Deep Cycle Storage Batteries

On the contrary paralleling batteries should statistically decrease final in series capacities variations that should be minimal. But statistics are often not enough so you should try to match according to actual capacities: The highest capacity cell paralleled to the lowest one, the second best to the second worst etc. S.M.

Thanks Simplemind for your response.

However, I'm not sure what you are referring to. All the batteries are the same size, so the capacities are all the same.

Cheers

Nominal capacity - actual capacity. Two different things. S.M.

Batteries from the same manufacturer, made on the same day are not identical.....

Even the cells within a single battery are not identical....many forget this.....one cell is always weaker than ALL of the others.....that one fails first....

A superior setup would be for a series bank of 8 batts at 48V, which would require your charge controller to be capable of that voltage, as well as the inverter, if you have one. Your system is less efficient because voltage losses will be less on the higher voltage system, mostly because of wire sizing. The advantage is minor.

The comments about capacity are simply reflective of aging, and the variables voltages do impact performance. What to do? Nothing, unless you just want to replace them.

If all you need is 24 volts out, then what you have is ok. One thing to pay attention to is the length of cables in the series batteries.Try to keep them all the same length, even if you have to use a lead longer than necessary to do this. A slight difference in resistance can have a large effect on the equality of the charge in a series circuit.

I have seen large fork lift batteries (Weighing thousands of pounds) using 2volt cells,in series to give 36 volts.Some of the cells were closer than the others, but the leads were the same length as the ones further away.I inquired as to why, and it was explained to me that it was critical to keep all leads the same length for proper charge/discharge balance.

I have since verified this with personal research, too long to post here.

Keep the terminals very clean,and use a protective paste to prevent corrosion.

....

One thing to pay attention to is the length of cables in the series batteries.Try to keep them all the same length, even if you have to use a lead longer than necessary to do this. A slight difference in resistance can have a large effect on the equality of the charge in a series circuit.

I'm sorry, but that is incorrect... the current will be the same in any part of a series circuit. The leads should be kept as short as possible (sized as rated) to minimize voltage drop across them.

He may have been implying parallel charging.....then the cable length will play a role.....

The curremt flow will be identical at all points but the voltage drop across the batteries will vary according to the circuit resistance up-or-down stream from each individual battery which will affect the level of charge at that battery.

If you do some research, you will find that batteries in series have a different set of rules compared to resistors in series.The current is not equal in each jumper connection.

The total resistance is important, and is the sum of all resistances, but the resistances between each battery must be the same for proper operation when charging, and as a result, discharging performance.

A very small difference in jumper resistance can cause the batteries to charge unevenly,and as a result of this imbalance, to discharge unevenly.The result is shortened battery life and less total power available.

Check out this link for further information.

http://www.nyc-arecs.org/Connecting_Batteries_and_Chargers_in_Series_and_Parallel.pdf

You are welcome.

Re: If you do some research, you will find that batteries in series have a different set of rules compared to resistors in series.The current is not equal in each jumper connection.

I think Mr. Kirchoff would disagree with you. ;-) Further, I see nothing in the document you cited to support what you say. Maybe you were looking at a series parallel connection?

You are right in that, if you charge while the batteries (cells) are in series you will get unequal charges to some extent in the cells (because the charge in a cell depends both on the current that has passed through the cell and the voltage across the terminals).

That is why (or, at least, one reason why) an equalizing charge is recommended at some intervals (depending on the battery type)--it is a fairly long but low current charge aimed at trying to get all the cells to the same charge state.

Still, unless you can charge each cell individually, charging batteries or cells in series is better than charging those batteries or cells in parallel.

But the ideal would be to charge each cell in accordance with its exact needs (i.e., neither in series or parallel).

I re-read my post, and you are absolutely correct.

"If you do some research, you will find that batteries in series have a different set of rules compared to resistors in series.The current is not equal in each jumper connection."

It should be VOLTAGE, not current.

Sometimes I am cixelsyd like that...think it has something to do with the salt or lime in my Tequlias

I think the link to the pdf I posted is a very good explanation of various charging strategies.If you mentally substitute a resistor for the jumpers, it is easy to see the difference jumper resistance makes in the charge of each battery,whether it is series or parallel.

Last time I had a birthday, I couldn't blow out the candles....heat kept driving me back.....

Your comment:-

If you do some research, you will find that batteries in series have a different set of rules compared to resistors in series.The current is not equal in each jumper connection.

is so wrong, and even your .pdf does not make this serious mistake, or at least I could not spot it while reading through.

Believe me, its wrong!!

OOPS!

You are right of course, in a purely series circuit, but the OP indicated he had a series/parallel connection.This is to which I replied.

What you wrote was wrong. Its as simple as that.......

You are right.I was wrong.What was I thinking?

They say your memory is the third thing to go when you get old...

I can't remember the other two.....

LOL

Nice dog..I had a Wiemaraner once, best dog I ever had.Very smart.Even taught him to play cards.He could keep a straight poker face with the best of 'em,but problem was,when he had a good hand, he would wag his tail.

He didn't understand what he was doing wrong.

I tried to paste a photo of him, but it disappeared when I posted......??

you can't post pics directly

click the little camera icon on the editor bar

Tankz!

Here it is.....

Really?

The factors which determine how you must connect them are the voltage and current ratings of your inverter and your solar panel configuration.

