Best Battery Selection

GreenPowerManiac

What are some good batteries for a reasonable price?

Inverter 2500 watt 
Max Load 2000 watts AC
Started with 15 12v FLA's in parallel.  120Ah's each.
Now 9 FLA's and it blows inline fuses about once a week.  10amp fuses.  Batteries are going on 8 years old.

Looking for some good clear batteries that can visually check levels....

Estragon

8 years for that many in parallel is pretty good! Assuming you need that much capacity you might want to look into locally available forklift batteries or 2v L16s.

GreenPowerManiac

Was thinking AGM , maybe 8 in parallel. 
TS-60 charge controller and diversion load to D.C. Pump and heating elements in tank of RV coolant.

Is 8 enough? 

Estragon

AGM will likely run about double the price of flooded for same amp-hour capacity. May be worth it for some applications where minimal gassing, flexible orientation, higher rate charge/discharge, and/or low self- discharge are important. Inability to check SG makes diagnosing problems more difficult. Is this a mobile(boat/rv) application?

More than 2 or 3 parallel connections can be a problem, so it's usually better to use a battery sized for your application.

In order to determine if 8 is "enough" you need to describe the load in terms of maximum current, total daily watt hours, and amount of time desired before needing to charge with generator or grid/shore power.

GreenPowerManiac

Greenanythingdotnet 
That'll give a clue. 
All house loads. About 1000 watts max draw during daylight hours. 

Marc Kurth

Help me understand what is driving the desire to change from what you had originally.
Are you seeking longer battery lifespan?
Are you most concerned about replacement cost? If so, is it more important than lifespan?
Is battery maintenance even a factor in your decision process?

As I see it, 8 years is reasonable for a lightly loaded battery bank with 9-15 parallel batteries, depending upon when the others died......

Marc

GreenPowerManiac

Soon they'll all be dead, hoping they get me till spring. 

Want more maintenance free batts. 
Must replace all of them or the old ones will drag down the new. 
Lifespan isn't too important, would like to go bigger batteries because 
the bigger they are, the longer lasting. 
Trying to decide if AGM is the way to go maintenance free.
Batteries are judged by weight usually, then price. 

Marc Kurth

Based on your statement of (15) 12v 150ah batteries in parallel, that's  15x150 = 2250 ah @ 12v = 27 KWH.
Yes, you can simply buy (15) new batteries of the same type and call it good. AGM's will be more expensive - and just like FLA, not all AGM's are created equal. (I am very opinionated about this subject )

My approach would be to use larger individual batteries. My favored method for larger systems is stick with L16 size batteries.

You could do it with (12)  6v batteries in 6 strings of 2 = 2400 ah @ 12v
Or
You could go with (12) 2v L16's @ 1200 ah each. Configured in 2 strings of 6 in each string for a total of 2400 ah at 12v. 

There are some good deals out there on FLA  L16's. But AGM's in the L16 frame size are expensive - they can range from around $400. to $650. each, depending upon the brand.

Estragon

One advantage to using big 2v is fewer cells to check.

6v=3cells so 12x6v=36 cells to check.

2v=1cell so 12x1v=12 cells to check.

mike95490

Estragon said:

One advantage to using big 2v is fewer cells to check.

6v=3cells so 12x6v=36 cells to check.

2v=1cell so 12x1v=12 cells to check.

And that's a big payoff over 7 years, much reduced time spent chatting with the batteries.  

Marc Kurth

mike95490 said:

Estragon said:

One advantage to using big 2v is fewer cells to check.
6v=3cells so 12x6v=36 cells to check.
2v=1cell so 12x1v=12 cells to check.

And that's a big payoff over 7 years, much reduced time spent chatting with the batteries.  

Looking at this example, it becomes an obvious choice when comparing 2v and 6v/12v FLA's. But deciding just how much that big payoff is actually worth, varies per person. For some, it is minimal. For others, it is enough to make them buy AGM's.

