Battery Advice and expansion

[theojkett]

Hello kids!

Three years ago I purchased a 4kw 48v Solar package. 9 panels, Magna Inverter/Controller, 8 Rolls 440 ah FLA batteries. In all honesty, I knew little about batteries and little about using them properly. That lack of knowledge led to the loss of all 8 batteries after only 4 months of use. That being said, I've learned a bit more since, won't repeat the same error and let's leave it at that.

So, for three years, I've had these 9 solar panels that are doing absolutely nothing, I now have the opportunity to get some batteries and put the system back in operation, but.....

The caveat to that is I cannot afford the 440ah batteries I once had and I am faced with creating a lower power system, which is fine. I was originally going to go with 220aH AGM batteries, but again, the price is out of reach. So now I have my sights set on some 130aH batteries. I have one question.

If I get (8) 6v 130aH AGM batteries to make up my 48v system, can I add more batteries later to increase my power(aH)/storage capacity?

I was told once a while ago that if I wanted to add more batteries to my then 440ah system for more storage I would have to wire the batteries differently. Parallel vs. Series I believe I was told.

Thank you for your help and suggestions in advance.

Ted

[Sunking]

Real simple, NO. AGM's cost twice as much and last half as long as FLA making them 400% higher in cost.

You did not mention how you destroyed a top of the line battery in 4 months, but I can only imagine you had to do two things:

1. You over discharged them every day and
2. Let them go dry.

Switching to AGM and 1/4 the capacity is not learning or proper corrective action. It will only take a month to destroy AGM. See what got you was a grossly undersized system to start with, and now you think downsizing will fix it. What is wrong with that picture?

A 48 volt 440 AH battery has a total capacity of 21 Kwh with 4 to 5 Kwh usable per day. You had to be using 20 Kwh per day to destroy them in 4 months. So if you were using that much energy it would be impossible for you to cut down 1.5 Kwh per day with a 48 volt 130 AH AGM. No one can cut usage 90% unless they have their power turned off and forced to quit using power.

[theojkett]

Boy I didn't want to get into this......

This system is installed on my remote second home in upstate NY. I'm only there every two weeks. I installed the system on Labor Day weekend in 2015 and it functioned brilliantly through November. Never let the power drop below 80% and it never did naturally through regular use. The panels got plenty of daylight/sunlight. The biggest draw we had was the well pump and that was only used at night most days. Other than that it was the refrigerator that ran all day, but again, I never let the power drop or did it ever drop below 80%, most days we were in the 90's.

Then winter came and I had to use the generator more often to keep the power up OR strictly use the generator on cloudy days when the panels couldn't provide and power would drop into the 70% range. The 1st mistake was not turning off the system when we left in the winter months, while nothing in the house was left on, including the fridge, there was still a draw and natural loss. They were stored in an unheated shed next to the panels. The second mistake was listening to the salesman who assured me they would be okay in that environment. The third mistake was not keeping the batteries warm.

December weekends I would arrive to battery power being in the 60% range. I'd run the generator until power was up enough to use (95%), use solar power during the day, generator at night. January came and that's when it all went bad. About the second week in January, the region had four consecutive days of -25 degree temperatures. I arrived at the end of that week to eight very expensive ice cubes, yes, they were frozen solid. No a little icy... completely solid ice blocks.

So there were many errors made, I understand them and I have learned a few things. Don't let the batteries get cold, shut the system off, keep the power at or near 100% and don't use FLA batteries again. I need a battery that is more resilient to cold temperatures, one that I can keep indoors or ones that are portable enough to take with me in the winter months. My power meter tells me i'm not using more than 400 watts, more near 200 watts daily, except when the well pump kicks in and that is briefly. I'm very frugal with my power, LED everything and if it's not needed it's off. Power tools are used on generator only. Do I need 4 to 5 kwh a day, probably not.

I have a budget problem as well. I only have $1500 to spend and I know that is a tough call. But the question here is, if I can start small, can I add to it later for more storage/power? You are telling me no, I can't. So what am I to do then. I have been functioning off of a 3200 watt generator for 3 years since with no problem, it is just costly and noisy and eventually, this generator will need replacing. In the 16 years of being there, I have gone through 3 generators and thousands of gallons of fuel. Those 3 months that the solar was working properly were the best years and the cheapest, I need to return to that.

So, let's hear the advice and suggestions. And please, I know there were mistakes made, let's keep the finger wagging to a minimum.

Thanks for your help in advance.

[Matrix]

What are you relying on to tell you you were at 90%/80%/60% .... with out testing the Specific Gravity you have no idea.

