Changed settings in Sunsaver 15 MPPT and now it only floats (no absorption). Help?

Hi Folks,

I wasn't sure whether this was a beginner category topic or advanced, so apologies in advance if I chose the wrong one. So a bit of backstory to give context:

I bought a Morningstar Sunsaver MPPT 15 to use with a pair of 100 watt flexible panels. The eventual use will be on my boat (small system), but for now I am using this setup on my RV, until I get a "permanent" (larger) panel system up and running. I've got the two panels wired in series, and hooked up to the Sunsaver 15, and thence to my bank of three Group 31 AGMs (Lifeline). I realize this is a bit of a mismatch with small panelage and large battery bank, but the bank is sized for my eventual 300-500 watts, and for a bit more draw in future. Right now I just have a small portable refrigerator (3.8a, less than 50% duty cycle), and my laptop charging (3.5 amps, maybe three hours a day).

Right away I had to customize the Sunsaver's settings, because the Lifeline batteries call for a float that seems to be lower than most pre-sets (13.3 volts, whereas the AGM preset is at 13.7 volts). So I set that, and left the rest of the parameters. "Time to float" was at 3 hours.

So, after using it and watching things for a few weeks, I found that I was rarely getting below 98% SOC, and yet I had absorption volts pumping into the batteries for 3 hours per day. This seems like over-charging. I had taken to unplugging the panels (MC-4 connectors) to control this, which seemed inelegant.

So I did some more reading to try to understand these settings better. I was kind of shooting in the dark the first time, for everything except the absorption and float voltages.

After the more reading, I came to understand (if I DO understand it correctly), that I basically have three "levels" to play with.

1) The every day "time to float" setting (combined with the "float low battery threshhold" volt setting).
2) The "Time before float - low battery" (which kicks in at the "float low battery threshhold"), and gives a longer absorption time when below that threshhold.
3) The "float cancel threshhold," which cancels the next day's float and so gives even more absorption time (I think?).

***
So, I went back in today to change some settings. I wanted to provide a shorter absorption setting so that when the batteries are at 98% they don't get "absorb charged" for so many hours.

So, I set the "time to float" at 90 minutes, and the "float low battery threshhold" at 12.6 (I think 12.5 was the original setting). I took this to mean that any day there was sun, and my batteries were above 12.59 volts, I would get 90 minutes of absorption voltage (which is 14.3 for these batteries, subject to temp compensation).

I then set the "time before float - low battery" at 180 minutes, and the "float cancel" threshhold at 12.3 v. I took this to mean that if the battery bank voltage was between 12.59 and 12.31, I would get 180 minutes of absorption, and if they went below 12.3 (for over 30 minutes, as that is the set "time until float exit") then the float would be canceled the next day, and it would be all absorption.

Okay, so far so good (for anyone who is still with me!).

So then I flipped dip switch #4 back to the remote meter position (from the Modbus programming position), plugged the meter back in, turned the power on/off to the controller, and then plugged the panels back in. Due to my overcharging concern, I had had them unplugged for the past three days, hence my SOC was at 91%, with resting voltage around 12.7.

So I expected the charger to go into absorb mode. I plugged the panels back in at high noon on a completely sunny day, and they showed as putting out 11.x amps. And yet the voltage showed at 13.4 (and still does, three hours later).

I don't understand why it didn't go into absorb? It seems that the way I have it programmed, it should ALWAYS go into absorb if there is enough sun (there is), and if the battery voltage is between 12.59 and infinity (it is). So now after three hours of "charging" it is still in float and my battery SOC is still 91%, and the charger has not gone into absorb at all (going by voltage - it has remained at around 13.4 only).

Have I done something wrong? Or are my things I "know" incorrect?

I had hours of absorb every day with the previous settings, but I felt that was not the best for the batteries since they would start at 98% most days, and quickly go to 100%, after which there would still be at least 2 hours of absorb voltage. So I was trying to account for that.

(Note that when I have the "permanent" panels up, I will also have more things hooked up and drawing; but this will be my setup for a couple more months at least. Then I will move these panels/controller to my boat, which only has one Group 31 battery and lower draws.)

