Batteries not reaching float

2twisty

Here's a bit of an update.  Right after I started my testing, my wife had a medical emergency and is still in the hospital almost a week later. (Prayers appreciated).

Anyway, the older string seems to need a lot of work.  even running the generator and in full sun for a couple days I can't even get it to absorb.  The newer string went to absorb rather quickly. 

So, for now, I am operating on the newer string.  I don't have a separate 48V charger, so I am thinking of rewiring the older string to 12v and using my 100A 3-stage 12V charger from back when I used to run a 12V system.

Should I do 4 parallel strings and charge them all or do 4 separate recovery operations on them?

Sadly, my 12v charger doesn't have an EQ setting.  But I was hoping that I may be able to bulk them with the 3-stage until (and if) they improve, then put them back together as 48V and let the charge controller handle the EQ to (maybe) bring them back in spec.

What think ye?

I've reduced my overnight loads to under 100W. THe Outback's resolution on that is absolutely HORRIBLE..100W resolution?  Really?

BB.

My prayers for your wife.

Regarding breaking the string up for 12 volt charging. You want the charger to hold around 15-16 volts and aproximatly 2.5% to 5% of the battery capacity as charging current (200 amp battery, 5-10 amps per string).

If you can get a DC Current Clamp Meter like this one from Sears, you can check each parallel string of batteries to make sure they are accepting their share of charging current.

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

Also watch the temperature of the equalizing batteries. 2.5% to 5% rate of charge can overheat the batteries after a few hours of constant charging current.

-Bill

jonr

> WBJr reports that I'm still putting 20A into the batteries, which is about all my panels can make. 
> Absorb time is 2 hrs

The Rolls formula may not apply to your batteries, but it says that bulk charging a 400AH bank at 20A would need up to 8.4 hours of absorb time to get to a full charge.   AFAIK, failing to get to a full charge every week or two means your batteries don't last long.

BB.

From what I have read... You do not need to get to 100% charge every day... Once or twice a week is probably better (100% charge every day involves lots of gassing and some heat--None of those a great for a battery).

There is an alternative cycling---Run from 80% to 50% state of charge, and over 90% once a week. It appears that your batteries will not sulfate if they are actively cycling. I believe there is a post here that one Rolls/Surrett engineer said that you can go as long as 28 days for >90% state of charge. Many vendors recommend equalization (100% SOC) once a month. Tall batteries and "industrial" batteries seem to need monthly equalization to stir the electrolyte (prevent stratification of "dense" electrolyte at the bottom of a cell and light (low SG) electrolyte at the top of a cell.

Not a battery engineer--Just based on what I am reading here and other places.

-Bill

Dave Angelini

If the end amps are set right there is zero problem in my opinion of not charging everyday in good conditions. Over 100 systems doing this and some for decades. The system does need to be cycled occasionally. Running cooling in summer at night, heating in spring and fall, or bad days of winter do this nicely. The lead acid needs to charge weekly in my opinion just for a sanity check and going longer probably is OK but I don't want to see that.

I do not ever want to see what is happening with the OP as most of my clients are not technical to do this and in my opinion, they should not have to.

In the OP case by not charging correctly, excessive loading, or measuring the SG in good conditions to calibrate the system is the real problem.

I do wish him well !

jonr

But I find no support for the plan Bill described  in the document below.

Looking at page 32, I'd say that Surrette is recommending a 100% charge (using their formula for absorb time) every day with equalization on top of this.   It explicitly talks about RE systems that charge at less than 10% not being ideal - because of lack of time to reach daily 100% charge.   I'd say the open question is just how much damage is done if 100% charge is reached less often (3 days, weekly, bi-weekly, monthly).  From Dave's comment, perhaps very little if every 3-7 days.

Equalization is discussed: "as needed" and "60-180 days". But (speculation) if daily 100% charge isn't being met, then maybe eq every 30 days is needed.

http://www.rollsbattery.com/wp-content/plugins/rollsbatteries/pdfs/Rolls_Battery_Manual.pdf

Estragon

There are lots of variations in off-grid situations, and any manual can only deal in generalities. A lower charging rate doesn't work well in a constantly occupied year round home, but can in a weekend setup because the deficit charging gets made up during the week with no loads.