Just for comparison, if we use $300 as a cost for FLA and $450 for AGM, that's $150 each x 12 = $1,800. penalty for going AGM. The difference will get even more extreme when you start looking at various brands.

One guy will tell you that is a great deal and the next guy will say "Are you crazy?" 

bill von novak

Marc Kurth said:

 But deciding just how much that big payoff is actually worth, varies per person. For some, it is minimal. For others, it is enough to make them buy AGM's.

Keep in mind, though, the big difference between AGM's and flooded cells:

If you overcharge a flooded cell, you have to replace the water that was split.  That requires distilled water, safety equipment and time.

If you overcharge an AGM cell, you have to replace the cell.  That requires a lot of $$.

You can avoid overcharging AGM's by never doing an equalize charge.  However, without doing equalize charges, the batteries will eventually drift out of balance.  At that point one cell will see (effectively) an equalize charge voltage, and will start losing water.  It will continue to get worse until that cell fails - at which point a new battery bank will be required.

Marc Kurth

Bill,

Yes, of course.

I would also add that 90%+ of the battery banks that die young (that we see) are damaged by undercharging. That is always the single biggest factor in my world. (Over estimating PV harvest and underestimating load are the enemy) Equalizing some brands of AGM's is standard practice and if done properly, the damage is minimized and battery life is extended. Obviously, some applications require more EQ than others. And some types of AGM's will suffer terribly from being equalized.

My experience has been that properly designed battery banks with high quality AGM's don't tend to develop major imbalance problems until the 6-9+ year point, which is nearing the normal end of life point for AGM's. (Yes I know that FLA's can go twice that long) Obviously many factors come into play and we do see earlier battery failures!

I never argue cost effectiveness because that is a personal financial decision. I only point out that 8-10+ year old off grid AGM battery banks are out there running with happy owners. As are FLA banks that are even older.........

It's kind of like the question: "How long is a piece of string?"
Answer: "Well, that depends......"

GreenPowerManiac

Marc,  I'd have to agree with the AGM overcharging.  It has been an issue here a couple of times.  
My Uncle works at Fermi Lab in Batavia, IL.  as an Electrical Engineer.  And says you judge a battery by its weight. Get the biggest ones you can get cheapest and maintainable.  In my case, Farm and Fleet sells the same that I have and one larger size, which I'll think I'll get next.   Trying to put this off until Spring since it's only 3 months away.

I'm thinking that a new battery arrangement is in order more than types, for easier maintenance.  Just wish the battery cases where transparent to check fluids every 3 months.  

Marc Kurth

Sounds like a plan to me. You got close to 8 years with 9-15, 12v low cost batteries in parallel - why change?

MyPrepperLife

Hello. New here.

I built a small and simple solar-electric system a few months ago and now am doing research to prepare for creating the bigger, better system I really want.

I'm pretty sure I'm going to use AGM batteries instead of FLA batteries.

bill von novak said an overcharged AGM battery would be ruined. Isn't the charge controller in a solar-electric system supposed to prevent overcharging? I'm just wondering under what circumstances a battery would get overcharged if the system has a charge controller.

And Marc Knuth stated that he's seen damage caused by undercharging. It's my understanding that undercharging should not happen if your PV array is capable of charging your battery bank to 100% capacity. What I actually want to do is have a PV array that is overkill for my battery bank, just to make sure undercharging isn't a problem. Is this a good approach?

Also - I've seen the term "hard charge" used in connection with solar-electric technology. What does it mean? 

Photowhit

MyPrepperLife said:
And Marc Knuth stated that he's seen damage caused by undercharging. It's my understanding that undercharging should not happen if your PV array is capable of charging your battery bank to 100% capacity. What I actually want to do is have a PV array that is overkill for my battery bank, just to make sure undercharging isn't a problem. Is this a good approach?

We just had 10 days with sun on only one of them, It's been a couple years but one November we had 14 days with 1 HOUR of direct sun. Quite easy to undercharge when there isn't any charging going on... Particularly in a daily operated system.

