Gen low voltage

palausystem
palausystem Solar Expert Posts: 124 ✭✭✭
in Off Grid Solar & Battery Systems #1
The inverter disconnected the gen for low voltage reasons. Can anyone tell me what might cause the generator to produce a lower than acceptable voltage?  We've not had this problem before. The inverter is set to accept the minimum and maximum it will allow.
Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Loading the generator near it's maximum can cause voltage to drop, high temperature of the windings will compound the problem. By "it" in this sentence "The inverter is set to accept the minimum and maximum it will allow." are you referring to the generator or the inverter?
    Have voltage/amperage measurement been taken ? Have all terminals been checked ? Sorry to answer a question with  questions but it's nesesary to establish a possible cause. 
     
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #3
    What is the generator .. ?
    If your baisic  one,    the voltage regulator capacitor may have failed . Easy to replace  $30.00 approx here .. Utube it .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • Mzee
    Mzee Registered Users Posts: 4 ✭
    #4
    It would be helpful to get more information: Generator brand, model, rated size, fuel type and voltage readings both when unloaded and loaded. Does it have adequate voltage until the inverter tries to connect or is it simply low even without load. Does the engine seem to be running normally or is it running slowly, missing etc?
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  • palausystem
    palausystem Solar Expert Posts: 124 ✭✭✭
    #5
    Thanks for all that. 
    I did the easy thing and reduced the load on the generator by a couple amps.  The output had been 117.3v under load, now it's at 119v. Not sure but I think the low voltage set-point was 117.
    The "it" is the inverter, it allows a certain window of fluctuation higher and lower than the 120 it's supposed to get from the gen. It's at its widest setting
    I have not checked V and A, other than via the inverter readout in real time. I have not checked the terminals.
    Generator is Kohler 8.5 RES.  Propane. Engine seems to run smooth. I haven't checked the V while not under load.
    Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #6
    Can the inverter use 240V as the input voltage rather than 120V, perhaps the imbalance of tapping half the generators output is causing the problem, just a thought. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • palausystem
    palausystem Solar Expert Posts: 124 ✭✭✭
    #7
    Good Question. Unfortunately the Sunny Island inverter only accepts 120. I was not too knowledgeable when I bought the Kohler. I was concerned about the potential imbalance, but it never seemed to be an issue. After running it for a few years I even had the wiring changed to use the other leg of the system. So I don't think that's it.  We had a technician come out to change a part a few years back and he tested output and all seemed good.   
    Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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  • palausystem
    palausystem Solar Expert Posts: 124 ✭✭✭
    #8
    Will be at the site tomorrow and will post voltage not under load.
    Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #9
    Ideally you would also check frequency.   Consider bumping up the rpm a little bit (1 hz  = ~2 volts unless a voltage regulator is controlling it).

    I am available for custom hardware/firmware development

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  • palausystem
    palausystem Solar Expert Posts: 124 ✭✭✭
    #10
    New info.  I poked around in the settings and found that the inverter will accept 80v to 150v from the gen. When under load the gen is showing 117.5 on average.  So seems like I don't need to adjust anything.  So either it was a strange anomaly, or there is something defective somewhere...in any event, I'm tempted to wait and see if it happens again. 
    Silicon controlled rectifier  (SCM) module is something in the gen manual that helps control voltage. There are some tests that can be done on it.  May need to become handier with the multimeter.
    Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #11
    A largish intermittent voltage drop sort of says problem connection(s) somewhere... not all that unusual given the vibration and temperature variation generator connections get.

    One trick I got from others here when I had problems diagnosing a generator issue is to add a load when checking continuity.  A multimeter only puts a tiny current through, and a problem may only show up with a load.  I rigged up a filiment bulb load, and sure enough a connection that previously test good wasn't.
    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
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #12
    It is always good practice on PV installations to do a yearly re-torquing :)  of all connections, copper does 'creep' :* under pressure. 
     
    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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  • palausystem
    palausystem Solar Expert Posts: 124 ✭✭✭
    #13
    Thank you,
    What a great forum. I will do some re-torquing today.
    Merry Christmas
    Off-grid 48v, 3 kw PV, Sunny Island 5048U, SunnyBoy, US Battery RE L16XC  6v, 800ah, Genset: Kohler 8.5 RES propane.
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