Voltage drop of panels

vince
vince Registered Users Posts: 79 ✭✭
I installed my solar panels last fall/winter and now with the higher outside temperatures above 80 F the voltage output of my array has dropped below 60V and my kid CC does not wake up from the resting state to charge my battery bank of 48 V. These were the specs of my solar panels although not guaranteed.
E20/435 SOLAR PANEL ELECTRICAL DATA
Measured at Standard Test Conditions (STC): irradiance of 1000 W/m², AM 1.5, and cell temperature 25° C
Peak Power (+/– 5%); P max 435 W; Cell Efficiency η 22.5 %; Panel Efficiency η 20.1 %; Rated Voltage V mpp 72.9 V; Rated Current I mpp
5.97 A; Open-Circuit Voltage Voc 85.6 V; Short-Circuit Current Isc 6.43 A; Maximum System Voltage UL 600 V; Temperature Coefficients
Power (P) – 0.38%/K; Voltage (Voc) – 235.5 mV/K; Current (Isc) 3.5 mA/K; NOCT 45° C +/– 2° C.

I understand that adding panels in series with the present ones is possible if the current rating is within 10%. I found some Renogy 100 W panels that come close to the Impp. What is the best voltage input for the Mppt CC Kid to charge a 48 V. Apparently 61V is not enough. Would adding another panel with a Vmp of 18.9 be enough?

By the way, my panels are angled and have good air circulation. 

Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
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Comments

  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited April 2016 #2

    Hi vince,

    It IS a bit surprising (to me) that the KID does nothing,  and just Rests.

    SO,  at any point in the day does the KID produce any power?

    What is the Input voltage from the PVs when the KID is resting?  You might try switching off the PV input breaker from the PVs that connects to the KID,  and measure the input voltage at the breaker terminal that is connected to the PV modules  --  this will be the Voc for the temperature that the PVs happen to be at that time.

    What is the battery voltage when this KID is Resting?

    Have you made any changes to the system recently?

    You might want to try a different operating Mode,  like Legacy O&P,  to see if the KID will produce some power.

    In answer to your real question,  when adding PVs in series with existing ones,  try to match the Imp within 5% of each other.  A 10% maximum Imp match should be OK,  but 5% is ideal.

    Your suggested addition of adding a PV with a close Imp match,  and with a Vmp of about 19 volts should help a lot,  if the only reason for the KID to be resting IS due to low Vin   ...   think that later FirmWare Revs for the KID probably have an RFR (Reason For Resting) number available.   This should be looked at when the KID is Resting,   The RFR at that time will be the Reason for the latest Rest.

    FWIW,   Vic


    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    It has been several beautiful days, completely sunny and NO charging happened all day. The array output was 61V in the morning and 59V in the afternoon. It went into Bulk mode for a brief time, clicked loudly, but then went back to resting mode. My batteries were at 50.4V at SOC of 71%. I checked the voltage at the breakers and the panels and they were all the same. I have made no changes, only the weather has been much warmer. I still have the original FW so maybe a reason to upgrade.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • vince
    vince Registered Users Posts: 79 ✭✭
    It had a complete charge in the last week before the warm weather began
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    OK vince,  thanks for the answers.

    You might get the KID to behave better by trying Legacy O&P,  where the KID sweeps much more slowly than it does in Solar Mode (perhaps for the time being) ...

    BUT,  am sure that you and the KID will be much happier if you were able to increase the PV input voltage by adding your suggested 19-ish  Vmp PVs,  in series with the existing PVs,  if  they match the existing PV's Imp fairly closely.

    This should allow the KID to Sweep to a good Vmp for Solar production,  and be a point where the KID will be happy and efficient.   And there is almost no  possibility that that you will encounter a high Voc issue when this string of those two PVs is cold.

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    The renogy poly panels have an Imp of 5.62 and Vmp  of 17.8 while the mono panels have an Imp of 5.29 and Vmp of 18.9. So the poly panels would be better?
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Hi vince,

    First,  would you please try changing the KID Mode to one of the Legacy Modes?  Have used Legacy O & P,  here,  and it works fine ...  What is the Firmware version in the KID?

    You could try a Firmware Update,  which is just a Drag and Drop operation.

    It is possible that a newer FW version could have changes to the Sweep algorithm.

