Gee Floyd, looks like you have been taking lessons from Tweedledum. I never said;
Which either makes you a simpleton or a liar.
Gee Floyd, looks like you have been taking lessons from Tweedledum. I never said;
Which either makes you a simpleton or a liar.
The trouble is that wayne has no idea what his system produces or uses. His best guess for both is that it is between 0 and 30 kWh/day with a 24V system. Laughable.
Why should I?
Perhaps you should get a degree.
Sorry, it doesn't work that way. Every design is different. There is no such thing as one size fits all.
Yes.
The answer was quite clear.
You did say "A diode is not a rectifier", which is hilarious.
If you think there is something wrong with the statement above, and given your response it appears that you do, then you might be some of these names you bandy about.
Parallel battery banks are not exactly uncommon... some of us have seen some fairly high capacity plants that use multiple parallel strings.
Regardless, you can rest assured that a diode is a rectifier by definition.
In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 15, 1:21 pm, snipped-for-privacy@apaflo.com (Floyd L. Davidson) wrote: |> snipped-for-privacy@gmail.com wrote: |> >> They can do things like ensuring that one bank does not cross change another. |> >> They can allow separate chargers for each bank. |>
|> >A diode is not a rectifier. |>
|> Why is anyone bothering to talk to you? |>
|> And I'll point out that the above is just the worst |> example, not the only one. |>
|> -- |> Floyd L. Davidson |> Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com | | Gee Floyd, looks like you have been taking lessons from Tweedledum. I | never said; | |> >> They can do things like ensuring that one bank does not cross change another. |> >> They can allow separate chargers for each bank.
How _not_ saying those 2 things somehow making your other statement more correct?
Have you even considered how to wire rectifiers in series with each battery string to ensure the current only flows in one direction with respect to where that rectifier is connected? Wired one way, the rectifier allows the string to discharge into a load at the other end of the connection (but it cannot be charged from that point). Wired the other way, the rectifier allows the string to be charged from a source at the other end of the connection (but it cannot discharge into a load at that point).
But your posts do seem to indicate you are limited to only doing things you have seen done before.
I can think of one good reason... the knowledge might have prevented your writing endlessly quackish posts, and readers of yet another newsgroup from finding out about them. Like the 150A/200A/150 ohm/8.5 ohm rheostat that you use for controlling field current on a 400W alternator
Battery monitor shunts are wired in series at the negative battery cable so that they count all battery current. For example, in my case that's routine PV and wind charging, occasional DC backup charging, rare AC backup charging, routine AC loads from 3 inverters and a tiny DC load.
Yes. One still needs to use a hydrometer occasionally to check for the need to equalize, and to verify that the monitor is synched.
Monitor features vary, but for a Link 10: Volts, amps, watts. Applies charge efficiency factor and Peukert to establish Ahrs below full, also displayed as SOC percentage, along with a 4 segment bar graph that can be set to display useable storage (usually the top 50%). With some juggling of breakers etc, the device can be used occasionally to compute individual sources and loads. The Link10 manual is a useful read.
Most batteries are rated at multiple discharge levels, one can make reasonable extrapolations as needed.
You're over-thinking the issue IMO, and you're unlikely to find independant testing results. But if you don't trust the maker then you might ask for clarification about exactly what some specs and warranty terms mean.
Dang, there goes my idea to market orgone to Usenetters. :-)
Wayne
You're quoting out of context. Read it again in full, I was referring to the need for regular complete charges.
Says you. My own charging period is 24 hours per day. Perhaps you meant your hypothetical to be limited to fixed PV without any supplemental sources.
Even using your worst tortured example, the user is likely to compare extending charging time with a supplemental source against enlarging storage 5X.
I do see what you're getting at with these hypotheticals. The thing is, they're not practical issues for anybody that I've ever heard of. I for damned sure have never heard anybody say "my charging rate is too high, I'm going to enlarge my storage to cure it", and I bet you've never heard that or anything like it either. If you really believe it's an issue, then I suggest you post some examples of where folks are asking for help with the problem.
Wayne
>
Um.. Lets look at the thread and context in detail.
Context, days of autonomy in an off grid system which it had been for most of the thread.
You changed it to days of autonomy for a grid tie systems.
He redirected it back to the subject that was in keeping with the rest of post in this part of the thread. That being days of autonomy for an off grid setup.
The subject and context of any general reply will be days of autonomy for an off grid system. AKA 1 to 10 days of autonomy. You made no mention of charging for that many days.
Subject, how do you do a proper recharge with 1 day of autonomy. I probably didn't make the context clear enough (sorry)
subject autonomy, in keeping with all the previous post.
