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Battery Health Best Practices of Grid Tied Solar System

  • 1.  Battery Health Best Practices of Grid Tied Solar System

    Posted 11-30-2021 08:54 PM
    I have a grid-tied solar system with battery back-up. I use a  SolarEdge StorEdge inverter with an LG Chem RESU10H lithium-ion for battery storage.  I recently purchased  a Tesla Model Y.  In using the Electric Vehicle there exists a wealth of videos/information regarding maintaining the health and longevity of the battery.  Tesla and many others stress the importance of only charging the vehicle to 100 % if you are embarking on a long trip.  In daily commuter short distance driving we are advised to only charge the battery to 70-80% maximum!!   Using this  system of charging we are told will maximized the useful life
    of the battery.
    As I have come to appreciate this advice , I find myself concerned about the cycling of my solar battery storage system.  Should not the battery health advice given for my Tesla also apply to my solar electric storage battery??  My battery currently discharges to 70 or 80% each night, then immediately charges
    back up to 100% in the morning.(assuming a sunny day).  So......is this charge/discharge cycle unhealthy for the long term health of my battery?? If so, what steps can I take to rectify the situation?
    Thank you,
    Michael


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    michael oellig
    cirrustoo@gmail.com
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  • 2.  RE: Battery Health Best Practices of Grid Tied Solar System

    Silver
    Contributor
    Posted 12-01-2021 10:35 AM
    "Should not the battery health advice given for my Tesla also apply to my solar electric storage battery??"
    YES!!
    About a month and a half ago, I got a call from a aggregator type contractor, who wanted me to look at a SolarEdge system that was having an issue. It was a Solar Edge Energy hub system with two 10H LG chem battery backups. I was not LG certified so I had to go through that "process" just to look at the system. Anyway, I did that and resolved the issue and in the process noticed that his backup packs were doing exactly the same charge/discharge on a daily basis as yours. One would charge then the other. He is in Central PA. No demand billing, no TOU, no variable rate of any kind. A residential customer. I explained to him that there was absolutely no upside to that configuration, only down sides: 1. When the grid fails you may not have you backup at 100%. 2. Less battery life do to the constant heavy DOD and daily cycling. Well as the old saying goes, "you can lead a horse to water.....". Wouldn't budge. But I met my professional obligations in explaining everything clearly and understandability. In part it "bugs" me because I can explain anything to anybody and get through..........usually.
    It is nice to see someone who comes to the correct conclusion on their own, and sees the value in changing....

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    william fitch
    Owner
    www.WeAreSolar.com
    fcfcfc@ptd.net
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  • 3.  RE: Battery Health Best Practices of Grid Tied Solar System

    Posted 12-01-2021 08:26 PM
    I have an LG RES10U (10 kwh) the battery for emergency backup circuits with a separate panel connected directly to the inverter so should commercial power fail I can at least run the refrigerator, freezer and a couple lights.  Due to IRS regulations (which are intended to keep people from arbitraging against the utility and TOD rates) I can only charge with solar in order to be in compliance for the tax credit for the solar system/battery.  As such I programmed the inverter is to keep 20% in the battery for reserve over the summer and 40% in the winter but allow the inverter to fully charge the battery when excess solar power is available and then use that charge when the sun goes down.  

    Right now the battery is on recall and shut down due to overheating issues LG discovered and will be replaced during 1st quarter 2022.  The question is should I keep the inverter from charging the battery all the way up if I can?  I think I can set a minimum but not sure about a maximum.

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    John Gillispie
    AARP
    johnp250@yahoo.com
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  • 4.  RE: Battery Health Best Practices of Grid Tied Solar System

    Silver
    Contributor
    Posted 12-02-2021 09:26 AM
    To keep this short'ish, I will only talk about Li batteries. 80% seems to be the sweet spot for them regarding life, generically speaking. Different specific Li tech make various claims about this topic though. If it were me, I would "float" them at 80%. However, say once a quarter, I would take them down 25% then let them charge up to max level, then down to float level again at 80%. That should get you max life on them. This keeps the cycles very low, stays off the top or highest voltage (except 4 times a year) and 25% drop before quarterly recharge keeps the DOD low.
    How much of that you can make automatic depends on the system settings and your creativity...
    LG has issues with some of their Li, like in the Chevy Bolts, etc...
    Happy Holidays...

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    william fitch
    Owner
    www.WeAreSolar.com
    fcfcfc@ptd.net
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  • 5.  RE: Battery Health Best Practices of Grid Tied Solar System

    Posted 12-02-2021 12:21 PM
    Thank you for your response William, confirming my suspicions.  I find it puzzling given the extensive technical knowledge that manufacturers like LG and SolarEdge have in the battery world, that they seem to fail to program these long life battery algorithms  into their systems????
    And then when I begin to look around at the massive number of Li rechargeable battery operated appliances, from cell phones to dustbusters to laptop computers to the entire rechargeable tool industry, et cetera,et cetera,et cetera, I am struck by the total lack of information/advice regarding battery life best practices!!!  It is only when you get to the electric vehicle market do you begin to see some awareness of this topic.
    Everyone else seems to be of the marketing mind set of "use em till they die and then just buy new ones". 
    Now I have to figure out how to reconfigure my battery charging system to stop charging at 80%?






