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Can DC connected battery reduce Solaredge inverter clipping?

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  • Can DC connected battery reduce Solaredge inverter clipping?

    I plan to oversize a 7.6 kW Solaredge inverter and connect a DC-DC battery thru a Storedge interface. Can the battery mitigate clipping by accepting DC power that exceeds 7.6 kW before it gets clipped on the AC side of inverter?
    Last edited by Steeler.Fan; 07-10-2019, 04:29 PM.

  • #2
    After no response here, I called Solaredge support. On monday 7/8, I was on hold for 2.5 hrs before I reached support. Today, I was only on hold for 15 min. The engineer that I spoke with said that batteries connected DC-DC via Storedge to Solaredge inverter can store energy in excess of the AC output limit and reduce inverter clipping. That is great news.

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    • #3
      That creates an interesting argument for oversizing a system. Often there are limits on the AC side because of panel size or POCO policy.

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      • #4
        Power drawn from a battery is quite expensive, since the number of cycles is limited. It
        might be cheaper to live with clipping. I limit it with E-W panel tilting. Bruce Roe

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        • #5
          Originally posted by bcroe View Post
          Power drawn from a battery is quite expensive, since the number of cycles is limited. It
          might be cheaper to live with clipping. I limit it with E-W panel tilting. Bruce Roe
          If I remember correctly from others threads, the OP is in Hawaii with no NEM and outrageous cost of energy from the local POCO. It all depends on where you are standing. But generally batteries are expensive if one has a less expensive grid tie/NEM arrangement.
          Last edited by Ampster; 07-11-2019, 10:14 PM.

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          • #6
            When I last did the calculation of cost of a KWH from a battery, it was most of an order
            of magnitude more expensive than from the grid. Plug in your own technology, depth of
            discharge, lifetime cycles, and battery cost, compare that to HI prices. Bruce Roe
            Last edited by bcroe; 07-11-2019, 11:05 PM.

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            • #7
              Originally posted by bcroe View Post
              When I last did the calculation of cost of a KWH from a battery, it was most of an order
              of magnitude more expensive than from the grid. Plug in your own technology, depth of
              discharge, lifetime cycles, and battery cost, compare that to HI prices. Bruce Roe
              Here is my math:
              I am in Northern California (PG&E)
              I have 15kWhs of Nissan Leaf batteries.
              They cost me an average of $150 per kWhrs.Total cost $2,250
              If I use 5 kWhrs every day for 5 years I use 9,000 kWhrs.over five years
              $2,250 divided by 9000kWhrs. equals $0.25 per kWhr.

              I already have two years out of these batteries. They were used when I bought them but I only use 30% of their capacity daily at very low C rates so I think my assumption of five years life is reasonable.I could get more life out of them. I haven't attributed any cost to my hybrid inverter and solar panels since they should last at least 10 years or more and provide backup and their own return on investment. My highest TOU rate is $0.46 per kWhr in the summer and $0.33 in the winter. The hybrid inverter allows all my solar generation to be credited at those rates plus some at lower mid peak rates. This is a hobby for me to try to be as self sufficient as I can. I still rely on the grid to charge my EVs at off peak rates of $0.15 per kWhr. The other benefit that i can't quantify is that I live in an area where my POCO (PG&E) is threatening to shut down certain areas when there is a risk of fire.

              I don't expect the average user to get this kind of result but I am inspired that the Los Angeles Department of Water and Power recently contracted for battery power at less than $0.5 per kWhr. Somewhere between their purchase of megaWhrs and my little system there is hope that the cost of battery storage may someday become more reasonable for more people.
              Last edited by Ampster; 07-12-2019, 12:19 AM.

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              • #8
                You will get different answers with different technology. I did new lead acid, with a chart
                of the depth of discharge vs number of cycles. Currently the charge here is about
                10.5 cents per KWH, your results will vary. If you do not have capacity and a depth of
                discharge chart you are just guessing. But even if the battery delivered cost of a KWH
                is the same as the the PoCo, the clipping/battery scheme will save no $. If you can
                get a real deal on used battery capacity, you could come out ahead. Bruce Roe

                Comment


                • #9
                  Originally posted by Ampster View Post

                  Here is my math:
                  I am in Northern California (PG&E)
                  I have 15kWhs of Nissan Leaf batteries.
                  They cost me an average of $150 per kWhrs.Total cost $2,250
                  If I use 5 kWhrs every day for 5 years I use 9,000 kWhrs.over five years
                  $2,250 divided by 9000kWhrs. equals $0.25 per kWhr.