I'm over paneled and think it's the way to go, as solar panels are pretty cheap now, in general.

AGM batteries are just a little more fragile, they are also harder to measure their state of charge (SOC) voltage is a poor indicator of the state of charge. You could have a voltage reading of 12 volts and be fully charged with a huge load or nearly empty while charging in direct sun. With a flooded battery you can measure the Specific Gravity (SG) of each cell and have a very good idea of it's SOC.

BB.

I am not sure--My definition would be a "high amperage" charging rate... Typically for flooded cell is ~10% rate of charge (200 AH battery bank at 20 Hour Rate * 0.10 = 20 amp).

For our typical needs--I suggest 5% to 13% rate of charge for solar... 5% is on the low side, but can work OK for weekend/summer cabin use. For full time off grid, 10% rate of charge is better--With ~13% rate of charge being typical for a "cost effective" maximum (various reasons).

I have read that some "pure lead" / AGM batteries like 20%+ rate of charge--And I would call that a "hard charge". (this is not an "equalizing charge" and AGM/GEL batteries should not be equalized with elevated charging voltages--In general as this will damage them).

Another possibility... When batteries get "old"--They can get "sulfation" on the plates (hard crystalline lead sulfate which no longer participates in the charging cycle--and is actually an insulator). And "equalizing" with elevated voltage (typically in the 2.5 to 5% rate of charge range)--getting the batteries to "gas" is thought to "knock" the sulfation off the plates and expose "virgin material" that can be cycled (discharged/recharged) again (a "hard charge"?). This probably would only be useful on "heavy duty" deep cycle batteries (such as forklift batteries) that have thick lead plates to start with.

Note that heavy equalization currents (and equalizing for many continuous hours at a time) can cause the batteries to over heat--Monitor the battery temperature while doing extensive equalization or you can damage them with excessive heat.

-Bill

MyPrepperLife

Thanks for your replies, Photowhit and BB.

Now I have even more questions.

Photowhit said, "Quite easy to undercharge when there isn't any charging going on... Particularly in a daily operated system."

Isn't it true that a well-designed solar-electric system includes electronics that warn you when your battery bank's state of charge is too low and/or even forces the system to stop outputting power when the battery bank's state of charge is too low? If in fact that is true, wouldn't this prevent an underharging scenario?

Photowhit also said, "I'm over paneled and think it's the way to go, as solar panels are pretty cheap now, in general."

As I stated in my post yesterday, that's what I think I'm going to do. It's my understanding that a good-quality charge controller will not allow batteries to be charged too quickly or to be overcharged even if you throw a massive amount of panel-generated electricity at the charge controller. Is that right?

And Photowhit also said, "AGM batteries are just a little more fragile, they are also harder to measure their state of charge (SOC) voltage is a poor indicator of the state of charge. You could have a voltage reading of 12 volts and be fully charged with a huge load or nearly empty while charging in direct sun. With a flooded battery you can measure the Specific Gravity (SG) of each cell and have a very good idea of it's SOC."

Too bad AGM batteries don't have a built-in SOC indicator. At least, I don't think any of them do; I've researched this a little.

I'm attracted to the AGM technology because I'd like to avoid doing the maintenance, for a few reasons: 1) I'm concerned that I might screw it up, 2) if I don't have to add water to the batteries, I can squeeze more batteries into a smaller space (because I won't need to leave room to get access to the top of each battery), 3) It's my understanding there is some danger an explosion could occur during routine maintenance, 4) I just would rather not have to bother with the maintenance.

BB said, "I have read that some "pure lead" / AGM batteries like 20%+ rate of charge--And I would call that a "hard charge". (this is not an "equalizing charge" and AGM/GEL batteries should not be equalized with elevated charging voltages--In general as this will damage them)."

The AGM batteries I've considered don't require equalization, according to the information I've found on line.

BB.

It has been suggested (I think by some mfg. too) that AGM batteries still do need equalization every 6 months or so (cell to cell balancing of state of charge). However for AGM, equalization is extended charging at normal absorb charging (4-8 hours???) to balance the cells.

