If using an ac battery charger to get power around the inverter to the batteries it would have to be rated for the full power of the PV array. Otherwise, you couldn't divert the full power of the array on the dc side. For a 24-volt battery, it would require a battery charger rated for over 80 amps. That alone seems risky with a 100Ah battery. To add to the difficulty of this approach the battery charger would add a delay time in the control loop that would almost certainly result in an unstable system.

Kent Osterberg


On 3/3/2020 7:53 PM, Jay wrote:
Or a charger such as Iota, or power max.

Jay
Peltz power.

On Mar 3, 2020, at 7:24 PM, d...@energysolarnow.com wrote:


You wrote that you would connect the Exeltech to just one of the service phases. But most GT inverters are 240 and require both phases. Is yours different? You did not mention which model it is. Also, as Kent Osterberg mentioned, the Exeltech will not charge its batteries from the AC output. Your scheme with the PLC controlling an SCR leaves unaddressed how any charge current gets directed into the batteries to allegedly raise their voltage. Is there a charger somewhere in this scheme? You still need some way to charge batteries from solar. How about connecting a charge controller to some of the solar panels?

Don Barch
Energy Solar

    -------- Original Message --------
    Subject: RE-wrenches Digest, Vol 13, Issue 59
    From: re-wrenches-requ...@lists.re-wrenches.org
    <mailto:re-wrenches-requ...@lists.re-wrenches.org>
    Date: Sun, March 01, 2020 2:19 pm
    To: re-wrenches@lists.re-wrenches.org
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    Today's Topics:

    1. OK, so what iwould happen if I do this... (Mark Frye)
    2. Re: OK, so what iwould happen if I do this... (frenergy)
    3. Re: OK, so what iwould happen if I do this... (Kent Osterberg)
    4. Re: OK, so what iwould happen if I do this... (Jerry Shafer)


    ----------------------------------------------------------------------

    Message: 1
    Date: Sat, 29 Feb 2020 15:27:32 -0800
    From: Mark Frye <ma...@berkeleysolar.com
    <mailto:ma...@berkeleysolar.com>>
    To: RE-wrenches <re-wrenches@lists.re-wrenches.org
    <mailto:re-wrenches@lists.re-wrenches.org>>
    Subject: [RE-wrenches] OK, so what iwould happen if I do this...
    Message-ID:
    <93731c38-40b5-7c63-1d74-a879fbdd9...@berkeleysolar.com
    <mailto:93731c38-40b5-7c63-1d74-a879fbdd9...@berkeleysolar.com>>
    Content-Type: text/plain; charset=utf-8; format=flowed

    I have 2kw of grid tied PV on my house.

    Suppose I:

    - Open the main breaker to disconnect from the grid

    - I open the PV breaker

    - I connect a small good quality inverter like an Exeltech XP 500
    to one
    of the phases of the service (120 VAC)

    - I put a small battery pack, 100 AH at 24 VDC on the inverter

    OK so far, I could run some small loads for a relatively short
    period of
    time before the batteries get low

    -I have a PLC with an AD input and DA output. On the input I
    measure the
    battery voltage, on the output I control a SCR. The SCR controls
    a 2kw
    immersion heater sitting in a big bucket of water. The PLC has a
    scan
    time of 2 mS and I program it to increase the duty cycle of the
    SCR as
    voltage of the battery rises above 24 VDC.

    OK so far nothing has really changed from above.

    - I close the PV breaker, the GT inverters see the battery inverter,
    sync and connect after five minutes.

    Voila, I can run house loads from 0 to 2kw with my existing GT PV
    with
    the balance of energy dumped as needed to the immersion heater.

    Right?

