Short Life of Storage Batteries

One possible cause is the depth of discharge.

Battery life goes down drastically when you allow batteries to discharge down to no less than 80% to 75% or so of their capacity. That means whatever the battery amp/hr rating is, you can use no more than 1/4 of its total charge before risking battery life.

Also, what type of batteries are you using?

Automotive and deep cycle marine batteries are very poor for solar battery banks. Many people have used golf cart batteries with good success.

Absorbed Glass Mat batteries (AGM) are the preferred battery to use.

Overcharging a battery could be another issue. What controller are you using?

You really need to tell us what exactly your whole system is and how deeply do your batteries discharge before the next charging interval.

'...Battery life goes down drastically when you allow batteries to discharge down to no less than 80% to 75% or so of their capacity....'

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AH, I don't think this is the case with lead acid batteries, whether starting, deep cycle or hybrid. My understanding is that while this is a problem for NiCad batteries, pretty much the opposite is true for lead acid.

Try it with your car battery if you like, but at your expense.

Lead acid is designed to discharge only a small amount to start the vehicle, then it is promptly recharged. They never deep cycle, except when you leave the lights on overnight. Do that a couple of times and it kills the battery.

Deep cycle lead acid batteries (marine) have thicker plates to withstand the degradation that occurs during deep discharge, but can not deliver the instantaneous current discharge that an automotive battery can due to the lower surface area.

Automotive batteries have a greater number of plates, but thinner. They allow more instantaneous current, but only for a short time as deep discharging deteriorates the lead plates.

While the deep cycle battery seems like a PV solar winner, it lower current delivery is not really effective. This is where AGM (Absorbed Glass Mat) batteries do a much better job at both high current delivery and deeper discharge cycles.

Anonymous Hero-

My experience, remember Dirty Harry though "Opinions are like A$s holes, Every one has one", runs somewhat counter to your statement. I have 2 sailboats, neither one is equipped with more that a 6 hp motor which hardly ever gets used. Lights, radios, fans, small heater all are run off the deep cycle battery. Only charge is from a charger in the boat when boat is dockside. During the winter one of my cars had a dead battery and I put the deep cycle boat battery in the car thinking it would maybe last till spring. The life of it is now 7 years old. 3 in the boat and 4 in the car. Never had a better battery in a car. This battery takes the deep instantaneous load of the starter, lights, electronics when the car is started. It also puts more out when the kid ran out of gas and kept cranking the starter till it wouldn't turn. Put jumpers on it and never charged it, the alternator did it. I now use the deep cycle batteries from the boats to replace OEM batteries when they die. It works so I'll stick with it.

It is possible to arc weld off a battery source, I tried it once myself. Deep cycles are preferred because they last longer but autos also work. 3/32" 6010 rod requires at least 70 amps. That is a substantial continuous load. Batteries were the first source of current for welding. It worked for me so I'll stick with it.

My suggestion would be to use deep cycle batteries or fork lift batteries.

Also swelling of the case is probably the most frequently indication of a consistently overcharged battery. Go to a battery distributor and ask them for confirmation. As battery recyclers they see hundreds in a day. If none are local go to a station that does electrical work or a shop that specializes in battery, starter and alternator work.

Good Luck, Old Salt

I have a battery in my boat, (lead acid), that is both deep cycle, and has plenty of cranking amps. Same experience.

I can run it down to almost nothing, recharge it repeatedly...no problems.

Okay, after reading your reply, I am pretty sure we agree about the deleterious effect of allowing a lead acid battery to discharge too much. I read the 'no less than' in your original statement to indicate you were warning against not deeply discharging batteries.

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It is much easier for me to accept that you wrote a somewhat ambiguous sentence (or that I read into it too hastily) than the idea of you posting something seemingly so off base on a subject like this. The universe has regained its order.

That was the intent. :)

Now I think you are just playing games by being purposefully ambiguous...

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What exactly was the intent?

"warning against not deeply discharging batteries"

Okay, that ambiguity is my fault.

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I took your original statement to mean that keeping the batteries charged and never deeply discharging the batteries would be detrimental, i.e, 'warning against not deeply discharging batteries'.

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That, as opposed to, 'warning against deeply discharging batteries'. Which is what I think (but am not completely certain) we agree on, i.e. deeply discharging LA batteries shortens the useful life.

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Your intent was to 'warn against deeply discharging', not to 'warn against not deeply discharging', correct?

Exactly. Sometimes I don't express what I mean perfectly, but it's good to have someone with another point of view catch those things.

I would direct this question to the battery manufacturer, with a much more detailed explanation of the output of the panel and a charge/discharge history of the system.

