the FNDC in 2 minutes. The 0 PV harvest is due to the Charge Controllers sleeping until the battery voltage falls to 53.1, the selected Float voltage.
OK, Thanks for that. I was re-re-reviewing settings this AM. I noticed that the FX EQ time can be set to .1 but on the FM its in one hour increments with the minimum being 1 hour with a 56v minimum. So using my idea, pressing EQ while the generator is operating would be one behavior and pressing during solar would be another. This is not good. Who knows what happens when both are operating? I was trying to find a way to make use of the EQ since I can't disable it from either device. The EQ button could be dangerous if a "button puncher" hit it. EQ execution is available from the Mate3 without any restrictions in a single place for both sources other than the warnings. As always, I'm trying to make the system dummy proof but the EQ is a problem waiting to happen with LI/PHIs.

So out comes the marker with "NO EQ" That's about the best there is for now.

My gosh things are working well. I so very much appreciate the efficiency of these batteries and I'm breaking into this at the worst possible time of the year. Come 'sun' days I will enjoy the benefits my friends in HI and the like enjoy most of the time.
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Re: LI battery tuning

Post by raysun »

A sage engineer told me a truism that served me well over my career:
You can make a system fool proof,
but you can't make it damn-fool proof.

EQ case in point.

It may suprise you that our annual sun hours are less than Detroit. We do enjoy clear mornings most days, and the low latitude does make for the sun being agreeably high in the sky for the most part. It would be different if we lived just 200' from where we do, as our entire property would be in a deep defile.

The irony of lithium is its affinity to partial state of charge. I'd think it ideal if I could find a way to charge them to 80% and leave it at that. Of course the issue is figuring out 80% on a consistent and repeatable basis. Can't be done with current tech adapted from Lead Acid legacy. As lithium BMS improve, and charging systems incorporate communication with the battery, "Super Smart" charging is likely to emerge. I took a serious look at AmpliPhi / Sol Ark as an early implementation of this, but decided to reinvest in the now-aging tech I deployed.
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Re: LI battery tuning

Post by provo »

raysun wrote: Sat Nov 28, 2020 10:39 am
I'd think it ideal if I could find a way to charge them to 80% and leave it at that. Of course the issue is figuring out 80% on a consistent and repeatable basis. Can't be done with current tech adapted from Lead Acid legacy.
I don't know much about Li-ion, but why doesn't coulomb-counting with the FNDC work the same as with
Pb-acid?
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Re: LI battery tuning

Post by raysun »

provo wrote: Sat Nov 28, 2020 11:09 am
raysun wrote: Sat Nov 28, 2020 10:39 am
I'd think it ideal if I could find a way to charge them to 80% and leave it at that. Of course the issue is figuring out 80% on a consistent and repeatable basis. Can't be done with current tech adapted from Lead Acid legacy.
I don't know much about Li-ion, but why doesn't coulomb-counting with the FNDC work the same as with
Pb-acid?
It does, more or less. I don't have a definitive answer to why it may be "less", rather than "more", but I have some theories.

Lead acid chemistry has been studied for a very long time, yet is still not fully understood. Battery monitors seem to aim for incorporating the theoretical with the empirical to derive a reasonable estimate of State of Charge. The "coulomb counting" approach seems to deliver the most consistent estimates.

Lithium is obviously a radically different chemistry, and is being studied in greater depth and with more sophisticated tools than Lead Acid over its lifetime. While the basic properties of electron (and charge) flow apply to Li as well as LA, the devil shows itself in the details.

Looking at the typical charge/discharge curves of the two chemistries gives a hint that the two chemistries behave very differently. It's expressed, for example, in the relatively flat discharge voltage of Lithium. Flat, that is, until voltage dives "off a cliff", at the end of discharge capacity. This behavior implies something different is happening under the covers.

Returning to the empirical, while both chemistries behave in a manner described by Peukert's Theorum, the constant in the equation is quite different, and is much lower for Li - around 1.05 and perhaps less for some L-ion compounds.

The Outback battery monitor (FNDC) fixes Peukert's Constant at Lead-Acid levels. I'm not sure, but am under the impression it does some "learning" within the range of the LA chemistries, but Li may be out of bounds for that. That's my motivation to ask Outback to develop an FNDC-li.

I have been using two battery monitors on my Li bank - an FNDC and a Victron BMV700. While they both report in agreement to a good degree, its not exact, and there's no real way to gauge the error of each unit. While I am suffering under the old saw:
"A man with a clock always knows what time it is. A man with two clocks never knows what time it is.", I accept the readings as being in the ballpark for my purposes.

The rub comes when the ballpark drifts. Repeated partial charges and discharges can cause the "coulomb counting" to report an increasing measurement error. Its not surprising, and isn't unique to Lithium batteries, or even battery monitoring. A standard practice in chemistry is to incorporate the cumulative measurement errors in the equations' results.