The question of how often a 100% charge and eq is needed is complicated by factors like the temperature of the bank and use pattern. A hot bank cycling between 50-75% is likely to be different than a cold bank cycling from 80-90%. There are also the variations in batteries (antimony etc).

jonr

Sure, but a conservative general recommendation is better than nothing.   Perhaps "set your absorb timeout according to the Rolls formula" and "get through a full absorb every week or two even if you need to use a generator".

Dave Angelini

It is all in the design requirements. Some systems and locations do not require a generator and so enough solar has to be specified.

2 % end amps and the solar goes to float is about as general as it gets and it works well.

The problem is people do not know if their absorb time or even their absorb voltage is correct unless they measure SG when full.
That is the calibration    It is different for different levels of usage also!

So they may check it once when the system is new (maybe) and they are not using as much energy as a year later.

The calibration is then wrong.

BB.

From an older thread:

http://forum.solar-electric.com/discussion/19562/what-is-the-optimal-soc-range-for-cycling-lead-acid-batteries

ChrisOlson said:

Re: What is the optimal SOC range for cycling lead acid batteries?

vtmaps wrote: »

What does this mean? Are you referring to more cycles per lifetime? Greater kwh stored per lifetime? Greater efficiency?

I learned from Surrette Tech Support that you can work a Series 4000 or 5000 battery for a month without fully charging it, and it won't hurt it and cause hard sulfation problems. I don't go that long - a week to 10 days usually between full charges. Cycling them below 85% SOC definitely is not a full cycle because it never causes any plate erosion (according to Surrette). And it's way more efficient - now that I have a ComBox I am able to see kWh into our bank and kWh out and compare to kWh to loads - and the efficiency drops dramatically (way less out than what you put in) when you absorb batteries every day. And I mean it's REALLY bad to the tune of 4-4.5 kWh/day lost in heat in the batteries on a bank our size.

I don't make RE power to turn it into heat in the batteries every day. I'll sacrifice some of it once every week to 10 days or so to keep the batteries healthy. But absorbing batteries every day is about as efficient as starting up a 20 kW generator to make yourself two slices of toast and a cup of coffee for breakfast.
--
Chris

And:

ChrisOlson said:

Re: What is the optimal SOC range for cycling lead acid batteries?

vtmaps wrote: »

This (if true) is the key to the puzzle. I've never seen that in any Surrette literature. It makes sense, though.

It is at odds with the advice over at gbbattery.com:

It is not in Surrette's literature. You have to talk to somebody at Surrette Tech Support that knows batteries. Steve Higgins is one of those people.
...

-Bill

mcgivor

The debate on charging is about as complicated as one on religion, with different sources of information, beliefs and opinions, it seems sometimes they are so polarized it's difficult to find a common ground. In the end it appears that there are general rules with differences based on individual circumstances, there are those who discharge to 50% on a regular basis to work the battery and others who believe in shallow discharge as a means to extend the cycle expectancy. There is no clear consensus, even from manufacturers, some independent literature supports the theroy of the 50% discharge cycle  to get the best value for money spent, despite the shorter life expectancy. All these different ideas, opinions and beliefs often lead the uninitiated in a quandary as to what the best choice is.

jonr

When it comes to published material vs a second or third hand verbal comment from the average phone support tech, take the former.  By a wide margin.  Even more so if it involves religion :-).

On the other hand, I haven't seen any manufacturer published materials on the effects of less than daily 100% charging.  If it were actually better, I'd expect them to document it and encourage on-grid battery charger manufacturers to implement it.  But they publish the opposite.

Trojan writes "charge your batteries fully after each period of use".  Ie, not "charge fully once a week or month".

Estragon

Battery makers are in the business of selling batteries. A cynic might point out that it's in their interest to publish advice which avoids warranty fights over sulfated batteries, but possibly shortens life. Just sayin.