    Mark Frye



    ------------------------------

    Message: 2
    Date: Sun, 1 Mar 2020 06:26:27 -0800
    From: frenergy <frene...@psln.com <mailto:frene...@psln.com>>
    To: re-wrenches@lists.re-wrenches.org
    <mailto:re-wrenches@lists.re-wrenches.org>
    Subject: Re: [RE-wrenches] OK, so what iwould happen if I do this...
    Message-ID: <c97234cd-4441-34d7-740c-51f07837b...@psln.com
    <mailto:c97234cd-4441-34d7-740c-51f07837b...@psln.com>>
    Content-Type: text/plain; charset=utf-8; format=flowed

    Mark,

    ??? ??? ??? OR, you change-out your inverter to an SMA with Secure
    Power Supply and during grid power outage, while there is some
    sun on
    the panels, you would have up to 2KW of 120VAC power on the SPS
    circuit
    by just flipping a switch. We usually install a 4X outdoor box
    with a
    120 VAC outlet ganged with a switch right under the inverter and
    let the
    customer run the power to the : frig, lights, battery charger, TV or
    whatever during an outage, though some romex could be run to
    close to
    the frig.

    Bill

    Feather River Solar Electric
    Bill Battagin, Owner
    4291 Nelson St.
    Taylorsville, CA 95983
    530.284.7849
    CA Lic 874049
    www.frenergy.net <http://www.frenergy.net>

    On 2/29/2020 3:27 PM, Mark Frye wrote:
    > I have 2kw of grid tied PV on my house.
    >
    > Suppose I:
    >
    > - Open the main breaker to disconnect from the grid
    >
    > - I open the PV breaker
    >
    > - I connect a small good quality inverter like an Exeltech XP
    500 to
    > one of the phases of the service (120 VAC)
    >
    > - I put a small battery pack, 100 AH at 24 VDC on the inverter
    >
    > OK so far, I could run some small loads for a relatively short
    period
    > of time before the batteries get low
    >
    > -I have a PLC with an AD input and DA output. On the input I
    measure
    > the battery voltage, on the output I control a SCR. The SCR
    controls a
    > 2kw immersion heater sitting in a big bucket of water. The PLC
    has a
    > scan time of 2 mS and I program it to increase the duty cycle
    of the
    > SCR as voltage of the battery rises above 24 VDC.
    >
    > OK so far nothing has really changed from above.
    >
    > - I close the PV breaker, the GT inverters see the battery
    inverter,
    > sync and connect after five minutes.
    >
    > Voila, I can run house loads from 0 to 2kw with my existing GT
    PV with
    > the balance of energy dumped as needed to the immersion heater.
    >
    > Right?
    >
    > Mark Frye
    >
    > _______________________________________________
    > List sponsored by Redwood Alliance
    >
    > List Address: RE-wrenches@lists.re-wrenches.org
    <mailto:RE-wrenches@lists.re-wrenches.org>
    >
    > Change listserver email address & settings:
    >
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    ------------------------------

    Message: 3
    Date: Sun, 1 Mar 2020 08:58:45 -0800
    From: Kent Osterberg <k...@coveoregon.com
    <mailto:k...@coveoregon.com>>
    To: re-wrenches@lists.re-wrenches.org
    <mailto:re-wrenches@lists.re-wrenches.org>
    Subject: Re: [RE-wrenches] OK, so what iwould happen if I do this...
    Message-ID: <9e32901e-c5d4-ff70-9c44-406cc6d48...@coveoregon.com
    <mailto:9e32901e-c5d4-ff70-9c44-406cc6d48...@coveoregon.com>>
    Content-Type: text/plain; charset=utf-8; format=flowed

    Mark,

    I believe that your plan would fail because you are forcing power to
    flow through the XP inverter backwards to charge the batteries. I
    don't
    believe the XP inverter can do that. The grid tied inverter would
    probably connect then immediately shut down, or connect and
    immediately
    ruin the XP inverter. It would work if you had a inverter with a
    bidirectional architecture like a Magnum, Outback, or Schneider
    inverter. But even then you'd have a hazardous situation because the
    cooling water is going to evaporate.

