Best Battery Selection

Wheelman55

Photowhit said:

 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% 

Appears to be a typo in the bottom formula. I think you meant (4000*0.75/29.4)??

Photowhit

Wheelman55 said:

Photowhit said:

 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% 

Appears to be a typo in the bottom formula. I think you meant (4000*0.75/29.4)??

Yep, thanks! must have been typing in my sleep!

bill von novak

MyPrepperLife said:

Hello. New here.

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.

 

A properly configured charge controller will not overcharge an AGM battery.  The conditions you have to watch out for are:

-Charge controllers designed for flooded batteries used on AGM batteries
-Programmable charge controllers that try to do an "equalize" charge

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?

It's a good approach but insufficient in and of itself.  You need a generator (or other reliable source of power) to ensure that your batteries do not sit at a low state of charge for any amount of time.  It can always be cloudy.

mike95490

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?

For this to safely work, you must insure your charge controller can LIMIT OUTPUT AMPS.
Both my Morningstar MPPT-60 and Classic 200 can have limits programmed into them just for this purpose, a battery too small for full solar power.

Marc Kurth

mike95490 said:

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?

For this to safely work, you must insure your charge controller can LIMIT OUTPUT AMPS.
Both my Morningstar MPPT-60 and Classic 200 can have limits programmed into them just for this purpose, a battery too small for full solar power.

Mike, Yes. Unless they are Concorde AGM's :-)

westbranch

Marc Kurth said:

mike95490 said:

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?

For this to safely work, you must insure your charge controller can LIMIT OUTPUT AMPS.
Both my Morningstar MPPT-60 and Classic 200 can have limits programmed into them just for this purpose, a battery too small for full solar power.

Mike, Yes. Unless they are Concorde AGM's :-)

Marc, re: Concordes?  How so? Is that a positive or a negative? Can you NOT use the 'Limit Output AMPS' option?

MyPrepperLife

bill von novak said:

MyPrepperLife said:

Hello. New here.

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.

 

A properly configured charge controller will not overcharge an AGM battery.  The conditions you have to watch out for are:

-Charge controllers designed for flooded batteries used on AGM batteries
-Programmable charge controllers that try to do an "equalize" charge

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?

It's a good approach but insufficient in and of itself.  You need a generator (or other reliable source of power) to ensure that your batteries do not sit at a low state of charge for any amount of time.  It can always be cloudy.

I would make sure the charge controller I buy is designed for AGM batteries, and I guess I would need to make sure my charge controller isn't going to just go off and do equalization because I've inadvertently configured it that way.

I do have a generator. I use it sometimes to charge the batteries for my small solar-electric system when we have extended periods of cloudy weather, which does happen quite often where I live. I've been allowing the SOC to drop to about 40%, but because of this thread plus some information I've gotten elsewhere, I'm not going to allow it to go that low anymore, so I'll be using my generator more often.

BTW, the batteries for the system I have now are AGM batteries.

When said I want an PV array that is overkill for my battery bank, my reasoning was that I would prefer not to use the generator a lot.

BTW, I do know that AGM batteries cost about twice as much as FLA batteries, but I might be willing to pay that extra money for the sake of convenience. I also know an AGM battery bank probably won't last as long as an FLA battery bank, but I might be wiling to live with that too, again for the sake of convenience. However, as I gain a better understanding of the advantages and disadvantages of FLA vs. AGM, I realize I might convince myself to go with FLA.

MyPrepperLife

Throughout this thread there have been comments about the importance of configuring your charge controller correctly. I am hoping that when I buy my batteries they will arrive with information about the parameters required for charging them properly, and I can then use those parameters to configure the charge controller. Is this how it's done?

(Note: The small system I have now is actually a collection of Goal Zero Yeti 400 power packs that are fed by four 160-watt monocrystalline solar panels. Each of the Goal Zero Yeti 400's contains an AGM battery, a charge controller, and a DC > AC inverter. Everything is pre-configured; I haven't had to do any configuration.)

I also want to get some clarification on the discussion (a couple days ago) about checking a battery's SOC. It was said that you can get a more accurate SOC reading from a FLA battery than you can from an AGM battery. Is that because you can use a hydrometer with an FLA battery but you can't use a hydrometer with an AGM battery?