Paralleling allows the batteries to better share the current at the expense of higher currents and therefore higher I2R losses.

Series-ing the batteries reduces the current flowing but the battery voltages/capacities must be monitored and any that start to lose capacity need a boost cycle to restore their capacity to some degree.

Dear Garyasta, the problem with paralleling is mainly that one leg will have more resistance than the other so current will tend to flow more in one than the other, - and on the discharge side as well, so after a period of time you can end up with one being overcharged and the other sulphating up because not charged, - and the regulator seeing the higher voltage from the sulphated leg will cut off even before the other leg is charged, so one side destroys the other then the other side destroys that one. - (Payback :) So, very important to put in series, - if you require higher amperage, just get higher amperage cells, - you will probably need to go to 2 volt cells, - available up to 3000 a/hrs, (@C10) and important to select manufacturers with stringent quality control, as each plate in each cell is affected by that same paradigm. However, the usual 6 volt cell is not high quality so won't last the couple of decades a high quality Tubular positive will last so you can luck out and the batteries will be OK for a reasonable time, - or not. Cheers, Geoff.

The system should be series because if you connect your system in series you are adding your voltage and if you connect your system in parallel your voltage will remain the same, only current will add. If you want to store much energy you should stick on series connection. The more you have high voltage the more you can store much energy in your system.

Huh ?

watts is watts

Watts is voltage times amperage, flow is height (pressure) times volume, friendship is understanding plus commitment, What is watts? Cheers, Geoff.

I just read a very sophisticated analysis of the proper way to connect batteries of this type of layout, and the figures for incorrect layout are startling! Because the internal resistance of batteries is so low compared to the connections, it is very important to have all the paths for both charging and discharging equal. I just reviewed about 300 images about series-parallel connections in Google. Couldn't find it. I recall only that it was on the Honda eu2000 yahoo group about a month or two ago. Yaay! Found it! http://www.smartgauge.co.uk/batt_con.html The key element is that EVERY current path has to have the same resistance, which is difficult to do.

Re: Found it! http://www.smartgauge.co.uk/batt_con.html The key element is that EVERY current path has to have the same resistance, which is difficult to do.

That's a very nice (and interesting) paper, but you should note that his entire discussion is based on connecting batteries in parallel. He is pointing out how important it is to have equal resistance paths when you parallel batteries.

What his article doesn't address is, given a choice, would it be better to connect batteries in series or parallel? (Restating, he apparently needs 12 volts for his load, and has 12 volt batteries, but needs more capacity (amps or run time) than he can get from one battery, thus he needs to parallel them to get more (ampere hour) capacity. A series connection is meaningless for his use--although I'll touch on this again below.)

It is my understanding that, in a perfect world, the ideal would be to:

• for discharge, use high (ampere hour) capacity cells in series to get a fairly high voltage (thus (1) minimizing power loss in cables (or trading off with the size of the cables), and (2) drawing the same current (which is close to the same power) from each cell
• in that same perfect world, the ideal way to charge the cells would be to disconnect the series string and connect each cell to a charger to give a customized charge to that cell based on its conditions (for a lead acid cell, those would be nominal 2 volt chargers (I know, 2.35 volts or something, and then tapering off as the charge builds up, ...)
• if you didn't have cells that had a high enough ampere hour capacity for the load (i.e., the cells won't let you run long enough), then you might be forced into using a series parallel connection of cells during discharge. Then you'd want to take this guy's advice and get the lead lengths very close to exactly equal, to equalize the current drawn from each cell, and minimize circulating currents between cells in parallel (which just wastes power and is bad for the batteries (as someone mentioned, drawing most of the charge out of one cell and tending to start sulfation in the other(s) in parallel to it).

In an even more ideal world, if you needed a series-parallel connection to get the required run time, you'd be better off setting up separate series strings of cells and a switching arrangement--run one series string to a certain level of discharge, then switch it out and run the other string. (And, if possible, start charging the first string (ideally as individual cells) as soon as possible after switching it out of service.

A few other notes:

• Note that battery manufacturers never build batteries with multiple cells in parallel within a battery, they are always in series. They use different physical size cells don't obtain different ampere hour capacities. I think they have a reason for that approach. ;-)
• I've occasionally (really, only occasionally) looked at batteries for laptop computers and been surprised by the number of connections. More than the two (or 3 or 4) needed two get the voltages out of the battery needed to run the computer (e.g., maybe 12 volts, + and - 5 volts, ...). I've sometimes wondered if they've got some really clever circuitry in there (or in the computer, or in the charger) to make an attempt at charging each cell in accordance with its exact requirements.

Probably not, but, it could be done. You'd sort of have to build a series string of chargers (or isolated chargers, not referenced to ground) and connect one across each cell. I wonder how much improvement in battery life (that is, longevity, not particularly discharge time in one cycle) with an approach like that. I wonder if it could be worth it?

Fixing some typos--I tried proofreading, honest.