    Suggest doing the above,  before buying more PVs.   What do you think?   Thanks,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    I have the original FW of 2014 and have not been able to get to the location to change the settings. As I already experience this problem in April at 80F and the hottest day in summer can easily go above 100 F with solar cell temperatures even higher, adding some panels now seem needed to get maximum output of my system. Is the recent FW 1791 stable?
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Hi vince,

    Am still running 1741 (IIRC)  on the KID here,  and it has been fine.

    Believe that FW 1791 has been out for about one year,  and seems to have been stable.

    Here is the KID CC area on the MidNite Solar Forum:
    http://kb1uas.com/mnsforum/index.php?board=52.0

    I had felt that there might be a simple Mode change that could,  possibly get you by for now,  without adding PVs.

    More later,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    that's good as my SOC is dropping to 60% and I need a charge soon.  Hopefully get a chance to go out and see if it helps. Thanks a lot
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    vince said:

    . What is the best voltage input...... to charge a 48 V. Apparently 61V is not enough.


    No, you will need about 68V Vmp, or more, at the lowest to charge your batteries,  though you should be getting 72.9 Vmp...  That < 61 V coming out of the Kid is your problem and why those batteries are dying a slow death...
    I think you are thinking you are getting the Voc but that is not what you get out an MPPT CC, it is the Vmp you need to use...
    As Vic said change one thing at a  time....for a day or so then another change...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • vince
    vince Registered Users Posts: 79 ✭✭
    Found out from Midnite support that an input voltage of 80V is the ideal for a Kid CC. My 60V from the array is too low to wake up the CC. Adding the 100Wpanels in series with each panel may still not be enough to get to the ideal input but definitely a lot closer. The Vmp is the voltage under test conditions and mislead me in estimating the array output voltage in summer.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    vince said:
    Found out from Midnite support that an input voltage of 80V is the ideal for a Kid CC. My 60V from the array is too low to wake up the CC. Adding the 100Wpanels in series with each panel may still not be enough to get to the ideal input but definitely a lot closer. The Vmp is the voltage under test conditions and mislead me in estimating the array output voltage in summer.


    Hi vince,

    Here is what I was basing my guesses on,  the I - V Graph for the SunPower e20/435 PVs:
    http://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/ds-e20-series-435-solar-panel-datasheet.pdf

    That blue line for an Irradiance of 1,000 W/ M2 (full sun),  appears to be for an ambient temp of 50 C.  It shows that there would still be 4 Amps of current available from one PV,  and still have about 75 volts from the PVs,  going into the CC.

    Every MPPT CC behaves a bit differently,  and the way that each one Sweeps for the MPP differs,  at least somewhat.  It has been my guess that,  perhaps a slow-Sweeping Mode for the KID might well allow it to become convinced that there is SOME PV power available,  to run its Converter,  and do some charging.   The Classic CCs in Solar mode,  Sweep in about one second,  believe that the KID uses essentially the same algorithm ...

    In rereading the first Post of this Thread,  the 61 Volt input that was noted,  does seem quite low,   and that really cannot be the Voc,  when the KID is Resting,  as one would expect that the Voc at 50 C would be just under 80 V (79.7 V),  in full sun with no shading of the PVs.

    If the Voc for this system is really 60-ish volts,  then there does seem that something is amiss.

    When you return to the site with this system,  vince,  you should probably open the breaker feeding the Vin to the KID,  and also open each of the breakers in the Combiner (assume that you have three input breakers,  as you have three PVs).  Then measure the input to each of these breakers (the output of each PV).   In good sun,  you should be seeing about 72 - 75 volts,  depending on the temperatures,  and  the actual Irradicance (to some extent).

    FWIW,   Vic


    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    That was indeed what I expected but the voltage at the 3 breakers and the panels was in the low 60 V, 60-61V with minimal drop in the wiring as the length is only 5 ft. When I was reading how to Vmp is affected by temperature due to the performance in summer dropping in voltage but increasing in current, I found out that the Vmp can drop as much as 20%, consistent with my finding whereas in winter it is the opposite as the voltage increases and current drops. At least, that is my current working theory. I cannot understand why the CC was able to fully charge my battery bank last week when it was 30 colder compared to this week. But I'm open to a better explanation of what is going on.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Is that measurement before or after the CB's? Can you measure at the PVs?  What wire did you use? Are the screws/clamps tight on the wire?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited April 2016 #16

    And,  vince,

    In your conversation with MidNite Tech,  did they mention anything about checking the Voltage Calibration of this KID?   Some early KID CCs had a bit of an issue with Calibration.   This mostly affected the Beta KIDs (assume that your KID is not a Beta).