Subject autonomy, in keeping with all the previous post. Context, autonomy in an off grid system.
How?
Lets look at that idea. To me, your original statement is stating that irrelevant of 1 to 10 days of autonomy, that if you "ignore the need to get batteries fully charged regularly and it won't matter whether they're 5 or 20 year batteries, whether they're wired in series or parallel, charged fast or slow, etc." that they are going to die.
You are stating that you were meaning to say irrelevant of 1 to 10 of charging that if you don't keep them fully charged, then they will die. That isn't in keeping with the subject of the post you are replying too, you didn't make any indication that that was the context and it don't really make logical sense for the post you are replying to.
You change the subject back to grid tie systems again!!!! Which has nothing to do with the conversation!!!
What does that have to do with the conversation? I am asking you how something could be done. Because you say it doesn't mater if it is did that way or not. If someone is doing it in the real world or not is irrelevant.
The only person that seems to be having problems staying on subject is you. How can people have a logical discussion when someone keeps changing the subject every time they speak? You are most likely just trying to mess with peoples minds. I am not going to carry on this stupidity any longer.
In alt.engineering.electrical N9WOS 100% in one day, which makes it *your* job to show some examples of |> such systems. | | All right. You stated "Whether it's 1 day or 10(days of autonomy)". | | Lets look at one day of autonomy for the winter months. 5 hours sunshine. | You have 19 hours between charging periods. To have exactly 1 day autonomy | would mean that you have to ride through two dark periods and one cloudy | charging period. Given an average power usage spread (lights at night and | other stuff in the day) that will give you about 44% capacity usage between | charging periods. So each charging day, you are starting from 56% SOC. | (close to my original guess) | | So I will refine that question. | | How do you get from 56% SOC to 100% SOC in one charging period. | | If it can't happen then it does mater if the system has 1 or 10 days of | autonomy.
After a few days of no available solar/wind energy, I would expect the SOC of a battery bank to be lower than usual (if less than a few days of no available solar/wind energy is usual). And I would expect that when the energy becomes available, again, it can take at least a few days to get back to 100% SOC.
So is the issue a matter of how _long_ the bank sits at below 100% SOC, even if it doesn't go below 50% SOC?
In alt.engineering.electrical N9WOS |> Further, science would tell you how they behave under various methods |> |> of connecting charging and discharging circuits. |> | |> | The science is that cells all have different internal resistances. |>
|> I guess you don't have an EE degree. |>
|> Not that I have one, either. But I respect the knowledge AND |> understanding |> real engineers need to have. The information I seek is what would be |> learned in an Electrical Engineering, Power Elective, curriculum (not all |> of it, of course ... just the parts I'm interested in right now). | | This paper may be what you are looking for. | |
I saw that from an earlier reference. Good paper. But I guess we need to keep it secret to protect the health of other people.
In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 15, 12:58 pm, snipped-for-privacy@ipal.net wrote: |> In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: |>
|> |> So you are a dealer of very large cells/batteries. |> | |> | No longer. Today the only solar work I do is helping people fix the |> | problems caused by poor design. |> |>
|> |> | I can only repeat what I learned getting my accreditation. That was |> |> | many years ago and I am sorry that I no longer have the notes to show |> |> | you. |> |> | |> |> | The science says that parallel strings do not charge and discharge |> |> | equally. Parallel strings should be avoided where ever possible and GC |> |> | batteries belong in a golf cart. |> |>
|> |> That's not science. Science would tell you why and how that happens. |> |> Further, science would tell you how they behave under various methods |> |> of connecting charging and discharging circuits. |> | |> | The science is that cells all have different internal resistances. |>
|> I guess you don't have an EE degree. | | Why should I?
It would make you recognizable as a _possible_ expert in the field. But it is the learning process behind the degree (even if you skip out in the last semester and don't actually get the sheepskin) that matters.
|> Not that I have one, either. But I respect the knowledge AND understanding |> real engineers need to have. The information I seek is what would be |> learned in an Electrical Engineering, Power Elective, curriculum (not all |> of it, of course ... just the parts I'm interested in right now). | | Perhaps you should get a degree.
If I had the time to go through all that, I would, actually.
|> |> You're taking the training you've been giving regarding certain finite |> |> methods to install battery systems, and calling it "science". Real |> |> science comes from research laboratories and investigative processes |> |> that explore all options and find out why things really happen and how |> |> control methods may or may not work. |> | |> | As you wish, but, all the systems I designed using my training have |> | worked to spec. |>
|> Are you talking about true design, or just mere deployment configuration? | | Sorry, it doesn't work that way. Every design is different. There is | no such thing as one size fits all.