Re: They use different physical size cells don't obtain different ampere hour capacities.

don't --> to

Re: More than the two (or 3 or 4) needed two get the voltages out of the battery needed to run the computer (e.g., maybe 12 volts, + and - 5 volts, ...).

two --> to

Yes rhkramer, it was only parallel connections he was discussing, and indeed painted a dark picture of the results of differing resistances between the paralled units. However, every cell contains a number of individual plates, - they are in parallel within that cell, each literally a single battery, more or bigger plates for higher amperage, so the same problem occurs unless stringent quality is observed, - Some years ago I had to change my Tubular battery manufacturer, so when I found a factory with what sounded like the batteries I required, I flew there, armed with a digital micrometer accurate to 100th of a millimetre, then much to the consternation of the factory tour managers, scurried around measuring plate thicknesses of the different capacity batteries, - I found the actual plates themselves to be accurate to the .001 standard I had only wished for, - the connectors, which are all soldered together in any case, varied a maximum of .004 mm. - I noticed that although the sales staff were disconcerted by my actions, the supervisors and engineers in the background were beaming approval. And then I found that they had gone one better than me, - every plate was weighed on an atomic scale with that same accuracy, and each plate put in a pile of the exact same weight, so ensuring that each cell has totally identical plates within. The same attention to detail occurred all the way along, and the burning in was 500 hours, compared to the 300 my previous supplier had used, and each battery was measured several times each shift and any anomalous cell rejected. With a claimed design life of 22 years, 16.5 yrs cycled 20% per day @C10, these batteries are still well ahead of the flow batteries, much as I love the concept. As I have now installed hundreds of these batteries, all working perfectly, I can I believe argue that not only in the ideal world, but in the real world, batteries can be built to the required standard. Of course these cells have humungous connectors and are torqued down so as to totally seal and bring the large connecting areas together. I hope that throws more light on this subject, Cheers, Geoff Thomas.

What Brand?

a testimonial such as you have written above would be acceptable

Hi Garthh, I guess I feel that is confidential info also not allowed by CR4, but I can say that in my understanding of the American battery industry, none of the big companies wanted to upgrade their plate making machinery, so instead of that they re-packaged their same old same old plates as Gel the wonder dog, - er battery, or made them stronger against shaking, (another advantage of the Tubulars) with AGM, - again same old plates generally speaking. You will have to go to Germany, China or South Africa, that I know of to get the good batteries, (don't worry we have the same problem in Oz,) but certainly it would be good to write to the big battery companies and ask them can they make Tubulars, - if enough folk do it they may feel they are losing market share so better adapt, - it is a much better use of the lead to put it into a battery that lasts much longer, - Some Tubular sets I know of have lasted over 30 years, - after all the world is getting quite short of lead, (Peak Lead?) so price is much higher, might as well use the stuff more adroitly:) Cheers, Geoff Thomas.

So in other words it's a fictional company

There's nothing confidential about a quality product...

Hi Garthh, it is my understanding that CR4 does not permit advertising, also I am not sure I want to share my sources as every one just goes on the internet and buys it direct, puts it in wrongly, usually pays more anyway, and how do I recoup my costs and R&D? If you choose to think someone who has found gold and won't tell you where it is, means they didn't find any, then that is fine, if assumptions can ever be fine, but my motivation is is to share my extensive learning and hands on experience in the field of batteries for every-one's benefit, most folk don't know how much the use of Tubular Positive batteries changes the game with Solar, Wind, etc. storage. For a start it allows the development of Battery Centric systems, a very important advance, although that might be going off topic to talk on that. Cheers, Geoff.

If you don't want to share why bring it up?

If you choose to think someone who has found gold and won't tell you where it is, means they didn't find any, then that is fine

more like you are claiming to have found something better than gold, But then claim you can't show it to us

if you are the dealer & don't want to lose money you should say that

By "Tubular Positive batteries" do you mean like Cyclon from Hawker Gates?

Advertising? Why not go here and explore the many many options GS offer in commercial space?

No 34point5, there is some more on Tubulars on an article I wrote some time ago now, on my website, - it doesn't mention brands so I guess is OK, http://www.iig.com.au/wind/batteries.html That will at least take some of the mystery away, apologies, Geoff.

What is your opinion of the new nano-phosphate lithium ion batteries?

Hi, I can't find any mention of efficiency, - how much power in to how much out, so hard to say. Cheers, Geoff.

Here is a link for further information.

http://www.a123systems.com/products-systems-alm.htm

Yes, I have already followed that one, and when I don't see efficiency specifically mentioned I wonder whether they might rather it just not be mentioned. What is fine with an external charging source where efficiency doesn't matter, may however greatly matter with stand-alone. Cheers, Geoff.

Basically it hangs with how deeply you charge and discharge. If you only charge to 70% capacity, you have about a 75+% efficiency.

If you charge to say 100%, then efficiency drops drastically. Battery life too.

The above are from memory, but I am fairly sure they are representative....

Hi Andy, on comment 55 we went over to the new nano-phosphate lithium ion batteries, the which I admit to having had no hands on experience with, are you saying if you don't fully charge those your efficiency is greater? or did you mean discharge? Cheers, Geoff.

Sorry, I was talking mainly about Lead Acid Batteries.....though it is also true of many battery's chemistry, there is always a loss of efficiency when charging/discharging to the limit, though I have had no dealings with the chemistry you mentioned.....

Take a look here for some further infos:-

http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

Though I did not find anything on efficiency on that one.

