Extending a part worn battery bank

xNYCMarc

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Seems to me like the thread should be considered solved at this point to avoid further phallus waving.
There never was any "phallus" waving. People are also confusing parallel strings with parallel cells. But I'm done arguing. It isn't worth it.
 

boondox

Chief Engineer, RedNeckTech Industries
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There was no phallus waving. There was some degree waving and it was hilarious. I am perfectly willing to grant that Mark has a degree. That doesn't mean anything to me in regards to this discussion. As I said earlier, I have known folks with degrees who knew nothing and folks without who were very knowledgeable. Let's forget the degrees. As the Borg would say, degrees are irrelevant.

As a topic for discussion on a DIY solar site, this is a good and important one. Mark, you have yet to post anything supporting your claims. I for one am still open to evidence. Nor have you answered any of the points that have been brought up. You haven't even told us the details of your experiments.

So Mark, what happens in this situation: You put two lead batteries in parallel. One is only capable of reaching 1.22 SG. The other is capable of reaching 1.28. When charging them, when you get to max charge voltage, what will be happening to the older battery? Then, after the sun has gone down, the new battery has a higher level of charge then the old battery. What happens to its level of charge? Then somebody fires up a heavy load. Maybe some midnight welding. Which battery is providing more of the power?

As I said earlier, I have seen this aging process in action on multiple occasions. At first the new battery will read higher, for a couple or few weeks. Then it will read the same as the rest of the bank. At that point if taken out of the bank and charged it will manage to charge fully. If left in the bank longer, for a few months, it will no longer be able to charge fully and will charge to the same extent as the average of the bank. I have seen and measured it.
 

xNYCMarc

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There was no phallus waving. There was some degree waving and it was hilarious. I am perfectly willing to grant that Mark has a degree. That doesn't mean anything to me in regards to this discussion. As I said earlier, I have known folks with degrees who knew nothing and folks without who were very knowledgeable. Let's forget the degrees. As the Borg would say, degrees are irrelevant.

As a topic for discussion on a DIY solar site, this is a good and important one. Mark, you have yet to post anything supporting your claims. I for one am still open to evidence. Nor have you answered any of the points that have been brought up. You haven't even told us the details of your experiments.

So Mark, what happens in this situation: You put two lead batteries in parallel. One is only capable of reaching 1.22 SG. The other is capable of reaching 1.28. When charging them, when you get to max charge voltage, what will be happening to the older battery? Then, after the sun has gone down, the new battery has a higher level of charge then the old battery. What happens to its level of charge? Then somebody fires up a heavy load. Maybe some midnight welding. Which battery is providing more of the power?

As I said earlier, I have seen this aging process in action on multiple occasions. At first the new battery will read higher, for a couple or few weeks. Then it will read the same as the rest of the bank. At that point if taken out of the bank and charged it will manage to charge fully. If left in the bank longer, for a few months, it will no longer be able to charge fully and will charge to the same extent as the average of the bank. I have seen and measured it.
My name isn’t Mark. I already terminated my discussion with you earlier and the fact that you can’t even respect someone enough to get their name right shows that I was right to terminate. As I said earlier, I gain no benefit from changing your mind. I don’t make any money from it, I’m not selling anything. So again, believe what you want. It’s won’t change my life. This particular part of the discussion wasn’t even involving you. You didn’t incorrectly say that my school didn’t offer the program that I earned my degree in. Someone else did.
 

boondox

Chief Engineer, RedNeckTech Industries
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My name isn’t Mark. I already terminated my discussion with you earlier and the fact that you can’t even respect someone enough to get their name right shows that I was right to terminate. As I said earlier, I gain no benefit from changing your mind. I don’t make any money from it, I’m not selling anything. So again, believe what you want. It’s won’t change my life. This particular part of the discussion wasn’t even involving you. You didn’t incorrectly say that my school didn’t offer the program that I earned my degree in. Someone else did.

I beg your pardon for getting your name wrong. My intent was to show respect by using your name.

However, yet again you make no logical argument. You bring no evidence to the table. You don't discuss the arguments that have been presented. You simply continue to maintain you are right.

Have you considered that the possible benefit you might gain is learning something, that you just might possibly be wrong? I have considered that possibility for myself and if you bring the slightest shred of evidence I will consider it with an open mind.
 

xNYCMarc

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I beg your pardon for getting your name wrong. My intent was to show respect by using your name.

However, yet again you make no logical argument. You bring no evidence to the table. You don't discuss the arguments that have been presented. You simply continue to maintain you are right.

Have you considered that the possible benefit you might gain is learning something, that you just might possibly be wrong? I have considered that possibility for myself and if you bring the slightest shred of evidence I will consider it with an open mind.
I did discuss the topic presented. Just because you disagree doesn’t make me “not discussing the topic”. People are also conflating the issue of “parallel STRINGS” and “parallel CELLS” in a single string. My argument is about parallel cells in a single string. But people keep arguing about “sets” and “strings” and such that aren’t matching what I’m talking about.
 

boondox

Chief Engineer, RedNeckTech Industries
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You have been asserting your position but not explaining why you think it to be true.

