connecting batteries in parallel or series, myth and theory

In alt.energy.homepower snipped-for-privacy@gmail.com wrote:
| God, you're funny. The only reason you asked is in the hope that
| someone will hold your hand and tell you it's ok to use parallel | batteries so you can feel good about making a choice that is stupid.
People might believe you if you were in a position to know. You aren't. So they know you just make stuff up.
| Remember this: | | "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." | | This is the kind of system used in home power situations.
But you still fail to describe the science behind this. Of course, I'm not in a real position to know if you understand the science or not. If you do, then you must have some reason for not saying it.
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On Aug 25, 4:22 pm, snipped-for-privacy@ipal.net wrote:

I most certainly did not make up
www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
This paper makes it quite clear that parallel batteries for a home power system is not suitable.
So unless you intend to run a float system for home power (the gods know you sound stupid enough to try) the paragraph below describes what you will be building.

The reason for not saying it is that you will call me a liar and deny that the reasons are valid.
The article at
www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
says it all.
If you don't like the paper or its conclusions about parallel batteries in a system that is designed for long discharges, but is subjected to frequent shallow discharges, I suggest that you take it up with the author, Jim McDowall, and tell him he as a fool.
I did not write the paper. But I did tell you the same thing.
Now, off you go and buy as many T105s as you can get you grubby little hands on and string them up in parallel to your hearts content.

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In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 25, 4:22 pm, snipped-for-privacy@ipal.net wrote:
|> |> | God, you're funny. The only reason you asked is in the hope that |> | someone will hold your hand and tell you it's ok to use parallel |> | batteries so you can feel good about making a choice that is stupid. |> |> People might believe you if you were in a position to know. You aren't. |> So they know you just make stuff up. | | I most certainly did not make up | | www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
No, but you do not grok the science behind it. You, instead, look for the conclusions and then assume it applies to every case.
| This paper makes it quite clear that parallel batteries for a home | power system is not suitable.
Only for home systems where the paralleling is done the way they described.
| So unless you intend to run a float system for home power (the gods | know you sound stupid enough to try) the paragraph below describes | what you will be building.
Since you don't grok the science, you wouldn't grok the alternatives. You'll have to wait for the PDF paper to come out.
|> | Remember this: |> | |> | "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." |> | |> | This is the kind of system used in home power situations. |> |> But you still fail to describe the science behind this. Of course, I'm not |> in a real position to know if you understand the science or not. If you do, |> then you must have some reason for not saying it. | | The reason for not saying it is that you will call me a liar and deny | that the reasons are valid.
You are a liar and your reasons are not valid!
There. Over and done with. So there's nothing new to fear. Now go ahead and post the science you think you know.
| The article at | | www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf | | says it all.
It might be all there is in your small world.
And, BTW, where in the paper does the author mention home power systems? Search for "home".
| If you don't like the paper or its conclusions about parallel | batteries in a system that is designed for long discharges, but is | subjected to frequent shallow discharges, I suggest that you take it | up with the author, Jim McDowall, and tell him he as a fool.
The fool is the one who misapplies what this paper says. For example, it discusses the discharge of one string into another. But this is clearly a case of the strings simply being hot wired to each other as the means to parallel them. He didn't cover the case of strings wires in parallel with isolation rectifiers.
| I did not write the paper. But I did tell you the same thing.
No, you only told me what the paper concluded, while thinking it applied to all of the designs I'm considering (it only applies to _some_ of them).
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On Aug 26, 6:00 am, snipped-for-privacy@ipal.net wrote:

As you wish.
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On Aug 22, 12:37 pm, snipped-for-privacy@ipal.net wrote:

Yes, and if they do gas off, the lost material is no longer there to recombine and the batteries capacity is diminished.