Hi Andy, apologies for misunderstanding and in advance for now contradicting you, - my experience and understanding is that in fact Lead acid batteries, particularly ones able to be very deeply cycled such as Tubular plate varieties, actually become more efficient the deeper you cycle them, this is partly because of the waste of energy getting the last 10% of charge in, when bubbling or heat occurs, as there is an element of overcharge getting all the lead converted, - and if one only cycles the battery 10% you can appreciate that you would always be charging in the most wasteful part of the cycle, but if you cycle deeply, say 80% per cycle, then most of the re-charging is done in the very high absorbency part of the cycle where efficiencies of 98% can predominate. This is in fact how batteries are used in industrial situations such as fork lifts, self powered assembly line carts etc. Exact user settable battery re-charge parameters can reduce the waste even further. The other area of loss is in the difference between incoming and outgoing voltage, Puekerts equation and the like, - again some styles of batteries are superior in this regard, and again good control and knowledge can help significantly. I would argue that the main problem with understanding these limitations and possibilities is that there are many batteries out there sold as "Deep Cycle", which can not in fact be taken down further than 50% without suffering damage, - the limitations of these pretend deep cycle batteries are then carried over to be applied to all deep cycle batteries, that ignorance being encouraged by the naughty false deep cycle companies as it allows their incorrectly described product to continue to be sold in the wrong, (although lucrative) market. If a petrol company was selling water as petrol, it would not be long before the consumers would rise up against them, but due to the long life time and deliberate misinformation with deep cycle batteries, - and the ease with which they can be mis-treated, it takes more knowledge than is held by many to spot these glossy brochure bogus deep cycle batteries. Hopefully discussions such as this help the knowledge available about this subject to be more widespread and we will see these false deep cycle batteries being treated appropriately. Cheers, Geoff.

Geoff,
Are then all true deep cycle batteries of the tubular construction type?

My knee jerk response to your comment that I considered Tubular Positive the only real deep cycle battery was yes, although I have occasionally seen good service from AGM Sealed lead acids in the appropriate situation, eg on my electric bike, although it must be recharged immediately, but there is another battery type which claims very high efficiencies and long life which is the Plante (named after the Inventor of the lead acid battery, Gaston Plante) type, - I have never used them, they don't seem to be readily available, and being pure lead, very difficult to transport without major damage. These were, I understand, used by Australia post in the telecom exchanges in major centres, - the plates were immersed in like a bath, unclear as to whether they were even covered, and certainly health and safety regs were not in force in those days and explosions did occur. Apparently, according to a couple of old timers I have talked to, the plates could be lifted out, and a new one soldered in to replace worn ones, the new one being made on site. Although certainly by todays standards that whole thing is un-acceptably dangerous, with modern technology and appropriate safeguards of course, Plante style might be another valid form of Deep Cycle battery. Cheers, Geoff.

Geoff,

Thank you for your sharing your insights and knowledge.

Regards

Bill

I can relate to all that you wrote and I can understand how doing that can significantly improve efficiency over the long term, it makes perfect sense, though I have not been lucky enough, up to today, to see it mentioned in print, thanks.

If you are aware of any links covering such knowledge, I would be most grateful.

Interestingly, I myself practice just that (almost unknowingly in some areas) with my caravan battery:-

I charge only to 13.4 volts and stop the charger automatically and if mains power is available, I start the recharge again from 12.6 volts (the value at which normal batteries start to sulfate) back up to 13.4 again.

That way it never gases or is warmed up, so that my own design charger can safely ignore temperature while charging as its only a valid parameter once you charge to 100% full. Mine is only around 70% full at its highest point - ever.

I do charge with a current of slightly under C/10 (10 amps on a 120 amp battery), which charges quite quickly. The charger also supplies such loads as lighting, ventilation and water pumps when they are also being used, if when using them takes the battery voltage under 12.6 volts (and mains is available).

If no mains is available, as its a leisure (deep cycle you call them I believe) battery, I can safely use it further, though it has never been completely discharged, as I do believe, even "good" batteries probably don't like the practice being repeated again and again, though I am open to correction on that last point! I never wanted to find out the hard way on mine!!!

I also believe that a rapid charge and no trickle, keeps the muscles of a battery fit longer.....cute of me.... don't you think?

Many thanks for your interesting post.

While this is an interesting and useful knowledge thread, I would make the observation that the focus of your theory is to reduce charging inefficiency. Certainly an approach that has merit, much like conservation, in that reducing energy needed to subsist is an outstanding way to reduce energy consumption.

When you are recharging batteries, Lead acid, agm, flooded, tubular, etc. the feasibility of the process rarely revolves around charging efficiency, it revolves around battery life and energy availablity, both variables critical to the design process before construction. (Cost) I just wanted to note that increasing battery life by reducing total energy storage window within the battery (particularly with solar when the timing of the charging window is relatively fixed, but variable in energy quantity, would require more batteries to meet the system requirements. You will be designing to meet, say a daily 10,000 watt load. Reducing available watts per battery means you need more batteries. Increasing storage space, cabling, battery count, imparts a cost. Is the increased efficiency of the charging cycle worth it?

Lastly, and or arguably, I believe this will induce reduced battery array life because of prolonged sulfation due to reduced maximum charge levels. (not C rates, but fill levels) One thing anyone on this board will confirm is that a fully charged battery will last much longer than one maintained at 70%.

Your last paragraph is written incorrectly to my mind, telling only part of a story, not the whole. It appears you are talking about storage, please correct me if I am getting the wrong impression.....lets say that I completely disagree....Please be so kind as to supply links that support your theory......

