inverter problem

johnd765
johnd765 Registered Users Posts: 2 ✭
in Off Grid Solar & Battery Systems #1
I have an Outback inverter connected to a 24v system, 1kw.  It has worked fine for a few years.  Recently, the inverter started to shut down under load, anything over 6 amps.  My controller app shows that when it kicks in, the inverter drains the battery in 5-20 seconds, even when the batteries are at float and the sun is high.  I am running hand tools on a job site, saw, drill, grinder, etc.  Nothing over 10 amps.  Is my inverter toast?  I have a Victron Energy controller that is less than a year old and has performed well.

If so, I plan to upgrade to a 48v system in about a year.  I have already upgraded my panels.  Is there an inverter than I can buy now that will auto-detect 24 or 48 volts, or do I need to upgrade the inverter and the batteries at the same time?  I plan on going with Li batteries, as opposed to my lead acid batteries that I am using now.

Thanks.
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  • 706jim
    706jim Solar Expert Posts: 521 ✭✭✭✭
    #2
    If this inverter "drains the battery" in 5-20 seconds it sounds as if there's a dead short somewhere. How big is the battery?
    Island cottage solar system with appriximately 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing due south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter which has performed flawlessly since 1994. Outback Flexmax 80 MPPT charge controller four 467A-h AGM batteries. Insignia 11.5 cubic foot electric fridge 1/4hp GSW piston pump. My 31st year.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #3
    Check the DC input terminals of the AC inverter... And the Battery Bus voltage too. Poor electrical connection, battery dying? 

    For a 24 volt system... Should see around 23.0 volts to 30 VDC at the inverter's DC input terminals. And if the terminal voltage falls below ~21.0 volts, the AC inverter will generally shutdown.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • johnd765
    johnd765 Registered Users Posts: 2 ✭
    #4
    (4) 6v Trojan batteries, 208 ah.  Voltage at the inverter terminal is 28+ volts.  Batteries are 4 years old with light duty usage, all during daylight hours.  All my connections look clean, but I'll go through them again.  What leads me to think it's the inverter is that this happened suddenly.  A solar tech told me it might be a bad capacitor in the inverter.

    When I turned on an 8 am power tool, my controller monitor showed the solar was inputting about 12 amps, but the inverter was drawing 56 amps from the battery.  That pulled the battery down quickly to 15v and the inverter shut down.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #5
    johnd765 said:
    (4) 6v Trojan batteries, 208 ah.  Voltage at the inverter terminal is 28+ volts.  Batteries are 4 years old with light duty usage, all during daylight hours.  All my connections look clean, but I'll go through them again.  What leads me to think it's the inverter is that this happened suddenly.  A solar tech told me it might be a bad capacitor in the inverter.

    When I turned on an 8 am power tool, my controller monitor showed the solar was inputting about 12 amps, but the inverter was drawing 56 amps from the battery.  That pulled the battery down quickly to 15v and the inverter shut down.
    Trojan 6v 208 ah doesn't jive with any that I'm familiar with. I think Sam's club had/has some 208 ah 6 volt batteries.

    Here's a Trojan Product spec brochure. I was wondering if they were gel or AGM batteries.

    TRJN0111_ProdSpecGuide.pdf (trojanbattery.com)

    If they are flooded batteries, have you equalized them? 56 amps on a 24 volt system would be a very large load, You specify a 24 volt 1kW system. Is the inverter a 1Kw inverter (or are you describing your array?) If so a a 1 kW inverter should shut down after a brief time at 56 amps, understand as the voltage goes down the amp draw goes up.

    With a high draw you are correct to check all your connections. 

    If it is a flooded battery bank, I'd suggest letting the charge controller go through the charging cycles and once you reach float to equalize your battery bank. Batteries actual 'like' to be cycle gently. 

    Trojan Tips 5 - Equalization is Key to Extending Battery Life and Performance - YouTube

    Understand that applying a 50 amp load to a 208 ah battery bank presents it's own set of problems. It's drawing 1/4 of the capacity per hour, so the battery bank will have a considerably lower capacity at this high of draw. The link to Trojan's product line will show their 210 ah battery at they 20 hour discharge rate is only 175 ah at a 5 hour discharge rate.

    If you happen to be in Missouri, I have a 360 ah 24 volt battery bank I could lend you for a while. I just picked it up for it's trade in value, but they appear functional, Held voltage as I ran my window unit on the...
    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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