Is 12.2 volts TOO LOW???

cupcake
cupcake Solar Expert Posts: 254 ✭✭✭
Hi guys - I have a quick question:

Since adding a refrigerator to the off-grid system I've noticed my daily 'min' voltage reading is 12.2 volts according to the controllers memory settings...
Before the fridge my 'min' was 12.5

The fridge cycles on an off through the night (normal operation) -- so my question - as far as battery-life is concerned is 12.2 volts OK during 'semi load' overnight on a continual basis? Or is 12.2 not accurate because its under a semi-constant load? (with the fridge compressor cycling on and off all night long)

FYI, during the day the bank gets a full charge...

I have 5, 100ah batteries in parallel..

So is 12.2 at night worry? or no-worry??

Thanks guys!

--cups-of-cake
~1.5Kw PV in parallel
Morningstar MPPT-60 controllers (2) in parallel
3 Trojan tr-1275's in parallel 450ah total
Samlex 2,000 watt 12-volt inverter hardwired


Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Is 12.2 volts TOO LOW???

    Do you have a hydrometer?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    (repost) Is 12.2 volts too low..??

    Somehow my original thread got locked/closed ..perhaps by mistake?

    I have SEALED batteries, I cannot use a hydrometer. My original question/post is below -- THANKS AGAIN!

    Hi guys - I have a quick question:

    Since adding a refrigerator to the off-grid system I've noticed my daily 'min' voltage reading is 12.2 volts according to the controllers memory settings...
    Before the fridge my 'min' was 12.5

    The fridge cycles on an off through the night (normal operation) -- so my question - as far as battery-life is concerned is 12.2 volts OK during 'semi load' overnight on a continual basis? Or is 12.2 not accurate because its under a semi-constant load? (with the fridge compressor cycling on and off all night long)

    FYI, during the day the bank gets a full charge...

    I have 5, 100ah batteries in parallel..

    So is 12.2 at night worry? or no-worry??

    Thanks guys!

    --cups-of-cake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: (repost) Is 12.2 volts too low..??

    Sounds about right. A lot voltage sag depends on your wiring to the inverter and the batteries ability to satisfy the current needed. Standing voltage and loaded voltage will always be different. Somewhere around 11.9V standing voltage ( unloaded ) is 50% DOD. Yours sounds good to me.
  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: (repost) Is 12.2 volts too low..??
    Sounds about right. A lot voltage sag depends on your wiring to the inverter and the batteries ability to satisfy the current needed. Standing voltage and loaded voltage will always be different. Somewhere around 11.9V standing voltage ( unloaded ) is 50% DOD. Yours sounds good to me.

    Thanks! - I appreciate your help... I know 12.2 on 'the chart' says 50%... but my nighttime 12.2 overnight reading is when there is a fluctuating load (refrigerator)...

    So I just wanted to make sure...

    I appreciate your help :)

    --cake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Is 12.2 volts TOO LOW???

    Sorry Cake,

    Doing posts on my touch screen phone and clicked thread lock.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: (repost) Is 12.2 volts too low..??

    Under load system nominal Voltage is about as low as you want to get (i.e. 12 Volts). If you've got two tenths over this by morning you're still in good range.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Is 12.2 volts TOO LOW???

    There lot's of charts that say a lot of things. Using the SG readings are the best, even they have a range because it does not change instantaneously. Second would be a battery monitor with a shunt and knowing the amp hrs removed if your peukert exponent is correct. Volt meters are another issue if you do not know the correct battery voltage. Reading to .1 you do not know if the voltage is 12.29 or 12.21, depending on the size of a bank that makes a difference. Another is dip and recovery ( Coup de Fouet ) to the load, the initial surge of starting a refrigerator may cause a voltage dip that takes awhile to recover from while under load.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Is 12.2 volts TOO LOW???
    cupcake wrote: »
    Since adding a refrigerator to the off-grid system I've noticed my daily 'min' voltage reading is 12.2 volts according to the controllers memory settings...
    Before the fridge my 'min' was 12.5

    I'm not sure what you are describing... is 12.2 the voltage in the morning? Or is the morning voltage higher than 12.2 (but the monitor tells you that the voltage sagged to a 12.2 minimum during the night)?

    What counts is your voltage in the morning. If your morning voltage is 12.5 under your normal baseline loads, it doesn't matter that the voltage sagged for an instant to 12.2 when the freezer compressor switched on. Different voltmeters will 'capture' different values for the minimum... it depends on how many times per second they read the voltage. The transient sag is very brief... to brief for many meters to measure.