And I suspect not every situation best fits a solitary string, either. It might look to be the best fit if you limit the parameters to only certain ones. Engineering does not limit itself that way. Engineering does not determine what is the technically best design and try to fit that into every scenario.
|> Bob needs twice the capacity as Carl, so you install a system for Bob |> that has a string of cells twice as big as those you installed for Carl, |> that's NOT "design". That's "configuration". You select a design (one |> single string) and you select a capacity based on available models. |>
|> Configuration is when you select from existing known designs. Have you |> ever installed a system which was wired different than _any_ example you |> ever saw before? | | Yes.
So it wasn't just a solitary string of batteries every time? You designed somthing different than that for at least one customer?
|> |> | If you want to use them, fine. But in the long run you will say, "That |> |> | bastard was right". |> |> | |> |> | The tests were done at Royal Melbourne Institute of Technology in |> |> | Melbourne. The test was done on a rig of six parallel strings of six |> |> | two volt cells. They tried all the tricks like isolating the strings |> |> | with diodes and fancy interconnecting of cells. The results were |> |> | always much the same. Unbalanced charging across the array. |> |>
|> |> What kinds of chargers did they use? Did they have separate chargers for |> |> each string? |> | |> | Shit, that was close to twenty years ago. Battery technology has not |> | changed much since. |>
|> But you didn't want to answer my question. Don't worry, you are under no |> obligation to answer it. And, besides, this is Usenet. Most questions go |> unanswered, anyway. | | The answer was quite clear.
I'm not looking for the one way you would do things. Among the things I do want to know is the "how you would do things" across a wide range of people. But I'd also like to know _why_ for each, if it is not the case that 100% would do things exactly the same way. And I have found that it is true that not everyone would do the same. Some people have explained some science behind what they do, or referenced papers or articles that explain that. So far I've not yet seen such a thing from anyone who is adamant that no battery system should be designed with parallel strings.
If lead sulfate sits for enough time on the plates it will crystallize. It is hard for you to convert it back to spongy lead and sulfuric acid. Most of the time it is just lost capacity. It doesn't mater if the charge level is
80% or 20%. If the battery never gets close to 100% charge, and the sulfate isn't disturbed , it will start to crystallize. You could hold a battery bank on float at 90% SOC and the 10% that is locked up in sulfate will crystallize after a while.It you get up to 95% regularly in a cyclic application, then usually all the sulfate will get cycled to acid once In a while. The thickness in sulfate and lead build up isn't exactly even across the working surface, so at 95% SOC all the sulfate on any one surface is sometimes consumed during charging, leaving a little more on a different part of the plate. During the next charging cycle there may be plenty left on that part of the plate but spot two that had some left last time is completely sulfate free. But if you only get to 85% charge or lower on a cyclic application then there is sufficient sulfate thickness that the lowest levels of sulfate will not get disturbed long enough to allow it to crystallize. And that capacity is permanently lost.
That is why you do a EQ charge once in a while to make sure you get all the sulfate converted to acid, down to the deepest levels, to prevent it from crystallizing.
It doesn't mater if the bank is cycled down to 10% SOC, as long as it is fully recharged in time enough to prevent any deeply locked up sulfate from crystallizing.
| Battery monitor shunts are wired in series at the negative battery | cable so that they count all battery current. For example, in my case | that's routine PV and wind charging, occasional DC backup charging, | rare AC backup charging, routine AC loads from 3 inverters and a tiny | DC load.
Current alone (which, BTW, is a single value for the whole string) is going to tell you what about the condition of each cell in the string?
You don't measure the voltage anywhere?
|>it would seem this monitor only checks the health of the whole |>string, not each individual battery/cell. | | Yes. One still needs to use a hydrometer occasionally to check for the | need to equalize, and to verify that the monitor is synched.
I'd like to figure out a means to have the check automated. That might mean a built-in factory-calibrated hydrometer interfacing to an optical sensor that can be attached over the window that accesses the hydrometer.
Then if the science tells me that for certain conditions, a different level of charge or discharge should be applied to that cell, then either that would be done if the design has the means, or the operator would be warned if it can't.
|>Exactly what parameter(s) does this monitor check? | | Monitor features vary, but for a Link 10: Volts, amps, watts. Applies | charge efficiency factor and Peukert to establish Ahrs below full, | also displayed as SOC percentage, along with a 4 segment bar graph | that can be set to display useable storage (usually the top 50%). With | some juggling of breakers etc, the device can be used occasionally to | compute individual sources and loads. The Link10 manual is a useful | read.
|>|>| No. Batteries have a finite life-rating usually stated as a number of |>|>| cycles at a particular discharge level. |>|>
|>|>Which is only a simplistic view of the usage patterns of batteries. |>| |>| Batteries are rated to supply a specific number of amp-hrs. The amount |>| will vary with the number and depth of discharge cycles, and can |>| certainly be less than spec if subjected to poor maintenance or bad |>| habits. But it can't be more unless you've discovered something that's |>| escaped everyone else. |>
|>If the manufacturer rates the battery for its most ideal circumstance, then |>sure, you can't get the battery to do better than the rating. | | Most batteries are rated at multiple discharge levels, one can make | reasonable extrapolations as needed.