    It might be worthwhile checking the Calibration,  when the KID is in the Resting state,  and check the accuracy of the PV input voltage,  and its readout of the battery voltage,  with a good,  accurate Digital MultiMeter.

    Realize that this KID has been operating well in the past (assumed),  but  some calibration error might be some part of this issue.

    What is your battery type,  and what is the Absorption voltage setting in the KID?

    It might be a good idea to check all of the connections from the PV modules all of the way to the KID's PV input connections,  and also for all of the connections from the KID's battery terminals to the battery.  Retorque all screw terminals,  which can tend to loosen over a period of time,   just for kicks.   Be careful with the PV connections,  as the Voc of your PVs could cause you to receive a possibly dangerous SHOCK.   Also,  there is a risk if a tool happened to short the battery connections,  resulting in a large current flow,  and instant heating,   and so on.

    Believe that your inverter does not have a built-in charger,  if so,   do you have any charge source other than the PVs,  and a generator,   or the Grid available at the site?

    FWIW,  Good Luck,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    Is that measurement before or after the CB's? Can you measure at the PVs?  What wire did you use? Are the screws/clamps tight on the wire?

    Both, no difference either side of breaker, or PV. My volt meter reading is not very accurate as the dial goes from 50V+. My cabling is 12 awg. and is clamped to the mc4 connectors. As I did not see a drop anywhere, I left it alone. All three panels have same readings. I was thinking of getting a clamp meter but the cheaper ones only go to 10A.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • vince
    vince Registered Users Posts: 79 ✭✭
    edited April 2016 #18
    Vic said:

    And,  vince,

    In your conversation with MidNite Tech,  did they mention anything about checking the Voltage Calibration of this KID?   Some early KID CCs had a bit of an issue with Calibration.   This mostly affected the Beta KIDs (assume that your KID is not a Beta).

    It might be worthwhile checking the Calibration,  when the KID is in the Resting state,  and check the accuracy of the PV input voltage,  and its readout of the battery voltage,  with a good,  accurate Digital MultiMeter.

    Realize that this KID has been operating well in the past (assumed),  but  some calibration error might be some part of this issue.

    What is your battery type,  and what is the Absorption voltage setting in the KID?

    It might be a good idea to check all of the connections from the PV modules all of the way to the KID's PV input connections,  and also for all of the connections from the KID's battery terminals to the battery.  Retorque all screw terminals,  which can tend to loosen over a period of time,   just for kicks.   Be careful with the PV connections,  as the Voc of your PVs could cause you to receive a possibly dangerous SHOCK.   Also,  there is a risk if a tool happened to short the battery connections,  resulting in a large current flow,  and instant heating,   and so on.

    Believe that your inverter does not have a built-in charger,  if so,   do you have any charge source other than the PVs,  and a generator,   or the Grid available at the site?

    FWIW,  Good Luck,   Vic

    No this tech was sceptical about adding a 100 W panel with the same current Imp in series. Only after explaining it three times, he told me to try it as it would not hurt the CC. Any suggestion for a good, affordable true rms meter? The Fluke 115 only reads up to 10 A. Checking the connections, I did that last month when I noticed that over a six month period there was no need to add any water to the batteries, making me suspicious that I was not getting the full power. I have a generator but have not needed to charge the batteries so far. Still need to decide on an affordable way to charge the batteries. I'm off the grid as this is a meditation retreat tiny house. If you are curious, here is a blog about the building process. www.vincentdummer.com/wp
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    edited April 2016 #19
    vince said:..... I noticed that over a six month period there was no need to add any water to the batteries, making me suspicious that I was not getting the full power.
    Your suspicions are correct, the lack of water use over that period of time is a good indication of degradation of the Batteries SoC, ie slowly decreasing, and now that you are not getting full power needed it is dropping fairly fast...
    you will need to get them charges asap and then probably do several EQ's to recover them ...
    If you are unable to get the single panels to produce, which they should, your options are those similar panels or 3 more of the same ones you already have... with 3 strings in series...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
     