As far as I know, alkaline batteries are the only common type of batteries that are made of a single cell. All of the other batteries we use are series of cells. With lead, each cell is 2V and usually are manufactured such that there are 3 or 6 cells in series. There are exceptions, fork lift batteries can be 2V and I think are usually placed in series only but I haven't worked with them much.

Perhaps define what you mean by parallel strings and parallel cells with examples of each.
 

circus

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Not taking sides. So helping my cheap old "parallel FLA marine's" is impossible?
 

boondox

Chief Engineer, RedNeckTech Industries
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Not taking sides. So helping my cheap old "parallel FLA marine's" is impossible?

We'd need more information. But if you are asking can you add some new batteries to your old ones I don't think it is a good idea. Nor does the battery manufacturing industry. If you have both the courage and time, read through the thread.
 

wiseacre

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Not taking sides. So helping my cheap old "parallel FLA marine's" is impossible?
I'm no expert but from everything I've read about adding to my Gel battery bank I'd say it's not a good idea to add new lead to old.
There is one disagreeing opinion but it's not enough for me to bet battery money on.
 

xNYCMarc

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Not taking sides. So helping my cheap old "parallel FLA marine's" is impossible?
My position is that it is very possible. But obviously others are disagreeing with me. My findings are that two (or more) paralleled cells will function as a single cell. If there is a “weaker” cell in that parallel “block”, then the “stronger” cell will simply “do more of the work”, but less than if the cell were by itself and not paralleled with another cell. But again, people are disagreeing with me about that.
 

xNYCMarc

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You have been asserting your position but not explaining why you think it to be true.

As far as I know, alkaline batteries are the only common type of batteries that are made of a single cell. All of the other batteries we use are series of cells. With lead, each cell is 2V and usually are manufactured such that there are 3 or 6 cells in series. There are exceptions, fork lift batteries can be 2V and I think are usually placed in series only but I haven't worked with them much.

Perhaps define what you mean by parallel strings and parallel cells with examples of each.
I’m going to do a set of engineering drawings and submit it to Rolls/Dekka/several manufacturers and ask if they see a problem and would warranty their cells in that configuration. Hopefully I will get a clear “no way” or “we see no problem” and “yes, we would warranty the cells”.
 

boondox

Chief Engineer, RedNeckTech Industries
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I’m going to do a set of engineering drawings and submit it to Rolls/Dekka/several manufacturers and ask if they see a problem and would warranty their cells in that configuration. Hopefully I will get a clear “no way” or “we see no problem” and “yes, we would warranty the cells”.
That would be great! I really am curious as to the truth of the matter. Please post the drawing here so we can look at it. We may all be talking at cross purposes.
My findings are that two (or more) paralleled cells will function as a single cell. If there is a “weaker” cell in that parallel “block”, then the “stronger” cell will simply “do more of the work”, but less than if the cell were by itself and not paralleled with another cell.
Yes. So in doing more of the work, it ages until it is at the same point as its neighbor, when they both start doing equal work. Work ages a cell. More work ages it more. We also run into problems in the charge side of the cycle. One battery has reached as full of a charge as it can. The other is still charging. So the weak cell boils. Once charge is complete for the day, even if there is no load, the stronger battery will attempt to charge the weaker battery because the charge seeks to reach balance. Since the weak battery can't accept more charge the energy is wasted as heat. Now the stronger battery sits over night at a lowered state of charge until the next charging cycle begins. This of course leads to increased sulfation, one of the primary aging factors of lead batteries.
 

xNYCMarc

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That would be great! I really am curious as to the truth of the matter. Please post the drawing here so we can look at it. We may all be talking at cross purposes.

Yes. So in doing more of the work, it ages until it is at the same point as its neighbor, when they both start doing equal work. Work ages a cell. More work ages it more. We also run into problems in the charge side of the cycle. One battery has reached as full of a charge as it can. The other is still charging. So the weak cell boils. Once charge is complete for the day, even if there is no load, the stronger battery will attempt to charge the weaker battery because the charge seeks to reach balance. Since the weak battery can't accept more charge the energy is wasted as heat. Now the stronger battery sits over night at a lowered state of charge until the next charging cycle begins. This of course leads to increased sulfation, one of the primary aging factors of lead batteries.
"more work ages the cell" so according to you (and what I've been saying) less work ages the cell less. So how is it worse to have two cells doing less work than having one cell doing all the work?
"We also run into problems in the charge side...." This is the fundamental misunderstanding. One cell will not be at a lower state of charge. Just like during discharge, one cell is doing "more work", the same is true during charging. The "stronger" cell will be taking more of the charge current. You can stop the charge at any given point and the SOCs of both cells will be roughly the same.
 

boondox

Chief Engineer, RedNeckTech Industries
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"more work ages the cell" so according to you (and what I've been saying) less work ages the cell less. So how is it worse to have two cells doing less work than having one cell doing all the work?
"We also run into problems in the charge side...." This is the fundamental misunderstanding. One cell will not be at a lower state of charge. Just like during discharge, one cell is doing "more work", the same is true during charging. The "stronger" cell will be taking more of the charge current. You can stop the charge at any given point and the SOCs of both cells will be roughly the same.

