what if I connect a battery bank to my grid tie inverter Instead of solar panels?

what if I connect a battery bank to my grid tie inverter Instead of solar panels?

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,013 ✭✭✭✭
    Not sure, but would be fun to watch!

    Seriously, a grid tied inverter is designed to create high alternating current to back feed the grid. Battery banks are DC and typically lower current.

    There are hybrid systems available, but if you already have a grid tied inverter and it wasn't designed to charge batteries, you would have to replace it...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    There appear to be GT Inverters that you can attach to a DC Battery bank... But I would suggest we discuss your power needs (type of loads, size of loads, etc.).

    Pure GT Inverters don't usually have much of an advantage in Off grid / Hybrid -- Technically, you can connect a GT inverter (solar panels->GT inverter) to Off Grid inverter--They will share powering the loads and it is even possible to drive power "backwards" through the off grid inverter and recharge the battery banks.

    To battery power a GT inverter -- Then connect the GT inverter to what? AC utility power? Could run your meter backwards (if meter is capable and utility is OK with this)--But cycling batteries are "expensive" and the system is "lossy" -- It typically cost you more in battery costs and losses than you would get paid for by the utility.

    Anyway--What is the problem you want to "fix"? Don't try to fit a product into a solution that may not be the correct one. (Almost) Anything can be done--But is it worth it...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • soloronesolorone Solar Expert Posts: 254 ✭✭✭
    BB. wrote: »
    Almost) Anything can be done--But is it worth it...

    LOL,, well said ! !
  • jonrjonr Solar Expert Posts: 1,313 ✭✭✭✭
    Some MPPT inverters may rely on the limited current output of solar panels as they look for the MPPT point. But I would guess that good designs would protect themselves and it would work fine. It's similar to the question of what happens when you connect 1000 watts of panels to a 250 watt MPPT inverter (typically nothing bad).

    I am available for custom hardware/firmware development

  • andersondiazandersondiaz Registered Users Posts: 22 ✭✭
    BB. wrote: »
    There appear to be GT Inverters that you can attach to a DC Battery bank... But I would suggest we discuss your power needs (type of loads, size of loads, etc.).

    Pure GT Inverters don't usually have much of an advantage in Off grid / Hybrid -- Technically, you can connect a GT inverter (solar panels->GT inverter) to Off Grid inverter--They will share powering the loads and it is even possible to drive power "backwards" through the off grid inverter and recharge the battery banks.

    To battery power a GT inverter -- Then connect the GT inverter to what? AC utility power? Could run your meter backwards (if meter is capable and utility is OK with this)--But cycling batteries are "expensive" and the system is "lossy" -- It typically cost you more in battery costs and losses than you would get paid for by the utility.

    Anyway--What is the problem you want to "fix"? Don't try to fit a product into a solution that may not be the correct one. (Almost) Anything can be done--But is it worth it...

    -Bill



    the idea is to charge the batteries With panels During power outages and when come back return the stored energy to the grid.

    yesterday there was a power outage, usually within a day like yesterday my installation produces 11kw and yesterday only produced 0.9kw due to power outage.

    but then I thought the batteries have more power than they can handle my 10 micro inverters

    you know one of those ideas when we can not sleep and want to invent something.
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Utilities are starting to prohibit battery powered grid tied systems because they don't want you to buy power at night and sell power during the day (many gt power plans have subsidies in them).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranchwestbranch Solar Expert Posts: 5,155 ✭✭✭✭
    Look up Solar City , and their efforts to add batteries, LiFePo4 from Tesla, to their systems and PG&E is stalling on approvals...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • solarpatsolarpat Registered Users Posts: 5
    So what if you connect a battery bank to your gt inverter? There would be a few different considerations, most gt inverters need from about 150 to 250 volts of dc minimum and usually the max is around 500, 600 volts is usually the absolute maximum, although there are 1000 volt systems and you have to make sure all conductors and terminations are rated for 1000 volts
    .
    You could tie your batteries in series and get the higher voltages, however you would have to check with battery manufacturers to find out the maximum voltage that their battery can be in series.

    Now you would have to have something to charge your batteries since a gt inverter is not set up for that. On battery backup systems you use a charge controller to keep batteries charged. you would have to install a charger with charge controller for the batteries. Now even if you take care of the previous concerns your gt inverter will still not operate when it is not seeing the "grid power" as in the case of a power outagehowever you could cycle the batteries at nighttime since you would still have grid power.
    The inverters have anti-islanding characteristics built into them so in the event of a power outage they won't back feed the utility and maybe electrocute any lineman working on the dead lines. So you are going to have to use a true sine wave generator if you want to trick the inverters into producing when there is no power. Also if you do that them a generator panel and a transfer switch is required for safety. So you would need all the aforementioned items and some ingenuity and I think you could do it, but like someone else said you would have to weigh the cost vs the benefits of such a system.
  • Ethan BrushEthan Brush Solar Expert Posts: 231 ✭✭
    what if I connect a battery bank to my grid tie inverter Instead of solar panels?

    Keep in mind that a typical GTI is programmed to MPP track power from PV modules. If you connected a battery instead of PV, I think the GTI would keep lowering its effective input impedance until it maxed out its current or power rating, since the batteries will provide more and more current as this happens. You either need a GTI that can be programmed to transfer a certain amount of power, or choose an inverter carefully so it will "max out" at an appropriate battery current.
  • AlexMorfeAlexMorfe Registered Users Posts: 5 ✭✭
    Hi guys! Good day... :)
    If i may, I would like to explore this idea further...

