Solar Generator batteries losing battery charge

lc0338lc0338 Posts: 67Registered Users ✭✭
edited September 11 in Solar Beginners Corner #1
I have a 6KW solar generator. It has 4ea full river 250-6 batteries wired in series to make a 24 volt system. 2ea 270 watt mono crystal solar world solar panels, and a xantrex 3024 inverter/charger, morningstar 45 amp mppt charge controller. It has been sitting in the sun all summer without much use but loaded it back onto my truck and parked the truck under a car cover for a couple day's. Looked at it today and the batteries were down to 55 percent. It has been sitting at 100% all summer and I have not hooked anything to it. I thought it odd that the batteries would drain down that quickly without anything attached to the system. seems like maybe a parasitic draw somewhere? Do you think this is normal and what should I do to prevent the drain off from the batteries?

Comments

  • mcgivormcgivor Posts: 2,212Solar Expert ✭✭✭✭✭
    Was the inverter on or off during this period? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • Marc KurthMarc Kurth Posts: 446Solar Expert ✭✭✭✭
    edited September 10 #3
    The devil is in the details:

    What does "without much use" mean with your 3,000 watt inverter?
    What is the exact float voltage that you have feeding the batteries all summer?
    How do you know that the battery bank dropped down to 55% in a couple of days?
    What was the load on the battery bank during that couple of days?

    Marc


    I always have more questions than answers. That's the nature of life.
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    mcgivor said:
    Was the inverter on or off during this period? 
    It has been off all the time.

    Marc Kurth said:
    The devil is in the details:

    What does "without much use" mean with your 3,000 watt inverter?
    What is the exact float voltage that you have feeding the batteries all summer?
    How do you know that the battery bank dropped down to 55% in a couple of days?
    What was the load on the battery bank during that couple of days?

    Marc


    Should have been "without any use". Full river recommends 29.4 bulk and absorb and 27.2 float. I have a TM-2025 RV battery monitor package installed. There has not been any load. It was sitting in the yard in the sun. loaded it up on the back of my truck and pulled it under a cover for a couple days but nothing has been connected to it nor has the inverter been turned on. I'm scratching my head.
  • mcgivormcgivor Posts: 2,212Solar Expert ✭✭✭✭✭
    Are the batteries flooded and if so what are the levels? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • lc0338lc0338 Posts: 67Registered Users ✭✭
    mcgivor said:
    Are the batteries flooded and if so what are the levels? 
    Full river 250-6 are AGM's
  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    Was the charge controller set up to use a remote temperature sensor?

    Have you measured voltage of individual batteries? Are you getting the 55% SOC reading from the Trimetric meter?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    Estragon said:
    Was the charge controller set up to use a remote temperature sensor?

    Have you measured voltage of individual batteries? Are you getting the 55% SOC reading from the Trimetric meter?
    mcgivor said:
    Get some sun on the panels and see if they accept a charge, a DC clamp on ammeter would be helpful to diagnose if there is a potential problem, I wouldn't rely on a battery monitor.
    When I noticed the low reading I pulled the truck back out from under the cover (Sunday morning) but it has been overcast all day. Checked it this morning and it is back up to 100% and 27.2 volts. I only use the battery monitor to check the battery health. Maybe it was a glitch. I pulled the truck back under the cover this afternoon when I got back from my horseback ride. I'm going to monitor it a little closer to see what happens. Maybe I bumped a button on the tm 2025 rv battery monitor and it was giving me some other data. Thanks for everyone's input. The system is supposed to have a remote temperature sensor. I haven't measured any voltages at the batteries. I have them covered pretty well to prevent any metal objects from touching them. I was reading from someone when I researched before I built the generator and they were pretty high on the battery monitors with shunt that it was all you needed to monitor the health of the system. I'll report back how it progresses.
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    As mentioned in my post yesterday I put the solar generator back under cover and have been monitoring the battery health by taking readings from the TM 2025 RV battery monitor. Below are the results:

        Date             Time           Volts        Watts (in or out)    Battery %
    10sep2018       2:00pm      27.2
    10sep2018       3:23pm      26.0          -1.56                     100
    10sep2018       4:15pm      25.7          -1.28                     100
    10sep2018       6:24pm      25.5          -1.78                     100
    10sep2018       8:33pm      25.4          -2.28                     100
    11sep2018       7:11am      25.3          -1.77                      100


    I'm going to leave the generator under cover and continue to monitor results.
  • mcgivormcgivor Posts: 2,212Solar Expert ✭✭✭✭✭
    Next step is to put a sizable load on the battery to see what actually happens to the voltage under load, a battery may indicate a voltage which appears to be 100% fully charged but collapses under load due to lost capacity. Please understand I'm not attempting to be negative in any way, these are just tests to establish condition of the batteries themselves, as voltage in and of itself, is a very unreliable gauge. After conducting such a test, recharge as soon as possible.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • lc0338lc0338 Posts: 67Registered Users ✭✭
    mcgivor said:
    Next step is to put a sizable load on the battery to see what actually happens to the voltage under load, a battery may indicate a voltage which appears to be 100% fully charged but collapses under load due to lost capacity. Please understand I'm not attempting to be negative in any way, these are just tests to establish condition of the batteries themselves, as voltage in and of itself, is a very unreliable gauge. After conducting such a test, recharge as soon as possible.
    No problem. With the generator still under cover I turned on the inverter and heated some water in my 1.7 liter 1500 watt water kettle. Not once but twice. Below are the readings before and after.

