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  • #91
    Originally posted by nebster View Post
    Because counting always exhibits some drift, and because that error accumulates over time, that estimation technique can readily be off by more than 5%. It is only good for a short while, and then it is not so good any more. That is why it must be "resynchronized" regularly, and it is also why people are developing better estimators.
    Agreed and that is my point, it drifts with every cycle. It is nothing more than the Hot Light or Check Engine Light.

    To resync requires a full discharge capacity test consumers are not capable of doing. I have no problem with lithium batteries, they have their place and applications. They are not ready for consumer residential applications for the simple fact they are not cost effective and too dangerous. EV's you can justify the cost and dangers, but not in a residential application. As of today using lithium batteries in a residential applications are 400% more expensive, and run very high risk of thermal runaway destroying cells. When that reverses itself I will change my professional opinion. Until that time I will push back and counter so people can make an informed decision, not hype by advocates of one side.

    MSEE, PE

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    • #92
      Originally posted by nebster View Post
      First of all, we don't measure storage systems in watts.
      What are you talking about? Solar power systems are measured in Watts aka power. Energy or battery capacity is just an end result to meet daily energy requirements.

      Not so sure you can call Golf Cart and EV Battery systems small as they are generally much larger than any off-grid or grid tied applications. How many off-grid and GT systems use 15 to 60 Kwh of storage? Answer very few and not the norm.
      Last edited by Sunking; 11-23-2018, 03:05 PM.
      MSEE, PE

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      • #93
        Originally posted by Sunking View Post
        What are you talking about? Solar power systems are measured in Watts aka power. Energy or battery capacity is just an end result to meet daily energy requirements.
        You are in the battery and energy storage forum, not the solar power system forum. What are talking about here are batteries. We measure those in energy.

        So, now that we are on the same page, can you tell us about your personal system? We want to know about your lithium-chemistry storage system(s).

        Not so sure you can call Golf Cart and EV Battery systems small as they are generally much larger than any off-grid or grid tied applications. How many off-grid and GT systems use 15 to 60 Kwh of storage? Answer very few and not the norm.
        You might be surprised how many residential-scale storage systems are in use in mobile applications and in remote geographies. It is a niche market, but one that is growing and that pushes the edge of the performance envelope.



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        • #94
          Originally posted by nebster View Post
          You might be surprised how many residential-scale storage systems are in use in mobile applications and in remote geographies. It is a niche market, but one that is growing and that pushes the edge of the performance envelope.
          Agree all niche applications. Just like over 150 or so Cellular applications that no commercial power is available at any cost. Using off-grid battery when there is commercial power available is foolish.

          MSEE, PE

          Comment


          • #95
            Originally posted by Sunking View Post
            Agreed and that is my point, it drifts with every cycle.
            Your point earlier seemed to be that it was better than an estimation tool that incorporates voltage.

            It is nothing more than the Hot Light or Check Engine Light.
            That's silly. A current-integrating estimator is much more useful than that. Within the bounds of reason (and time), and much moreso with sync events.

            To resync requires a full discharge capacity test consumers are not capable of doing.
            Incorrect. Most monitors will resync at a "full" charge, and many are programmable to stipulate what "full" means.

            I have no problem with lithium batteries, they have their place and applications. They are not ready for consumer residential applications for the simple fact they are not cost effective and too dangerous.
            This sounds like a reasonable opinion, and I mostly agree with you. But to put it in absolutes like that is a mistake: costs are coming down, safety data is piling up. LFP-based ESS are a booming business in some parts of the world, where the needs and demands are different. Cobalt-based ESS offerings are on the market and not burning down houses left and right, yet. The future is soon.

            EV's you can justify the cost and dangers, but not in a residential application.
            Don't assume there is only EV and residential.

            There is also mobile residential -- boats and RVs -- which is a niche market that nevertheless is sizable and growing. This is where you find large packs, operated at low rates, augmented with multiple charging solutions. Mostly LFP, for safety.

