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?
«1

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,574 ✭✭✭✭✭
    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, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 31,680 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: 255 ✭✭✭
    BB. wrote: »
    Almost) Anything can be done--But is it worth it...

    LOL,, well said ! !
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    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: 31,680 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: 5,183 ✭✭✭✭
    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: 235 ✭✭
    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: 9,274 ✭✭✭✭✭
    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: 3,814 ✭✭✭✭✭✭
    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 with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, 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? :)

  • happymehappyme Registered Users Posts: 1
    A number of post keeping on indicating GT needs over 200V. The Solis 4G can start on 60V. I would think the boost converter with current limit should work. 

    It seems like the whole system is not understood well. Batteries can be charge with PV from the GT during the day and with spare capacity this can be used to input in the place of solar. One would then perhaps need a transfer switch to disconnect the PV and connect the boost converter output. 
  • mike95490mike95490 Solar Expert Posts: 9,274 ✭✭✭✭✭
    happyme said:
    A number of post keeping on indicating GT needs over 200V. The Solis 4G can start on 60V. I would think the boost converter with current limit should work. 

    It seems like the whole system is not understood well. Batteries can be charge with PV from the GT during the day and with spare capacity this can be used to input in the place of solar. One would then perhaps need a transfer switch to disconnect the PV and connect the boost converter output. 
    Most GT inverters use a MPPT algorithm to extract max power from PV panels which are Current Source devices.
    Batteries are Voltage sources and electrically are very different from PV panels and don't work well with MPPT gear.
      But you may have found new gear that works differently than gear I have.  Good luck
    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 ,

  • eboxebox Registered Users Posts: 2
    I upgraded to a GTI with dual string inputs. PV strings should always be matched ( same number of panels /voltage ) but I found myself 1 panel short, but I wanted to test the GTI just the same so I hooked up 3 12v batteries in series with the second string of the panels. The GTI worked flawlessly and I have been monitoring the system constantly. It's been a week now and not a hitch. My longterm intention to install another panel, but in the meantime, the system works well so those who are curious. Would not recommend run this long term. 

    I would note and confirm what some.here already mentioned, second string runs at a lower voltage but higher amperage than the 1st string as the GTI can't have the batteries increase or decrease voltage when power demand increases.
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    I wouldn't connect a GTI to batteries if it lists a maximum input current.   For example, an Enphase IQ7 lists "Max DC short circuit current (module Isc)" as 15A.

    I am available for custom hardware/firmware development

  • RCinFLARCinFLA Solar Expert Posts: 1,351 ✭✭✭
    edited August 2020 #22
    I also would not recommend it.  GTI is expecting a current source PV panel.  You never know precisely how a given GTI works its MPPT algorythm.  Some pull a full current sink momentarily to reference the given instance of illumination Isc current to help speed their MPPT search.  It is probably self protected against overcurrent but there are several things that might waste battery power at the minimum.

    More then likely it will come up against something that it cannot make sense of and will just refuse to connect to grid.
  • cheapforlifecheapforlife Registered Users Posts: 6 ✭✭
    Hello, this is my first time posting. I had to join due to this discussion.. The GTIL2 is designed to be used with direct pv power or a battery. The grid tie inverter has settings to limit the amps used from the dc source so there’s is no problems with the inverters mppt. The inverters operating range is 45-90v. A charge controller is used to charge the battery. The inverter has settings that allow for inverter cutoff and reboot voltages. The inverter has optional limiting to prevent any power from being produced over the amount the loads use. The power from the charge controller-pv is fed directly across the battery terminals (bypassing the battery) and to the loads. Whatever amount of excess pv power is available (after loads are fully powered) goes into the battery to charge it up. If the pv power isn’t enough to fully power the load then the battery is also used. If the pv and battery isn’t enough to fully supply all of the load (or inverter is to small to supply all of the load) then grid power is used to supply the remaining amount of the homes loads while pv and battery are still utilized by the loads at the same time. 
    I have connected an offgrid inverter to the batteries to manually switch on when there’s an emergency. A lot cheaper than using transfer switches and all kinds of circuits to be offgrid. If a user has enough battery capacity to supply all of their homes loads than the grid tie inverters will run 24/7. 
    I am in the USA and I use two single phase 240v 2kw inverters. My inverters run 24/7 (supplying 100% of my loads) unless it’s summer time because air conditioning uses a lot of power in Tennessee. 
  • AmpsterAmpster Registered Users Posts: 172 ✭✭✭
    edited August 2020 #24
    Sounds like you have a good system.

    This old thread continues to get comments even thought the OP was asking about connecting batteries instead of solar panels to the solar input of a GT inverter. 
  • boBboB Solar Expert Posts: 984 ✭✭✭✭

    Doing this will probably just drain the battery, if you're lucky.   :D



  • cheapforlifecheapforlife Registered Users Posts: 6 ✭✭
    Bob yes the GTIL2 will drain the battery but that’s the purpose. To use the stored energy in the battery (that came from pv panels) that wasn’t used during the day. Same as an offgrid inverter would do
  • cheapforlifecheapforlife Registered Users Posts: 6 ✭✭
    The GTIL2 allows the extra power from pv not used by loads to be stored in the battery (using a charge controller) and battery can be used whenever pv power alone isn’t enough (due to clouds or night or an undersized inverter) to fully supply the load. 
  • littleharbor2littleharbor2 Solar Expert Posts: 1,599 ✭✭✭✭
    The GTIL2 allows the extra power from pv not used by loads to be stored in the battery 

    If grid tied, isn't the grid the ultimate "load"?

    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, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • cheapforlifecheapforlife Registered Users Posts: 6 ✭✭
    Not really sure what you mean by that. I guess I agree. Using the GTIL2, During the day when consumption is fully covered by the pv panels directly, the excess pv power is saved in a battery. This saved power can be used throughout the day whenever there’s not enough available pv power to fully supply all of the consumption. The excess power needed above what the pv can supply (due to clouds or whatever) is used from the saved battery power. And since the GTIL2 is a GTI, the grid can supply the rest of the remaining load if the pv and save do battery power isn’t enough, or if the consumption is over the inverters max output capacity 
  • littleharbor2littleharbor2 Solar Expert Posts: 1,599 ✭✭✭✭
    edited August 2020 #30
     Referring to  the grid being able to accept ALL excess power production. Sounds like you are set up in a zero export configuration. For all intents and purposes it's acting like an off grid inverter that can use grid power to charge your battery bank.
     I must admit, I haven't read through this entire thread so I may be making a fool of myself here.

    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, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • rhino 660rhino 660 Registered Users Posts: 6
    Im a solar contractor and
    I live offgridand have a 24.5kw pv array with 70KWH of model s modules wired for 48v
    I need more storage so  
    My idea is to use a tesla model 3 battery full pack 400vdc (only $8k for 75kwh) and an sma7.7 grid tie inverter with a zero export controller. Charge it with a model 3 charger when the current battery is full 
    And discharge it to cover the AC load whenever possible.
    Its a way to add cheap storage to my setup if the sma will do it.
    The menus in the sma allow all kinds of parameters to be adjusted. I don't see why it wont work they use the same inverter for the sunny boy storage from what i can tell the last time i installed a SBS i looked it over really good.
    Off grid.
     Temporary system while i build house 
    8.5 kw pv, 70kwh's tesla model S batteries, 4548 xantrex 
    2 60A xw cc 1 80A outback cc. 25kw diesel gen 
    Looking at skybox for 20kw ac 18.5kw dc pv when done

Sign In or Register to comment.