I'm very grateful to anyone who has read through and may help

Thanks!
Piney Woods Pat

Comments

  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    I went back in to MS View (painful!) and double checked that the settings were what I had changed them to. They are. I just can't think why the charger would not go into absorb now. Previously, it went into absorb even if my batteries were at 98%, and now they are at 90% and..... no absorb at all.

    I thought, well maybe it needs to be morning of a new day. But that doesn't make sense because I plugged the panels in at noon with the new settings and it's not like the controller has a clock and decides this isn't a new day. I mean, for all it knows the sun just came up.

    Then I wondered if you coudn't have an "odd number of hours/minutes" in the absorb setting. It DOES use minutes (not hours), but it came at 180 (three hours), which is what I used for the first two months. Today I set it at 90 minutes (which would be 1.5 hours). So, grasping at straws, I changed that setting to 60 minutes, so it would be back to an "even" number of hours (vs. hours plus minutes).

    Plugged everything back in, and with still plenty of sun, .... still no absorb. Meter is showing 9.32 amps, but still only at 13.3 volts. My independent battery meter also shows 13.35 volts and 91% SOC. I have my laptop plugged in (~3-4 amps) but the refrigerator compressor is off (just between duty cycles).

    I'm so confused! With a small ratio of panels to batteries, I don't want to get too far behind. Also, I don't have a way to program the controller (Mac only). I'm currently camped with a buddy who has a Windows simulator program, plus the serial port adapter, so he is able to program it for me. But in a couple of days we are going separate ways, and I won't have a way to program the controller or go into MS View.

    It's really bugging me that I can't see any reason for it or make sense of it. (As you can probably tell!) I know the controller CAN work, as it did for a couple of months already. Hours of absorption every day (whether I wanted it or not...).

    Piney Woods Pat
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    I did one more experiment. I changed dip switch 1 to go back to stock "flooded" cell settings (dip switch one down, jumper removed). This should be around 14.4 absorb and 13.7 float at 77 degrees F. My batteries are at 66 degrees F, so I would expect to see over 13.7 volts at float, and over 14.4 at absorb. Yet it's still only showing 13.4 volts battery voltage on the battery screen, (also 6.5 amps). The solar panel screen is showing about 31 volts (it's late afternoon).

    Now I'm even more confused and wondering if it's working at all?

    (The reason I went to flooded cell stock setting is that when you set custom parameters they override the stock AGM settings. But by flipping dip switch #1 down, I could go to stock flooded settings, which wouldn't hurt anything short term, but would let me see if it would go into absorb in that mode).

    Independent battery monitor is still at 13.3 volts and 91% SOC.
  • BB.BB. Super Moderators, Administrators Posts: 31,153 admin
    Hmmm...
    So, I set the "time to float" at 90 minutes, and the "float low battery threshhold" at 12.6 (I think 12.5 was the original setting). I took this to mean that any day there was sun, and my batteries were above 12.59 volts, I would get 90 minutes of absorption voltage (which is 14.3 for these batteries, subject to temp compensation).

    I think that is the point when the charger thinks the battery bank has been "discharged" and needs to go through a complete bulk/absorb/float cycle.

    You are using around 56 AH per day... A 200 Watt array would supply around (guessing):
    • 100 AH / 17.5 volt Vmp = 5.71 amps Imp
    • 200 Watts * 0.77 panel+controller derating * 1/14.4 volts charging * 5 hours for nice summer day (depending on where you live) = ~53 Amp*Hours of charging
    So--you are really close on your power usage--The array is a bit on the small side (I would suggest a larger array for these loads).

    What would a 200 Watt array output?
    • 200 Watts * 0.77 panel+controller derating * 1/13.4 volts = 11.5 amps (typically noon time estimated "nominal" maximum current).
    You are showing 6.5 amps middle of day charging at ~13.4 volts?

    What is the length of wire from the array to the charge controller, and AWG wiring size?

    What is the length of the wire from the charge controller to the battery bank, and AWG wiring size?

    I am not a big fan of flexible solar arrays--If they are flexed a lot and/or left out in the sun for a few years--They could be having reduced output current/voltage.

    But, it is also possible that you are having controller problems.