  • 6.  RE: Battery Health Best Practices of Grid Tied Solar System

    Silver
    Contributor
    Posted 12-02-2021 12:47 PM
    Edited by william fitch 12-02-2021 12:49 PM
    Yes, well... its the throwaway/commodity based mentality. If is cheap and made by the millions, make it low quality, last a couple of years then throw away. If it is more expensive than put a bit of quality into it, etc.. 
    The whole planned obsolesce that maximizes profit, like forever, is a direct contradiction to sustainability. If fact to be blunt, Capitalism is mutually exclusive to sustainability. Its like trying to be satiated and starving at the same time. Not possible.

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    william fitch
    Owner
    www.WeAreSolar.com
    fcfcfc@ptd.net
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  • 7.  RE: Battery Health Best Practices of Grid Tied Solar System

    ASES Life Member
    Posted 12-03-2021 04:07 PM
    In 2019 I installed a grid-tied battery backup system in my barn using Simpliphi LiFePO4 batteries.  My system uses an Outback Power inverter, and brings the battery up to full charge every day.  Once charge parameters are met, battery voltage is allowed to fall (due to internal inverter consumption) until the next day's charge cycle, which again brings the batteries back up to 100% SOC. Simpliphi's Outback integration guide does not specify limiting the daily max SOC to 80%. The daily charge holds the battery at absorb until charge current falls to 2% of the battery's rated C2 charge, per Simpliphi's guide.  Long story short, Simpliphi does not recommend an 80% SOC max for their lithium batteries.  FWIW

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    Mike Curran
    Retired from (dare I say it?) Fossil Plant Mgt.
    joacchim57@gmail.com
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  • 8.  RE: Battery Health Best Practices of Grid Tied Solar System

    Silver
    Contributor
    Posted 12-03-2021 05:28 PM
    Edited by william fitch 12-03-2021 05:32 PM
    Yes, well, I will just leave this screen shot from Battery University (Not aligned with any company) for posters on this thread to read. They can draw their own conclusions.
    Li battery tech
    Here is the link to their website that also deals with other Li issues.

    https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries


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    william fitch
    Owner
    www.WeAreSolar.com
    fcfcfc@ptd.net
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  • 9.  RE: Battery Health Best Practices of Grid Tied Solar System

    Posted 12-03-2021 09:10 PM
    Thanks Mike,
    Is that because it is a LiFe battery? Is it perhaps not as affected by the broad charge/discharge swings and don't heat up as much when
    approaching 100% charge?
    Michael






  • 10.  RE: Battery Health Best Practices of Grid Tied Solar System

    ASES Life Member
    Posted 12-04-2021 06:26 AM
    Edited by Mike Curran 12-04-2021 06:34 AM
    I don't know.  I posted this to show another manufacturer's view.  I suppose only time will tell if it's the right call or not.

    But yes, my system uses the grid normally and the batteries don't come into play unless there's a grid outage (aside from inverter draw - about 100W).  Here's a screenshot from my system monitoring software yesterday showing the charge pattern.  Not shown is state of charge, but it was 100% throughout the day except at the 7:00 am hour when it hit a minimum of 99% for the day, briefly.  Note the green box is showing voltages for the 7:00 am hour only, not the entire day.  Also note the grid energy bars (pinkish color) are incorrect.


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    Mike Curran
    Retired from (dare I say it?) Fossil Plant Mgt.
    joacchim57@gmail.com
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  • 11.  RE: Battery Health Best Practices of Grid Tied Solar System

    Posted 12-06-2021 12:10 PM
      |   view attached
    I have a 30KWH LiFePo4 battery bank (3  10KWh units in parallel). Mine are from YIY in China. I have my Magnum system set up so that the charging stops when the charge current (total) drops to 10A. This gets me to 99%, sometimes 100%. My YIY batteries never heat up, whether charging at 75A or discharging at whatever my house + Electric dryer requires. While LiFePo4 batteries are not impacted by partial charge/discharge, getting them to 99 or 100% makes me feel warm and fuzzy about my system. My system is happy with this setup. Take it for what it's worth.

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    Joe Utasi
    PV Solar Consultant
    Cinci Home Solar, Keowee Home Solar, DIY Solar Helper
    joe@cincihomesolar.com
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  • 12.  RE: Battery Health Best Practices of Grid Tied Solar System

    Posted 12-07-2021 01:59 PM
    So, I'm late to the party on this thread. But here's my 2 cents. I've had a Tesla Powerwall in service for about 4 years on a grid tied system (SolarEdge inverter, 6.09 kW panels). I'm configured with the zero export code, as my utility (a co-op) has very unattractive rates for net metering. So I keep all my power. I dump excess into the EV during spring and early fall. I generate about 2/3 (8 MWh out of 12 MWh consumption) of usage. Rarely (but it does happen) the system curtails power of the battery is full and house demand is low. I have never tried to manage the Powerwall for anything other than making sure I could maximize self consumption. I raise the "power backup" floor up in the winter simply because the battery never fills in December and January. I treat the Powerwall as a smart appliance, and it's done a great job for me. It works "automagically." Your mileage may vary 😎.

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    Joel Dunn
    Joel Dunn
    joel@jdunns.com
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