Dave Angelini

Estragon said:

Battery makers are in the business of selling batteries. A cynic might point out that it's in their interest to publish advice which avoids warranty fights over sulfated batteries, but possibly shortens life. Just sayin.

Definitely agree!  

I really miss Chris Olson, I do not know Bill that he was typical of Offgrid as he had some very large loads (electric cooking in winter) and other just out of the norm loads. Also generator load supporting many times a day. Too bad he can't be invited back after being banned here. He did lend perspective!

The new LFP batteries and their controllers will really help mcgivor!  It will take the calibration/religion out of the loop for the user.
It does have some new problems for large systems but should really help alot of the folks here at Wind & Sun.

Estragon

I'm curious. Without talking about any particular case (Olson, coot, et al), what generally constitutes banishable comment? I remember them from back when I was researching for my system.

BB.

The interaction with the moderators and Chris was not our finest hour and things went downhill from there. Since none of them post here anymore, and I really do not want to say more. I am really sorry for what happened. The VBB and new Vanilla software issues at the time did not help either.

My personal policy is that most discussions are fine as long as they are done with respect. I, personally, only ban folks for spamming or direct attacks. Spamming is 99.9% of my banning. Behavior on the forum--I have only banned a couple in my entire time here.

I do not ban because somebody disagrees with me on technical subjects (or politics, etc.). I enjoy reading about other folks views and learn a lot. I learn nothing from repeating my own views/biases.

If anyone has concerns about my "editorial" actions (I am the only moderator here at this time)--Anyone is welcome to contact David or Rick at:

David Lauzon <david@wind-sun.com> President of NAWS
rick Forbes <rickf@wind-sun.com> Admin for Forum (and other software projects at NAWS)

He and Rick are my "bosses" here (I am just a lowly volunteer here--I have no business relationship with NAWS). This is something I sent to David a couple years ago when trying to understand my (and other moderators') role here.

"Moderating" is "Moderation". Try not to let people get to you. Take the steam out of difficult discussions. Walk away and let another moderator help--And be open to letting posts stand on their own--It is not our job to delete/edit posts that we may not agree with. Of course there are "red letter" items that are flat out dangerous that need to be addressed.

If there is a poster who otherwise is forum member in good standing, let the posts stand and make a new post with your warning (I a few times have made editorial comments/warnings in the offending post itself). "User Time outs--Temporary Bans" should only be a last ditch effort to get the poster back on track--Understanding that even Temporary Banning an active poster is going to probably drive them away--And make problems for everyone here (loss of poster's knowledge, hurt feelings, involvement of NAWS, etc.).

On the forum itself--Always address the post, never your observation of the poster him/herself. It is very easy to misunderstand the intent/psychology/thoughts of the poster themselves. As a moderator, we should never fall into that trap. If poster's intent needs to be addressed, do it off-line and/or ask for help from another moderator or Dave and Rick (I usually try to go to Rick first--As a common point of contact/history. I assume that Rick will talk with the appropriate folks at NAWS and take it to David if appropriate).

If there is a desire for more discussions about editorial decisions/actions (or software issues/questions)--Please start a new thread at "in the weeds" sub-forum.

I will not discuss specific questions about posters--It is unfair to those not here.

If anyone that has been banned believes that I made a mistake (it happens--A few first time posters I banned, looked like spam, contacted me and I have reinstated them), please feel free to contact me via PM or David/Rick.

Back to on thread topic--discussion.

-Bill

Photowhit

Bill, this is by far the best run forum/BB I have participated in. Bar none in my many years going back to usenet BB's.
Perhaps because 'Sungod' isn't here...lol, I hope god blesses you for all the time and energy you put in here.

Perhaps you could collect some of your information and formulas and put together a digital book. There are so many bad info books out there it would be refreshing.

jonr

My cynical view is that the LA battery manufacturers want to see their batteries perform as well as possible (so you don't switch to lithium).  But they don't care about practical realities - like the cost of adding more panels and generator hours.