    And with AGM batteries, it is difficult measure their true state of charge--Cannot use a hydrometer. If the batteries are not full (say they are 50% discharged), it could take several days of charging (and no loads) to fully recharge the battery bank (50% * 315 AH @ 12 volt batter bank = 157.5 AH needed to recharge battery bank--And you would be getting and estimated 53 AH per day).

    What is the battery bank voltage at night? Are you running your loads every day right now?

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    BB. wrote: »
    So--you are really close on your power usage--The array is a bit on the small side (I would suggest a larger array for these loads).

    Understood. I have a 400-500 watt setup in the works, with rigid glass/aluminum panels on the roof. The flexible panels are destined for a small boat (1 Group 31 battery; minimal loads), but I "borrowed" them for a couple of reasons. One is that I wanted to get some idea how 200 watts would do, so that I could use that information to size my "real" array. The other was that I was heading to visit a friend who lives off the grid, so I needed to be able to have the minimums on my own (no "plugging in"). Hence, I put this system together as a trial balloon of sorts. Actually, I've been surprised how well it has worked.

    I think the refrigerator's duty cycle has been quite a bit less than 50%, which has contributed to the 200 watts being enough for now. Also, it is mid-summer, so the best time for insolation. And, my other loads (LED lights, small fan) are still being taken care of by the RV's original system (dated and inadequate, but enough for those ~10 ah per day draws).

    I agree with you that flexible panels have many limitations. However, heavier/rigid panels aren't appropriate for my small boat, hence the flexibles (3# each).

    That said, I'm now thinking I will keep these two flexible panels with the RV to supplement the "real" panels on the roof. Reason is, it's great to be able to park in the shade in hot weather, yet put the panels in full sun.

    Anyway, so far my batteries have stayed up at around 12.8 volts/98%, and I've been taking in anywhere from 20 ah to 60 ah per day (less when I only had the fridge running; more when I charged the computer/the phone/batteries/etc.) From what I understand, the panels only "put out" what the batteries take. This seems like what has happened, because the days in question were basically all full sun, at 7500', right around June 21. Couldn't ask for much better/more consistent conditions. Of course my "real" system will need to be sized for adverse conditions, not the best ones.

    But anyway, my big puzzlement here is why the controller suddenly stopped ever going into absorption phase when I reprogrammed the "time to float" from 180 minutes to 90 minutes. I just felt it wasn't good for 14.4 amps to be pumping into fully charged batteries day after day. Maybe I'm wrong?
    BB. wrote: »
    Hmmm...

    I think that is the point when the charger thinks the battery bank has been "discharged" and needs to go through a complete bulk/absorb/float cycle.

    I interpreted "time to float" (or sometimes they say "time before float" as the absorption time. Morningstar's glossary says this:

    Time Before Float
    Defines the length of time the controller is to remain in the Absorption stage before transition to the Float stage.



    BB. wrote: »
    What is the length of wire from the array to the charge controller, and AWG wiring size?

    I have 30 feet of #8 tinned duplex cable running from the panels to the controller (one way distance). The panels are wired in series. They have a VMP of around 17.5 volts and IMP of around 5.5 amps. Hence I have 5.5 amps at around 35 volts from panels to controller.
    BB. wrote: »
    What is the length of the wire from the charge controller to the battery bank, and AWG wiring size?

    The one-way distance from the controller to the positive bus is around one foot. I have #2 cable running from the controller to the bus. The distance (one way) from the positive bus through the battery jumpers is 2.5'. That cable is 2/0. I wanted to shoot for under 2% voltage drop at full possible output, and I think I have done so.

    BB. wrote: »
    And with AGM batteries, it is difficult measure their true state of charge--Cannot use a hydrometer. If the batteries are not full (say they are 50% discharged), it could take several days of charging (and no loads) to fully recharge the battery bank (50% * 315 AH @ 12 volt batter bank = 157.5 AH needed to recharge battery bank--And you would be getting and estimated 53 AH per day).