Dave Angelini

Marc Kurth said:

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

Cool !   I do have an Indian reservation that is building Offgrid homes. I was going to use the Concord but they have delayed the homes because of the rainy winter. Please drop me an e-mail if you could supply the Full River to Central California and also maybe convince me which of the 2 AGM's you would use for a really non'technical user that may not be able to or want to care because the US gov is paying the bill.
I am a Dealer for Concorde but is the Full River better in my specific case in the 1100 AH 2V.

I am not knocking the Indians but rather the Feds. The big guy knows how badly we treated the original occupants here. 

Photowhit

MyPrepperLife said:

Throughout this thread there have been comments about the importance of configuring your charge controller correctly. I am hoping that when I buy my batteries they will arrive with information about the parameters required for charging them properly, and I can then use those parameters to configure the charge controller. Is this how it's done?

(Note: The small system I have now is actually a collection of Goal Zero Yeti 400 power packs that are fed by four 160-watt monocrystalline solar panels. Each of the Goal Zero Yeti 400's contains an AGM battery, a charge controller, and a DC > AC inverter. Everything is pre-configured; I haven't had to do any configuration.)

I also want to get some clarification on the discussion (a couple days ago) about checking a battery's SOC. It was said that you can get a more accurate SOC reading from a FLA battery than you can from an AGM battery. Is that because you can use a hydrometer with an FLA battery but you can't use a hydrometer with an AGM battery?

If the power packs have an internal charge controller it should be setup for the battery it has inside. If you were to be purchasing a charge controller, it will almost always need to be set via jumper or switch to FLA of AGM and some have a separate gel setting.

Yes, FLA can be checked for specific gravity (SG) is the reason!

MyPrepperLife

Photowhit said:

If you were to be purchasing a charge controller, it will almost always need to be set via jumper or switch to FLA of AGM and some have a separate gel setting.

Right, but my question is: where would I get the parameters to set the charge controller's jumper or switch? I assume the battery manufacturer publish these??

Photowhit

MyPrepperLife said:

Photowhit said:

If you were to be purchasing a charge controller, it will almost always need to be set via jumper or switch to FLA of AGM and some have a separate gel setting.

Right, but my question is: where would I get the parameters to set the charge controller's jumper or switch? I assume the battery manufacturer publish these??

Yes, there should be a manual somewhere, unless they specify what they are for. I think Specialty Concepts makes some that are specifically for one or the other. If you point at one I can look into it for you. sometime a DIP switch, but often a jumper. Sometimes you can just read it on the board.


I just had Midnite's Brat manual open for another person, they have several dip switches;



...and say in the manual what the profiles refer to;

Marc Kurth

westbranch said:

Marc Kurth said:

mike95490 said:

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?

For this to safely work, you must insure your charge controller can LIMIT OUTPUT AMPS.
Both my Morningstar MPPT-60 and Classic 200 can have limits programmed into them just for this purpose, a battery too small for full solar power.

Mike, Yes. Unless they are Concorde AGM's :-)

Marc, re: Concordes?  How so? Is that a positive or a negative? Can you NOT use the 'Limit Output AMPS' option?

Mike, the limit for Concorde AGM's of all flavors is literally 5C - subject to a battery temperature limit of 135F. Keep in mind that you would be looking at a very few minutes before the battery began to taper down its current draw on its own.

I have customers going to 1C to 2C on a regular basis. I honestly cannot see any degradation in lifespan after doing this for the last 8 years.

Marc

Dave Angelini

The place where I have seen AGM's degrade faster than flooded is once you start cycling them daily. I also think that a flooded gives a longer warning period before failure and a smoother crash landing, if there is such a thing offgrid....

AGM's are nice for a cabin or limited use and unattended low maintenance.

I also do not see why someone would want to charge any battery that fast offgrid, we have plenty of time and wonder how much longer the battery would last if it was not hit that hard. A nice sized array can slowly bring the battery to absorb and be done by 1 or 2pm
9 months of the year, in most places. Add in a tracked array and 11am or noon is the norm for going to float and more months of the year than 9. 

Marc Kurth

Dave Angelini said:

The place where I have seen AGM's degrade faster than flooded is once you start cycling them daily. I also think that a flooded gives a longer warning period before failure and a smoother crash landing, if there is such a thing offgrid....