Vic

Couple of comments,

The Surrette Formula for Absorb time,   uses 50% DOD in the example.   Many off-grid users do NOT discharge to 50%,   but  the formula should still hold for shallower discharges,  it adjusted.

Any Charge controller (or inverter/charger that becomes "confused" when there is insufficient energy available to maintain Vabs,  should be returned for correction of this BUG,   or defect,   and not accepted until the defect is corrected,  of just thrown on the junk pile.   Any manufacturer that does not know how to program for this situation is not worth considering as a supplier (IMO).

Have not seen Surrette's definition of PSOC.   Assume that what BB Bill described is at least a form of PSOC operation.

For the battery banks here,   do my version of PSOC cycling by maintaining Vflt for three days,  from PV,   and do a full-charge on the fourth.   Would bet that this type of operation DOES require more frequent EQs,  verses a full-charge every day.   But this does reduce battery heating,  plate erosion,   etc.   Seems to work,   so far ...   have always used EA as the Absorb terminator,   which works quite well ...   however,  the proper EA setting does depend somewhat on the DOD of the battery.

AND,   IMO,   quality battery manufacturers are in the business of making the best battery that they can,   for the target market that they are  addressing.   They are in the business of selling batteries,   BUT,  a happy customer  will tell friends/neighbors when they know that they have a quality battery,   generation more sales.   Every manufacturer can make a dud or two,   and that is what the warranty is for,   but,  would bet that most good quality battery banks that perform poorly are ruined by the user.

All of the Surrette battery banks here are in their 12th year of very good service ...  Surrette has always been a very supportive partner in my off-grid system.

Just more opinions,   FWIW,   Vic

jonr

Looking at page 10, I see no indication that the formula needs adjustment for DOD.  There is reference to a 50%, but it pertains to the available charge current during absorb.   They suggest an EA of 2-3% (page 11).   It would be interesting to know how long people using proper EA (ie, accounting for loads) find that it takes to reach it (ie, time for start to finish of absorb, for various charging rates).   Is the formula realistic or worst case?  Probably more the latter (ie, the time to use if you can't do EA and the safety timeout if you can  use EA).

http://www.rollsbattery.com/wp-content/plugins/rollsbatteries/pdfs/Rolls_Battery_Manual.pdf

Trojan is designing to reduce PSOC damage with their SmartCarbon batteries.  But I don't see any materials from them indicating that PSOC is actually better.  Or any talk about absorb time.

boB

While under charge with a good amount of current into the batteries, check the temperature of the batteries, if even just with your hands to see if one of them is HOT.  A temperature imaging camera is the best but we don't always have one of those laying around.

Temperature seems a good way to find where all the extra wattage is going.

mike95490

boB said:

While under charge with a good amount of current into the batteries, check the temperature of the batteries, if even just with your hands to see if one of them is HOT.  .......

Back of your fingers is much more sensitive than the fronts.   (many years in electronics labs)

Vic

jonr said:

Looking at page 10, I see no indication that the formula needs adjustment for DOD.  There is reference to a 50%, but it pertains to the available charge current during absorb.   They suggest an EA of 2-3% (page 11).   It would be interesting to know how long people using proper EA (ie, accounting for loads) find that it takes to reach it (ie, time for start to finish of absorb, for various charging rates).   Is the formula realistic or very conservative?

http://www.rollsbattery.com/wp-content/plugins/rollsbatteries/pdfs/Rolls_Battery_Manual.pdf

Trojan is designing to reduce PSOC damage with their SmartCarbon batteries.  But I don't see any materials from them indicating that PSOC is actually better.

For the Surrette Flooded batteries in use here,   the length of the Absorption stage  varies directly with the DOD of the previous discharge.

Is there any argument that the time required for a full Absorb stage varies directly with the DOD of the battery in the previous discharge cycle,   when using a constant Vabs?

Have never used the noted formula to try to determine the ideal Absorb time,   as have ALWAYS used EA to terminate Absorb.   Had felt that that formula was for a different charge profile than the Constant Voltage Absorb commonly used with RE (Solar) power sources.