    I did start with the batteries fully charged for sure. Because I had stored them for some months before bringing them online, I followed Lifeline's procedure for "boost charging" them (essentially a constant voltage charge at 14.4-15 volts (temperature compensated for variation from 77 degrees F) until they are taking less than .5% of the 20-hour rated capacity (so around .5 amps for my batteries). They were at around 12.75 volts in storage before boost charging, so not terribly low. But after boost charging you know for sure they are at 100%. So that was my baseline. At that point I hooked up the panels/system, plus a Balmar (Merlin) Smartgauge. I also have a coulomb counter type monitor (Victron), but haven't hooked that up yet (since this system is temporary).
    BB. wrote: »
    What is the battery bank voltage at night? Are you running your loads every day right now?

    Battery bank voltage at night and in the morning before the sun comes up is around 12.8 or sometimes 12.7. Both the Smartgauge and the voltmeter on the Morningstar remote meter agree on the voltage. The Smartgauge says this is around 98%, or sometimes 97% SOC.

    The reason I became concerned that the 3 hour absorption (aka time-to-float) was too long was that after the batteries reached 100%, the controller would still be putting 14.3 or 14.4 volts in for an hour or two every day. I think the three hour absorption would be fine if I had more loads (and the panels would be totally inadequate at that point), but meanwhile I don't want to consistently keep overcharging the batteries (they cost too much to shorten their life unnecessarily!). So I changed the "time to float" (i.e. absorption time in Morningstar speak) to 90 minutes. But then.... no absorption at all, even though the batteries were down to 91% and 12.6 volts (because I disconnected the solar panels for three days, until I could get the absorption time reduced). So I can't see why the controller would not go into absorption (since it was happy to pour 14.4 volts into my batteries when they were full, ahem). Seems too much of a coincidence that it happened right when I changed a setting, but my friend and I went over everything we did many times, just to make sure we didn't make a mistake. So far we haven't found any logical culprit. It's baffling.

    I do run the loads every day, but they are pretty minimal. I'd say around 26 amp hours for the refrigerator (has around a 30% duty cycle where I am right now - it is cool weather), and maybe 6 amp hours for the laptop (in a 24 hour period).

    If you have any idea as to why the controller suddenly "decided" not to do absorption stage anymore (just at the moment I changed the setting), I'd be most grateful to hear them.

    Thanks,
    Pat
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    So, after using it and watching things for a few weeks, I found that I was rarely getting below 98% SOC
    <snip>
    Due to my overcharging concern, I had had them unplugged for the past three days, hence my SOC was at 91%, with resting voltage around 12.7.
    <snip>
    but I felt that was not the best for the batteries since they would start at 98% most days, and quickly go to 100%

    Where are you getting these SOC numbers from? I'm not sure I believe them.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    vtmaps wrote: »

    Where are you getting these SOC numbers from? I'm not sure I believe them.

    --vtMaps

    I am getting them from a Balmar Smartgauge. It reads out the SOC. I also questioned it, but then the resting voltage (being read by both the Smartgauge and the Morningstar remote meter) tend to agree with it. i.e. resting voltage in the early morning before any charging starts is around 12.7 or 12.8.

    The other thing is that my amp hours in (from the Morningstar meter) and the number of amp hours I'm using also add up. Since I only have two loads on the system (52-quart refrigerator with around a 30% duty cycle and a few hours per day of 3 amp computer charging), it's pretty easy to know how much I'm using. It's around 26 amp hours per day on days I don't charge computer much, and maybe up to 50 amp hours a day if I go all out, using laptop a lot, charging phone, etc.

    Since the Morningstar has shown me taking in an average of around 30 amp hours per day (anywhere from 22 to 56), the numbers seem to add up.

    I lived on a boat for years with REALLY minimal systems, so I'm pretty good at using minimum energy, and really used to keeping track of it.

    So, for a couple of months now I've been running the system with a 3-hour absorption setting (default), but I was concerned because it would stay in absorb for an hour or two on full batteries. So I re-set it to 90 minutes. Since then.... no absorb at all, even though I let the batteries fall to 91% (12.65 volts) over a period of a few days (I unplugged the panels so no solar charging). Whereas before absorb was happily charging away at 14.4 volts even with "more full" batteries.

    Today I plugged the panels in at high noon with the new setting, and it was full sun, so I can't see why it didn't go into absorb ever? Seems too coincidental, but we can't see anything we did wrong in the settings either. So we're puzzled.