            As of today using lithium batteries in a residential applications are 400% more expensive, and run very high risk of thermal runaway destroying cells. When that reverses itself I will change my professional opinion. Until that time I will push back and counter so people can make an informed decision, not hype by advocates of one side.
            I'm all for pushing back on hype and people with an agenda, but the way you choose to do it is unproductive and detrimental to the forum. I can't stop you (this isn't my forum; I'm not a moderator), but when you post wrong or incomplete or biased information, expect to be corrected.

            Comment


            • #96
              Originally posted by nebster View Post
              That's silly. A current-integrating estimator is much more useful than that. Within the bounds of reason (and time), and much moreso with sync events.



              Incorrect. Most monitors will resync at a "full" charge, and many are programmable to stipulate what "full" means.
              No it is not, 100% SOC has nothing to do with capacity unless you know what full capacity is of the weakest cell. Only way to find that is with a Capacity test which is always going down with each cycle. 100% of nothing is nothing. That is the problem using voltage as SOC.



              This sounds like a reasonable opinion, and I mostly agree with you. But to put it in absolutes like that is a mistake: costs are coming down, safety data is piling up. LFP-based ESS are a booming business in some parts of the world, where the needs and demands are different. Cobalt-based ESS offerings are on the market and not burning down houses left and right, yet. The future is soon.

              Originally posted by nebster View Post
              Don't assume there is only EV and residential.
              I do not, those are your words, not mine. Bottom Line is battery monitors are up-sales for greater profits. About all they are good for is to tell you that you need to shut down and recharge which is the good ole Idiot Light in autos. There are way to many variables that no algorithm can predict with any meaningful significance.

              Now there is one method that is useful and can at least tell you when your battery is at 80% rated capacity, and thus time to replace the battery because after 80% capacity death is around the corner. That would be the battery Internal Resistance. When it doubles in value, capacity is at 80% of rated capacity and time to replace. Makes no difference what the chemistry is. To do that takes a simple 1-minute load test using Dv/Di test.Sounds like complicated calculus which it is to laymen, but is stupid simple.


              Last edited by Sunking; 11-23-2018, 04:35 PM.
              MSEE, PE

              Comment


              • #97
                Originally posted by Sunking View Post
                Agree all niche applications. Just like over 150 or so Cellular applications that no commercial power is available at any cost. Using off-grid battery when there is commercial power available is foolish.
                Niche applications are often where the most interesting problems and novel applications of technology. Many of the threads started in this forum are from people looking at a mobile application.

                Sometimes those folks are also misguided (either by a salesperson or their own optimism), but that's true with just about anything.



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                • #98
                  Originally posted by Sunking View Post

                  No it is not, 100% SOC has nothing to do with capacity unless you know what full capacity is of the weakest cell. Only way to find that is with a Capacity test which is always going down with each cycle. 100% of nothing is nothing. That is the problem using voltage as SOC.
                  You seem really interested in your peculiar (and largely useless) definition of "SOC". When most of the rest of use a tool to estimate "SOC," we care about how much usable energy we have available, right now. Not how much theoretical reaction space is left in the chemistry of each individual cell.

                  In real life, in an actual system with a conservatively-managed pack that is healthy, the available storage is dominated by the need to stay away from the limits of the charge envelope, not the cell that happens to be a few percent weaker than its cohort.

                  I'm not going to debate this with you again, because it's a matter of subjective opinion. But for the benefit of other readers, please do not allow yourself to be dragged off course by sunking's perversion of this common, useful concept.

                  I almost forgot: you have chosen not to tell us about any of your lithium ESS experience. When do we get to learn about what you've done?

                  Comment


                  • #99
                    Ben here for 8 years, all you gotta do is look. When I came here the forum was buried deep in search pages. Today the number 1 hit aand I have a lot to do with it. Folks come here to get straight answers [B][COLOR=#FF0000]Karrak[/COLOR][/B]. You only came here to harass me and a 1-trick lithium pony as you have admitted many times on other forums.
                    Last edited by Sunking; 11-23-2018, 07:15 PM.
                    MSEE, PE

                    Comment


                    • Originally posted by nebster View Post
                      .........