AGM are still lead acid batteries--And while they are functioning during normal life, they do not vent (gas/electrolyte mist)--They can vent near the end of life when the catalyst has worn out. At that point, the batteries can vent hydrogen (and oxygen) gas.

Also, if you have charge controller failure (or miss-programmed), over charging AGM can also cause them to vent/overheat.

AGM's are almost ideal batteries (clean, more efficient, low maintenance, support higher surge current, and frequently higher charging current when at lower state of charge)--But they still are lead acid and have similar issues (sulfation if left to sit at low state of charge) and some issues that people cannot measure the state of charge with a hydrometer. And, I would suggest that AGM batteries have a bit shorter life than similar quality flooded cell lead acid (typically catalyst wear-out). And they tend to be ~2x more expensive than flooded cell lead acid.

While some folks tend to think that AGM batteries don't need ventilation and access--I would suggest that they be installed just like normal flooded cell batteries with good access and ventilation--They will eventually age/cycle out and fail (for example, do not install under a bed or in a bedroom closet). And, like any battery, if subjected to extremes (electrical/thermal), they can cause (in worst case failures) a fire.

Another aspect of good ventilation is that the batteries can be kept cooler--Giving you longer life too.

-Bill

Marc Kurth

MyPrepperLife said:

Thanks for your replies, Photowhit and BB.

Now I have even more questions.

Isn't it true that a well-designed solar-electric system includes electronics that warn you when your battery bank's state of charge is too low and/or even forces the system to stop outputting power when the battery bank's state of charge is too low? If in fact that is true, wouldn't this prevent an underharging scenario?

I snipped the above from your post for simplicity.

It is important to remember that undercharging can be charging at too (low? -Bill) of a voltage. It can also be not charging long enough to reach full charge. It ALSO includes letting the battery sit in a partially discharged state for extended periods. While you are waiting for an opportunity to charge, the batteries are beginning to sulfate.......

Gently equalizing many brands of AGM batteries (but not all) will generally have a net positive effect as opposed to rigidly avoiding equalizing while sufation marches on. Some brands tolerate equalizing far better than others, but all batteries are subject to sulfation when undercharged.

Marc

Dave Angelini

All batteries Marc?

 I have a client in your state, can I send him your way and could you get him a set of flooded golf cars for 48v

MyPrepperLife

Marc Kurth said:

It is important to remember that undercharging can be charging at too (low? -Bill) of a voltage. It can also be not charging long enough to reach full charge. It ALSO includes letting the battery sit in a partially discharged state for extended periods. While you are waiting for an opportunity to charge, the batteries are beginning to sulfate.......

Gently equalizing many brands of AGM batteries (but not all) will generally have a net positive effect as opposed to rigidly avoiding equalizing while sufation marches on. Some brands tolerate equalizing far better than others, but all batteries are subject to sulfation when undercharged.

Marc

So please help me understand this.

When you're designing a solar-electric system, one of your data points is "number of days of autonomy," correct? And I know this means "number of days without sun or with very little sun." The more days of autonomy you want, the bigger your battery bank must be and the bigger your PV array must be.

During those periods with no sun or little sun, you don't get as much from your panels as you do on sunny days. Does this constitute "charging at too low of a voltage"? If so, what, if anything, should a person do during these days of autonomy to prevent damage to the battery bank? I mean, I know of course you could use a generator to charge the battery bank when the weather isn't sunny, but if that is what you're supposed to do, why plan for days of autonomy at all?

Also, when you warn against "letting the battery sit in a partially discharged state for extended periods," what do you mean by "extended periods"? A few days? A few weeks?

Here is some context so you'll know a little more about my situation.

The solar-electric system I'm designing will be installed at my off-grid house, which is my full-time residence. Therefore, it won't be sitting unused for extended periods of time, and it will be closely monitored.