    If your actual morning voltage is 12.2, that means you are using more power overnight and your battery has a lower voltage because it is at a lower SOC.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    vtmaps wrote: »
    I'm not sure what you are describing... is 12.2 the voltage in the morning? Or is the morning voltage higher than 12.2 (but the monitor tells you that the voltage sagged to a 12.2 minimum during the night)?

    What counts is your voltage in the morning. If your morning voltage is 12.5 under your normal baseline loads, it doesn't matter that the voltage sagged for an instant to 12.2 when the freezer compressor switched on. Different voltmeters will 'capture' different values for the minimum... it depends on how many times per second they read the voltage. The transient sag is very brief... to brief for many meters to measure.

    If your actual morning voltage is 12.2, that means you are using more power overnight and your battery has a lower voltage because it is at a lower SOC.

    --vtMaps


    ^ Thank you -- good points and excellent info:

    To answer your inqusitions:

    My MORNING voltage is 12.5 or 12.8 according to my wife who gets in the control-room at 7am each morning.

    The "12.2" is the controllers 'log' of the overall 'miniumum' voltage... which begs the question: does the controller just log the minium voltage for that day OR the *average minimum voltage for the day... THAT would tell me a lot!

    The controller is the moringstar MPPT-60 cotroller...

    if its NOT the 'average minumum' for the day then it would make sense that the compressor 'surge' would kick it down to 12.2 momentarily...


    Thanks for all your help - all of you...

    --cup-o-kake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Is 12.2 volts TOO LOW???
    cupcake wrote: »

    I have 5, 100ah batteries in parallel..

    OUCH!!! Not good.
  • Desert Rat
    Desert Rat Solar Expert Posts: 138 ✭✭✭
    Re: Is 12.2 volts TOO LOW???

    I've noticed the same thing with my Morningstar TS-MPPT-60 controller--the logged Battery Vmin is always lower than the observed morning battery voltage. I've always figured that the logged number represents an instantaneous dip when my chest freezer kicks on during the night.
  • DMJ72
    DMJ72 Solar Expert Posts: 131 ✭✭
    Re: Is 12.2 volts TOO LOW???
    cupcake wrote: »
    ^ Thank you -- good points and excellent info:

    To answer your inqusitions:

    My MORNING voltage is 12.5 or 12.8 according to my wife who gets in the control-room at 7am each morning.

    The "12.2" is the controllers 'log' of the overall 'miniumum' voltage... which begs the question: does the controller just log the minium voltage for that day OR the *average minimum voltage for the day... THAT would tell me a lot!

    The controller is the moringstar MPPT-60 cotroller...

    if its NOT the 'average minumum' for the day then it would make sense that the compressor 'surge' would kick it down to 12.2 momentarily...


    Thanks for all your help - all of you...

    --cup-o-kake

    I have / had that same controller in my first solar setup, it ran a 13 cu. ft fridge. I know what you mean, I would get up and look on the logs, and see V-minimums of 23.6- 23.2 volts (even though my pre-sunrise voltage was 24.6+ on the meter-display). The first time it happened, i rushed outside and did a hydrometer reading .. its was 70%+ SOC. Turns out my fridge loved defrosting cycles @ 3am approx.. = load voltage sag.
  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Is 12.2 volts TOO LOW???

    Check batts with a volt meter before the sun comes up. Then compare your log for min volt.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Is 12.2 volts TOO LOW???
    Slappy wrote: »
    Check batts with a volt meter before the sun comes up. Then compare your log for min volt.

    That does not work, I can chart my minute interval logs, and see as loads come and go at night, the battery sags, and then recovers a fair amount over an hour, when the load (fridge) shuts off.
    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 ,

  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    OUCH!!! Not good.


    Why not??


    --cake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    Desert Rat wrote: »
    I've noticed the same thing with my Morningstar TS-MPPT-60 controller--the logged Battery Vmin is always lower than the observed morning battery voltage. I've always figured that the logged number represents an instantaneous dip when my chest freezer kicks on during the night.

    Yeah... this is basically what I'm exepreincing... a low 'logged' Vmin voltage (12.2)... I guess I'll get up before sunrise to read the actual voltage....

    --CC
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    Slappy wrote: »
    Check batts with a volt meter before the sun comes up. Then compare your log for min volt.


    I will do this tomorrow morning - thank you...
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    mike95490 wrote: »
    That does not work, I can chart my minute interval logs, and see as loads come and go at night, the battery sags, and then recovers a fair amount over an hour, when the load (fridge) shuts off.


    So basically you're saying if I get up at the crack-of-dawn tomorrow AM and the fridge just got done the compressor cycle, the batteries might show a false low voltage?

    --cakey
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: Is 12.2 volts TOO LOW???