                      I'm not going to debate this with you again, because it's a matter of subjective opinion. But for the benefit of other readers, please do not allow yourself to be dragged off course by sunking's perversion of this common, useful concept.

                      I almost forgot: you have chosen not to tell us about any of your lithium ESS experience. When do we get to learn about what you've done?
                      I have just recently chosen to ignore SK's rants. It is too much work to pick through all the BS to find a snippet of useful information..
                      I too would like to hear about SK's Lithium experience, especially if he has found a way to extend the life of those Nissan Leaf modules. He advocates bottom balancing but offers no evidence about how it can extend the life of those modules in an ESS.

                      Comment


                      • Originally posted by Sunking View Post
                        Ben here for 8 years, all you gotta do is look. When I came here the forum was buried deep in search pages. Today the number 1 hit aand I have a lot to do with it.
                        So, I think we've gotten to the bottom of things: you don't have any operational experience with a residential-scale lithium ESS.

                        Folks come here to get straight answers [B][COLOR=#FF0000]Karrak[/COLOR][/B].
                        I'm not sure who Karrak is, but I can promise you this: when you post incorrect or misleading comments, I'll be one of the first to set you straight. Not because it matters what you think, but because the rest of us deserve a productive place to share information while not behaving like my seven-year-old.

                        Here's to the next eight years!

                        Comment


                        • Originally posted by Ampster View Post
                          I have just recently chosen to ignore SK's rants. It is too much work to pick through all the BS to find a snippet of useful information..
                          I too would like to hear about SK's Lithium experience, especially if he has found a way to extend the life of those Nissan Leaf modules. He advocates bottom balancing but offers no evidence about how it can extend the life of those modules in an ESS.
                          Yeah, it's almost a worst-case scenario: lots of great historical experience, but absolutely no contrition, no ability to carry on a measured debate with other adults, and a willingness to double down on his outdated or mistaken understandings when push comes to shove. (And a lack of timely, real-world experience.) I think the rest of us can carry on without him, though, just fine.

                          Comment


                          • Originally posted by Sunking View Post
                            I do not, those are your words, not mine.
                            They were your implication. I challenged your understanding and experience with certain lithium topologies as used in residential-scale ESS, and one of your responses was that lithium only makes sense for traction applications and doesn't make sense for residential. But there are whole other categories of users where it also makes sense, some of which involve using very large packs.

                            Bottom Line is battery monitors are up-sales for greater profits.
                            The term "battery monitor" is overloaded, so you'll need to be specific. However, I agree with you in part: active battery management systems are generally a waste of money, and they introduce risk with almost no reward.

                            State estimating monitors, however, are very useful. You might not realize that, because you're not living with one every day like some of us are.

                            About all they are good for is to tell you that you need to shut down and recharge which is the good ole Idiot Light in autos. There are way to many variables that no algorithm can predict with any meaningful significance.
                            Incorrect. We've had a lengthy discussion up thread about various monitoring algorithms. Each have tradeoffs. The very newest designs ameliorate most of the downside, and they take into account many of those "variables" to which you allude. Moreover, they appear to have good accuracy -- more than usable for making determinations about what to do when.

                            Now there is one method that is useful and can at least tell you when your battery is at 80% rated capacity, and thus time to replace the battery because after 80% capacity death is around the corner.
                            Can you link us to studies that show that 80% SOH lithium cells are about to die? That would be interesting reading.


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                            • I wonder if it might be time to close this thread. It seems to have gone off the rails.

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                              • You absolutely do not need to cool Tesla batteries. I'm testing with 100 constant amp draws the temperature doesn't go up more than 1 degree.
                                Last edited by 355spider; 11-30-2018, 06:53 AM.

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