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In alt.engineering.electrical snipped-for-privacy@gmail.com wrote: | On Aug 22, 12:37 pm, snipped-for-privacy@ipal.net wrote:
|> |> | wrote: |> |> |> |> |> |> | Looking at the stated purpose of the paper and the "test setup" drawn |> |> in |> |> |> the |> |> |> | paper it would seem that the test conditions do not match the |> |> purpose. |> |> |> As I |> |> |> | understand it, in a VRLA cell the electrolyte has only limited |> |> contact |> |> |> with |> |> |> | the plates. Determined by capillary action in the separator material, |> |> |> |> |> |> Are you confusing VRLA with AGM? |> |> |> |> |> | |> |> | If I am it is due to reading this paper: |> |> | |> |> |http://www.battcon.com/PapersFinal2006/LandwehrlePaper2006.pdf |> |> | |> |> | I'll look up AGM in a minute. |> |> |> |> What kind of capillary action exists in VRLA? |> |> |> | |> | Did you read the cite? AGM, from what I read is a Gell Cell. VR (Valve |> | Regulated) LA is made with an absorbent plate separator, under some pressure |> | between plate/separator/plate, and a limited amount of electrolyte. |> | Separator materials vary. Now. I am familiar with flooded cell and gell |> | cell, having worked with both for many years, and I have seen the insides of |> | what I now know to have been a VRLA cell as well as Silver Zinc flooded |> | cells in the military ( the battery shop guy was a friend of mine and showed |> | me how to inspect, test, and repair the AgZn cells ) but my responses in |> | this thread are extracts from certain cited sites alongside already |> | accumulated experience. If you must question something it would help if you |> | actually read the cited paper before asking the question. That way you might |> | not need to ask. |> |> AGM is absorbent glass mat, not gel cell. |> |> VRLA is a class of batteries (includes AGM and gel cell) that includes a |> regulated valve to control the gas release at a certain pressure. | | Yes, and if they do gas off, the lost material is no longer there to | recombine and the batteries capacity is diminished.
Yes, that is a problem. Replenishment is needed. Hopefully there is no lead in that gas. Loss of hydrogen, oxygen, and sulfer can be dealt with in a flooded cell. Both gel cell and AGM make this replenishment impossible. I guess that is an acceptable tradeoff for the benefits they provide for certain usages.
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On Aug 18, 11:36 pm, snipped-for-privacy@citlink.net wrote:

Ah, no. parallel strings in a home power system is wasting money. I know this from training that told me that the same thing as the paper at:
http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf
which says,
"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."

Well after twenty five years of using solar power, living on solar power and twenty years of designing and installing solar power for others. Yes I do know what I am doing. While you still have no idea what your system produces or uses.

Ah yes. Another lie. Nearly all deep cycle batteries will withstand a discharge of up to 80% (Maximum Depth of Discharge) wayne confuses this with the Daily Depth of Discharge. Still you can believe wayne if it make you feel better about not understanding system design.

Well the first was a result of bad judgment in that I followed the advice of a wayne clone and used parallel strings. The next three sets of batteries were second hand and kept things going untell I had the cash to install a single string of the correct Ah capacity. Of this crime I am guilty, please forgive me.

Listen to wayne and you too can do what I did.
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snipped-for-privacy@gmail.com wrote:

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.
mike
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Yes. It is true that most batteries are murdered. OTOH golf cart batteries commit suicide.
The point is that batteries are the heart of a system. Bad heart, bad system.
You're right, there is nothing wrong with golf cart batteries, they make great door stops.
I'll tell you something about golf carts.
This guy goes to his doctor and the doc says that there is nothing a bit of exercise won't make better and suggests that the guy take up playing golf. The idea is of course that the guy will be walking around the golf course at least once a week.
The guy says, "Hey that sounds great." He goes out and buys a golf cart to drive himself around the course. A year later he drops dead from a heart attack climbing the four front steps to his house after a round of golf.
This is the same mentality that buys golf cart batteries for a house system and wires them up in six parallel strings.
Buying your heart from the cheap shop is suicide.

Yep, but they still buy the limo.
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.

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In alt.engineering.electrical snipped-for-privacy@gmail.com 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.
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The only problem with GC batteries in a solar power system is normally the design of the solar power system, not the batteries. GC batteries are designed to be used in a certain way. But people design solar power systems with GC batteries without taking that into account.
A solar power system that discharges/charges it's battery bank by 60 to 70 percent capacity on a daily basis will quickly kill the GC batteries. Heck, it will kill almost any normal battery. If there is a cloudy day the system will stop working. Or, basically 0 days of autonomy. Yet, in most sunny places, that is the design spec.
Most normal deep cycle batteries are designed for a C/20 charge rate. (ie) capacity /20 = charge rate. A 200Ah battery is designed to be charge at 10A. About one day to go from dead to full charge. You can not charge a battery bank by 60 to 70% of it's capacity in 4 hours of sun with a C/20 charge rate. Usually, the charge rate is in the order of C/5 or higher. That is hard on most batteries. The high price "solar" batteries that companies cell are designed to take that, but that doesn't mean that they wouldn't do better if they were charged at a more modest C/10 to C/20. Just because they can take it, doesn't mean they like it.
A system 12V system that has to have a 1200W (100 charging amps) of solar panels should have about 2000Ah of battery capacity. That would support about a 200W average load. It would support about 5 days of autonomy.
So, a basic rule for GC batteries is, if you put them in any system that doesn't have at least 5 days of autonomy, then you are going to kill them. That is because the charging , and discharging rates are going to kill them. As for as GC batteries go, it's mainly the charging rates that get them.
If you keep the charge/discharge rate in line with design specs then they will last for decades.
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Bullsh*t.
And yet, somehow, we EVers manage to get thousands of miles out of golf cart batteries, discharging them daily to 50-80% at amp draws up to about 500 amps.
I had about two years on my last pack when I sold the car. That's 2 years worth of daily driving. You can count the cycles. I had my controller's battery amps programmed to 400 amps max, a limit that I hit fairly often. No significant loss of capacity or range.
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 Unable to locate Coffee -- Operator Halted!
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wrote:

