Magnum Inverter, low power cut off, cutting of before set point?

CVN-71
CVN-71 Solar Expert Posts: 54 ✭✭
in General Solar Power Topics #1
Hi, so I lost grid power again and as usually switched to my off-grid system. At 24.4 volts in the battery bank, the LPCO engaged even though it was set for 23v. I've never taken it this low before but it was an emergency and I wanted to use everything in the batteries that I could. (My generator wouldn't start so I couldn't recharge off that and my panels were covered in snow) Is this normal or is something wrong with the inverter? Thanks
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    How old are your batteries and how big of a load were you running?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    I guess you turned it back on? What did the battery voltage drop to with a moderate load?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • ramloui
    ramloui Solar Expert Posts: 109 ✭✭
    #4
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    Hello CVN,
    I will take a crack at this.
    Is it possible that there is some voltage drop between the battery bank and the inverter? If you think this might be an issue, you can verify by comparing the voltage measured at the bank itself and then at the connections on the inverter.
    The other thing that I would check is the dip in voltage as an inverter load is turned on. The batteries may be at 24.4V at rest but if you put a load on them then they drop below the LVCO.

    I'm sure others will chime in with other ideas. Good luck!
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #5
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    I guess also are you sure it was disconnected for that reason? you didn't leave your water heater hooked up? or wife decided to bake on an electric stove?

    ...or as Ramloui iluded to, you do have heavy enough wiring to your inverter?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • CVN-71
    CVN-71 Solar Expert Posts: 54 ✭✭
    #6
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    Thanks guys,

    After it tripped off the first time I shut it off and reset it. When I put load back on, it ran for a few minutes before it shut down again. Load was 200w electric aquarium heaters and 100w aquarium pumps, 300w total, not much. It had run for 17hrs with this continuous load, plus a coffee pot for 5 mins and the refridge for a few hours. I would think a bank of 8 AGM L-16's at 24v, 800amp 20-hr rate would be able to power this much for longer. The batteries are about 7 yrs old however but normal use has been small discharges. I've only had a 50% discharge once. There is not much voltage drop from batteries to inverter, cable is only 3'.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #7
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    The reason I asked about the age of the batteries. Batteries loose capacity as they age, still you drew out 5.1 kwhs from the aquarium loads and likely another kwh or 2 from the fridge depending on size and age. The inverter took over a kwh between the efficiency converting and self use. So you were near 1/2 capacity if they were new, if they are in un heated space that could account for less capacity as well....

    No additional loads, lights, heat strips, wall warts...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • CVN-71
    CVN-71 Solar Expert Posts: 54 ✭✭
    #8
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    Thanks Photowit, but why would the inverter LVCO even activate, it's getting it's own reading which was 24.4v?
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #9
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    If there was another appliance that tried to turn on the V drop may not have shown up on the Inverter readout, &/or there is a loose connection too. Have you re-torqued them ALL in the last year? It should be an annual event.
    Also have you checked their electrolyte level and have you checked the SGs lately? you may have a low SG cell or 2..
     
    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
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #10
    Re: Magnum Inverter, low power cut off, cutting of before set point?
    CVN-71 wrote: »
    Thanks Photowit, but why would the inverter LVCO even activate, it's getting it's own reading which was 24.4v?

    I think that reading was when you saw it, after it rebounded. If you have diminished capacity you might have had an event that triggered the low voltage cut off, indeed if it was a major appliance that tried to cut on, as I was trying to suggest as a likely reason for a cut off that was due to overloading the inverter rather than a low voltage, since the voltage was so high. I really don't understand the voltage reading that high, and having triggered a LVCO unless it was from too small a wiring or as westbrach suggested a loose connection.

    You might take the time to disconnect the 2 strings of batteries and see if there is a voltage difference between the string and individual batteries. If still connected the voltage reading will represent both strings, they just need to be dis connected at one point for each string. This could give you some information on the state of your batteries a bad cell should be readily apparent, but a weak cell might take a little while to appear low since the string will try to balance out.

    The 24.4 is a pretty good voltage after such a large draw down, it might indicate reasonably good batteries. Checking the connections then I might turn things back on once again and watch the voltage reading. Batteries under load will have a lower voltage reading than batteries at rest. Also you might be getting some minimal charging going on even with snow covered panels, if any current is coming in the charge controllers will bring in the voltage above the resting voltage of the battery so the current will flow into the battery. This is the higher voltage might be what your seeing when the inverter is disconnected.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #11
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    Since you have an E-panel it should be simple to turn off the breakers to and from the charge controllers.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • CVN-71
    CVN-71 Solar Expert Posts: 54 ✭✭
    #12
    Re: Magnum Inverter, low power cut off, cutting of before set point?

    That makes sense, I'll check connections, haven't done that in a while.
    Photowhit wrote: »
    I think that reading was when you saw it, after it rebounded. If you have diminished capacity you might have had an event that triggered the low voltage cut off, indeed if it was a major appliance that tried to cut on, as I was trying to suggest as a likely reason for a cut off that was due to overloading the inverter rather than a low voltage, since the voltage was so high. I really don't understand the voltage reading that high, and having triggered a LVCO unless it was from too small a wiring or as westbrach suggested a loose connection.

    You might take the time to disconnect the 2 strings of batteries and see if there is a voltage difference between the string and individual batteries. If still connected the voltage reading will represent both strings, they just need to be dis connected at one point for each string. This could give you some information on the state of your batteries a bad cell should be readily apparent, but a weak cell might take a little while to appear low since the string will try to balance out.

    The 24.4 is a pretty good voltage after such a large draw down, it might indicate reasonably good batteries. Checking the connections then I might turn things back on once again and watch the voltage reading. Batteries under load will have a lower voltage reading than batteries at rest. Also you might be getting some minimal charging going on even with snow covered panels, if any current is coming in the charge controllers will bring in the voltage above the resting voltage of the battery so the current will flow into the battery. This is the higher voltage might be what your seeing when the inverter is disconnected.
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