The practical operational approach is to sync the monitor at known 100% SoC as frequently as possible. Accumulated days at partial state of charge likely accumulate errors.

In my system, I use the "Bulk until Full" charging approach. At the end of the charge cycle, the FNDC registers 100% SoC about 3AH short of the battery indicating end of charge (by a rapid rise in voltage followed by a rapid decline in charge current.) For a 450AH battery, 3AH is about 0.7%.

I'm happy enough with how the "coulomb counters" work with Lithium, but must confess that, were they more precise, I would figure a charging / discharging scheme that kept the battery between 80% and 20%.
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Re: LI battery tuning

Post by JRHill »

Oh, dang++. I wrote a detailed plan for combination settings of Profile 1 and Profile 2 above for user input but I didn't copy it before submitting. POOF! As Sodamo said, "I'm not going to do (write) it again." And yes, it took more than the few minutes to write it cause I was planning, editing and going to other threads at the same time. I should've known better but thought it was fixed....

I'll let you know if I trash my new battery bank. I will take out my frustrations tossing hay bales now.
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Re: LI battery tuning

Post by raysun »

JRHill wrote: Wed Dec 02, 2020 11:15 am Oh, dang++. I wrote a detailed plan for combination settings of Profile 1 and Profile 2 above for user input but I didn't copy it before submitting. POOF! As Sodamo said, "I'm not going to do (write) it again." And yes, it took more than the few minutes to write it cause I was planning, editing and going to other threads at the same time. I should've known better but thought it was fixed....

I'll let you know if I trash my new battery bank. I will take out my frustrations tossing hay bales now.
I've lost more time on disappearing posts than I want to recount. The upside is the follow on post is quite to the point (like a sharpened pencil point in the eye.) Most of the loss is my own doing, but still...
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Re: LI battery tuning

Post by raysun »

My charging philosophy is: 100% SoC is unnecessary, and even harmful to LiFePo4 batteries.

My charging target is trending toward 99% SoC at maximum, but I have not calibrated everything to meet that.

I'm quite happy with my Float @ 98-99% strategy. Once the battery is charged, the entire Float cycle is continuous discharge ranging from 100ma to 10A, depending on instantaneous conditions. By the end of Float, roughly 10AH will have bled off the battery.

I expect to document my approach, once I have objective measures, and consult SimpliPhi on the efficacy. It would be nice if there was an OB/Phi webinar at some point where we could discuss these sorts of things first-hand.
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Re: LI battery tuning

Post by sodamo »

Anxious to see your 99% plan. Meaning to contribute to this this with both my input and questions but haven’t got it put together yet. And I. Sure don’t want to lose it when I do. Had mine in service just over a year so I intendto pull the OpticsRE report and glean for data such as highs, lows, durations. Hoping it’s meaningful.
Curious as to why 100% is bad. At first glance it appears my system doesn’t linger at 100%, but that is part of the data look.
I do think I disagree with the 80% as that would be giving up to much headroom in event of a non charging day, meaning the difference of running generator or not. I prefer to stay above the 20% on the bottom end.
November has been my absolute worst month, 9 days when I didn’t replace what I used. Weather related or the fact I changed settings to be in line with that later Integration paper? Both?

Most days, I don’t hit 100% until afternoon. Another data point I’ll be looking at.

I’d like a way to track PV/Charging capability, perhaps separate from system so as not to be influenced by load etc. Wondering if maybe the UV sensor for my weather station could be appropriate. While it wouldn’t be same for my 4 arrays, it could provide a common value to allow comparison over time. Thinking something that would give me a watt/amp reading daily that I could compare with each individual CC.
David
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Re: LI battery tuning

Post by sodamo »

Add to above.
I look at Voltage, then SOC, but overall I want to see my PV production replaced what was used the previous period/day. I use an old fashioned house watt meter that captures what the Radian output. I don’t know if that is affected by good sun daytime use vs pure battery, but should capture everything except internal loss.
David
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Re: LI battery tuning

Post by JRHill »

raysun wrote: Wed Dec 02, 2020 11:33 am It would be nice if there was an OB/Phi webinar at some point where we could discuss these sorts of things first-hand.
Yup. 100% (of usable range) is just wrong except in any instance. Regardless of the battery in the use case it was undersized if ya get to that. A webinar would be most interesting. It would likely be heavily influenced by PHI marketing and hence less useful. But we already know there are a myriad of use cases. I have a weird one and someone else has another and on and on.

In short, my lost composition had to do with the FNDC. And the VFX. And the FM80. And the AGS. Overall I am really happy but I have to be actively involved daily (as I always have been). It sure is not the hands off system once programmed - in case I bonked my head on a rock and was out for a while. All along that's been my goal. It is elusive. But I've never gotten to hands off system programming. I guess if one wants that they move into the city.