The biggie 2V Surrette cell (shown in the PDF file) had a lot of them listed.
In alt.engineering.electrical snipped-for-privacy@citlink.net wrote: | On Fri, 15 Aug 2008 06:20:32 -0700 (PDT), snipped-for-privacy@gmail.com wrote: | |>On Aug 15, 12:58 pm, snipped-for-privacy@ipal.net wrote: |>> In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | |>> I guess you don't have an EE degree. |>
|>Why should I? | | I can think of one good reason... the knowledge might have prevented | your writing endlessly quackish posts, and readers of yet another | newsgroup from finding out about them. Like the 150A/200A/150 ohm/8.5 | ohm rheostat that you use for controlling field current on a 400W | alternator |
A good laugh, especially that last one. I was wondering why it seemed that almost everyone else was ignoring him, or at least not responding to him.
Sat down and read the article. It describes commercial battery back up systems (float systems). It also describes exactly what I said as to charging and discharging. See paragraph 2 under Technology issues.
Thank you for your supporting information.
I think another key point is how often the batteries are fully recharged as well. In Neon John's use of a golf cart, I would bet that he recharges the thing every day or so depending on how much he uses it. Recharging from grid power through a dedicated charger is pretty straight forward and not at all hard to get a full charge overnight.
But a solar installation may not have quite that luxury. A partial discharge each day for a couple of days, followed by only a partial recharge might be more problematic. A couple of cloudy days, and although the batteries are not fully discharged, the chances are that one sunny day will
*not* put back all the charge.Seems that type of duty is a lot harder on a battery than even 'typical' golf cart usage.
Unless of course you want to buy a lot more solar cells so you *can* recharge the battery in one sunny day ;-)
daestrom
Hmm. Perhaps you should have a look at wayne's assertion that increasing the daily load will reduce line losses.
Listening to the Tweedle brothers Tweedledee and Tweedledum will have you at serious of loss of money and a system that only works in a pink fit.
While you are trying to understand batteries and parallel strings READ;
The second paragraph supports my position as to parallel strings in home power systems.
Now *THAT* is a good argument for using parallel battery strings. But keep in mind what you are effectively saying is, "Although parallel GC batteries may not be the best solution, some of the benefits of using them outweigh the shorter life." You're just weighing how often you want to fuss with swapping out a dead battery and how often your power goes out versus how much money you want to spend replacing batteries.
But FWIW, when one "250 lb monster cell" goes bad, when you have just a single series string you simply jumper out the cell and reset the voltage settings. Running 2.1 V lower is not a big deal when you're talking +250VDC (a slight reduction in capacity) and power is restored. Of course, if you lose several cells and have to jumper them out, it's time to start thinking of a new battery. :-)
Yes, but I was trying to point out that inverters are not limited to 48vDC input. That was all.
daestrom
Supporting information in part, but not in total.
It points out that you can have problems if you parallel two lead acid batteries of different design, (high rate/low rate) when you have a shallow cycling system. Two designs where the internal resistance is way different by design. The one with the lowest resistance discharges first.
Like paralleling a deep cycle battery and an engine starting battery. The engine starting battery has a lower resistance and it will support the same current at a higher output voltage. The starting battery will support more of the load until it discharges to a lower SOC than the deep cycle battery and then the deep cycle starts carrying it's part.
But if you have two similar AH batteries from different manufactures that are designed for the same general service (with similar ,but not the exact same, discharge characteristics). Then the load sharing becomes more even through the load/charge cycle.
And two different AH size batteries designed for the same general application, from the same, or different manufacture, with similar plate spacing and size, will share a load more evenly. The battery that is half the size of the larger one will have twice the internal resistance, and contribute half as much current to the load as the larger one, with the same SOC.
The only thing the article points out as problematic in shallow discharge situations is paralleling two completely different lead acid battery designs. High rate/low rate, AGM/flooded/gel, starting/deep cycle/marine. And paralleling different battery technologies. Lead acid/nicad/NMH/Li Ion./nickel iron/or the like. Nothing more, nothing less.
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