    Time              Volts                watts(in or out)               % battery
    9:35am          25.3                 -1.01                                100
    heated water
    9:49am          25.1                 -0.50                                  96
    heated more water
    10:03             25.0                 -0.25                                  92

    I waited about 5 minutes after water heated before taking readings so they would stabilize
  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    How long did you have the kettle on for each time?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    edited September 11 #14
    Estragon said:
    How long did you have the kettle on for each time?
    I didn't actually time how long it took to heat 1.7 liter water from ambient to boiling but from my measurements above is was roughly 5 minutes.
    Also, I did shut off the inverter between the first and second heating. As soon as the kettle shut off I turned off the inverter.
  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    Hmmm. The reason I asked I'm wondering about the TM settings / calibration.

    If my arithmetic is right, 1500w÷85% inverter efficiency ÷24v ÷ 60mins * 5mins run time = ~6ah, or ~2.45% of a 250ah bank. Not that far off the 4% shown on the TM, but still...

    Could be the inverter efficiency guess at 85% is off, voltage sag in batteries, or higher wire losses though. At 1500w, the draw would be ~70-75a. Did you happen to notice the amp reading on the TM with the kettle on?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • jonrjonr Posts: 1,078Solar Expert ✭✭✭✭
    edited September 11 #16
    +1 on it being time for a full load test.  Your batteries may be near end of life.

    >  5 minutes after water heated before taking readings

    You need more like 5 hours if you are going to use voltage to determine SOC.  Ie, measure resting voltage, apply load for 25% of batteries rated AH capacity, wait 5+ hours, measure voltage again.
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    Estragon said:
    Hmmm. The reason I asked I'm wondering about the TM settings / calibration.

    If my arithmetic is right, 1500w÷85% inverter efficiency ÷24v ÷ 60mins * 5mins run time = ~6ah, or ~2.45% of a 250ah bank. Not that far off the 4% shown on the TM, but still...

    Could be the inverter efficiency guess at 85% is off, voltage sag in batteries, or higher wire losses though. At 1500w, the draw would be ~70-75a. Did you happen to notice the amp reading on the TM with the kettle on?
    No, I have the TM set to monitor watts versus amps
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    jonr said:
    +1 on it being time for a full load test.  Your batteries may be near end of life.

    >  5 minutes after water heated before taking readings

    You need more like 5 hours if you are going to use voltage to determine SOC.  Ie, measure resting voltage, apply load for 25% of batteries rated AH capacity, wait 5+ hours, measure voltage again.
    The TM is measuring voltage but it is also measuring watts/amps (I have the unit to measure watts) into and out of the batteries which seems to be a good way of determining soc. You do not agree?
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    edited September 11 #19
    lc0338 said:
    Estragon said:
    Hmmm. The reason I asked I'm wondering about the TM settings / calibration.

    If my arithmetic is right, 1500w÷85% inverter efficiency ÷24v ÷ 60mins * 5mins run time = ~6ah, or ~2.45% of a 250ah bank. Not that far off the 4% shown on the TM, but still...

    Could be the inverter efficiency guess at 85% is off, voltage sag in batteries, or higher wire losses though. At 1500w, the draw would be ~70-75a. Did you happen to notice the amp reading on the TM with the kettle on?
    No, I have the TM set to monitor watts versus amps
    I did a little research and to boil 1 liter of water with a 1500 watt kettle would take 4.2 minutes so 1.7 liter should take approximately 7.14 minutes
  • lc0338lc0338 Posts: 67Registered Users ✭✭
    Does anyone know of a contact in the Northeast Oklahoma, Northwest Arkansas area that is in the business of servicing solar generators? I would like to get a check-up for mine. Someone who might be able to do a load test and check all components to make sure the settings and performance is good to go. It was originally designed 12 volt but after burning up a samlex 2000 watt inverter I decided to upgrade to a 24 volt system and also upgraded to an 3000 watt inverter_charger. Sometimes have new eyes look can find some weak spots or possible performance enhancements.
  • jonrjonr Posts: 1,078Solar Expert ✭✭✭✭
    edited September 12 #21
    > into and out of the batteries which seems to be a good way of determining soc

    Unless it self calibrates, that's a lousy way to measure actual SOC (vs SOC as % of rated/entered AH).
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