Power fails with load

seamonkey
seamonkey Registered Users Posts: 9 ✭
in General Solar Power Topics #1
Two 12V marine deep cycle batteries wired in series.

24V Inverter

two 17V panels

Checked - 24V going into the inverter

I set up the system for a small office. When I plug in a printer, it starts then stops over and over. Its as though it loses the power when placing a load.

Any ideas?

Thanks
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Comments

  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #2
    Re: Power fails with load

    Laser printer? Those use a high wattage lamp (light bulb) to heat the fuser and they draw a lot of power until they are "warmed up".
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #3
    Re: Power fails with load

    I also understand A lot of printers do not like msw (modified sine wave) inverters. Can you give more details as in what type of equipment you have?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Power fails with load

    What is the inverter input voltage when the load is active? Most 24 volt inverters will cutoff around 21 VDC.

    By the way, what is the unloaded/resting voltage of the battery bank... A fully charged bank should be around 25.4 volts.

    24.0 volts is around 50% state of charge.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • seamonkey
    seamonkey Registered Users Posts: 9 ✭
    #5
    Re: Power fails with load

    Thanks for responding.

    The Battery shows 24.7V with no load.

    24.2V with load (two light bulbs turned on)


    I just put the meter on output on inverter (24V, Vanner IT). It jumps from 119V to 3 to 44 all over the place mostly at zero. I guess the vanner inverter is shot.


    BTW,
    How many watts do I need to power a little office compared to a small 800sqf house?

    Thanks!
    Dave
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Power fails with load
    seamonkey wrote: »
    Thanks for responding.

    The Battery shows 24.7V with no load.

    24.2V with load (two light bulbs turned on)


    I just put the meter on output on inverter (24V, Vanner IT). It jumps from 119V to 3 to 44 all over the place mostly at zero. I guess the vanner inverter is shot.


    BTW,
    How many watts do I need to power a little office compared to a small 800sqf house?

    Thanks!
    Dave

    Well my little office is the second largest daily power consumer in the place, next to the refrigerator. That is with no laser printer. Dropping the desktop computer in favour a of a laptop was a major power save.

    BTW, your battery Voltage is too low (my system is normally over 25 Volts when not charging or floating) and it could be the wire size to the inverter is insufficient, resulting in further Voltage drop. Is this a MSW or PSW inverter?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: Power fails with load

    What is the 24 volt bus reading at the Inverter DC input? If it drops below ~21 volts--The inverter will cutout...

    We always suggestion conservation first, then measure your loads... Both Peak and average Watts, and Watt*Hours / kWH. Towards that end a Kill-a-Watt meter is a great way to do that.

    Once you know your kWH per day use, then you can work backwards and size the battery bank and solar panels for your loads (based on your location).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • seamonkey
    seamonkey Registered Users Posts: 9 ✭
    #8
    Re: Power fails with load

    Interesting. I didn't know the battery should produce more than 24V.

    The inverter is a Pure Sine Wave (if that is what you mean by PSW) Vanner IT 2400.

    I only plug in my laptop once in a while. In the office there is only one outlet for the printer, charging the lap top and a light. So I use very little power.

    I was reading something about 'Islanding" where the inverter put out pulses to see it you are on a grid or not. In my case. The office is completely off the grid.
    Which is what I am trying to accomplish.

    I was reading something about "islanding" where the inverter sends out impulses to check for connection to a grid. NOt sure if that explains the pulsing AC voltage I saw on the meter.

    Anyway, I will charge up the batteries and see if there that makes a difference.

    Thanks
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Power fails with load

    Two different types of inverter: grid tie and off grid. Except for a few "hybrid" exceptions, they aren't interchangeable. If yours runs off batteries it is probably an off-grid inverter. It won't be looking for any AC power.

    In short, it shouldn't be "pulsing" or varying output Voltage much at all. The usual cause of output variation for off-grid is DC input Voltage dropping suddenly due to loads overwhelming the battery bank. Most of the time this will be because the wires to the inverter are too small to carry the current load necessary to maintain output.

    That's not very clear. Sorry.

    So how many Watts is this inverter, and how large and long are the wires connecting it to the battery?
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #10
    Re: Power fails with load

    You are describing a standby search where a inverter, to save power when there is no load, will wake up periodically to see if there is a load and then stay active until load drops to a low wattage again.

    Islanding, is a term used for grid tied inverters, where the inverter verifies a valid grid presence by attempting to wobble its phase lock with the grid. The grid, if present, will absolutely resist any such attempt. The inverter will detect an increase in current as it tries to shift its phase relative to the grid.

    This prevents a grid tied inverter from powering an open circuited grid. This may include your neighbors house when grid goes open circuit.
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  • seamonkey
    seamonkey Registered Users Posts: 9 ✭
    #11
    Re: Power fails with load
    Cariboocoot wrote: »
    Two different types of inverter: grid tie and off grid. Except for a few "hybrid" exceptions, they aren't interchangeable. If yours runs off batteries it is probably an off-grid inverter. It won't be looking for any AC power.

    In short, it shouldn't be "pulsing" or varying output Voltage much at all. The usual cause of output variation for off-grid is DC input Voltage dropping suddenly due to loads overwhelming the battery bank. Most of the time this will be because the wires to the inverter are too small to carry the current load necessary to maintain output.

    That's not very clear. Sorry.

    So how many Watts is this inverter, and how large and long are the wires connecting it to the battery?

    Thanks.

    Vanner IT24-3500: literature says 3500 watts output.
    I'm using the thick battery cables in series.

    I measured 24V at the input of the inverter, so the Batteries must be connected properly and I am using really heavy battery cables. I wonder if one of the batteries is bad (one I just bought from Walmart. the other is an older one but measured 12 Volts)

    I put the charger on it and the charger indicated low. How is that when the multimeter measured 12volts?

    Anyway, I need to assess the batteries and see if charging makes a difference if so then the battery(ies) are not holding the power.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: Power fails with load

    Voltage isn't a very good indicator of a battery's condition. Over time, a large battery can become sulphated; it will still read "12 Volts" but instead of having 100 Amp/hrs capacity it could be much less.

    To know if the batteries are any good, either check each cell with a hydrometer (if they're not sealed) or measure the Voltage with a heavy load on. If the load causes the battery Voltage to drop (and it's a judgment call as to how much is too much, because there are a number of factors involved) significantly the inverter's output may drop.

    I doubt you're pulling anyplace near the inverter's maximum capacity of 3500 Watts. Probably not even 1/10 that. At 240 Watts you'd only be drawing 10 Amps.

    What constitutes "thick" wire? For some people it's 8 gauge. For inverter use it's more like 2 gauge.

    I think you may be right to suspect your batteries. If you have no hydrometer (or they are sealed) charge them up fully from a good battery charger. They should read at least 12.5 Volts afterward. Then leave them sit for a day with no draw or charge and check the Voltage again. It should still read 12.5 Volts. Don't be surprised if it doesn't.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #13
    Re: Power fails with load

    Laser printers pull 1000-1200 watts when active ... I bet your battery's aren't charged and are collapsing under the load causing the inverter to shutdown
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #14
    Re: Power fails with load

    here is a good basic read about battery voltages http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery%20Voltages jump on down to "battery voltages" but the whole page is a good read ;)
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