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Thread: Inverters Wired in Parallel?

  1. #1

    Default Inverters Wired in Parallel?

    I was looking for a 5000 watt inverter and a friend told me he has two 2500 watt inverters he would give me that could just be wired in parallel for the same result. Anybody here done that???

  2. #2

    Default Re: Inverters Wired in Parallel?

    Most inverters you cannot because they would be out of phase. A few, such as some Trace/Xantres, Outback, and Magnum can be paralleled. Without knowing which model he is talking about, unable to say.
    Northern Arizona Wind & Sun Forum & Website Administrator

  3. #3
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    Default Re: Inverters Wired in Parallel?

    Quote Originally Posted by BajaGringo View Post
    I was looking for a 5000 watt inverter and a friend told me he has two 2500 watt inverters he would give me that could just be wired in parallel for the same result. Anybody here done that???
    Most folks that do that, only make that mistake one time !!

    To wire inverters in parallel, you need a Sync connection, to keep the inverters in phase with each other, like in a car, you use a clutch to prevent grinding gears when going from 2nd to 3rd. No sync, and it gets tough in a transmission, in an inverter the magic smoke comes out from the insides.

    There are no Mod-Sine inverters that can be ganged, that I know of, only pure sine wave inverters.
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    Default Re: Inverters Wired in Parallel?

    What are you wanting to run off a 5000w inverter? if you have many loads that add up to about that just wire the two inputs of the inverters to the batteries and divide the load over the 2 inverters..

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    Default Re: Inverters Wired in Parallel?

    The other question is what voltage battery bank are you looking at for 5kW of loads--hopefully 48VDC.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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    Default Re: Inverters Wired in Parallel?

    I have a question:

    Not sure why a 48 volt Battery bank is necessary. It seems as long as you have the proper size cable running to each inverter you should be fine.

    Are there battery stresses just from running loads that require a lot of amps to be pulled from the battery bank. I understand that a 48 volt battery bank would have 1/4 the amps as a 12 volt battery bank. But what is there to consider if you want to pull say 10,000 watts from a 12 volt battery bank? Will the battery voltage drop too low if you draw that much at 12 volts? even if your connector cables are huge?

    Thanks

  7. #7
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    Default Re: Inverters Wired in Parallel?

    One is the current at 5kW and 12 volts:

    • 5,000 watts * 1/10.5 volts cutoff * 1/0.80 eff * 1.25 NEC safety margin = 744 amp circuit

    If you are looking at running those load level for any appreciable amount of time--you are looking at a C/5 or C/2.5 discharge rate minimum at 12 volts:

    • 744 A * 2.5 hour rate = 1,860 AH rate battery
    • 744 A * 5 hour rate = 3,720 AH rate battery

    The largest cell our host sells:

    Surrette 2KS-33PS Deep Cycle Battery
    1766 Amp-Hour, 2 volt

    208 lbs...

    The other issue is wiring drop... The cutoff voltage for a 12 volt device is typically 10.5 volts. Low battery voltage is around 12 volts... That gives you ~1.5 volts for all the rest of the wiring/fusing/breaker/switching drops in the harness (at 744 amps).

    • 12 volts - 10.5 v = 1.5 volt drop
    • 24v - 21v = 3 volt drop
    • 48v - 42v = 6 volt drop

    So--just from a practical point of view--your voltage allowed voltage drop is much better (6 volts) and at 1/4 the current--you can just ship a power a whole lot easier at higher voltages.

    Also, generally high current values require paralleling battery banks--more fusing/breakers, more expenses, more difficult to share current among multiple parallel strings (I like to recommend no more than 2-3 parallel strings--although many people out there do put more banks in parallel).

    -Bill
    Last edited by BB.; April 4th, 2010 at 19:10 PDT.
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  8. #8

    Default Re: Inverters Wired in Parallel?

    The problem is that I have one wire run from my power room to where the main breaker panel is in the new place. My idea was to setup my power room with the ability to switch between solar/wind to generator with just the flip of a switch. I only have three wires in the conduit from the power room to the main panel and so dividing up the breakers between two inverters is not an option unless I do some major drilling on the walls. My home is steel reinforced concrete fill cinderblock so drilling through walls is not a simple task.

    Maybe it is a really good thing I am asking this question as it also makes me stop to consider that maybe I am just looking at overkill on the inverter. I estimate my daily average power usage at just a hair over 4kw and perhaps just one 2500 watt inverter will do me just fine. I have six 150 watt panels and a wind turbine feeding my battery bank of six 12v 8D batteries rated at 225 ah each wired in series/parallel for 24 volt output.

  9. #9
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    Default Re: Inverters Wired in Parallel?

    I estimate my daily average power usage at just a hair over 4kw
    I use between 6 and 7 KWh a day and do it on a 4,000 watt inverter. System is 24v but want a 48 v system, some day..
    As Bill says; best to limit banks to 2 or 3 ... I have 6 banks and its a pain! When this bank dies, not to soon I hope, I will go to 48 v. If I stay with FLA batteries, they will be the largest 2 v they make!!
    MIke
    Off Grid: 3150 Watts pv, FX80 & MX60, Xantrex 4024+, 24 L16H, EU2000i & 20hp Listeroid 12KW Diesel

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