    vince said,

    "No this tech was sceptical about adding a 100 W panel with the same current Imp in series. Only after explaining it three times, he told me to try it as it would not hurt the CC. Any suggestion for a good, affordable true rms meter? The Fluke 115 only reads up to 10 A. Checking the connections, I did that last month when I noticed that over a six month period there was no need to add any water to the batteries, making me suspicious that I was not getting the full power. I have a generator but have not needed to charge the batteries so far. Still need to decide on an affordable way to charge the batteries. I'm off the grid as this is a meditation retreat tiny house. If you are curious, here is a blog about the building process. www.vincentdummer.com/wp"<

    OK vince,

    Fine on the MidNite Tech ...

    Regarding checking the output of each of the PVs for Voc,  you will need to switch OFF each of the breakers in the Combiner,  and then,  measure the cable coming into each Combiner breaker from the individual PVs,  Place the other lead on your meter on the Negative Buss in the Combiner.  In good sun,  your PVs with the breakers should have an output voltage of about 80 Volts (Voc),  or a bit more in good sun.

    I had wondered about the orientation of your three PVs.   Are they all at the same elevation angle,  and all facing at the same compass heading,  toward the sun?   What is the approximate elevation angle/s and compass heading/s ?

    From what you are saying about your meter,  it DOES seem that it may not be up to the tasks that most of us need.

    I have no suggestion for an inexpensive Digital MultiMeter (DMM) that does True RMS.  The Home Centers in the US often have some Name Brand meters starting at about $40-ish (US).  These will NOT do True RMS,  but should be OK for many of your tasks.  I assume that you may have an Analog meter,  that you are using now,  and no Multimeter at all. 

    I did buy DC Clamp DMMs at Radio Shack for about $50.00,  its Clamp DC function has a 40 A,  and a 400 A DC Clamp full-scale ranges,  IIRC.   BB Bill - Moderator - Recommends the Sears Clamp DC meter (probably also a DMM).  Most of these inexpensive Clamp meters have a perfectly acceptable DMM function,  but generally,  are either Auto-Range,  or Manual range select,  via multiple button pushes to get to the range needed,  which is a bit inconvenient,  and could possibly mislead one,  if the selected range is not carefully checked.   Perhaps for now,  you could get an inexpensive meter,  and save for a better one later.   Here we use our best meter as a fairly frequent check on the inexpensive ones that are used frequently,  and save the best one for tough tasks and as the Reference meter,  FWIW.

    Have not had a chance to check your Tiny House build at the site noted,  but will check in later,  very busy here with Spring chores,  some design work,   and today is a transit day.

    More Later,  Good Luck,   Vic


    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    The panels are all heading south at an angle of 22.5 deg. No obstructions till 7 pm. I went ahead and ordered the Sears clamp meter so I can get some accurate data to work with. I'll charge all the batteries this weekend as I believe now that they are really  low.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited April 2016 #22

    Hi vince,

    OK,  fine on that meter,  good.   Your PV orientation should be fine.

    One other comment,  is that if you cannot get the KID CC to do any real charging,  YOU  can become a CC.   By disconnecting the output of the circuit breaker that goes to the PV in of the KID,  and connecting it directly to the positive battery buss.

    Your batteries are probably quite a bit behind charge,  so catching up could take two or three days,  possibly,  depending upon weather and just how low your batteries are (obviously).

    You can leave the KID's battery breaker connected to the battery,  as an accurate battery voltage monitor.

    Connecting the output of the Combiner directly to the battery positive is not as efficient as is an MPPT CC,  but it will certainly be much better than no additional charging.  You will probably want to be above 58 volts for a number of hours,  perhaps six hours or so,  just to catch up on charging.   Of course,  you would NOT want to leave this configuration in place in your absence.   It is probably a good idea to switch off the KID's input breaker at night,  and then,  back ON the next day when you are around your house.

    When the dust begins to settle,  and you have the KID operating well,   you will probably want your Absorb voltage at about 59 V,  or so,  and Absorb time will depend upon the Depth Of Discharge of the batteries in the previous discharge.   Probably 2 - 3 hours,  but since this is probably more of a weekend place,  that amount of Absorb time will probably be too long.

