connection of two 3.3 KW inverteres

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hi Guys, we are new here.
we have a system to run a 3.3 KW, 6 x 140 watts solar panels plus 2 wind turbines rated at 400 watts each, this than going to a bank of 2v time 12 bataries (at 1000 ampH)and going to a 3.3KW inverter 24v to 230V,
we are running one house on it with no great difficulties however we want to run our other house too...
can we therefore have say extra 3 panels at 230 watts each to feed more power to the bateries and than take another connection through a bus bar from the same bank of bataries to go to a second inverter of 3.3KW?
will this work without damaging the bateries ?
thanks guys
us in south sunny Spain
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: connection of two 3.3 KW inverteres

    Welcome to the forum.

    Let's break it down into steps and see what we get.

    First off, it is possible to run more than one inverter from the same battery bank. Each needs its own wiring and circuit protection of course.

    So the issue comes down to: is there enough charging for the battery bank and can the bank withstand additional loading?

    It would help a lot here if you had a battery monitor that would tell you how much is going in/out of the battery bank and what sort of SOC you are able to maintain at this time. If you are now using up to 50% of the battery capacity daily, adding a second inverter is inadvisable. If you are using less than 25% it would not be a problem providing the additional load did not exceed 25%. In other words together the two inverters' draw should not exceed 50% of the battery bank capacity. That is roughly 250 Amp hours @ 24 Volts or 6kW hours daily (including the inverter's power consumption).

    Simply adding more panels will not make a difference unless you can guarantee that the majority of power use is during the day when the batteries are already fully charged. To that end you have an 840 Watt array now, which is hardly adequate for that battery bank which means you must be relying on the wind turbines. I hope they're good ones. Unfortunately small wind turbines tend to be greatly over-rated in their output estimates. In AC Watt hours, you could expect about 2kW hours from the array you have now. If you can't replace the Watt hours used each day you will have deficit charging. This means the batteries will eventually go dead. In the mean time, their capacity will be going down and you will not notice it.

    We're it me, I'd want to see two arrays on that battery bank, each with its own controller and capable of 50 Amps @ 24 Volts or 1200 Watts which would be probably a 1600 Watt array. If the turbines put out anything, consider it a bonus. This way you'd have 3200 Watts of panel which should be capable of 8kW hours per day which would probably serve two houses.

    But you really need some hard numbers on your production and usage now before you can determine if it's feasible to add the second inverter.
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  • TnAndy
    TnAndy Solar Expert Posts: 249 ✭✭
    #3
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    Re: connection of two 3.3 KW inverteres

    Yes, you can run two inverters. That is how mine is setup, I have two 2500w, 120v inverters that produce a 240v output. ( required by my utility to grid tie ).

    I had two arrays of 1750w, two 60amp charge controllers feeding a 24v 1200amp/hr battery bank. In the photo below, you can see one of the charge controllers ( the other is just to the left out of photo ), that feed to a small SquareD brand panel tucked under the inverters ( breaker for each charge controller ), then feed the battery bank. From the battery bank, up to that white Xantrex double 175amp disconnect on the far right, then into the pair of Outback inverters ( black, center ), then into the Flexware AC panel. The Outback Hub on the side of the Flexware box controls the two inverters to synchronize phase output of a pair of inverters ( black box on the Flexware left side )

    Since the photo was taken, I've added another array of 2450w and an 80 charge controller to the mix. I did that so I'd max out the ability of the inverters to back feed the grid. ( Just under 6kw total panel wattage ). We do 30kw/hrs/day on a nice, sunny day like today.

    ry%3D480
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