Of course, the bank will be propped up a little longer with adding a new battery to the bank. That is (I think) in my very first post in this thread. But, if the old batteries are pretty beat and the new battery quickly drops to the same capacity of the old batteries it is not worth it. As I have said, I will do a replacement if the old batteries are still reasonably strong. But that is rare. Most cells do not fail in the first 20% of their lifespan. And it is most often a single cell that starts the problem.

Yes, one cell will be at a lower state of charge. Again, I have measured it many times. The old battery reaches the maximum charge it is capable of holding. The new battery has not and continues to charge. Once a lead battery has reached the max it is capable of it simply won't go higher. You can charge it all day and it won't achieve 1.28 or whatever the max for that battery is. It just starts to cook. This isn't really a problem as long as it is a flooded battery and you replace the water. It does drop your charge efficiency but with most systems you will never know or care. But no matter what you do you cannot make the maximum SG of a battery improve once it has lost capacity. If you could you could keep batteries alive forever.

Here is another example. I replaced my FLA bank last year. Four of the batteries were hotter than the others. It would have cost too much to ship them back to the manufacturer and they were being a PITA so I just ate it. I tried everything I could, repeated EQ's, long absorb times and so on. Nothing would bring the weaker cells up. I just had to add more water than usual. And within a month or so the hot batteries read the same as the others. As was noted earlier in the thread, best practice is to get cells from the same date and even better sequential serial numbers. I live in the middle of nowhere and the nearest place to buy batteries is 2.5 hours away one way. I was busy and decided to take a chance on having batteries delivered and I got burned. Next time I will find a way (if I use lead, hopefully next time LFP) to go and pick them up in person and test before I pay.
 

Short_Shot

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All of this is kind of unimportant without data on how quickly this occurs.

Without that you can't determine if it's worth it or not for your own needs.


If I NEED the extra capacity *right now* this whole debate is meaningless.

Even if it reduces the life of the new one by 50%, and I very much doubt it's that extreme, it is still often worth it.

And the fact that you're pulling less current from both batteries and likely have a lower DOD could even send the whole equation into a net increase in lifespan as shallow lead acid use can make them last a really long time.
 

boondox

Chief Engineer, RedNeckTech Industries
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Yeah, the math and problem are fuzzy, for sure. So are the conditions that cause battery failure. What I have arrived at over the years is that in general it isn't worth it if the old batteries are less than ~ 80% of capacity. I don't claim to have solid research on that, it is just one man's opinion and as always things are situational. I'm definitely not saying one should never, ever mix old and new. But you should be aware of the pros and cons. As you point out there are different priorities depending on your needs, desires, financial situation and so on. The battery makers don't want warranty claims and want to sell you batteries. I want to squeeze the maximum life out of my investment. Others may as you say just need the extra capacity now. And if it prevents deeper discharge they might come out ahead. All I am saying is that when you mix old with new the new battery will indeed lose measurable capacity in a fairly short period of time. You can easily measure it and see. I know for sure that mixing truly beat batteries (under 50% capacity) results in a rapid loss of capacity. Again, I have measured it. In my early off grid days I was making do with whatever I could get my hands on and have seen it time and again. Whether or not that is a deal breaker totally depends on the situation.
 

Tecnodave

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Mar 22, 2021
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I was born in the backwoods just after WWII, on a homestead in upper Matanauska Valley, Alaska We did not have a power grid, it was miles away, we did not have utility power, we produced our own. My dad was a WWII hero, fighting the invaders of the Aleutian Islands, being military we has access to military surplus. We used large format 2 volt cells which were about 32” tall and about 8” x 12” about 1100-1400 a.h. heard that they were submarine cells, but no proof of that. We had the exact same issues of one weak cell taking the whole bank down. we were 32 volt running these 2 volt cells 2 in parallel then 16 in series for maybe 2200-2800 a.h. at 32 volt nominal. Hamilton Beach Freezer, Refrigerator, washing machine, household appliances were all 32 volts DC , lights, (incan) and so on. that is where i first learned about batteries charged by a military surplus generator, U.S. Navy all over it. Do not remember who manufactured that diesel, its still there, still runs.

We had a huge dynamotor which inputted 32 volt DC and outputted 120 vac

We had no inverter as transistors had not been developed yet.
I quickly learned about measuring each cell with a hydrometer, making our own distilled water, etc. So I do have just a bit of experience on this subject......This was long before I ever saw “higher education”, schools were very limited in rural Alaska

I learned first hand from work in the fields...much later i earned a “full tilt education” at the college of my choice directly due to my radio skills much needed in the “good Friday incident“ around Anchorage which drew in many needed skills.
This also resulted in my first Federal License, 1st Class RTO (Station engineer) (1963)
In Alaska either you learned to survive or you didn’t (survive) Im a survivor

Born off gridder? lol what else would you call it....

So with that experience, I choose to ignore persons who make claims that i know from life experience that are not true
 

740GLE

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Ahh the Good Friday incident, wasn’t born yet, but does share my birthday, good times!
 
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