Regarding equalization for AGM batteries: I guess I need to do some more research so I can understand this better.

westbranch

I'll try to be clear,
day 1, no or little sun, use 15%
day2,no or little sun, use +15% = -30%
day3 , no or little sun,use +15% = -45%
at this point you consider the weather forecasts etc and decide if you will go to -60% or ?? OR fire up the genny now, tomorrow morning or tomorrow night. You also might get a few % everyday so it softens the deficit..

make sense?

Marc Kurth

Dave Angelini said:

All batteries Marc?

 I have a client in your state, can I send him your way and could you get him a set of flooded golf cars for 48v

LOL - you got me, Dave. I stand corrected, Sir!  I put my fingers in motion with my brain still in neutral..............  

With an evil grin I will restate it to: "All cost effective, commercially available, field proven, lead acid formulations are subject to the problem "

Dave, I pulled out of the flooded battery business awhile back. Running a completely Non-Hazmat business selling only AGM's has some distinct advantages. Last year was the slowest for us since 2009 when I started. Now, selling only Concorde and Fullriver, we already blew away any previous January/February combined. Seems to be some real confidence building up in the marketplace, including my export work.

Marc

Marc Kurth

westbranch said:

I'll try to be clear,
day 1, no or little sun, use 15%
day2,no or little sun, use +15% = -30%
day3 , no or little sun,use -15% = -45%
at this point you consider the weather forceasts etc and decide if you will go to -60% or ?? OR fir up the genny now, tomorrow morning or tomorrow night. You also might get a few % everyday so it softens the deficit..

make sense?

Well stated!

MyPrepperLife

westbranch said:

I'll try to be clear,
day 1, no or little sun, use 15%
day2,no or little sun, use +15% = -30%
day3 , no or little sun,use -15% = -45%
at this point you consider the weather forceasts etc and decide if you will go to -60% or ?? OR fir up the genny now, tomorrow morning or tomorrow night. You also might get a few % everyday so it softens the deficit..

make sense?

Yes, I understand completely, and now the fog is beginning to clear!

The tentative plan I've formulated will take this into consideration, Here is what I did: I used a "calculator" at altestore.com to come up with recommended sizes for my battery bank and panel array. Built into the calculations are 8 days of autonomy assuming a maximum 50% discharge. So it would seem I'd have plenty of wiggle room. If we have more than 8 contiguous sunless days, and if my battery bank starts getting close to 50% DOD, I'll fire up my generator. (I'm assuming the brains of the system, whatever they turn out to be, will give me a DOD reading on demand.)

I also want to mention that I've added 50% to the panel-array sizing recommended by the altestore.com calculator because I want to be over-paneled.

One more thing: I see that Marc Kurth leans toward the AGM technology. Though I'm seriously considering what the pro-FLA people here have said, it's good to know somebody here is an AGM fan.

mike95490

westbranch said:

I'll try to be clear,
day 1, no or little sun, use 15%
day2,no or little sun, use +15% = -30%
day3 , no or little sun,use -15% = -45%
at this point you consider the weather forceasts etc and decide if you will go to -60% or ?? OR fir up the genny now, tomorrow morning or tomorrow night. You also might get a few % everyday so it softens the deficit..

I live by the forecasts, and usually day 2 I start the genset, because I can get to it, and if day 3 is total white out or pounding rain, I can stay indoors.  My power shed is 900 feet (walking)  from house (120' as crow fly's)  Day 4-9, I HAVE to brave elements regardless.
 (pic is after 6 days of clouds and rain)

BB.

Generally... 2 days of "no sun" and 50% maximum discharge (or 4x your daily load) seems to work out pretty well.

I am not sure how well lead acid batteries would do with a slow discharge over time (i.e. 8 days).

The other issue is you really need a minimum of 5% rate of charge--With 10%+ being better for full time off grid and where some of your power is used during daylight (your loads are "stealing" some of the solar array current from charging the battery bank). With 10%+ rate of charge, you generally do not have to "micro manage" your loads near as much--Plus you can recharge the battery bank pretty much from 50% to >90% over a couple days with 10% rate of charge.