And I might be wrong, but the problem in the cold might not have been Flood Acid Batteries, but rather (as you noted) not keeping them a bit warmer, and more specifically it seems if they froze solid they were not fully charged and / or badly stratified. Acid at the bottom, water at the top. Never fully charged, never EQ'd. Hard to tell from your details. Rolls says at -22*F the battery will have limited capacity down to about 40% but I cannot find on their site where they say do not operate below -XX *F. If I understand correctly, a fully charged Lead Acid battery will not freeze until -92*F

I would think a better alternative to the AGM for the cost would be Trojan SPRE 06 255

[soylent_green]

you can't add batteries to a current system.

A lot of people will steer you away from AGMs because of the cost and lifespan, but for a place you are at every few weeks its a great option. I run 4 x 6v DC250 fullriver batteries for my every other weekend place no strain or pain, but 8 of these would blow your budget.

If you had 8 Rolls 440 ah batteries and you use only 200 to 400 watts a day, you should have been fine. Seems weird. I guess the cold - something I don't deal with.

[Sunking]

Boy I didn't want to get into this......

Well be glad you did because you have a lot of facts wrong. Lets start with this:

I understand them and I have learned a few things. Don't let the batteries get cold, shut the system off, keep the power at or near 100% and don't use FLA batteries again.

FLA batteries are good to -40 if fully charged, same as AGM. Cold is good for batteries because it slows down chemical reactions and aging. Last thing you want to do is store batteries in a warm climate. Shutting the system off is the exact wrong thing to do. Rather than shut the system off, remove the load, and set Bulk/Absorb/Float to 54 volts. Note 54 volts is Float Voltage, so no gassing occurs. But what it does do for you is keeps the batteries at 100% SOC and a little warming. Same exact advice I would give you with AGM.

Lastly Rolls has a pretty good warranty and stands behind their product. Something does not add up, they should replace them unless there is something you are not telling us like gross negligence and so far I have not heard that.

When you left, what was the Bulk/Absorb/Float set to?

[theojkett]

Matrix - My inverter has a digital display that reports what the existing battery power is among other information. And it is likely the batteries were completely discharged when they froze.
Soylent Green (is people) - Support at Wholesale solar told me I should not have let them get that cold (-25). Should have told me that when I showed them where they were being stored!
Sunking - When I said shut off the system, I meant remove the load, sorry for not clarifying. Always had the system set to Float/Auto and it worked well. Rolls would not warranty them against freezing and would offer no exchange/credit/discount.

Thank you for all of your comments. Greatly appreciated. But I still don't know what I should do. I cannot afford another (8) 6v 430aH FLA batteries. I have a $1500 budget and that should be enough to get me into some sort of battery power even if it is and likely less than 430ah. FYI, I have (9) Canadian Solar CS6K-270P Solar Panels.

[SunEagle]

Matrix - My inverter has a digital display that reports what the existing battery power is among other information. And it is likely the batteries were completely discharged when they froze.
Soylent Green (is people) - Support at Wholesale solar told me I should not have let them get that cold (-25). Should have told me that when I showed them where they were being stored!
Sunking - When I said shut off the system, I meant remove the load, sorry for not clarifying. Always had the system set to Float/Auto and it worked well. Rolls would not warranty them against freezing and would offer no exchange/credit/discount.

Thank you for all of your comments. Greatly appreciated. But I still don't know what I should do. I cannot afford another (8) 6v 430aH FLA batteries. I have a $1500 budget and that should be enough to get me into some sort of battery power even if it is and likely less than 430ah. FYI, I have (9) Canadian Solar CS6K-270P Solar Panels.

Just be careful that if you use your large solar pv system to charge a smaller (Ah) battery system you could end up cooking them quickly.

If you can't afford a big battery system you should cut back the number of panels proportionately to stay within the C/8 to C/12 charge rate range.

[Sunking]

Matrix - My inverter has a digital display that reports what the existing battery power is among other information.

There is a critical mistake. No battery monitor system can tell you anything about a FLA or AGM battery other than it is low or dead. Only a temperature compensated hydrometer can tell you the State of Charge, and a fully charge FLA battery is good to -45 degrees either C or F.

I take it from your comments your battery jars cracked and all the electrolyte leaked out? That is a dead giveaway your batteries were not fully charged and why Rolls would not replace them is my best guess.

AGM's have their place, but understand doing so is going to cost you big bucks in the end. As you have noticed AGM cost twice as much. They last half as long as FLA.

Good luck to you. Hope you have better luck.

