New 4x100W system with 4 Sunforce controllers. AGM Battery voltage reaching up to 17v. Inverter cuts

nkgeicher Registered Users Posts: 2
This new hobby developed during Covid isolation period. Live in Troy, Michigan, 48098
got 4sets of Sunforce 100W panels and 8.5 A charge controllers. Put them in Parellel.
the output from Controllers on a single wire to 80 AH new Werner Deep Cycle AGM battery.
Fixed one 1000W inverter. Load is only 15-17W fixed, for my WiFi. So in 24 hours I don’t need more than 500WH.

Now the problem I am facing is the charging rate from controllers to battery is very high, up to 17.5V, once the battery is full. They are not cutting off at 14.2v, as mentioned. 

The result is my inverter gets cut off at 15v (high input voltage). If I remove the input charging wire to battery, then the voltage drops to 13.1, and everything works well till battery depletes about half to 11.6v.

Question. — how to make four charge controllers cut off when battery is 14.2v.

is there anything else I am doing wrong?


  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    With a battery voltage of 17.5V it would appear that a controller has failed short circuit allowing the maximum panel voltage to reach the battery, which will ultimately result in the death of the AGM battery through loss of electrolyte.

    To diagnose this connect each controller individually when the battery is fully charged to verify it is regulating the voltage, if a single controller is at fault, the resulting higher voltage would cause the remaining controllers to regulate making it impossible to pinpoint the cause, divide and conquer is the approach.
    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.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Be sure each controller is configured properly, and has any needed thermal sensors connected.

    Connect the controller first to the BATTERY to allow it to boot up, and then to the PV panel.
    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

    gen: ,

  • nkgeicher
    nkgeicher Registered Users Posts: 2
    Dear MCGIVOR and MIKE.

    Thanks a ton for your valuable inputs. In fact I just came back to my home yesterday and today followed the tips. I made following trials and now problem resolved:
    1. I brought charger/s closer to battery. From 40’ to 2’. 
    2. Also connected the battery before solar panel, as suggested by Mike.
    3. Then tested all 4 chargers. Perfectly cutting at 14.2 V, as required.

    This is a Great forum and you guys are Greatest!!!

    Thanks again.