I am probably making a big mistake jumping into the line of fire, between you two, but it appears to me that both of you have valid points. And both of you are providing information to support the idea that Golf Cart batteries can be useful, when the charging and discharging characteristics (as provided by their makers, for their intended purpose) are taken in consideration and adapted to how they would apply to the new purpose.
EV use, (and a Golf Cart is an EV) would certainly involve heavy discharge rates into a motor, the GC battery would have been designed with that in mind. It is my understanding that batteries are more open to degradation during the charging process than the discharging process.
Neon John's post speaks to the hardiness of the GC battery during discharge, and should be taken to indicate no problem with the occasional discharge below a 60% design level. Fortunately a home running on wind or PV power, has many smaller loads/demands instead of a single large motor to feed.
N9WOS's post points to the need for sufficient capacity so that the slower charging rate from alternative sources, are practical. The less aggressive charging should indeed extend the operating life of the battery bank, ( with proper maintenance including a schedule of "maintenance overcharging").
Golf Cart batteries may be less efficient or practical than a number of newer alternatives but they have a long history of availability and low cost for less demanding homepower use.
If you are thinking of powering John Edward's house, you should probably give the Golf Cart batteries a pass.
Luck; Ken
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Ken Maltby wrote:

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
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Agreed, and there are a number of factors related to that issue. One, relates to the size of the array, as you mentioned. Another relates to the site and how much actual sunlight will be available to the array, not just the amount shown on an "Insolation" table. Another is the amount of use made of, or demand on, the system. A perfect balance of these factors may be unlikely but a very workable and practical solution can be arrived at that has a minimal impact on the battery bank's longevity. (Keep in mind there will be some using up of any battery system, it's in the nature of the beast.)
And there is always the option of having a generator handy on the occasional totally dead days for local energy production. (Even a combined PV and Wind setup can have a break down that can necessitate a wait for parts. Even micro hydro can dry up or break.) A generator sized for just the job of an "overnight" recharge of your battery bank, and the occasional EQ charge when the local production is marginal, would not be that big, (or such an environmental disaster for the overly sensitive types out there) nor require that much fuel for the rest of us frugal types.
One of the advantages of the Homepower system is that you can go without for a period, if you really need to, and not find yourself hurting that much. If you are a business that may not be the case.
Luck; Ken
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| 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.
In cases of a long period of autonomy, once the energy flow is back, but you do not know how long it will stay back, is it better to grab all you can and charge fast, or stick to the slow charge, knowing that if the energy quits before a full recharge, you could be discharging again from a point of not having gotten back to full charge. Part of the question is what is the effect on a battery/cell of sitting for some length of time at less that full charge, even if not discharging.
| 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 ;-)
But is that wise?
I could average out what my typical sun/wind energy input is over a long period of time, like a year, and what my usage would be, and size the PV arrays and windmills to provide all the energy I need, plus a reserve. But that does not size the batteries. If the batteries might need a quicker charge because the effect of sitting for time in a low charge state is worse than a fast charge, then I have to up the energy input size to deal with the batteries.
And of course all this is done statistically, since we cannot reliably predict how long these periods of energy availability and unavailability will be, as the Earth warms up and changes its weather and climate patterns around rather significantly in some places.
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Yes, but how fast do you charge them? Amperes over what time period? I would say that it isn't close to the rate at which you charge them. The key isn't how fast or how much you discharge them, it's how fast you charge them.
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Typo's I would say that it isn't close to the rate at which you DIScharge them.
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|> And yet, somehow, we EVers manage to get thousands of miles out of golf |> cart |> batteries, discharging them daily to 50-80% at amp draws up to about 500 |> amps. |> |> I had about two years on my last pack when I sold the car. That's 2 years |> worth of daily driving. You can count the cycles. I had my controller's |> battery amps programmed to 400 amps max, a limit that I hit fairly often. |> No |> significant loss of capacity or range. | | Yes, but how fast do you charge them? Amperes over what time period? | I would say that it isn't close to the rate at which you charge them. | The key isn't how fast or how much you discharge them, it's how fast you | charge them.
Charging a battery is similar to electroplating. While they do try to find ways to speed up electroplating, doing it well is something done slowly. Slow charging is something I've always done, with a few exceptions in urgent cases.
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Baloney. Batteries can be well-maintained and last the maximum with zero days autonomy. It's done all the time with grid-connected setups that only have storage enough to last through short outages.

Nonsense. The #1 cause of premature failure of home-power batteries is chronic undercharging.

No. Batteries have a finite life-rating usually stated as a number of cycles at a particular discharge level.
Wayne
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