(I was late submitting this comment. Amazingly it was still around, Others chimed in so this should be further up the line.)
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Re: LI battery tuning

Post by raysun »

sodamo wrote: Wed Dec 02, 2020 12:28 pm Anxious to see your 99% plan. Meaning to contribute to this this with both my input and questions but haven’t got it put together yet. And I. Sure don’t want to lose it when I do. Had mine in service just over a year so I intendto pull the OpticsRE report and glean for data such as highs, lows, durations. Hoping it’s meaningful.
Curious as to why 100% is bad. At first glance it appears my system doesn’t linger at 100%, but that is part of the data look.
I do think I disagree with the 80% as that would be giving up to much headroom in event of a non charging day, meaning the difference of running generator or not. I prefer to stay above the 20% on the bottom end.
When I have some time to keep hands on the throttle, I'll play with charging at the top end. I'm using the simpler (for me to understand) charging model that is essentially Bulk until the battery enters its natural charge termination state - rise in voltage and drop in charge current. The point recommended by Phi: 56 - 56.4V and 1.5 - 2A per monoblock (3.8-48) is a definitive end point. I've held the battery at 56.4 and watched the charge current fall from high amperage (25-30A) to 0A in the 6 minute "Absorb" window. Pretty much solid indicator, 100% SoC has been reached.

Actually, 100% SoC has likely been reached well before this termination event. So what's happening? Good question. There's research that indicates no energy at all is stored between 3.75 and 3.5 VPC. What IS going on then? Far as I understand, lithium ions are being pushed further into the anode lattice in a process called intercalation.

Why is 100% SoC not necessarily great for a lithium battery? It has a bit to do with how a lithium battery discharges and charges. The process is called (over simply) a "rocking chair". Lithium ions are shuttled between anode and cathode during discharge, and cathode to anode during charge. The chemical reaction is minimal, the process is largely physical shuttling of ions. During charge, the ions tend to "pile up" on the surface of the anode. The charging force pushes the ions into the anode lattice, but the movement isn't uniform. In spots on the surface of the anode, the ions tend to pile up in structures called dendrites. These needle-like dendrites can continue to grow until they pierce the membrane separating anode and cathode, creating micro short circuits, capacity loss, and eventual cell failure.

Since 100% SoC essentially exists over a broad range of ion movement, my opinion is minimizing the "100%-ness" of the State of Charge minimizes the potential of dendrite buildup.

That leads to the "ideal" range of charge, with the above being the a major consideration. Often stated is lithium loves partial state of charge, and the true love is found in the range of 80% to 20%. For most folks, the 20% floor is acceptable. In fact we "leadites" think its a bonus. I consider 20% SoC the absolute floor, and mentally consider 30% the lower limit to leave room for measurement errors by the battery monitor. The top end give-away of 20% of capacity is hard to accept, both operationally and economically. (Even though, over lead-acid, it still represents a 10% capacity gain over the nominal 50% discharge limit.)

So, since living with less than 100% starting capacity is hard to countenance, even for me, but for a different reason, my intent is to find a "kinder, gentler 100%".

My 450AH battery is an embarrassment of riches for our consumption and daily cycling. Others are "closer to the bone" in terms of capacity, consumption, or days of autonomy needs.

My ideal charging model would be to touch 100% SoC (or nearly so) as gently as possible, then remove my proverbial "fingers from the stove" as quickly as possible.

The latter, I believe I have achieved by the method of managing Float. SimpliPhi recommends, without explanation, against Float operations for their batteries. IMO, the reason is related to the 100% SoC battery stress issue described above. However Outback, and other, charge controllers enter Float automatically and maintain it until the sun goes down. It can't be defeated, and IMO, if handled properly, needn't be.

Enter what I refer to as "leaky Float". SimpliPhi recommends a Float voltage = 54V. This quite neatly maintains 100% SoC for the Float phase, something i do not want. I'm happy, however, for the battery to exit Float at 99 - 98% SoC, so played with voltages that achieved that target. Float = 53.1V was found to be ideal for my objectives. Once the battery is fully charged, the charge controllers go silent until the battery falls to the Float voltage. With a 450AH battery, about 4.5AH or 1% drains off by the time 53.1V is reached. When the charge controllers enter float at 53.1V, the battery maintains a small rate of discharge, generally, depending on load, a few hundred milliamps to a few amps for the duration of the Float stage. Typically, the battery exits Float at 98% SoC.
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Re: LI battery tuning

Post by sodamo »

Think I understand Raysun’s post, just need to reread another dozen times.
Jim, if my stuff isn’t appropriate to your thread just say so.