From here, we can't tell what happened.

Overcharging might be the problem. With a gel battery bank I run now year 4, without any noticeable problems. This is by far the best I have had, but it is very expensive to buy.

Personally I prefer single element batteries ike used in forklifts. I run 20 kAh and a 35 kAh @ 48 volts too. Charging up to 56 Volts and discharging down to 46 Volts. This works for one year now.

These are deep cycle golf cart batteries 6 Volts each liquid acid deep cycle.

Sounds to me like the batteries were allowed to discharge to a low state and then frozen.....is this possible? Otherwise I'm at a loss.....

you cooked them too much! thats why they were bulging. fix the charging circuit or the replacement batteries will repeat this condition.

The batteries in my APC UPS unit bulged and failed after only a year or two. I'm pretty sure they were the recommended absorbed glass mat. Sealed, with little rubber caps under the seal. I added distilled water, maybe too much, and tried to charge and desulphate. No luck. These batteries are not cheap in the long run. I got better luck using an old car battery.

Old or pre-used batteries are wonderful things!

Good Luck, Old Salt

It is absolutely necessary to have a good charge controller between the solar panles and the battery assemply, of sufficient amperage to prevent over chanrging of batteries and the resultant deformation of batteries.

While many suppliers give an inverter, with an in built charge controller, it does not work sometimes, resulting in failures. There is no harm in having an extranal, additional charge controller for safety of batteries.

The life of batteries will be maximuy, if they are charged and recharged regularly. Even trickle charging would do.

In fact. I left my system, a 70 w one, unattended for 5 months, and when I returned, it was as good as new. I am yet to see how long the battery would last.

I guess the batteries are sealed valve regulated (VRLA), either Gel or AGM as a flooded/vented battery normally won't bulge.

The bulging is due to pressure build up from overcharging which could be a result of a faulty charger or the charger being set to the incorrect charging regime such as to charge vented batteries. It can also be caused by a short circuited cell, but this generally won't cause other cells in the bank to deform. Whilst over discharging will kill a battery, it won't deform the case.

Vented battery charging regimes generally include an equalisation cycle which imposes a higher voltage on the cells for a prolonged period in order to induce bubbling and heavy gassing which assists the cells rejuvenation process.

This equalisation cycle can quickly kill a sealed (VRLA) battery and should be avoided as it will cause an uncontrolled build up in pressure which will either cause the valve to open, thus disgorging large quantities of electrolyte (which can't then be replaced), causing the case to bulge or even split and/or, in the case of gel batteries, forming pockets of space between the plates and the gel electrolyte which significantly reduces their capacity..

A lead acid deep cycle battery's life is primarily determined by its treatment. Overcharging, over-discharging, failing to recharge soon after discharge, number of deep discharge/recharge cycles, temperature of operation, etc all contribute to shortened life.

Most deep cycle batteries can be discharged to 20% state of charge (Soc) regularly but their life span is reduced, for instance, a battery that is regularly cycled to 80% Soc may have a life of 5000 cycles, but take it down to 20% Soc and it could be reduced to just 500 cycles.

An audit of your battery capacity versus recharge capability versus usage patterns will show what load you are subjecting your batteries to.

IEC 896-2 is the standard for the test procedure of VRLA batteries.

The 50% rule is often used as a rule of thumb, where the cost of the batteries is amortized over their lifespan to give a cost per usable amp hour.

According to this rule, designing for an average 50% depth of discharge provides best value for money.

Consider LiFePo4 batteries for your replacements, the bank will be smaller for the same usable capacity, they charge more rapidly without any reduction in current as they approach full charge and they can be discharged much more robustly without damage.

You need to get your charging set up absolutely right for them though.

Hi,

Check your CCU output voltage and current, defenetly it will be more than required by your battery, in my experiance battery bulging happens because of over charging. adjust the charging voltage and current as per the required level mentioned in battery data sheet.

Depth of discharge is critical. 50% is a safe level, so you can look at having a reasonable battery life. Cycles to 50% DOD are the most important factor in lifespan, and that number is determined by the discharge (demand) contrasted with the charge capacity, which is of course variable with solar. If you don't get sun, don't over discharge and ruin your batteries. Set your low voltage disconnect at no less than 95% of your nominal battery voltage. AGM and flooded batteries are both lead acid.

Batteries bulge sometimes in response to extreme temperature swings created by hard charging (high C-rates) in low temperatures, or overcharging, which is just plain old abuse.

Sometimes perfectly good batteries bulge. One year life is usually because of poor electrolyte maintanance or excessive discharge rates or depth of discharge. I see it regularly, and undersizing a system is false economy..