AGM's are nice for a cabin or limited use and unattended low maintenance.

I also do not see why someone would want to charge any battery that fast offgrid, we have plenty of time and wonder how much longer the battery would last if it was not hit that hard. A nice sized array can slowly bring the battery to absorb and be done by 1 or 2pm 9 months of the year, in most places. Add in a tracked array and 11am or noon is the norm for going to float and more months of the year than 9. 

Agreed, of course! I have never seen an offgrid that could do that - let alone need to.

But only a part of my business is offgrid, and my focus is always on the needs of my customers. Mentioning industrial applications is only to show what can be done if/when needed.

Marc

MyPrepperLife

Dave Angelini said:

The place where I have seen AGM's degrade faster than flooded is once you start cycling them daily.

What is meant by "cycling them daily"? Drawing any amount of power out of the batteries (even a very small amount) every day and charging them fully the same day, or drawing the batteries down to a very low SOC every day and charging them fully the same day, or drawing them down moderately every day and charging them fully the same day, or something else?

PNjunction

Cycling means daily or semi-daily use, with a discharge of at least 10% capacity.  For industrial users, it can be spelled out in more specific terms like in the Enersys agm application manual.

Dave is correct - those who cycle them daily tend to pamper agm's to death prematurely.  One needs to be on the high-side of the manufacturer specs because our charge source is not constant - which is what the manufacturer's base their specs on - constant charge until full.

The big issue with AGM, is that even after you have reached your "end amps" for the day (which is usually hard to do in the first place for many), an *additional* 6-8 hours of lower voltage float is needed.  Catch-22 - for most of us, that kind of daylight is impossible!

So, you either buy specialist agm's which can take an agressive EQ once in awhile, or at the best, run on the high-side of the battery charge specs.

OR, if you are daily cycling an agm, you can forget all about float, and just run your absorb all day until the lack of sun throws the switch!  Set your float voltage and absorb voltage the same!  Or at the very least, run the float voltage as high as the controller will allow, not exceeding your absorb voltage of course.  Remember, this is ok for daily cycling, but not for a standby/ups solar setup.

Much of the problem stems from our innate fear of over-charge.  Much of this fear comes from those using cheap trash used / old agm's. 

The other problem is that many like to do highly paralleled strings, and merely slap the batts together upon arrival without giving each one an *individual* good first charge!  This leads to balance issues and other phenomena which results in an unfair conclusion of agm's being waaay too sensitive to overcharge.

Moral: daily cycling - forget about float and just absorb until the sun sets and stops the process.  That is for SANE agm setups with no more than 2 in parallel.   Simple eh?

MyPrepperLife

PNjunction said:

Cycling means daily or semi-daily use, with a discharge of at least 10% capacity.  For industrial users, it can be spelled out in more specific terms like in the Enersys agm application manual...

- snip -

...Simple eh?

Thanks for all the detailed info, PNjunction. Some of it I don't really understand at this point, but I probably will after I do more research.

just starting

On my second year of used agm battery 1500$ for 896 amp hours. After this year I'm happy with them have pulled about 1200kwh out of them.

MyPrepperLife

PNjunction said:

...that many like to do highly paralleled strings, and merely slap the batts together upon arrival without giving each one an *individual* good first charge!  This leads to balance issues and other phenomena which results in an unfair conclusion of agm's being waaay too sensitive to overcharge.

I haven't mentioned it until now, but I have had a 12V 3200WH solar-electric system since last November. The batteries for it are AGM batteries. When I received the batteries I did just what you said: I charged each of them fully before connecting them together. I just used a couple inexpensive little battery tenders to do it.

The bigger and better solar-electric system I plan to build later this year will probably use FLA batteries. Should I charge each of the FLA batteries individually before connecting them together?

mvas

MyPrepperLife said:

 Should I charge each of the FLA batteries individually before connecting them together?

Absolutely, yes.  Get all of the FLA batteries to the same fully charged state before connecting.
Get baseline SG & voltage readings before doing anything.
Verify the Date Codes are the same and fresh.

Estragon

Charge parallel strings separately. Charging individual batteries in series strings probably not needed IMHO unless some are way off.