connecting batteries in parallel or series, myth and theory



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.
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Hold it one second here...You are messing with my mind. "grid connected"? Why did you attach that into the sentence? What does grid connected system have the slightest to do with the post you were responding to?
Yes I didn't realize that you shifted the subject to grid connected system which had nothing to do with my post. My mind wasn't able to comprehend why anyone would use a design of a grid connected system to argue the point that zero day autonomy off grid systems (a system that can't ride through one day of overcast weather) are perfectly viable.
It sounded like you were saying
"Batteries can be well-maintained and last the maximum with zero days autonomy. It's done all the time"
Followed up by
"Nonsense. The #1 cause of premature failure of home-power batteries is chronic undercharging."
Which sounds contradictory. Yesh.....
My responses are going to be gibberish if the person I am debating with can't even stay on subject.
That is my excuse and I am sticking to it!!! :-)
.
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On Aug 14, 5:32 pm, snipped-for-privacy@ipal.net wrote:

I have never sold GC batteries, but I sure have replaced lots of them with single series strings of 2V cells of the correct Ah rating for people who thought that they were saving money buying GC batteries. I have also swapped out parallel strings of batteries, not just GC batteries, for single series cells.
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.
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.
Feel free to use GC batteries. They will work. For a while. You might get five years maybe six in a home power system. I have seen single series string 2V cells last 26 years.
Good luck

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In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 14, 5:32 pm, snipped-for-privacy@ipal.net wrote:
|> |> | Now you can take that as an insult if you like. But, Golf cart |> | batteries only last for decades if they are used as door stops. Most |> | people who are capable of learning only ever buy one set of GC |> | batteries for their house system. Those that have bought two sets have |> | a learning disability. |> |> The real question is, who knows the science behind why this is so? Maybe you |> do or maybe you don't. I'm not expecting you to write papers for me. But if |> your knowledge is limited to hearing people say things like "I had GC batteries |> and I will never do that again", that isn't ruling out to me that someone just |> didn't build it right. If you know of the science behind this, please point |> it out (e.g. PDFs of papers with graphs and charts and basis in physics, etc). |> Otherwise, its doubtful I'd ever get anything useful from you. | | I have never sold GC batteries, but I sure have replaced lots of them | with single series strings of 2V cells of the correct Ah rating for | people who thought that they were saving money buying GC batteries. I | have also swapped out parallel strings of batteries, not just GC | batteries, for single series cells.
So you are a dealer of very large cells/batteries.
| 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.
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.
| 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?
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On Aug 15, 3:07 am, snipped-for-privacy@ipal.net wrote:

No longer. Today the only solar work I do is helping people fix the problems caused by poor design.

The science is that cells all have different internal resistances.

As you wish, but, all the systems I designed using my training have worked to spec.

Shit, that was close to twenty years ago. Battery technology has not changed much since.

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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.
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).
|> 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?
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?
|> | 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.
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This paper may be what you are looking for.
http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
Bealiba may have an aneurysm if he reads it though.
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My brain if frying today. The smoke is coming out of my ears right now. That is the paper that Ron linked to at the beginning of this thread. Just ignore the previous message please. :-<
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Using Tweedledee as a reference. He can't even tell you about his systems design.
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|> |> 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. |> |> 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. | | http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf | | Bealiba may have an aneurysm if he reads it though.
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.
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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.
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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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Plus, no article can trump practical experience, which is that parallel strings of like batteries are routine and generally successful. I visited a setup recently with 6 (IIRC) parallel strings of GC batteries. About the last arrangement I'd ever recommend to anyone, and they had been replaced recently. But the previous ones lasted 5 years, which was reasonable considering their low cost and hard life.
Wayne
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On Aug 16, 10:43 am, snipped-for-privacy@citlink.net wrote:

You have no experience. Nuff said
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On Sun, 17 Aug 2008 06:35:39 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

My personal experience is getting >95% of my home energy from solar and wind, and choosing a first set of batteries that's lasted 13 years so far. Beyond that, I live in an area that has thousands of off-gridders, and I take every opportunity to visit. I've probably seen >100 off-grid installations, such as the one I mentioned above. Some are really low-budget and many have had multiple owners. Even so, I've never personally seen, or even heard of anyone, who's been through as many batteries as you have. 5 sets is a record as far as I know, and that's assuming that 5 is the real number and not another of your prevarications. Considering that and your penchant for posting nonsense about batteries (samples available here http://www.citlink.net/~wmbjk/tbfduwisdumb.htm ), it's a mystery why you'd expect anyone to accept battery advice from you.
Wayne
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On Aug 18, 10:12 am, snipped-for-privacy@citlink.net wrote:

How about because I'm right. Parallel batteries in a system use for home power is a waste of time and money.
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On Sun, 17 Aug 2008 17:59:33 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

LOL That "ignore my undeniable foolishness, believe what I claim" position seems to be your answer for everything. Here's a clue for you: the market for home power is in a stage of unprecedented expansion. And yet you, the self-titled "power consultant", after decades of trying to make a living in the trade, are still getting more than 95% of your home energy from anything-but-solar, still need to start a generator for even minor loads like laundry, and still need to find another career to bungle. The joke is that there's so much work out there that even a screw-up ought to be able to find a niche. But it takes a true Renaissance nitwit to write a ton self-busting foolishness into a permanent, searchable, public archive.
Wayne
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Only from laughing so much.
Read the whole thing from beginning to end, This report refers to float systems as use for backup in industrial applications and "NOT" home power systems and in fact says that
"This is not a problem for occasional discharges, or for more frequent discharges that are taken to completion. It can become an issue, however for a system that is designed for long discharges, but is subjected to frequent shallow discharges. In this case, the high rate battery will receive the brunt of the cycling duty, and may age prematurely as a result."
Given that in parallel strings one string will always have a higher rate than another string, batteries /cells never being perfectly matched, failure is always an option. The paragraph above gives a pretty good description of a home power system.
Whether you like it or not, no matter how you try to rationalize it, no matter how you twist the words of the author to meet your needs, a home power system with parallel batteries is not a good idea.
The real problem is the Tweedledee's and Tweedledum's of the world spot such a report as this on the net, read the title and jump to the conclusion that it says that parallel strings are ok for a home power system, never bothering to read the article to find out that it describes industrial float systems which may or may not ever be called upon to fulfill its intended use.
Sorry, the report really has nothing to do with home power systems.
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On Aug 15, 12:58 pm, snipped-for-privacy@ipal.net wrote:

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.

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On Fri, 15 Aug 2008 06:20:32 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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 http://groups.google.com/group/alt.solar.photovoltaic/msg/280d1994dfda27b7 . Or the "300 kOhms" wire that you recommend for a substitute http://groups.google.com/group/alt.energy.renewable/msg/99bcc1d3c8cfc9f8 . Or the 300mm nichrome wire that's 25 ohms http://groups.google.com/group/alt.energy.homepower/msg/782f4bb5531ca70d?dmode=source . Not to mention all the other hilarious quotes at http://www.citlink.net/~wmbjk/tbfduwisdumb.htm
Wayne
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