I personally believe that inactivity is for at least some battery chemistry types not a good idea. A battery that is constantly being charged, used and charged again works well over long periods. I base this on many years of active experience with NICADS, NIMH and LA batteries.....

Leaving a battery fully charged is really bad for many chemistrys. Sony video batteries (whatever they are for type), NICADS, NIMH to name but a few.....Its better to leave them with a small say 10% charge. Not more, for long storage.....Also read the battery tips supplied with Sony video batteries, they recommend leaving in the state at which the Video camera first says now "re-Charge".

Before answering you for Lead Acid, you need to define for me which one your comment was for, as it changes on the type of LA a little......leaving in a so called "Dry charge" state will allow a battery to remain good for very long periods. Top up with acid and a short time later the battery is tip top and ready for work!

BUT, what I was talking about was not long term storage, it was active usage, which is another kettle of fish!!!

Leaving all the chemistrys that I use regularly, in a 100% charge condition, accelerates aging.....dramatically. The Sony method works best I find for non LA ones.

All of this is knowledge gained over many years, where I have also believed in the beginning that your statement is correct. It keeps customers buying new batteries so perhaps some battery sellers promote the idea for their own gains?

The charging infos on the web and in manufacturers books are for 100% charge, with temperature correction etc. (talking about LA types), I simply disagree that this method is good in the long term. I am allowed to......because the manufacturer is NOT interested in a life longer that 5 minutes after the guarantee runs out!!

Since I learnt otherwise, I rarely need to buy any new ones. For a new telephone system I bought some 1600ma AAA recently, otherwise it must be at least 5 years or more that the old ones just get recharged, but have not needed replacement....maybe even longer. Some of them were in a device I used in the office and I haven't worked since January 2006 for that company......high quality Japanese NICADs....

My charge method for leisure batteries has kept my caravan battery going for 9 years plus, it may even be 10 years this summer......and still going strong!! Its NEVER charged to 100%. Nor is it every fully discharged......I am going to keep using it the same way till either it or me dies first!! it could be me......

Please translate your last paragraph so that it is easier to understand fully, if in fact I have misunderstood you. Apologies also if true....

Sorry about the ramble......

We were discussing power storage. Storing batteries at capacity, when flooded, increases life, dramatically. Depleting the charge, then restoring it, constitutes mechanics of the aging cycle. Storing them at low levels makes them much less useful (the point of my post). If somehow, you could magically know in advance when to charge them so as to make them useful (storing energy, after all, is what a battery does, and is why we need them), the cycle from low to high is what is doing the damage, not the fact that they are full and awaiting discharge. My experience is with larger systems. 10KWH's to 100KWH's +. We use mostly AGM's now, with some LA flooded.

I am not referring to a NMH or NiCad 1600 Miliiamp AAA battery or Sony camera batteries. I did not know that about them, thank you.

Also, ten years of life is not uncommon for a well treated Flooded lead acid battery. As for your caravan, I'm guessing that you have reduced the amplitude of your charge/discharge cycles. A very good strategy. It is the amplitude (maybe magnitude is a better word) that matters. However, if you routinely go below 40% DOD, you are stressing the plates ability to completely regain capacity. That's what gassing and heat (Equalization) helps with, which certainly lowers the efficiency of the charge process when instituted. But the goal is to retain capacity.

Am I interpreting correctly what you are writing? I think you are dead wrong about the impact of that strategy on useful life, that being defined as being able to supply a given output in a given amount of time, for a finite number of cycles. Altering charging processes to make a smaller bank capacity probably will make the bank last longer. That is just not usually economically sensible.

You are interpreting some of what I wrote correctly. Some of what you write makes sense to me too.

My personal take on the LA battery scene is simple, don't charge above about 70-80%, don't regularly go below about 40-50%.

I found an interesting website at here:-

http://www.progressivedyn.com/battery_basics.html

The following list was there:-

What are the most common mistakes made by owners of lead acid batteries?

• Undercharging - Generally caused by not allowing the charger to restore the battery to full charge after use. Continuously operating a battery in a partial state of charge, or storing the battery in the discharged state results in the formation of lead sulfate (sulfation) on the plates. Sulfation reduces the performance of the battery and may cause premature battery failure.
  
• Overcharging - Continuous-charging causes accelerated corrosion of the positive plates, excessive water consumption and in some cases, damaging temperatures within the battery. Lead acid batteries should be charged after each discharge of more the 50% of its rated capacity and during or after prolonged storage of 30 days or more.
  
• Under-watering - In lead acid batteries water is lost during the charging process. If the electrolyte level drops below the tops of the plates, irreparable damage may occur. Check your battery water level frequently.
  
• Over-watering - Excessive watering of a battery results in additional dilution of the electrolyte, resulting in reduced battery performance. Add water to your battery after it has been fully charged, never when the battery is partially discharged.

Its good info.....

My method allows the different cells in a battery to never be reversed polarized by too low a discharge and reduces further damage by not overcharging as to get to a real 100% means gassing etc.......that's bad in the long term.

I agree that almost 10 years is still not complete "proof", but its going a long way in that direction I feel......at least I am testing myself, on my time at my cost.....many do not!!

"Undercharging - Generally caused by not allowing the charger to restore the battery to full charge after use. Continuously operating a battery in a partial state of charge, or storing the battery in the discharged state results in the formation of lead sulfate (sulfation) on the plates. Sulfation reduces the performance of the battery and may cause premature battery failure."