[Matrix]

Based on the discussion above, It re-enforces to me the budget idea of Trojan SPRE 06 255. They can be had for about $190 (worse case) and can often be bought locally so you avoid freight shipping. At 48v they will give you 4-5 kWh of usable stored energy, But as SunEagle said, I would reduce the array size or change settings in the Charge Controller to keep the current between C/8 - C/12.

The Trojan SPRE 06 255 will be my next battery unless something unforeseen pops up in the next 3 -5 years.

You could save a bit by buying T-105 or the SSIG 06 255 (but based on the weight, this might just be a relabled T-105 and the 105 would probably costs less) My local dealer can get me a cash price on the T-105 for $125.

[theojkett]

There is a critical mistake. No battery monitor system can tell you anything about a FLA or AGM battery other than it is low or dead. Only a temperature compensated hydrometer can tell you the State of Charge, and a fully charge FLA battery is good to -45 degrees either C or F.

I take it from your comments your battery jars cracked and all the electrolyte leaked out? That is a dead giveaway your batteries were not fully charged and why Rolls would not replace them is my best guess.

AGM's have their place, but understand doing so is going to cost you big bucks in the end. As you have noticed AGM cost twice as much. They last half as long as FLA.

Good luck to you. Hope you have better luck.

Well... .perhaps I misunderstand the words... "Current Battery Power: 90%" Of course that number will change depending upon the usage yadda yadda.

The batteries NEVER cracked. The casing didn't bulge, no leaks. They just froze solid.

I may take Matrix advice and get the Trojan batteries. Though I do need to learn more of the C/8 - C/12 exactly what that means. I've started with Battery University. That should edgamucate me good.

Thanks guys.

[Matrix]

Well... .perhaps I misunderstand the words... "Current Battery Power: 90%" Of course that number will change depending upon the usage yadda yadda.

Those are the "words" of the LED Battery Monitor Display ... and you cannot trust it. It is just a vague generalization. You MUST have a Temperature Compensated Hydrometer so you can check the specific gravity of each cell. I have 3, all different kinds (well one of my 3 is actually a refractometer) so that I can get a very accurate reading. The more you learn your batteries, the more you can "trust" the LED battery monitor display as a good guess. But you first have to learn your batteries thru careful monitoring of the SG.

A good starting point is to know What the SG is when the batteries are first commissioned AFTER a full charge and EQ (something I regrettably did not do because of newbie mistakes), and then monitor closely until you get the charge parameters of the solar dialed in to reach that commissioned SG at least a few times a week. And then as the seasons change, the charge parameters will change from winter to summer. As you can see, there is a lot more involved than reading the % State of Charge (SOC) from a Digital display.


C = the Amp Hour Rating of the battery divided by 8 would be the max charge rate. C/10 is a good middle ground and C/12 would be about the minimum I would charge the battery bank. You want to make sure your charger / Solar charge controller is not exceeding a C/8 limit for Flood Acid Batteries . So C/8 on a 225 Ah battery would be 225/8=28 max amps of charging current. With the AC battery charger from the Generator you want to make sure you set the limits in the charger to not exceed that C/8 max. But in the solar Charge controller you can be a little more liberal as you will not often hit max charging current due to solar conditions. And in Float on the solar CC you will never hit it while you are away.

Before I left the cabin I would make sure the batteries are at 100% or very near it, that the loads are off, (and as SunKing said) that Bulk / Absorb / Float is set to 54v

[Mike90250]

Well... .perhaps I misunderstand the words... "Current Battery Power: 90%" .....

The meter cannot do anything bu make a guess, and it is only right when it says battery power 0%. If you know how cold it got,
you can figure out the state of charge before freezing.

Freeze point Pb battery.jpg

[Sunking]

Though I do need to learn more of the C/8 - C/12 exactly what that means. I've started with Battery University. That should edgamucate me good.

That is simple 5th grade math.

Where C = Battery capacity in Amp Hours
Where the Integer = Hours

Amp Hours = Amps x Hours
Amp = Amp Hours / Hours
Hours = Amp Hours / Amps

So lets say you have a 80 AH battery and want to charge at C/10. How many Amps is C/10

80 Amp Hours / 10 Hours = 8 Amps.

Easy Peazy

[Sunking]

The meter cannot do anything bu make a guess, and it is only right when it says battery power 0%. If you know how cold it got,
you can figure out the state of charge before freezing.

Freeze point Pb battery.jpg

You can bet his battery was no where close to 100% because no way it got down to - 77 F. 1000's of people would have died.