connecting batteries in parallel or series, myth and theory

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:
|
| |>> 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 | 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
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.
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On Aug 16, 7:52 am, snipped-for-privacy@ipal.net wrote:

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;
http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
paying close attention to the section "Technology issues". The first two paragraphs say it all.
The second paragraph supports my position as to parallel strings in home power systems.
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On Fri, 15 Aug 2008 17:16:20 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Perhaps you should show a quote to support that contention, which is exactly the type of BS that got you a free parody site. Regardless, how can anything that others write ever help mitigate your posting definitive proof that you don't know Ohms from apple butter?
Wayne
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In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 15, 12:58 pm, snipped-for-privacy@ipal.net 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.
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| snipped-for-privacy@gmail.com wrote: | |> You sound like a guy |> looking for an excuse to use golf cart batteries. | | I take that as a personal insult. There is nothing wrong with golf cart | batteries if his storage needs are modest. If the discharge is kept at | some respectable level, they will last decades. Most batteries don't | die, they're murdered. | | Not everyone needing a car needs a limousine.
I think he's upset that I haven't ruled out golf cart batteries long before the time to make the decision(s). Who knows, maybe I will rule them out at that time. Or maybe I will find an effective way to manage a dozen strings of them.
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On Aug 14, 5:27 pm, snipped-for-privacy@ipal.net wrote:

Not at all. Many people use GC batteries. Most only once.

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In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 14, 5:27 pm, snipped-for-privacy@ipal.net wrote:
|>
|> |> | |> |> You sound like a guy |> |> looking for an excuse to use golf cart batteries. |> | |> | I take that as a personal insult. There is nothing wrong with golf cart |> | batteries if his storage needs are modest. If the discharge is kept at |> | some respectable level, they will last decades. Most batteries don't |> | die, they're murdered. |> | |> | Not everyone needing a car needs a limousine. |> |> I think he's upset that I haven't ruled out golf cart batteries long before |> the time to make the decision(s). Who knows, maybe I will rule them out at |> that time. Or maybe I will find an effective way to manage a dozen strings |> of them. | | Not at all. Many people use GC batteries. Most only once.
Most probably didn't install them, or use them, correctly. Then they come crying to someone to fix it for them, and since their existing batteries are dead (or worse), they will take anything that comes along with a promise, especially if it is a design used for commercial ride-through emergency systems that have nothing to do with home power.
You sound like a battery salesman.
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On Aug 15, 3:11 am, snipped-for-privacy@ipal.net wrote:

Don't know much about commercial installations. I only did standalone home power.

Now that sounds like an insult:-) Yes I sold batteries, as part of a home power system. The batteries were chosen for their suitability for the job.

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No need to feel offended by anything the ghinius writes, particularly if it's about batteries. Consider that he's on his fifth set with his own very small power setup. Do you know of anyone else who's gone through so many? I sure don't, it's a record. In his own words:
"I have just installed my fourth set of batteries in 14 years" http://groups.google.com/group/alt.solar.photovoltaic/msg/b1d8014809ab83e5
"1st System 4 sets of batteries. 3 sets of which were second hand. 2nd system 1 set of correctly sized batteries" http://groups.google.com/group/alt.energy.homepower/msg/55bed756f3d60cef
Anybody with even a little common sense could have used GC batteries and needed only half as many replacements.
Nevertheless, you could reasonably think that someone who's learned the hard way might know *something* worth relating. Unfortunately that's not true either because those quotes demonstrate that he can't keep his stories straight. We don't know if it's 4 sets or 5 or maybe more. As if that point needed any reinforcing, consider another quote from him:
"Then I went shopping. I bought what was required (all top quality) and assembled it correctly and turned it on, fifteen years ago." http://groups.google.com/group/alt.energy.homepower/msg/cc0f45c7feda2c60
In fact, from the first two quoted posts we know that his current installation is only about 7 years old.
So, George Ghio not only holds the record for most dead batteries in a home power setup, he also lies so much that one would need a second opinion before accepting his word on the time of day. His battery lectures are about as credible as someone giving healthy-living advice based on their claimed personal good health, while alternating between drags on a cigarette and an oxygen cannula.
Many more examples of his astonishing BS here http://www.citlink.net/~wmbjk/tbfduwisdumb.htm .
Wayne
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On 8 Aug 2008 20:09:04 GMT, snipped-for-privacy@ipal.net wrote:

Read that paper again and work out the physics. Assume two strings of the same make/model/size but one is older. Note that the older string will have a lower capacity. Think about the relative resistances. Which string will supply most of the initial load? That will be the string that cycles most for shallow discharges, and will most likely age the fastest.