If you have a "way oversized" battery bank--Then that also pushes your array larger too... I.e., a 4 day bank = X watts of charging... And 8 day reserve bank would like 2X larger array--For the same loads.

Regarding how long batteries can "sit" at less than (say) 75% state of charge... The lead sulfates (fluffy from discharging cycle) start to harden into black crystals in hours--And the process is well under way in ~24 hours (I think--I am not a battery engineer).

Storing a battery bank--Recharge to >90% state of charge and recharge within the next 30 days (if not float charging)--Before the batteries go below 75% state of charge (typical self discharge rate for flooded cell deep cycle batteries).

However, as an example, there is a different way of "running" your battery bank. Basically actively cycle from 50% to 80% state of charge daily, and recharge >90% SoC once or twice a week (I think Rolls Surrette engineer told one of the folks here, can go as long as 28 days between full recharging).

Otherwise, trying to recharge your lead acid bank to ~100% state of charge every day (or even several times a week) is kind of hard on the battery bank. That level of charging usually causes batteries to gas which erodes the plates and causes positive grid corrosion (oxygen forms on the positive plates during recharging/gassing).

-Bill

Marc Kurth

MyPrepperLife said:

One more thing: I see that Marc Kurth leans toward the AGM technology. Though I'm seriously considering what the pro-FLA people here have said, it's good to know somebody here is an AGM fan.

But in my opinion, for regular owner occupied homes, flooded batteries can offer a better bang for the buck ratio - as long as you operate and maintain them properly. And that is not a difficult process.

My lean is because I have been serving niche markets that need the features/benefits offered by high quality AGM's, since 2009. So I have a lot of hands on, detailed field experience with them. Roughly half of the batteries that I sell go to regular plain vanilla residential off grid PV.  But I send an equal number of customers over to flooded batteries from someone else. It's all application specific as far as I am concerned.

The remainder of my applications are batteries applied in industrial/remote unattended/arctic applications/racing and a bunch of really bizarre stuff like super high drain/charge applications. It seems that my specialty has become application and system design for weird stuff. Some of the apps are considered to be impossible by some folks here and they doubt.........

Marc

Photowhit

I see you've gotten a lot of very good advice and information from some talented people. I didn't mean to drop you in a lurch, I've not had a lot of time and had one other person I was trying to help out. I will say your system will look much like mine in the winter. In the winter I use perhaps 1.5Kwh a day, and thought I owned a 19 Kwh battery (forklift) Though I've discovered, through informed people on this forum, that I had actually closer to 15Kwh battery.

I've just been through a 10 day period with 1 partly cloudy day with direct sunlight, I do get some charging on the cloudy days so there isn't a huge drop in capacity, but I did manage to get down below 50% at one point. I am damaging my battery because I choose not to have a generator, it sounds awful to put that in print. But I'm over paneled and will do some equalizing at the first opportunity to regain what capacity I can. I'm not overly worried, but I now the trade offs, I've had just a few such periods in the life of this battery, maybe once a year in it's 5 year life.

Flooded batteries tend to accept current at a maximum rate of 13-15% before they lose much of the energy as heat (not a good thing) In general charging cycle, prevents the possibility of heat build up unless the battery has been severely discharged. I have a max charging amperage of about (4000*.75/24=) 125 amps or a whopping 19.5% of my battery's @640 ah rating. But in reality, it will do much of the bulk charging before the sun is at an angle to provide that much current and will be charging at @29.4 volts or (4000*29.4/29.4=) or about 16% and will likely be in the absorb stage and accepting less energy. I can throttle back the max each charge controller puts out and still have panels to gain a bit extra harvest on those cloudy days, as the charge controller will limit the production from what energy is available. I actually intend to add a morning/east facing array to spread my charging time, and bring my array to about 5-6000 watts.

AGM batteries vary in the amount of current they can accept. I can see advantages to a battery that can accept a 20-25% Charge rate. Particularly in Mountain climates (or anywhere) where the sun can pop out for an hour and be gone for a couple days...