    Kent Osterberg
    Blue Mountain Solar


    On 2/29/2020 3:27 PM, Mark Frye wrote:
    > I have 2kw of grid tied PV on my house.
    >
    > Suppose I:
    >
    > - Open the main breaker to disconnect from the grid
    >
    > - I open the PV breaker
    >
    > - I connect a small good quality inverter like an Exeltech XP
    500 to
    > one of the phases of the service (120 VAC)
    >
    > - I put a small battery pack, 100 AH at 24 VDC on the inverter
    >
    > OK so far, I could run some small loads for a relatively short
    period
    > of time before the batteries get low
    >
    > -I have a PLC with an AD input and DA output. On the input I
    measure
    > the battery voltage, on the output I control a SCR. The SCR
    controls a
    > 2kw immersion heater sitting in a big bucket of water. The PLC
    has a
    > scan time of 2 mS and I program it to increase the duty cycle
    of the
    > SCR as voltage of the battery rises above 24 VDC.
    >
    > OK so far nothing has really changed from above.
    >
    > - I close the PV breaker, the GT inverters see the battery
    inverter,
    > sync and connect after five minutes.
    >
    > Voila, I can run house loads from 0 to 2kw with my existing GT
    PV with
    > the balance of energy dumped as needed to the immersion heater.
    >
    > Right?
    >
    > Mark Frye
    >
    > _______________________________________________
    > List sponsored by Redwood Alliance
    >
    > List Address: RE-wrenches@lists.re-wrenches.org
    <mailto:RE-wrenches@lists.re-wrenches.org>
    >
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    ------------------------------

    Message: 4
    Date: Sun, 1 Mar 2020 07:31:36 -1000
    From: Jerry Shafer <jerrysgarag...@gmail.com
    <mailto:jerrysgarag...@gmail.com>>
    To: RE-wrenches <re-wrenches@lists.re-wrenches.org
    <mailto:re-wrenches@lists.re-wrenches.org>>
    Subject: Re: [RE-wrenches] OK, so what iwould happen if I do this...
    Message-ID:
    <camufgmvybnmmzge__tjds9xpfsou59jdf3wwskfhjw291vg...@mail.gmail.com
    <mailto:camufgmvybnmmzge__tjds9xpfsou59jdf3wwskfhjw291vg...@mail.gmail.com>>
    Content-Type: text/plain; charset="utf-8"

    Mark
    What you are saying is to AC couple but most likely this would
    fail as your
    battery fills not enough loads HBCO or to much loads and your
    battery does
    a LBCO, either way you would be better off spending the money in
    a maybe a
    Outback Skybox easy install and is high voltage PV input and even
    a small
    48 volt bank but think about storage
    Jerry

    On Sat, Feb 29, 2020 at 1:27 PM Mark Frye
    <ma...@berkeleysolar.com <mailto:ma...@berkeleysolar.com>> wrote:

    > I have 2kw of grid tied PV on my house.
    >
    > Suppose I:
    >
    > - Open the main breaker to disconnect from the grid
    >
    > - I open the PV breaker
    >
    > - I connect a small good quality inverter like an Exeltech XP
    500 to one
    > of the phases of the service (120 VAC)
    >
    > - I put a small battery pack, 100 AH at 24 VDC on the inverter
    >
    > OK so far, I could run some small loads for a relatively short
    period of
    > time before the batteries get low
    >
    > -I have a PLC with an AD input and DA output. On the input I
    measure the
    > battery voltage, on the output I control a SCR. The SCR
    controls a 2kw
    > immersion heater sitting in a big bucket of water. The PLC has
    a scan
    > time of 2 mS and I program it to increase the duty cycle of the
    SCR as
    > voltage of the battery rises above 24 VDC.
    >
    > OK so far nothing has really changed from above.
    >
    > - I close the PV breaker, the GT inverters see the battery
    inverter,
    > sync and connect after five minutes.
    >
    > Voila, I can run house loads from 0 to 2kw with my existing GT
    PV with
    > the balance of energy dumped as needed to the immersion heater.
    >
    > Right?
    >
    > Mark Frye
    >
    > _______________________________________________
    > List sponsored by Redwood Alliance
    >
    > List Address: RE-wrenches@lists.re-wrenches.org
    <mailto:RE-wrenches@lists.re-wrenches.org>
    >
    > Change listserver email address & settings:
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