Off-grid "Brown-Outs" - Need to Diagnose the Cause

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mjp24coho
mjp24coho Solar Expert Posts: 104 ✭✭✭
in Off Grid Solar & Battery Systems #1
I'm looking for some advice on trouble shooting a recent problem with my offgrid system. I'm at my cabin this week (it's been a few months), and run it 100% off solar/battery (see specs in my signature). During the day, my batteries are charging well, and my loads are minimal. At times the power will go down for a half or full second (a bit more pronounced than a brown-out, but the inverter is not fully shutting down). The lights will go off for under a second, and then everything returns to normal. Sometimes it is when no loads are kicking in, but at other times it is when the 1/2 HP booster pump surges on, or the compressor on the fridge kicks on. A few times it happened while running a small vacuum (not while it kicked on). None of these loads were running at the same time, so I don't think it's an issue of 2-3 high-amp surges hitting all at once. The inverter should be more than capable of handling a surge of any of these loads (only other loads running are a few lights, IP cameras, and internet equipment). My forklift battery has been ranging between 25.5V-24.6V when this occurs. I never really experienced this the first year after my system install, but it has happened my last two times at my cabin over the past 5 months. It is becoming a problem, because each time this occurs it restarts all of my electronics equipment (router, satellite internet dish, IP cameras, WEL monitoring system, etc). Any thoughts on how to best diagnose the issue?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #2
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    My first guesses are:
    1. Loose electrical connections (retorque all electrical bolts/screws)
    2. Dirty electrical connections (check for hot connections, look for corrosion)
    3. Corroded battery cables (electrolyte wicked up cables--Look for heat/melted plastic insulation)
    4. Battery cell failure (cracked battery post/plates)
    5. AC inverter problems (measure voltage at input to AC inverter--See if there is DC bus voltage drop when AC fails)
    My guess are probably 1, 2, & 5 are most likely (given that problem comes and goes). Try tapping the electrical connections (and even give the the inverter a few whacks--carefully) with a plastic/wood hammer -- Flex cables -- etc... Looking for the problem to get worse (or even temporally better).

    You might have problems with a typical volt meter "catching" a voltage drop out a the DC inverter input--Most simple volt meters just sample/display the voltage once a second or so... Fluke has some min/max hold meters:

    How To Use Fast-Peak Min-Max On Your Digital Multimeter

    Perhaps somebody here can give you some less costly meters that would do a min-voltage capture.

    I would also give Magnum a call directly and see if Tech Support has seen this problem with their inverters before.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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