How do you avoid this condition by recharging to 70%

70% of capacity is NOT undercharged......misconception from many!!!

Charging to "Full" is to my mind bad for the battery as it wastes energy, warms it up (it is possible to boil a battery if you are not careful by the way!), causes gassing which drives off water as an explosive mixture of Oxygen and Hydrogen, easily ignited by a burning cigarette or spark from clothing.

I take the 70% as the full level if you like.......

I sincerely believe (am I the only one who has tried this out?) that charging and discharging between the set voltage points I mentioned earlier, or close to, results in a fit battery, with none of the problems seen with a high or very low charge.....also it does not sulfate or gas.

In fact my battery only needs a small amount of water each year, which is probably lost in the high temperatures from summer weather, certainly not from gassing.....

I spent a long time, many years ago, reading specs from battery manufacturers, they tend to support this in their writings.....sort of reading between the lines. Since then I size batteries for a job at 70%, not at 100%, with about 10 systems running in friends caravans and similar, since around 5 years, nobody has changed out a battery yet, some batteries are even slightly older, one set were already 2 years old......but it is far too early to be certain.....my battery will be 10 years old in August and is still going strong......

I usually add a small amount of electronics to an existing charger system to control the voltage levels, its actually a kit I buy from Conrad Electronics, Germany, for very little money, but I set it up completely different to their instructions....

I also "add-on" another small bit of extra electronics to shut off the mains to the charger when the battery is in a good state and not needing a charge, further reducing current drain from the mains....

Also, the electronics stops the charger being switched on (it takes itself some current from the battery) when no mains is available (I have about 6 LEDs to indicate various states, these would take a small current away from the battery if left active and I want the longest battery life possible, even though its probably only around 100ma total!

If you look at this .pdf here:-

http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

The first graph shows the Battery State of Charge (SOC) in Percent (%). You will notice that the graph is almost a flat line between 40% and 70%. This is the area to keep a battery working in for the best life. The graph is headed:-

"12 Volt Lead Acid Battery State of Charge (SOC) vs. Voltage while battery is under charge Battery".

I hope this helps.

Andy, no one disagrees that derating a battery will make it last longer. If you choose to charge a 100 Amp Hour battery so that it never contains 100 amp hours of capacity, you must use more storage (batteries) to meet the same load. 30% more. You are avoiding dealing with the consequences of the diminished capacity of the bank. In order to meet the load, you will need more derated batteries. Yes, it's possible that they will last longer. But you will need more of them. I am simply making an economic observation based on life cycle costs.

The loads and voltages I am working with, the extra 30% is accounted for by buying a single larger battery! Mostly the batteries in caravans are usually fairly big for the loads required.....I have actually spent a week or so on camp sites with no mains, all I did was connect the car and run the engine for 10 minutes. Problem solved. The charger sorts out the charge from the car engine just as well as from the mains!!

Even if for some reason it is not possible to place a bigger battery when battery replacement occurs, for instance space does not allow it, it still does not really matter with caravan batteries. I hardly worry about it at all.

Why you may well ask, well firstly they are mostly used where the mains is always available on campsites, secondly while underway, the batteries are charged from the car engine in most cases. So even though less capacity might be available, it just gets charged back up again......

You did not read my post carefully enough, I am sure I mentioned battery sizing! Here is my comment that you appear to have missed completely, from my previous post:-

I spent a long time, many years ago, reading specs from battery manufacturers, they tend to support this in their writings.....sort of reading between the lines. Since then I size batteries for a job at 70%, not at 100%,

Also a point many forget with any type of battery composed of 2 cells or more, one of the cells is weaker than the other(s). If the battery is run down too far, this cell will be reversed biased and damaged. Eventually this cell stops working, usually then the whole battery will be replaced.......for one bad cell.

Therefore NOT discharging to that level probably alone doubles the battery life... That's where my 40% comes in, though with car type batteries I use a higher value as these batteries like to stay above 12.6 volts if at all possible, to reduce the onset of sulfating. Leisure & deep cycle batteries are far less sensitive in this area and could be emptied further if needed.

So in actual fact, I usually set my lower voltage to start charging again to 12.6 volts, good for car batteries and to make sure that the (any type of) battery is "fuller", in case of a mains loss.....that way the charger "cycles" between 13.4 and 12.6 volts......it appears to keep them in good working order for longer......

Caravan batteries are special case in the way they are used and my fix may not be adaptable to all other battery situations, do not forget that!

Though for example, as most UPSs are connected to the mains 99+% of the time, I am sure that my charger, if correctly set up, would extend the life of the batteries dramatically......though the time "UP" may be reduced slightly, though once the batteries in a normal UPS are 2 years old or more, the capacity has probably dropped more than the so called "missing" 30% you mentioned, when using a charger that fully charges the batteries......like mine does not!