I would only use parallel strings if I had no other choice. In my case, I have two parallel strings, but that's because I could not obtain batteries of the size and capacity I wanted to set up a single string. When these need to be replaced, it will be with a single string of 2V cells (which are now available in a suitable capacity for me). Maintenance is much easier with fewer cells to care for. --ron
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| On 8 Aug 2008 20:09:04 GMT, snipped-for-privacy@ipal.net wrote: |
|>| |>|>If the effect is that the _older_ strings gets _older_ faster, |>| |>| And if it is the newer string that gets older faster? ... Well, maybe you |>| won't get the longevity you thought you'd paid for. |> |>Right. So we need to know which it is ... which string gets older faster. | | Read that paper again and work out the physics. Assume two strings of the | same make/model/size but one is older. Note that the older string will | have a lower capacity. Think about the relative resistances. Which string | will supply most of the initial load? That will be the string that cycles | most for shallow discharges, and will most likely age the fastest.
As long as there are no other "hidden" issues, that makes sense. I just don't want to jump to such a conclusion before ensuring that all the issues are known. I am not trusting any one single paper/article to cover all the issues.
|>| In any event, the "best" setup does depend to some extent on the |>| application and goals. |> |>How about a power backup system (charged by the grid) that gradually shifts |>to a renewable power system (charged by solar, wind, etc) and then eventually |>to a completely off-grid system (or at least a sell-only grid system). | | I would only use parallel strings if I had no other choice. In my case, I | have two parallel strings, but that's because I could not obtain batteries | of the size and capacity I wanted to set up a single string. When these | need to be replaced, it will be with a single string of 2V cells (which are | now available in a suitable capacity for me). Maintenance is much easier | with fewer cells to care for.
Are you going for the 33 plate Surrette 2KS33PS cells?
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On 9 Aug 2008 19:13:52 GMT, snipped-for-privacy@ipal.net wrote:

I haven't yet measured accurately, but it appears as if they will fit into the same footprint as my 8CS25P's. That being the case, they would be at the top of my list today. They have a bit more capacity, and I'd have half the cells to care for. Of course, when the time comes, I'll see what's available. --ron
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snipped-for-privacy@ipal.net says...

Starting batteries are often paralleled (though have isolation diodes) for higher current. Most large trucks have such a setup.
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I have often seen truck batteries connected in parallel, particularly on diesel pickups, but have never noted isolation diodes.
I have also seen one at least one near-truck fire that was apparently caused by shorted cells in one of the paralleled batteries on a truck, which led to the good battery forcing a high charge current through the bad battery. Ironicly enough, it was a fire truck.
Vaughn
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wrote:

Yes, I've done some anlalytical work in this area. And you are right, if one cell in a series-parallel setup fails for some reason. The string in parallel will discharge itself into the defecitive cell and in fact reverse charge the other good cells in the series string with the defective cell in it. Depending upon the energy content of your cells, you could really have a nice fire. Yes, a diode in each string that is then connected in parallel with another string would prevent this. The added burden is that of added cost for the heavy duty diode you might need and of the voltage drop you would experience from that diode while inoperation. And, of course, you wouldn't be able to charge the string.
My work was with a battery pack that consisted of mutliple series- parallel D cells set up as a back-up for a medical device. Yikes! I hope they took my advice and added the diode to each series string.
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In alt.engineering.electrical snipped-for-privacy@yahoo.com wrote:
| Yes, I've done some anlalytical work in this area. And you are right, | if one cell | in a series-parallel setup fails for some reason. The string in | parallel will discharge | itself into the defecitive cell and in fact reverse charge the other | good cells in the | series string with the defective cell in it. Depending upon the energy | content | of your cells, you could really have a nice fire. Yes, a diode in each | string that | is then connected in parallel with another string would prevent this. | The added | burden is that of added cost for the heavy duty diode you might need | and of | the voltage drop you would experience from that diode while | inoperation. And, | of course, you wouldn't be able to charge the string.
Paralleled strings mean "-" connected to "-" and "+" connected to "+". That is the correct charging polarity. If one string is longer by one cell than another, the shorter one won't be reverse charged. But it can be _over_ charged. But you face that risk of overcharging even if your charger applies the voltage for N cells when the string only has N-1 cells.
The current flow during charging is reverse of that during use. So it is heavy usage that has the possibility of reverse charging a weak cell.
| My work was with a battery pack that consisted of mutliple series- | parallel D | cells set up as a back-up for a medical device. Yikes! I hope they | took my | advice and added the diode to each series string.
For alkaline cells, which might be what gets put in such a pack, charging them at all could be a major hazard. One string in parallel with another, especially if one is weaker, could lead to that. So with this battery technology, I'd say the diodes are essential.
But my question is focusing on lead-acid cells/batteries intended for power reserve, as typically seen in off-grid systems and in backup power systems.
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The difference between the "charging voltage" and the "dischange voltage" on the lead cells is on the order of 0.2 volts. If there are more than 10 or so cells in series the "normal" stack would not excesively charge a "one shorted cell" stack. But a nominal 12 volt system might be a problem which may explain why that fire truck mentioned in another post almost set itself on fire.
The "one short" stack would tend to be over charged and monitoring the the chargin voltages would show that something is wrong.
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| The difference between the "charging voltage" and the "dischange voltage" on | the lead cells is on the order of 0.2 volts. If there are more than 10 or | so cells in series the "normal" stack would not excesively charge a "one | shorted cell" stack. But a nominal 12 volt system might be a problem | which may explain why that fire truck mentioned in another post almost set | itself on fire.
I'm thinking that I would go with a 48VDC system, so that would be 24 cells. But my concern also includes the issue of _reverse_ charging a bad cell in the string. It would seem to me that the higher system voltage raises the voltage point where a bad cell could fail to keep up and end up reversing.
| The "one short" stack would tend to be over charged and monitoring the the | chargin voltages would show that something is wrong.
Would it be good to have separate charging controllers per string?
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Mine has 4. No isolation diodes, just short jumper cables between like poles.
John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN It isn't Global Warming.... It's Jerry Falwell arriving in hell.
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Not compression start? I'm disappointed.
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