I think you are using Lead Acid Sealed for life batteries of Gas Combination type.

These batteries are very sensitive to rate of charge (the charging current). If overcharged these swell.

Rule is to charge these batteries with charging current at rate lower than specified by manufacturer for the ambient temperature.

That means your charging current regulator is not functioning properly. Some time back I was searching web for charging regulators and noticed that Smart Regulators are available at reasonable price.

Either change the batteries and charging current regulator.

Or go for Sealed Gel type batteries (similar to used in cars for starting / cranking duty). These are less sensitive to rate of charge and last 3 years +.

Actually, Gel batteries are the most sensitive to charging voltage and rate of all of the lead acid chemistries. Their charge voltage must be strictly controlled to around 20% less than AGMs to prevent gassing which forms bubble voids between the plates and the electrolyte. This propensity to gassing requires them to be charged at a slower rate than either AGM or flooded types.

Overcharging of batteries produces heat, and for a Gel battery, that heat can cause the Gel to dry and harden, shrink away from the plates and lose capacity.

Gel cells are the most expensive, have the shortest life expectancy of the 3 types and are generally of a larger physical size for the same capacity.

Gel cells are best suited for slow drain applications, and as such are generally not used in motor cranking duty.

I would not accept the design of a system that didn't allow for at least 7 years from the batteries.

I may be wrong in saying that engine cranking batteries are gel type?? But the facts are that

1. Batteries used for engine cranking have to feed in heavy inrush current.

2. Are charged up at high current rate of 5 to 6 hours.

3. Are Maintenance free (may require to check electrolyte once in a year).

The guaranteed life of engine batteries is 3 years and easily last up to 4 years in a car or a Taxi (where there are frequent starts).

Hence as per my experience these are best suited for such application.

You can expect a gas combination, maintenance free batteries to even last more than even 7 years (your wish) but have to be maintained at a constant ambient of around 24 to 26 Deg C (exact one has to refer to manufacturer's recommendation) and has to be charged at rate specified by the manufacturer so that there is a chemical equilibrium between forward and reverse chemical reaction is maintained and net Gas generated is Zero.

The battery of member on Forum has swelled and that is because of overcharging. So please suggest him something which can be use to him rather than .... I am not a battery expert but have used batteries and was suggesting engine starting duty batteries from my experience. Also in India we recover 25% of battery cost from scrap value of consumed batteries.

Over charging may be the possible reason. Overcharging may happen because of a fault with the charge controller, or with a shorted cell plate inside the battery.

Frequent monitoring of Open Circuit Voltage of a fully charged battery and replacing the battery with new one when the OCV becomes low, is the only solution to avoid the recurrence of the same.

Musthafa.

I'm just throwing this up, although maybe not available to the OP. This is what's in my boat, and they are great batteries. Nothing likes to be overcharged, but these would probably be a reasonably priced option for solar storage.

http://www.walmart.com/ip/EverStart-Maxx-Group-Size-29-Marine-Battery/20531539

If we are talking lead acid batteries then the usually cause is over charging. The case on most these batteries is ABS. Upper working limit is 176°F(80°C). Getting the electrolyte to hot for too long a period will cause the plastic to soften and sag with the weight of all the lead suspended from the top.

Even on a trickle if the current is too high and the surface area of the case can dissipate the heat they will do this.

You need to look at the charging circuit that it is not over charging or that not charging at a rate too long that the battery can't dissipate the heat.

Guessing, you are using Sealed LA batteries, or they would not have Bulged.....

If you want your batteries to last a long time, you need to control the charge and discharge very carefully.

If you know roughly how much power you need, you need to buy LA Batteries that 70% of the charge will supply all your needs.

Then only charge to 70%, which is around 13.3 volts max (assuming a nominal 12 volt battery).

This also prevents gassing and water loss......

If they are deep discharge or leisure batteries, they can accept being heavily discharged, whereas other LA types may not!!!

It has been discussed here very, very often already.......

Andy,

I have always learned a lot from your posts, I thank you.

I have a lot of experience with battery storage for solar and genset operations. We have used Unigy industrial AGM's configured to 48V in very large (400KW) installations all the way to (4) flooded 6V golf cart Deka's or Johnson Controls in a 12V or 24V config. We use HV Xantrx charge controllers (up to 600VDC strings, nominal to charge 48V) or Outback or Morningstar controllers, all configurable, so that we can carefully design system ops, on both the charge and discharge side, and to match storage capacities and charge rates.

