Midnite Classic 250 - Whining noise when running (?)

JimNAZJimNAZ Posts: 26Registered Users ✭✭
As the title says, loud whining noise when running. Any thoughts on trouble shooting?



  • littleharbor2littleharbor2 Posts: 1,072Solar Expert ✭✭✭✭
    Is this an old controller? The 3 fans in these controllers can be quite noisy. What voltage are you inputting and charging batteries at? The higher the differential the harder the controller will be working. If it's got some miles on it you may need to replace a failing fan.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • JimNAZJimNAZ Posts: 26Registered Users ✭✭
    It is just over 3 years old. Have a bank of 20 batteries wired for a 24v system with 2000+ watts of panels.
  • mcgivormcgivor Posts: 2,336Solar Expert ✭✭✭✭✭
    Are you young with good hearing? There may be radio frequency that younger ears can hear which go unnoticed by older people who have lost the upper frequency detection, or perhaps your hearing is more acute, if of course it's not the fans.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • EstragonEstragon Posts: 2,962Registered Users ✭✭✭✭✭
    What is the voltage into the classic from the array, and what is the battery voltage when you hear the whine?

    Mine make a high pitched sound when Varray is close to Vbatt (eg. Varray 54v, Vbatt 52v), typically when they try to bulk in gloomy weather. Normal Varray is ~100v in decent light. IIRC, there's a setting you can disable (might be arc fault) to minimize the noise if it's driving you nuts, but it isn't hurting anything.
    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
  • Raj174Raj174 Posts: 648Solar Expert ✭✭✭✭

    It has a 5 year warranty, call  Midnite Solar tech support.

    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • littleharbor2littleharbor2 Posts: 1,072Solar Expert ✭✭✭✭
    The Classic 250 is rated at 62 amps @24 volts. 2000+ watts is pretty much overpaneling it. Again, what is your input voltage/ string configuration?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    The classic has 2 normal cooling fans and a 3rd "Turbo" fan that kicks in if the others are not enough,  Since you are overpaneled, I expect it to be running hot and needing the fans,
    They also use a switcher supply, which operates in the ultrasonic range, and you may be hearing that, or sub-harmonics.
    (You are not hearing RF, unless you have implants that allow for that.)
    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 ,

  • JimNAZJimNAZ Posts: 26Registered Users ✭✭
    At 9:30am 110v coming in and it's at Bulk MPPT with no noises. I'll check again in the afternoon when the fans are loud.
    I have bad hearing so any funky frequency sounds are not heard by me. 
    The original setup was 4 250w panels. This spring we added 4 265w panels. The 250's are wired together and the 265's are wired together for 2 sets coming in to the controller. This is how Northern AZ Wind & Solar told me to wire and said the controller could handle it.
    As a side not, the controller is very warm to the touch when making the noises.

    thanks for everyone's feedback!
  • PhotowhitPhotowhit Posts: 4,747Solar Expert ✭✭✭✭
    It is just running hot, it's converting the 110 volts coming in, to charging voltage for the 24 volt battery bank. Usually suggest about double the battery bank voltage.

    Often the 200 and 250's are sold due to long wire runs so people can run higher voltage and save the cost of heavy wire for long distances. Since you have 2 strings of panels it also saves you from having to buy a combiner box.

    The 250 is designed to handle the higher voltage so I don't think it's a real problem just and annoyance. Is this a new sound? I know they had an issue with very early software and the turbo fan kicking in before it was needed (or at least that's my memory of the situation) I would suggest finding your firmware version and contacting Midnite. They have very good customer service!


    You could even look and ask question on their forum;

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
Sign In or Register to comment.