                  I already have two years out of these batteries. They were used when I bought them but I only use 30% of their capacity daily at very low C rates so I think my assumption of five years life is reasonable.I could get more life out of them. I haven't attributed any cost to my hybrid inverter and solar panels since they should last at least 10 years or more and provide backup and their own return on investment. My highest TOU rate is $0.46 per kWhr in the summer and $0.33 in the winter. The hybrid inverter allows all my solar generation to be credited at those rates plus some at lower mid peak rates. This is a hobby for me to try to be as self sufficient as I can. I still rely on the grid to charge my EVs at off peak rates of $0.15 per kWhr. The other benefit that i can't quantify is that I live in an area where my POCO (PG&E) is threatening to shut down certain areas when there is a risk of fire.

                  I don't expect the average user to get this kind of result but I am inspired that the Los Angeles Department of Water and Power recently contracted for battery power at less than $0.5 per kWhr. Somewhere between their purchase of megaWhrs and my little system there is hope that the cost of battery storage may someday become more reasonable for more people.
                  So, in winter you're saving ($0.33/kWh - $0.25/kWh) = $0.08/kWh by not using peak POCO power ?

                  Comment


                  • #10
                    Originally posted by J.P.M. View Post
                    So, in winter you're saving ($0.33/kWh - $0.25/kWh) = $0.08/kWh by not using peak POCO power ?
                    Yes that is the math. It is not an expensive hobby. The important issue for me is I am not using the grid. The collateral benefits are I get a backup that can be charged by the sun and I get a hedge against price increases and erosion of peak hour generating periods.

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                    • #11
                      Originally posted by bcroe View Post
                      You will get different answers with different technology. I did new lead acid, with a chart
                      of the depth of discharge vs number of cycles. Currently the charge here is about
                      10.5 cents per KWH, your results will vary. If you do not have capacity and a depth of
                      discharge chart you are just guessing. But even if the battery delivered cost of a KWH
                      is the same as the the PoCo, the clipping/battery scheme will save no $. If you can
                      get a real deal on used battery capacity, you could come out ahead. Bruce Roe
                      Wow, Illinois power is at $0.105 per kWh. I looked up the average rate for HI and it is $0.37. My brother pays $0.34 on Maui and recently installed a Powerwall when he installed his solar. I will have to ask him what his financial analysis looked like.

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                      • #12
                        Has anyone been able to use a DYI battery with SolarEdge Storedge? Only find support for LG and maybe Tesla. I wanted use Leaf or 1860 cells. Looks like I might have made a big mistake going with SolarEdge. Night time power is only $0.02, love to charge at night and peak shave. Thank you for your help. Us newbs , ughh

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                        • #13
                          Originally posted by azheat9 View Post
                          Has anyone been able to use a DYI battery with SolarEdge Storedge? Only find support for LG and maybe Tesla. I wanted use Leaf or 1860 cells. Looks like I might have made a big mistake going with SolarEdge. Night time power is only $0.02, love to charge at night and peak shave. Thank you for your help. Us newbs , ughh
                          The Storedge spec sheet says the battery voltage is 400 to 500 volts and I don't think the Tesla Powerwall comes in a high voltage DC coupled version any more. I think your only option is the LG Chem battery. I am using Leaf cells on a Outback Skybox which runs at 48 volts. I would not recommend messing around with that high a voltage DC.

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                          • #14
                            Originally posted by Ampster View Post

                            The Storedge spec sheet says the battery voltage is 400 to 500 volts and I don't think the Tesla Powerwall comes in a high voltage DC coupled version any more. I think your only option is the LG Chem battery. I am using Leaf cells on a Outback Skybox which runs at 48 volts. I would not recommend messing around with that high a voltage DC.
                            I hate being held hostage by proprietary interface. 400v is also the input from the panels, so not a big deal. It's easy enough to configure the battery module from leaf. My other option is to get a charge controller/ inverter and hook up to the AC side. Old SE5000 supported other battery and BMS. I heard SolarEdge is rolling out their own batteries. Anyone tried to connect on AC side a second inverter? How to phase match?

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                            • #15
                              I don't know if there is anything proprietary about the interface. It is just a DC buss. I think it goes beyond just a BMS however.

                              From what little I understand you would need your BMS to communicate with a DC to DC converter which would control the charging and discharging of the battery with the DC buss in the SolarEdge inverter. Any bidirectional DC to DC converter that can run at 400 to 500 volts is likely to be expensive. Finding one that is programmable with a CC CV charging algorithm for 400 to 500 volts will be the next challenge. When the generation 1 Powerwall came out that seemed like a simple solution. Tesla abandoned that concept and went to AC coupling with the Powerwall 2.. I suspect that change was driven by the larger market of AC coupling with any inverter, They had already developed inverters for the PowerPack so why not leverage that technology,.

                              Yes, I saw the announcement that SolarEdge is coming out with their own batteries. Let's hope they end up somewhere south of $1,000 per kWhr of storage and that it is reasonable scalable.

                              https://solarbuildermag.com/energy-s...-wave-updates/
                              Last edited by Ampster; 07-13-2019, 08:11 PM.

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