You cannot control charge on solar systems to anywhere close to that you can achieve on grid or with a genset, because the production window can be short and of practically any magnitude, making your decision to use a conservative charge rate a decision to potentially not use available charge supply. Sometimes, that is the right decision, but it is a compromise.

I have to disagree with you about your battery state of charge to prolong life. A battery system charged to 100% (correctly with finely controlled staging), then discharged to 50% SOC , compared to a battery charged to 70% then discharged to 20%, before recharging to 70%, will last significantly longer. Both personally, and professionally, I can find no documentation to support your premise. Of course, overcharging a battery can kill it. Lot's of things can kill them, so I am not suggesting that you don't need precise equipment, which is readily available.

I am testing my theories on a Leisure battery that I bought in he summer of 2001. It is used in my caravan. It is still working perfectly....Capacity appears to be as near as dammit as it was when new....though my testing of that is fairly primitive I do admit....

During the winter it sits on the same charger (used in the summer time and on holiday) that I designed and built using the values I mentioned (have mentioned many times on CR4!).

Have you tested any batteries over a similar (or longer period) yourself, using the values you mentioned? I would be most interested to hear of any other testing and life expectancies of the Batteries concerned.....its a lonely business testing!!!

Andy, I suspect the disagreement between you and PFR is probably more related to semantics than vastly different observations/experience with lead acid batteries. I suspect that a battery charged slowly up to 13.3 volts (and presumably held there) is not what PFR would consider only 70% charged.

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I doubt there is much additional usable charge provided to the battery above the mid 13 volt range. The purpose of the higher voltage is often claimed to be insuring the electrolyte is well mixed (which I don't see as a problem in a car that is driven often).

You did not look at the link I posted, nor did you read the post I made.....

Try looking at the graphic on the second page.

This is why I wrote that the battery would be charged with between 60 and 100%, depending upon the charge level.......

May I say that my value of 70% falls within this range? So what I wrote was technically correct?

Do you still now have a problem with my statements? Please let me know how/why.

Andy, I didn't have any problem with your statements to begin with. I was just pointing out a likely difference (not a fault) in terminology.

The difference will only be due to the charging current relative to the battery size, clearly catered for in the SOC diagram that I posted in that .pdf file.....

There was no discussion of charge current (either relative to capacity or anything else!) by ANYONE except myself......

It is also patently obvious here that very few understand anything about LA charging, discharging and/or maintenance.

I tried to (maybe OVER) simplify the points that need to be addressed...but on CR4 you are damned if you do and damned if you don't as there is always some half trained clever clogs that only picks at what is written......

That .pdf I posted recently here is a good start for anyone who really wants to learn something, a sort of" LA Batteries 101" if you like!!

I hope that this post will now satisfy all the "Clever Clogs" here....

The first problem that anyone should have with those graphs is that it is just not possible to ascertain battery Soc from voltage readings whilst a battery is under charge. Scuba Engineer is possibly the only website that suggests this method. Manufacturers state that a rest period (no charge or discharge) of at least 4 hours and preferably 24 hours is required before a reasonably accurate indication of Soc can be determined from voltage alone.

The measured terminal voltage when under charge will be very close to whatever the charger is outputting. So - if you had a charger set at maximum 14 volts, you could be seeing that very soon after starting the charge cycle no matter what the actual Soc is. Up the charge voltage to 15 volts and the terminal voltage will closely follow it within minutes. Does that indicate that your 200Ah battery has gone from say 50% Soc to 80% (or for that graph, 120%+) in a couple of minutes? Not likely.

Second problem, the statement at the very bottom of page 67 extending to page 68 is totally at odds with the accepted tenet of battery resting to take a voltage reading.

Third problem, they are showing charge voltages in excess of 16 volts, you don't even go this high to equalize a flooded battery.

Fourth problem, they show a battery Soc in excess of 120% - how do you do this? Maybe it's more than 20% over full charge???

Fifth problem, they say that those graphs represent flooded cell voltages (which they don't), we're talking about VRLAs here, which will necessarily have a Calcium chemical makeup, and they specifically say that the graphs will not then apply.

Seventh problem. They state that they are using Trojan batteries and that at 100% Soc the specific gravity is 1.26 whereas Trojan's own literature lists an SG of 1.277 for their battery when fully charged. That's a difference of almost 10% in Soc.

Eighth problem. They state that the percentage of acid in the electrolyte is 25%, whereas it is closer to 37% for SG of 1.277. At 25%, the SG would be around 1.195, which is roughly equivalent to 60% Soc, in other words, the battery could never become fully charged.

The only ways to get a true indication of Soc is by Hydrometer if the battery is a vented type, or by Coulomb counting if of a sealed type.