The OP has a solar system. You have implied that by reducing the capacity of the battery, he could extend the life of his battery array. No one is denying that what you are saying is true. Battery life can be extended by reducing cycle magnitude. This is a well known fact. Reducing capacity reduces usefulness. If you need a reliable energy system, you must analyze storage capacity/energy demand/time

Let me draw an analogy. If you reduce the size of a gas tank in a car by 30%, it takes less fuel to get a full tank. And because a smaller tank weighs less, your fuel efficiency may improve, because you are moving less weight, on average. If you want to travel 1000 miles, you will still need about the same amount of fuel, but you will have to fill up more times with the smaller tank. Now what if the stations are 300 miles apart, but the range of the smaller tank is 250 miles. Or what if the act of filling up more often consumes the savings. Or what if the solar power array can charge 10 amps at 24V for 4 hours a day, but your battery array is at 70% after 3 hours. What do you do with that unusable supply. You could reduce the size of the PV array. Your solution is to buy a bigger battery, and derate it. But a bigger battery costs more.

Go back to earlier posts where you are implying that battery manufacturers are trying to sell you equipment along with instructions on how to prematurely destroy them, by charging inappropriately. Battery life is relevant to usefulness. You are minimizing the usefulness requirement, which is primary.

I'll make it simple for you:-

Iif you need (assuming a full charge) 70 AH, then buy a 100 AH battery but only charge it to 70.

Luckily for us, the battery voltage is a clear indicator of percentage of charge.

Do you understand now?

With regards to some manufacturers complete lack of relevant info's, or some others "hide" the info's somewhere strange on their website, or they give tips on how best to 100% charge batteries, yes I do think that they want the battery to go wrong shortly after the battery is out of the guarantee......

Re: If you need (assuming a full charge) 70 AH, then buy a 100 AH battery but only charge it to 70.

I would have thought you'd say: If you need (assuming a full charge) 40 AH, then buy a 100 AH battery but only charge it to 70 and only discharge it to 30 AH.

Did I miss something?

Aside: I like your idea, and intend to try it sometime (once I get a charger that (and discharger ;-) that I can use that way, but the linearity looks pretty good even beyond the 30 to 70 % range that you mention. I might try 20 to 80, or even 10 to 90, just staying out of the real extremes.

The test would be great, but may I say once you decide on your parameters and your battery type, stick with it so that you can make some conclusions from your test parameter.....

Best of luck and do keep us informed (probably in 10 years or so!!) what happens.

Andy,

From the charge/Discharge graphs the terminal voltage during discharge voltage is below 12.6 for any reasonable discharge rate most of the time.

How does your charger differentiate between the discharge and rest states to initiate charging?

If you had read my previous post more carefully, you would understand that car type batteries (if used) start to sulfate when below 12.6 volts for any length of time (a car usually recharges immediately after starting!) , so although I use myself Leisure batteries, it could be that someone else doesn't.

Also, recharging from 12.6 means that the battery is held "fuller"......not "full"! Condition. Though allowing the battery occasionally (if leisure/deep cycle) to go down to around 40% should not be a problem.....

Hey! anyone here who has no real interest in such things should ignore this whole lot of posts from me. Its just a small hobby of mine that appears to work, at least up to now.....Though I am not certain.

I don't mind explaining my thoughts, but I am not interested in any arguments about it as until my battery craps out, I feel I am still on "soft ground".....maybe still even after!!

Though I am normally not averse to a good strong argument here....as most of you know.

Andy,

I think you misunderstood my question. I will attempt to re-state it in more detail:

You stated in a previous post:

"So in actual fact, I usually set my lower voltage to start charging again to 12.6 volts,"

However from the Discharge the graph in:

http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

A 12VLA battery at 80% charge state and experiencing a c/10 discharge will have a terminal voltage of about 12.3V.

How does your charger differentiate between this state and a Battery at a rest voltage of 12.6 to initiate charging? or doesn't it care, and start charging anyway?

It simply looks at the battery voltage, when the voltage drops for any reason below 12.6 volts, it simply switches on charging.

Originally I made provision for many factors, including temperatures and voltage under load. It was simply a waste of time.....just sensing the voltage for both upper and lower ranges, not over charging above 70%, ignoring temperature has proved to be just the same as before......

It appears that the charging/stop charging between these two voltages keeps the battery fit for long periods.....and reduces water usage.

My apologies if I misunderstood you.

Reducing water usage is an important point

as is the amount of outgassing, which is corrosive to connections

manhours spent on maintenance is a very real expense, which is often not included in the overall cost of a battery

Interesting, thanks!

problem you will have is the batteries in the middle will not be charged we figured out that each battery needs a charge controller so it can be charged in the pack and not as a mass.

make sure every 6 months you move the battereies in the pack and they will live longer without a sulfate problem.

look at some of the new storage types as well we saw one from this company

http://www.redflow.com.au/

Ya gotta love all these new flow batteries! Move over lead acid, there's a new sheriff in town.

Hi All

Thanks for the hotly debated discussion. The finer points bear witness to the depth of experience that appears to be prevalent.

The blunt message appears to be that it is better to use a series system and that if parallel setup needs to be used to increase the storage capacity, then this form of linking should be kept to a minimum.

Cheers
garyasta

Something that has not been mentioned (I think -- I blasted through pretty quickly) is the value of battery balancing systems. If you poke around the archives of the EVAlbum site, you can find inexpensive battery balancing systems that you can make yourself. Most of these just shunt the higher voltage cells to bring them down to the same voltage as the rest of the cells. Individual cell access is not built into most lead acid batteries, but one can modify the battery to gain access, or (worse) treat individual batteries as if they were cells. (In big installations -- telecom UPS, etc -- individual cells are common.)

