Inverters Wired in Parallel?

BajaGringoBajaGringo Posts: 40Solar Expert ✭✭
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???

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  • WindsunWindsun Posts: 1,164Solar Expert ✭✭
    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.
  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    Re: Inverters Wired in Parallel?
    BajaGringo wrote: »
    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 !!:cry:

    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.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • john pjohn p Posts: 814Solar Expert ✭✭
    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..
  • BB.BB. Posts: 28,088Super Moderators, Administrators admin
    Re: Inverters Wired in Parallel?

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

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • www.HyperionLED.comwww.HyperionLED.com Posts: 7Registered Users ✭✭
    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
  • BB.BB. Posts: 28,088Super Moderators, Administrators admin
    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:

    wind-sun_2095_821490Surrette 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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BajaGringoBajaGringo Posts: 40Solar Expert ✭✭
    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.
  • audredgeraudredger Posts: 272Solar Expert ✭✭
    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!!
  • solarhousesolarhouse Posts: 1Registered Users
    I have a project that would involve 6 units of 5kva KP series inverters from Felicity solar, and I intend to wire them in 3 parallels of 2 units each, so that each unit has an output of 10kva and so also so that I can have a 3 phase system with 10kva on each line.
    My challenge is that on the operations setting option "program 28", the parallel and 3pase options seem to be alternate to each other and I need the both options since I Will be have 2 inverters on each line wired in parallel and to have the 3 lines linked to a common neutral and expect them to be at about 120degrees phase apart.
    So I need your helpful advice's.
    I am also available on WhatsApp (+2348036511632)
  • gusscottgusscott Posts: 1Registered Users
    I have a 24kWH lithium battery bank. I run a 2kW inverter at 24V. I have a spare identical inverter and was wondering if I can put them in series and rewire my battery bank to 48V? I know phasing (and blue smoke!) is a problem/issue when you parallel two inverters but I was wondering if putting them in series would be OK. So would still then get 4kW from 48V??
  • mcgivormcgivor Posts: 2,334Solar Expert ✭✭✭✭✭
    edited November 10 #12
    gusscott said:
    I have a 24kWH lithium battery bank. I run a 2kW inverter at 24V. I have a spare identical inverter and was wondering if I can put them in series and rewire my battery bank to 48V? I know phasing (and blue smoke!) is a problem/issue when you parallel two inverters but I was wondering if putting them in series would be OK. So would still then get 4kW from 48V??
    Pretty sure you would be dissapointed with the results should you attempt that, go parrallel but not series on the DC side.. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • littleharbor2littleharbor2 Posts: 1,072Solar Expert ✭✭✭✭
    edited November 9 #13
    Connecting both inverters to your 24 volt battery bank shouldn't cause a problem. Bringing the output together in parallel (120 Vac. ) or series (240 Vac. ) WILL be a problem unless said inverters are designed to be ran in this configuration, is there any series stacking cable input port on the inverters?

    Here is a couple wiring diagrams for inverters that are designed to be parallel or series stacked., BTW what inverters do you have?

    http://www.xantrex.com/documents/Inverter-Chargers/Freedom-SW-NewGen/97-0026-01-01_Rev-A(Freedom%20SW%20Stacking%20Guide).pdf

    https://www.solarpanelstore.com/pdf/xan-dri.pdf

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    You cannot series the DC side of inverters to make 24VDC inverters run off of 48V. 

    Unless the inverters have a "Stacking Cable" you cannot connect the outputs of them to each other. (series or parallel)
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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