With Coulomb counting, Temperature, age and Peukert's effect must be taken into account. Many manufacturers provide a Peukert's exponent for their particular battery for this purpose.

Not sure how you arrive at that 70% state of charge voltage being 13.3 volts for a 12 volt battery.

Typically, a 12v battery has a rested terminal voltage when fully charged of 12.73 volts.

When discharged to 70% Soc, the rested terminal voltage will be a tad under 12.4v.

I use the word "rested" because a lead acid battery is a chemical engine, charge and discharge processes take a finite time to affect the entire structure of the cells.

When under charge, the voltage presented to the battery affects firstly the outer surfaces of the plates, this takes a while to penetrate deeply, and is thus known as "surface charge".

If you take a voltage reading from a freshly (but only partly) charged battery you will likely get the voltage that was presented by the charger. That voltage will, at first rapidly, and then more slowly fall as the surface charge is absorbed into the plates. The reverse effect occurs in discharge mode.

The only way to ascertain the true charge voltage of a sealed battery, because you can't take a specific gravity reading, is to rest it with neither charge or discharge for at least 4 hours.

It sounds as though you have reversed the reading, not a problem as long as one knows about it. See below for a better way to read the capacity or SOC.

Also, it was a "charging to voltage". Obviously I did not make that clear enough for "Newbies, my apologies.

May I draw your attention to the diagram on page 2 (marked page 67 I believe) on this website pdf:-

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

It agrees roughly with many other manufacturers data as well....

13.3 volts equates to between 60 and 100% capacity, depending upon the charge current, which is of course battery dependent. As you have probably already guessed, I use a C/10 chrge level, except when I am moving site and the battery is seriously "down", then I use a C/4 charge to get some charge into the battery quickly.

As you can see, the "Rest" voltage barely goes above 12.6 volts, never to 13.3 for example (except maybe a defective 24 volt Battery!!

12.6 is considered by manufacturers, as the start of Sulfation in many batteries, so my charger cycle between 12.6 and 13.3 volts trying to avoid Sulfation at all costs.

Though going below 12.6 for short periods is not dangerous to battery health, especially a leisure type, though I myself define short as less than a day, but how correct that is I cannot say.......

In a standard car battery, the charge must be replaced as quickly as possible after starting the engine to give the battery a reasonable life. Also not good, charging well above 14 volts is often arranged by car makers, which also shortens life too, as well as causing gassing and eventual water loss.

Car battery design is done just to allow large starting currents, but it also shortens its life over other battery types and applications.....but they are therefore relatively cheap and easily found.

Caution-

When speaking of marine batteries there are 2 types!

The one most commonly meant in this discussion is the deep cycle type. This is what you would relate to a trolling motor, a boat without an engine equipped with an alternator, sailboat which is under sail most of the time and who's engine is seldom used and other applications where the battery is deeply discharged and then recharged usually with a battery charger. These are available in both a sealed or unsealed versions. This is most often referred to as a "marine deep cycle battery.

The second type of battery is a marine starting battery. This is for starting and operating the engine(s) under normal situations. This battery is most similar to an automobile battery where it has a large load (starting), medium recharge rate and finally charged while it is also providing power to electrical devices used during the engine operation. These are available in sealed or unsealed types. These are often referred to as "marine starting battery" of "marine operation battery". The main difference between these and auto batteries is these are more rugged and more suited to a salt water environment. Otherwise they are identical to an auto battery.

A sample of these would be a 42' power boat equipped with twin diesels and an auxiliary diesel generator with a 10kw output. The engines are started and operated with the starting/operating batteries. While underway they also supply power to all other devices. The alternators are also rigged to charge these and the deep cycle batteries but not discharge from the deep cycle. While the engines are not in use but power is needed the generator is started and provides power to the boat. It will not charge the main batteries unless the generator battery (deep-cycle) is fully charged, its power requirements are met and the main batteries are not charged.

This is done to facilitate each battery being used for what it is best for and maintaining as high a total charge possible.

Good Luck, Old Salt

It appears, your electrical system has deficiency. It allowed the battery to discharge beyond its full recovery level and again it charged to the level, which the battery bank could not take it.

May be your battery bank is not deep cycle type,with thick plates. A car battery can not recover even if it gets discharged beyond 40% depth of discharge.

So true. I left my car door ajar once, which put the overhead lite on all night. In the morning the battery was discharged. I was sick, and could not charge it for a couple of days. That was it, the battery never recovered.

What was the exact Lead Acid Battery type?

For a car, in the US at least, over 99% of the time it is going to be thin/porous plate flooded lead acid starting battery.