    AGMS + no SOC monitor = tricky to tell whats going on. You can get familiar, and you will over time, with the morning rest voltage. I did for a year, and soon got a feel for SOC from it. Technically true rest voltage should be after several hours of no loads. A fridge cycling will thus make the voltage read a tad low, but not excessively so in my experience. Our bank never gets much exercise, and morning rest is usually 24.7V. However turn on a 1kW load like an iron or blender, then itll dip to 12.4V alright.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Is 12.2 volts TOO LOW???
    cupcake wrote: »
    I have 5, 100ah batteries in parallel..
    OUCH!!! Not good.
    cupcake wrote: »
    Why not??

    Parallel battery systems are problematic because when you charge them the current does not divide up equally among them. They will have a shorter life. You have 5 times as many battery cells as you need to have. The chance of having an outlier weak cell is almost 5 times greater than if you had just one string of battery cells, and your entire battery bank is no better than the weakest cell.

    short discussion here: http://www.wind-sun.com/ForumVB/showthread.php?14674
    more recent discussion here: http://forum.solar-electric.com/showthread.php?23600

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    vtmaps wrote: »
    Parallel battery systems are problematic because when you charge them the current does not divide up equally among them. They will have a shorter life. You have 5 times as many battery cells as you need to have. The chance of having an outlier weak cell is almost 5 times greater than if you had just one string of battery cells, and your entire battery bank is no better than the weakest cell.

    short discussion here: http://www.wind-sun.com/ForumVB/showthread.php?14674
    more recent discussion here: http://forum.solar-electric.com/showthread.php?23600

    --vtMaps



    ^ Alrighty,... I am all ears.... so what do you suggests as an optimal battery setup for a 12-volt system such as mine??:

    2X280w panels --> monningstar mpp6-60 controller --> 5 'deep cycle' batteries from autozone (yes, I know..) all in PARALLEL --> Samlex PST-2000w-12v inverter hardwired to --> standard AC panel box...

    all off grid FYI... and in the desert (ie no cloud cover issues..ever)

    Thank you...

    -cake cups
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    cupcake wrote: »
    ^ Alrighty,... I am all ears.... so what do you suggests as an optimal battery setup for a 12-volt system such as mine??:

    2X280w panels --> monningstar mpp6-60 controller --> 5 'deep cycle' batteries from autozone (yes, I know..) all in PARALLEL --> Samlex PST-2000w-12v inverter hardwired to --> standard AC panel box...

    all off grid FYI... and in the desert (ie no cloud cover issues..ever)

    Thank you...

    -cake cups

    You've got a total of 560 Watts of panel. Expect about 36 Amps of peak current. That means a maximum battery bank capacity of 720 Amp hours, which you won't like because the charging would be far too slow to be practical. 360 Amp hours would be 'ideal' but there don't happen to be any batteries right at that level.

    Some options:
    Two parallel strings of GC2's giving 440 Amp hours @ 12 Volts (four batteries). 8% peak charge rate, only two parallel connections, very inexpensive batteries. Approximately 2.6 kW hours total.
    Two L16 320 Amp hour 6 Volt batteries in series. 11% peak charge rate, only one battery string, more expensive batteries. Approximately 1.6 kW hours total.
    Two L16 390 Amp hour 6 Volt batteries in series. 9% peak charge rate, only one battery string, more expensive batteries. Approximately 2.3 kW hours total.

    Important thing to do: look and see what sort of real deep cycle batteries are available locally.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Is 12.2 volts TOO LOW???

    You could always get 6 , 2 volt custom batteries made to size for about $250 + each. or do like the all my customers do, put 8-10 Sams golf cart batteries in parallel for $84 each and get 4-6 years out of them and smile all the way to the bank.
  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Is 12.2 volts TOO LOW???

    Do you have your battery sense wires hooked up. It does make a difference on the controller reading.
  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: Is 12.2 volts TOO LOW???

    Just goes to show that theres always an exception to every rule. ;)
    You could always get 6 , 2 volt custom batteries made to size for about $250 + each. or do like the all my customers do, put 8-10 Sams golf cart batteries in parallel for $84 each and get 4-6 years out of them and smile all the way to the bank.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    Slappy wrote: »
    Do you have your battery sense wires hooked up. It does make a difference on the controller reading.



    No I don't -- that's a good point though - I probably should hook up the battery sense wire.....

    Thanks


    --cake in a cup
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Is 12.2 volts TOO LOW???
    zoneblue wrote: »
    Just goes to show that theres always an exception to every rule. ;)
    Thats why you always look for the source of the " Rule ". Most are repeated often, but they are not necessarily true.