A little imbalance tends to be self-perpetuating or self-reinforcing. The lowest voltage cells will tend to get lower yet, and the higher voltage cells can be driven to gassing and overheating (given that the charger continues to put out its full voltage... 24 v nominal can be 10v + 14v) . Given that these cells are built into battery units typically, you can easily find yourself in the position of having to replace entire batteries.

With lithium ion batteries (as used in EVs) battery management systems (which do balancing as well as preventing over-charge and over-discharge) are the norm, partly because the cells are so blasted expensive that the cost of the BMS seems relatively low.

Could you expand on where we would find balancing schematics?

Yes. If you go here and scroll down to "battery management", there are schematics and instructions that Lee Hart has put together.

Has anyone tried ultrasonic bath to help remove sulphate deposits on battery plates?

A bath large enough to accommodate the battery, and a coupling medium like water surrounding the battery.I am sure the case will attenuate the power to some degree, but maybe not enough to totally mute it.

If so, removing the case would be required.

I thought of it last night while sipping a little brandy, and in that mellow state of mind, it seemed like a good idea.

Would it work? I realize that the phosphate has to go somewhere, probably to the bottom of the battery, and would have to be washed out.I also realize that the battery mass of lead is reduced, thereby reducing the capacity of the battery, but it may be economically feasible if one has a large number of say, traction batteries.

Anyone know of a good adhesive\sealant to use on a battery case?

Comments? Suggestions?

One of the plusses with Tubulars is that because of the tiny powder grains they are very resistant to sulphation, they approach very closely to the limit of lead, - 1500 full 100% cycles and then more and more of the lead will just not react anymore, - almost as if it gets tired, but interestingly if you melt it down and go again in a battery it is like born again. There are commercial high voltage pulse generators that some folk swear by to de-sulphate old style lead acid batteries, - but they will not work on the "tired" lead, only in the case that there are big sulphation crystals. Cheers, Geoff.

I understand that tubular is far superior to plate-type batteries, but there are many more plate type in service as traction batteries.Do you think ultrasound would make the plates shed the sulphate coating?

What is your opinion of chemical rejuvenators for plate type batteries?

Such as sodium sulphate,magnesium sulphate, chelated iron, EDTA, etc?

Perhaps combining chemical and ultrasonic methods?

I realize that the proper thing to do is replace the battery at end of life, but even a short extension of lifetime would be beneficial.

Whether it would be lucrative or not is undetermined at this stage.

Your opinion is highly regarded, and I appreciate you taking time to answer my questions.

Dear HiTek, I have not tried ultra sound on batteries, although it does seem to loosen fine dirt, - if you are in possession of old batteries that are otherwise dead, I guess it can't hurt to try, although it might clean the active material off as well. The Crystal smashing high voltage pulses seem good, there was a crusty old Clockmaker on the small wind forum, Donald Plisco <dplisco@cox.net> - hopefully he is still alive, did excellent experimental stuff on them, and claimed to have rejuvenated heaps of batteries, and experimented with different makes, you could try emailing him. I have tried the Cadmium based "battery rejuvenator" (Inox?) but with in-conclusive results, but if you find any joy with either the ultrasound or chemicals I would appreciate your' sharing that as I get enquiries from many folk with just one or two batteries in a bank dying who may have several more years out of that bank if they could revive those, and would likely buy the Tubulars from me in the end anyway, doesn't matter if it is some years down the track, life is long. Cheers, Geoff.

Hi Geoff,

I understand that the normal Lithium-Iron Phosphate batteries are around 97% efficient, so I would expect their Nanophosphate cells to be similar, but perhaps not yet proven.

They are likely, however to be significantly more expensive than your tubular lead acids.

Do you know of a good website that will give me more information on their physical construction .... cross sections, etc.

Have you had any contact with the CTEK battery chargers? If you have, I would be interested in your opinion.

Regards

Bill (ex Townsville)

Hi Bill, I have come across the CTEK, - 8 steps charging etc, personally I prefer chargers that I can vary the voltage precisely, to cope with varying usage situations. If your question about structure is concerning the Tubulars, I used to get batteries from Hoppecke, - http://www.hoppecke.com/content/view/full/1209 but too expensive now, - my current supplier uses identical technology from Hoppecke, - bought their plate making machinery from them in fact, but do the extra checking, which Hoppecke can't afford. Very good batteries however, had many good years with their batteries. Batteries with Tubular plates are designated OPzS (flooded) and OPzV (sealed). Cheers, Geoff.

Geoff,

Thank you very much, I will try to look at their site tonight - It sounds like interesting technology, I hadn't heard of it previously.

Regards

Bill

Hey guys,check out the leading edge in battery technology:

http://www.gizmag.com/3d-thin-film-batteries-recharge-in-minutes/18187/

As long as you have less than 3 parallel strings you're fine. Having more than 3 parallel strings shortens battery life.

Hi Vee, any parallel string shortens life, that is why it is so important to get the plates themselves each as identical as possible, - you can imagine that in a 9 plate individual 2 volt cell, you have exceeded your rule of thumb by another magnitude of 3, - unless manufacturing is extremely conscientious, no parallel strings are acceptable. Within an individual battery which you have ascertained the manufacturer is totally committed to exact plates as I said earlier, parallel plates may be fine, - but with separate whole batteries, forget it, they will sooner or later self destruct, - must. Don't let anyone tell you otherwise, as they don't understand the realities. Cheers, Geoff.