    I have a 5kWp grid-tied (Solis 5k-4g) with limiter (no netmetering), and a 2kWp offgrid with 600Ah 24v (2s6p) battery bank.. I now live in a place where there is not much outage. The offgrid setup powers the lights in my house 24/7 -- approx 3-5 kWh per day -- plus the essentials when there is outage. The GTI is sufficient to cover my day-time loads. My main issues are:
         1. the night-time loads: mainly the A/C (8kWh per night)
         2. the under-utilized offgrid

    is it possible/safe to connect the battery bank to the PV input of the GTIL? or will it just surely go KABOOM? has this been done before (please share URL)?

    the setup would be: 24v_batt_bank --> dc_boost_converter --> gti_pv_input
    -- boost converter is this: https://www.ebay.ph/itm/1200W-20A-DC-Converter-Boost-Car-Step-up-Power-Supply-Module-8-60V-to-12-83-I4H4/113243982972?hash=item1a5dde0c7c:g:L2MAAOSwzyBbl9Ds
    -- boost converters will be connected in series to make the nominal input voltage of the GTI (parallel is confirmed, but series is still pending quey)
    -- each boost converter will have its own 24v isolated bank 
    -- boost converters will be set to limit power output (maybe 3 to 5A)
    -- setup will discharge up to 30% DoD only 

    the aim is to utilize a fraction of the battery bank to cover part of the night-time DU consumption (with what i have or what i can easily get).

    i understand that this is not efficient and lossy, but for the sake of my education, please guide me.
    i also understand that netmetering is the best option, but it is an option that i cannot avail right now.

    hoping for your prompt guidance.
    thanks!

  • mike95490mike95490 Solar Expert Posts: 8,434 ✭✭✭✭✭
    Your GT inverter will try to extract 5kw from your batteries.  Generally, GT inverters want to see 300- 500VDC input, which is rare for batteries.

     What are the specs for your GT inverter, or even it's model # ?
    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 ,

  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    The boost method seem like a complicated way to tackle a simple problem, which may or may not work.

    Having an auto transfer switch controlled by a timer would allow AC loads to be switched between different sources during certain hours, this is something I do to make use of an otherwise under utilized second off grid  system, In my case the main inverter is programed to disable, or block invert, overnight 10 pm to 9 am. 

    Using the grid as the primary source and inverter output as backup source, a timer could be used to drive a suitable contactor which effectively turns off the grid input causing the transfer to switch to battery powered inverter. As soon as the contactor restores grid input the transfer switches back to grid.

    The loads needed would need to be on the essential sub panel, this is the transfer switch I used https://m.aliexpress.com/item/32868401442.html?pid=808_0000_0101&spm=a2g0n.search-amp.list.32868401442&aff_trace_key=1f5a158981114b37ab6b64f7fe2fc8e6-1564382013135-00741-KnSGCh6&aff_platform=msite&m_page_id=4097amp-ZXkLFFJjLTwwvWd9Q8WQJQ1567581006295
    Make sure the one used is in compliance with local requirements. 


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • AlexMorfeAlexMorfe Registered Users Posts: 5 ✭✭
    mike95490 said:
    Your GT inverter will try to extract 5kw from your batteries.  Generally, GT inverters want to see 300- 500VDC input, which is rare for batteries.

     What are the specs for your GT inverter, or even it's model # ?
    hi Mike,
    thanks for the response.
    the GTI is Ginlong-Solis 5k-4g. http://www.ginlong.com/Uploads/file/c0a16104c18870f42add488815e216ce.pdf
    the boost converter is constant current and should limit the drain from the batteries (much like a shady day).
    thanks.
  • AlexMorfeAlexMorfe Registered Users Posts: 5 ✭✭
    mcgivor said:
    The boost method seem like a complicated way to tackle a simple problem, which may or may not work.

    Having an auto transfer switch controlled by a timer would allow AC loads to be switched between different sources during certain hours, this is something I do to make use of an otherwise under utilized second off grid  system, In my case the main inverter is programed to disable, or block invert, overnight 10 pm to 9 am. 

    Using the grid as the primary source and inverter output as backup source, a timer could be used to drive a suitable contactor which effectively turns off the grid input causing the transfer to switch to battery powered inverter. As soon as the contactor restores grid input the transfer switches back to grid.

    The loads needed would need to be on the essential sub panel, this is the transfer switch I used https://m.aliexpress.com/item/32868401442.html?pid=808_0000_0101&spm=a2g0n.search-amp.list.32868401442&aff_trace_key=1f5a158981114b37ab6b64f7fe2fc8e6-1564382013135-00741-KnSGCh6&aff_platform=msite&m_page_id=4097amp-ZXkLFFJjLTwwvWd9Q8WQJQ1567581006295
    Make sure the one used is in compliance with local requirements. 


    hi mcgivor,
    thanks for the reply.
    i have something like that too. but my concern is on the A/C which is not in the essentials sub panel. :)

  • AlexMorfeAlexMorfe Registered Users Posts: 5 ✭✭
  • AlexMorfeAlexMorfe Registered Users Posts: 5 ✭✭
    any inputs please? :)

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