    Forget if you have the MidNite WBjr,  and a Shunt.   BUT,  you were noting fairly precise SOC numbers,  so you may well have the WBjr.   If so,  it can allow you to set a Shunt End Amps value that will terminate Absorb based on actual battery charge current (this you probably know)  Using EA can be a large help,  especially for a weekend retreat,  where the batteries experience a fairly large variation in the DOD from day-to-day.

    Using a MidNite Battery Temperature Sensor (BTS),  is very important for proper charging of batteries.   Many of the GC batteries now use a Temp Compensation value of --3mV  per cell per degree C.

    An EQ voltage should approach 62 V ...   there have been Posts here that have noted the recommended Charge and EQ voltages for these common GC batteries,   will try to look for them.

    Later,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    I have a temp sensor and WB jr plus shunt and have used the auto setting in the kid settings menu as I didn't know how to program the other settings. May come back to that later. Thanks
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • vince
    vince Registered Users Posts: 79 ✭✭
    Today I had a chance to measure the voltage with the breakers off. I discovered that only one panel had 79-80V, while both others were only 59V and 61V. This explains why I had such a low voltage. With the temperature drop, I have had some charging the past few days but not much. SOC was down to 30%. When I opened the breaker with the 80V voltage, the system started charging again producing 200+ watt, as it was getting close to 5 PM. Tomorrow I want to find the source of the poor connection in the other two panels, so I can get back to a fully charged system. 
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    OK vince,

    Thanks for the update ...   sounds like you are making progress,  BUT,  with all breakers open in the Combiner,  you are seeing the Voc for the temperature of the PVs at that time.   That is,  with no current flowing.  It could be a connection problem,  but,  one wonders about those PV modules,  themselves,  as there would probably  need to be a current-shunting path to drag down the Voc of those two PVs.

    Since you do have a genset,  perhaps,  you can run the genset at night,  to try to avoid discharging your batteries even lower.  30-ish% SOC  is quite low,  and could cause battery damage.

    Good Luck!   Thanks,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    vince said:
    When I opened the breaker with the 80V voltage, the system started charging again producing 200+ watt
    huh?  When you open a breaker you are disconnecting that panel.  Do you mean that you closed the breaker?

    --vtMaps

    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vince
    vince Registered Users Posts: 79 ✭✭
    edited April 2016 #27
    vtmaps said:
    vince said:
    When I opened the breaker with the 80V voltage, the system started charging again producing 200+ watt
    huh?  When you open a breaker you are disconnecting that panel.  Do you mean that you closed the breaker?

    --vtMaps

    Ok, I closed the breaker and opened the circuit.
    Vic said:

    OK vince,

    Thanks for the update ...   sounds like you are making progress,  BUT,  with all breakers open in the Combiner,  you are seeing the Voc for the temperature of the PVs at that time.   That is,  with no current flowing.  It could be a connection problem,  but,  one wonders about those PV modules,  themselves,  as there would probably  need to be a current-shunting path to drag down the Voc of those two PVs.

    Since you do have a genset,  perhaps,  you can run the genset at night,  to try to avoid discharging your batteries even lower.  30-ish% SOC  is quite low,  and could cause battery damage.

    Good Luck!   Thanks,   Vic

    Can you elaborate what can account for these low Voc for the 2 panels. There is only one connection of MC4 connectors for each panel. You think there could be a problem with the panels? Can I reliably measure the Voc at the connectors?
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Hi vince,

    The first thing that comes to mind about low Voc at the breaker inputs,  is the PVs themselves,  as almost nothing else could drag the "Voc"  that low,  as this would equate to a considerable current shunting to get the voltage that low.

    Yes,  you should be able to measure the PV output at the MC4 connectors,  and you should do this  --  the MC4 connectors need a Tool,  to part the connection,  as you probably know.

    You will probably want to carefully inspect each PV module for obvious or subtle visible defects on the front of the PVs (discoloration,  signs of moisture,  cracks in cells,  etc.

    It does seem that two of your PVs are dragging down the output voltage of the third one,  so,  obviously,    you have a a small amount of PV charge capability.  This means that you really should avoid any additional discharge of your batteries until you get additional charge capability (also obvious).

    Would suggest that you run all loads only from the genset,  and allow the batteries to slowly catch up on charge ...