    Thanks for your assistance,
    Pat
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    I forgot to answer a question that BB asked:
    BB. wrote: »
    You are showing 6.5 amps middle of day charging at ~13.4 volts?

    Before today (today is when I changed the absorption time setting) I would be seeing 14.4 volts in the middle of the day (for the absorption time) and I think around 10 amps at peak. That said, I usually keep the meter showing the total amp hours for the day (so I'd see the running total of amp hours more often than the minute-by-minute amp output). But I cycled through the meter display a lot today, trying to figure out the issue. Never once was it over 13.3 or 13.4 volts, even though I had not had the solar hooked up for three days (to try to control over-charging while we got set up to change the absorption time setting).

    After changing the absorption setting, I was only seeing 13.3 volts, even though it "should" have been in absorption stage. This was still in mid-day full sun so panels were fully able to crank it out.

    Later, after I went back and changed the absorption time again (to one hour in case it didn't like the 90 minute setting because it was not a whole number of hours), then the panels were only putting out 6 amps, but by then it was closer to evening, so the sun was much lower.
  • BB.BB. Super Moderators, Administrators Posts: 31,153 admin
    I am out of ideas... It is possible that the charge controller is bad.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    BB,
    Thanks so much for taking the time to try to help me with this.

    As far as the controller goes: Well rats! I just hate "coincidences" that seem too coincidental to be true. I'll just summarize in case anyone else wants to take a crack at it. I think what I'm writing here will hold true no matter what the details of my wiring, SOC, etc.

    1) For two months, system has been up and running and giving me all the amp hours I need to run my small loads.
    2) I would see it go into absorption for about three hours per day (~14.4 volts).
    3) The absorption time was set for three hours, so this made sense.
    4) But I wanted the absorption time to be shorter, so I changed that parameter to 90 minutes.
    5) Thereafter, no absorption time was seen at all (just saw 13.3 or so volts, all day).
    6) Whether or not my meters or etc. are correct, I know it should have gone into absorption, because I had the panels unplugged for three days while my loads were still running. So I would have had at least a 50 amp hour deficit. Hence, system should go into absorption mode. But it didn't.

    Maybe it is just a coincidence and the controller broke on the same day I re-programmed it. I mean, things break when they break. But I just figured I must have done something (although I'll be darned if I can figure out what it was). There is always the chance it will "fix itself" today (although then I still might have an intermittent problem... ugh). If it does not, and if no-one else here has any ideas, well, my buddy had just ordered a new solar controller on Monday which should arrive tomorrow, so I can "take" that and then he can order another. Annoying though as this setup was just under $400, and it has two months on it. (I will try to see about a warranty claim, but meanwhile I need to have a way to charge my batteries.)

    If anyone else has any thoughts, I'm all ears.

    And thank you very much to those who already took the time to respond and try to help - I appreciate that. I've read here on the forum for a year or so, and gleaned some great information.

    Pat
  • BB.BB. Super Moderators, Administrators Posts: 31,153 admin
    I would call MorningStar tech support... Perhaps somehow resetting the control could fix the problems (would not be the first controller to be sunk by memory corruption).

    Otherwise, a "user reset" would be to:
    1. Disconnect (or open breaker/fuse) the + wire from the solar array to the charge controller
    2. Disconnect (or open breaker/fuse) the + wire from the charge controller to the battery bank
    3. Wait a minute or so
    4. Reconnect + wire to battery bank (first connection)
    5. Reconnect + wire to solar array (second connection)
    In general, most charge controllers are designed to connect to the battery bus voltage first. Some controllers (I think this is one of them), measures the battery bank voltage to determine if 12 volt or 24 volt battery bank (if the battery is over ~15 volts, the controller assumes a 24 volt battery bank--or something like that).

    If you connect the solar array first (when the sun is shining), the electronics can be confused since there is no DC battery power.

    -Bill "clutching at straws here" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    Hi Bill,

    Your "straws" are most welcome! I, too, understood that one should first connect the controller to the battery bank, and then the solar panels to the controller. And so I used to do it that way religiously. Although that said, then I read the manual for the Sunsaver for the hundredth time and saw this in it:

    Note: A recommended connection order has been provided for maximum safety during installation. The controller will not be damaged regardless of the sequence of connections.