I pulled 2 OpticsRE reports 11-22-2019 to 12-02-2020, both the 15 minute and the 1 hour intervals. Doubt the 24 hours would have any benefit.
15 min report is over 35,700 rows, 1 hour over 8900, so dare I say WOW, maybe achallenge to my very rusty spreadsheet skills. Just scrolling thru is a challenge on these old eyes.

What I have done is create a new table combining both Bat Voltage and Bat SOC. Thinking I might add the From Bat voltage as well. Doing so keeps the appropriate values together when I sort.

A couple of quick observations. Appears both Voltage and SOC values are the average for the time period and the actual highs/lows not available. So I still see 54.6 as my Max. I think hitting at higher value as Ray suggests gets lost. Ray, how are you seeing that value? Have you viewed the OpticsRE reports?

A quick good news is over that year period I only saw 16 15 min periods with value less than 50.8 with single lowest 50.1. I need to look what those circumstances, but initial thought is how nicely stable these batteries.

Any thoughts on this appreciated.

Jim. I think once settings are dialed inthese batteries can be very hands off. Of course I’ll still monitor just as I currently do. I’m retired.😁
David
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Re: LI battery tuning

Post by raysun »

sodamo wrote: Thu Dec 03, 2020 9:40 am Think I understand Raysun’s post, just need to reread another dozen times.
Jim, if my stuff isn’t appropriate to your thread just say so.

I pulled 2 OpticsRE reports 11-22-2019 to 12-02-2020, both the 15 minute and the 1 hour intervals. Doubt the 24 hours would have any benefit.
15 min report is over 35,700 rows, 1 hour over 8900, so dare I say WOW, maybe achallenge to my very rusty spreadsheet skills. Just scrolling thru is a challenge on these old eyes.

What I have done is create a new table combining both Bat Voltage and Bat SOC. Thinking I might add the From Bat voltage as well. Doing so keeps the appropriate values together when I sort.

A couple of quick observations. Appears both Voltage and SOC values are the average for the time period and the actual highs/lows not available. So I still see 54.6 as my Max. I think hitting at higher value as Ray suggests gets lost. Ray, how are you seeing that value? Have you viewed the OpticsRE reports?

A quick good news is over that year period I only saw 16 15 min periods with value less than 50.8 with single lowest 50.1. I need to look what those circumstances, but initial thought is how nicely stable these batteries.

Any thoughts on this appreciated.

Jim. I think once settings are dialed inthese batteries can be very hands off. Of course I’ll still monitor just as I currently do. I’m retired.😁
Yes, I had to read it a dozen times myself. The hazards of 4 years of lithium battery study being excreted into a late night brain dump.

So far, I've given the Voltage v.s. SoC question a wide berth. I've only been "sanity checking" the FNDC's calculations by tracking the round-trip discharge/charge numbers. So far, in daily cycling to the depth of discharge I'm experiencing, I'm happy with its "coulomb counting". It seems to be off by 1% or less. Multiple days at PSoC may tell a different story.

To capture the "real time" V v.s. SoC @ A (discharge), I'm planning on hooking a Victron BMV700 battery monitor up to a P.C. It will graph the data in a continuous stream ala WattPlot, though I could never get WP to do so properly. I bought 3 BMV700 and will pick the one that seems to track most accurately. Since I have no way to gauge absolute precision, I'll select the one that most agrees with the FNDC. Sort of selection by confirmation bias.

The voltage of this battery has been markedly stable. So much so, I scarcely regard it. Phi, however, says its the truest measure of SoC, but its dependent on discharge rate, and they only publish "C" rates too high for my usage profile. C/2, C/3, C/5 is nowhere near my consumption, or that of anyone I know. I'd be better served by C/20 and C/50 curves. Guess we're going to need to develop our own, though I'm loathe to draw my battery to 0 SoC to confirm the numbers. We should lobby Phi to provide us more useable charts (or tell us it can't be done for low discharge rates, and why.)
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Re: LI battery tuning

Post by JRHill »

David, your info is entirely appropriate. Thanks!

My timeline with the PHIs is too short to establish trends like you are doing. About all I can do right now is try to identify any adjustments for my use case. For example, last night I fully charged the batteries so I could reset the FNDC. As I watched the Mate3 charge to the batteries the genset output stayed consistent to 54.7 and then dropped off rapidly. For my daily use I had the absorb limit set at 54.4 so it seemed reasonable to bump it up a little to make best use of the run time. I have always grit my teeth at having to run the generator as the charge to the batteries was ramping down to almost nothing - but that is what FLA batteries required. The inverter's absorb setting is in .4 increments so now I'm at 54.8. The generator is still set to fire up at 50.8 and yesterday AM is the first time I had seen an AGS since putting the PHIs in service as I would do a manual run nightly to the prior absorb set point and time (1 hour).

I am pondering a reduction to the Absorb time now to something like 30 or 45 minutes. We'll see how things go for the time being.

[I'm going to click submit now and yes I copied this 1st]
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