    More Later,  Thanks,  Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Should add,  that even slight shading of PV modules can significantly reduce their output,  so please also check for ANY shading of the PVs,  at all.

    Also check the back of the PVs for any discoloration, holes or tears in the back sheet,  and  especially around the Junction Box for discoloration,  or any voids in the adhesive that usually holds the box onto the rear of the PV.

    Also look for any signs that water has gotten into the PVs  --  signs of condensation or similar signs,  especially in the early morning or late in the afternoons,  etc.

    In the past,  SunPower PVs were not sold to retail customers,  just Installers (IIRC),   so there could be some chance that there are some defective or reject PVs floating around in the secondary market ...  not to try to create too much concern,  just something to possibly consider.

    I have no experience with SunPower PVs.

    Hope that you have a Hydrometer at that location,  as battery Monitoring devices tend to get less,  and less accurate for each day that the batteries do not get a Full Charge,  where the SOC can be fairly reliably reset to 100%.

    As you know,  this situation is really an emergency,  where,  at all cost,  those batteries need to get charged ASAP,  to try to minimize damage that occurs from them staying at a probably LOW SOC  for a number of days.   You may need to consider some external charger (assuming that the Inverter that you are using has no built-in charger).

    Please ;let us know how you are doing.  Good Luck,   VIc

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vince
    vince Registered Users Posts: 79 ✭✭
    All my batteries have been charged again, filled up with water and having an equal charge of 7.56V-7.58V after charging. When I hooked it up, the system went in absorb mode for another hour until it showed a full charge and 200 ah in the systems with 56.7 V. I have a WBjr and shunt and Temp adjustment. The good panel is producing 73-80 V and at times above 400W. That is good enough as my daily use is less than a kW. if I don't use the split level heat pump.
    I checked both of the bad panels and they have almost the same Voc at the MC4 connectors of 59.8V and 60.3V. The amp function of the multimeter no longer works and a new one is coming in this week. No obvious discoloration, condensation, tears or holes. Actually, everything still looks new. I'll contact the company I bought these from on Monday and see what the deal is. Thy don't have any of these panels in stock anymore, so I have no idea what they will do.
    With 120 cells in a panel, are all these cells in series or could a section of 30 cells be disconnected? Would checking with an infrared thermometer be able to identify cells that are dead?
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited April 2016 #31

    Hi vince,

    Thanks for the update.

    So that voltage reading for the batteries seems encouraging,  and the balance between batts also seems very good.

    If you have a Hydrometer (or Refractometer)  you can measure the SG of each battery cell,  and this is really the best and only accurate way to determine the actual State Of Charge of the batteries.

    SO,  was the KID doing the charging with the one good PV,    or,  did you need to jump around the KID,  and use the PV directly to the battery?

    SOC indications from Monitors like the WBjr,  can be misleading,  so you will want to use your Hydrometer of Refractometer to measure the SG of each cell of your battery to confirm the actual SOC.

    (Just lost 15 minutes of typing by doing the Right Click,  Paste attempt and,  this Forum software usually deletes 1,000 words,  and there is NO recovery from any Saved Draft ...  wonder why this is the only Site that has this "Feature"?  Am told that this is just my Computer,  but no other site ever has done this ...   Right Click/Paste has been the industry standard for  about 35 years ...)

    Anyway,  your SunPower PVs have 128 Cells.  The current generation 72 Cell PVs often have a Vmp of about 36.5 Volts ...  two of these in series should yield almost exactly the Vmp on one of your SP PVs.  Topoint 200s,  listed on the wind-sun Site,  and the Solarworld 315 - 325 W PVs connected two in series per string would have a String Vmp of 73 volts,   which could work.  wind-sun no longer lists those SW PVs,  so here is a Link to another listing for them:
    http://www.solarpanelstore.com/pdf/sunmodule-pro-series-solar-panel-xl-315-320-mono-46mm-frame-ds.pdf

    EDIT (I hope):  Here is the Link to the Topoint 190 W 72-Cell PVs,  two of these in series,  paralleled with one existing,  good,  Sun Power PV  would have an almost identical Vmp,  although it is unknown how temperature variations would affect the Vmp differential of one of these non "Maxeon" cell PVs verses the SP PV:
    http://www.solar-electric.com/topoint-jtm-190-72m-solar-module.html

    More Later,  Thanks,  Good Luck,   VIc

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.