    So I may have "relaxed" a little in my order of connections. And maybe it can't become damaged, but can become confused? At any rate, it can't hurt to re-do the connections, and I have appropriate switches to do so. So I will now do your recommended reconnection order and see how that affects it. Thanks for that.

    Additional notes:

    Also, since yesterday, I found that the RM-1 meter has a self-diagnostics feature. I ran that this morning and it showed no stored error codes, and also confirmed the absorption setting as 14.29 volts (bank temp was at 64 degrees when ran test). Also the controller itself shows the green lights indicating all is well (ahem).

    Panel voltage (all as shown on Morningstar meter) is now 29.38v, and "battery current" is 11.21 amps. And yet..... still at only 13.8 volts? Normally it would be in absorb now. Battery resting voltage this morning before sun came up was 12.55-12.6. My SOC seems to be holding at 91%, so I guess that's because float is keeping it stable, but not actually improving it.

    I'll let you know what happens after I do your recommended reconnect order.

    Thanks again,
    Pat

    PS: It's not possible to connect with Morningstar tech support by phone, in my experience. One must start a support ticket and then wait for a response. Fair enough, as I'm sure they are busy -- and when I have asked questions via support ticket I have always got an answer back. But sometimes it takes a week or so, and I don't want to think about my SOC in a week if I don't figure something out!

    PPS: Actually, a buddy had just ordered a solar controller that will arrive today via UPS, so if I have to I can "buy" that one from him and then figure this out later. I still want to use this Sunsaver 15 controller on my boat (it was sized for that system) so I want to figure out what is going on with it. And plus, well, I'd rather not have to "suddenly" buy a new/different controller today. But if all else fails I think the Sunsaver is under warranty.
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    Well, I have good news (I think?).

    After being in the direct summer sun for about four hours this morning, and when I was just about to do the reconnect procedure again, I saw that it was at 14.0 volts. Now, I don't know what that would mean exactly, as the batteries are at 64 degrees F, so float should be about 13.5 and absorb should be about 14.5, but I decided to watch it for awhile. After another half hour or so, voila, 14.5 volts. Absorb! (Edit, although a half hour later I see it is back to 13.6, but maybe it did absorb for 60 minutes, which is what my last setting was - seems like it was shorter, but I was not watching it like a hawk every minute.)

    This still seems weird to me as we have programmed my buddy's Morningstar TS 45 MPPT a couple of times, and there was never any "lag" when the panels were in full sun. And I can't find anything in the manual indicating something like "don't expect to see absorb for a day or so after you change settings," but.... I guess it has healed?

    I would just have waited a few days without worrying except I had already had my panels "off" for three days and plus I am not going to be with my programming buddy after the weekend (he has the Windows simulator program needed to run MSView).

    Let's hope it was just a glitch.

    Of course now I have to go back in and program it AGAIN, because I had reduced the "time before float" to 60 minutes to see if a "whole" number of hours would help (I wanted it at 90 minutes). But now I know it needs to wait a day or two to get back to working again, so I expect it.

    Thank you to everyone who read and responded. Very much appreciate your time and effort! I will update the thread if anything more of note occurs.

    Pat
  • BB.BB. Super Moderators, Administrators Posts: 31,153 admin
    11 amps is about the typical maximum current. Controller seems to be in bulk. That is correct.

    Your 13.xx battery voltage is purely set by the battery and charging current. As the battery fills, the voltage will hit the absorb set point, then run the 90 minute timer.

    Your battery is simply less that (roughly) 80 to 90% state of charge.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    BB. wrote: »
    Your battery is simply less than (roughly) 80 to 90% state of charge.

    That makes sense. Your batteries are not as full as you think. That's why I asked earlier in the thread where you were getting your SOC numbers from. I don't trust anyone's SOC numbers on a sealed battery. In hydrometers I trust, everything else is a guesstimate.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Pat Piney WoodsPat Piney Woods Registered Users Posts: 10
    BB: Very interesting. I didn't realize that "bulk" was lower voltage than absorb. That would explain it. (So bulk is around 13.4 volts?)

    vtmaps: Well, my batteries yesterday WERE much lower, as I had purposely disconnected the panels for three days.

    Otherwise, I am with you on trusting SOC, however, I have two other reasons to believe it (besides the Smart Gauge).

    1) I am using about 30 amp hours per day plus or minus a bit. My Morningstar display shows that an accumulated 25-50 amp hours per day are going in to the batteries (the 30 amps used can vary slightly, because on some days I charge my laptop more than others; that is about 3.5 amps and takes a couple of hours for a full charge). The reason I know so clearly what I am using is that I have precisely two circuits on this system. Each one has just one 12-volt cigarette lighter socket on it. Nothing else. One of the sockets has the small cooler/refrigerator plugged in; the other has nothing unless I plug my computer in, which I keep track of (hours/amps). On the days I do the latter more, I tend to take in around 45 amp hours. On the days it's only the fridge, it's more like 30 amp hours taken in (has been full sun every day lately).

    To me if I use around 40 amp hours, and I put 45 back in, why wouldn't the SOC be 100%? I definitely started with them at 100% back in the beginning (mid-June), because they were constant-voltage boost charged until they were taking about .5 amps (as per Lifeline Manual), just before I hooked them up.

    2) Also, the resting voltage is around 12.9 in the very early morning, before the sun comes up.

    I do hear you on trusting SOC, especially with a coulomb counter type monitor, which can gradually "slip" for various reasons.

    Pat

  • BB.BB. Super Moderators, Administrators Posts: 31,153 admin
    The "standard" solar charging definition is that "Bulk" is the maximum charge controller current (or based on available sunlight) that the controller can output... There is no "specific voltage regulation" by the charge controller.

    The battery voltage is simply the present "State of Charge" + charging current + battery temperature (+ battery condition, etc.).
    Re: Working Thread for Solar Beginner Post/FAQ

    New poster "leaf" has a really nice set of charts that compare battery voltage against different rates of discharging and charging (as well as resting voltage readings).
    leaf wrote: »
    Am trying to upload the charts I am using...

    Attachment not found.Attachment not found.

    attachment.php?attachmentid=3655

    attachment.php?attachmentid=3654

    [note charts are from: I believe those charts are from Home Power #36, August- September 1993. Lead-Acid Battery State of Charge vs. Voltage ©1993 Richard Perez.
    Here is a link: http://www.scubaengineer.com/documen...ing_graphs.pdf

    vtMaps
    ]

    I don't quite a agree with the resting voltage line (I think the voltage is a bit low)--But it shows how to estimate a battery's state of charge while operating.

    Note, where the charts "flatten out"--the room for error estimating state of charge is pretty high.

    -Bill

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    I didn't realize that "bulk" was lower voltage than absorb. That would explain it. (So bulk is around 13.4 volts?)
    Bulk is NOT around 13.4 volts. Bulk is charging the battery with constant current while the voltage rises to the absorb set point. When the voltage reaches the absorb set point, the controller will not let the voltage rise any further, and the current begins to decline. After a period of time, the current stops declining and that final, steady-state current is called 'end-amps'. At that point you switch to float.

    Some controllers do absorb charging based on time. They may not achieve end amps in that amount of time, or they may stay in absorb longer than is needed. Other controllers actually measure battery current and switch to float when end amps is achieved.
    To me if I use around 40 amp hours, and I put 45 back in, why wouldn't the SOC be 100%?

    It might be, or it might not. There are losses. If the absorb voltage is a bit too low, you can pump amphours into the battery forever and it will not get to 100% SOC.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • mike95490mike95490 Solar Expert Posts: 9,089 ✭✭✭✭✭
    Bulk and Absorb voltage settings are the same. It's the AMPS that is different, Bulk allows max amps to the batteries, When you finally reach 13.325V, the system converts to Absorb, and limits amps to regulate the voltage to 13.325V (did not want to scroll back to see what YOUR voltage is) After the controller has been in Absorb for the programmed amount of time (generally long enough for the amps to drop to about 5% of Capacity) the controller drops into Float, which is a lower voltage than Bulk/Absorb. At least that's the way I understand it.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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