Yes,   Surrette does recommend  2 - 3 % of 20 hour Capacity for the EA value (2% for new installations).   But the correct EA value will depend upon the chosen Absorb voltage  --  if one needs an Absorb voltage in the high range of Vabs,   then the EA setting will probably need to be higher,   than if the Absorb voltage is in the lower range of reasonable.

When using measured battery charge current (Shunt EA),   have run EA settings ranging from about 1% of 20 hour C when the batteries were young,  to about 1.5% of C now.   Some of this increase is most probably due to the necessity to increase Vabs to allow a full charge with increasing battery age.   The increase in Vabs was need to achieve a full-charge

Regarding "proper EA",   and Tabs,   with a constant voltage Absorb,   the charge Rate is determined by the battery's Charge Acceptance,  not the charger's ability to force current into the battery.

Not to try to put too fine a point on any of this,   just my opinions

Estragon

Absorb always seems to take about 2 hours using WBjr end amps with good sun for me, irrespective of DOD (assuming it was more than ~10%). Bulk obviously depends on DOD.

jonr

This is interesting.   Talks about 3-6 hour absorb times once every 5-7 days.  And using a higher than normal absorb voltage when time is limited.

https://www.homepower.com/view/?file=HP89_pg120_IPP

I'm surprised that this stuff isn't clearer.

jonr

Sounds like some people have systems that are working great, but the knowledge they have isn't readily available.  Perhaps some of them will post a years worth of data on absorb time to reach end amps, bulk time, voltage and current used, etc.

Dave Angelini

You are overthinking this Jon.
 On my systems the users measure SG at the float transition when new. We adjust Abs voltage, Abs time, and then we are done for a year or unless something causes us to do this again. They are told to measure a pilot cell occasionally for a sanity check. Most do a 1 hour EQ every 3 months. Use the lowest settings that will get the SG that the battery maker specifies.
Do all of this and design/use about 20-30% of the capacity (on a regular basis) and you will approach 10 years of life. They spend about 20 minutes a month on this. Once a year look/record  the SG of all the cells.

mcgivor

jonr said:

Sounds like some people have systems that are working great, but the knowledge they have isn't readily available.  Perhaps some of them will post a years worth of data on absorb time to reach end amps, bulk time, voltage and current used, etc.

All the data one could supply is meaningless as each systems demands vary, hours of sun, array capacity, daily loads, battery capacity, charge controller etc etc What works for one system doesn't nesesarally  translate to another, it takes time to understand the demands and the requirements to replenish what is taken out. Often I relate it to a marrige, one has to nurture the relationship and understand it's requirements. Some consult engineers to do the thinking  for them, for the rest of us it's trail and error. The old adage you will probably kill the first bank of batteries couldn't be more accurate, it's a learning curve, only the curve may be steeper than first expected.  By no means is this a discouragement, it's just the reality, the suggestions offered are to guide to assist, not nesesarally solve the problems, be patient, read as much as possible on battery requiments, charing profiles, every system is different  Especially read the battery manufacturers recommendations, sometimes they are more aggressive than initially thought, Surrette is a prime example. 

Estragon

FWIW, my bulk time is about an hour for each 10% DOD < ~85%, 2 hour absorb at 58.8v to 1%C, float at 52.4v. Eg. If at 50%SOC that would be roughly 3.5 hrs bulk, 2hrs in absorb. In mid summer about 5hrs float. In winter I wouldn't get to Vabs on solar alone from 50%SOC. EQ roughly every two months with SG check.

Current varies with sun - tends to be around 30a in bulk. I adjust sometimes, for example I might increase Vabs for shorter or a run of dull days. Mine are US Battery L16s.

As others have said, although this is working for me, it might not for you. I'm replacing 8yr old boat GC batteries this year that had quite different charging and use (abuse) pattern.

Like Macgivor says, it's a bit like a marriage. Every situation is different.

mcgivor

Estragon said:

FWIW, my bulk time is about an hour for each 10% DOD < ~85%, 2 hour absorb at 58.8v to 1%C, float at 52.4v. Eg. If at 50%SOC that would be roughly 3.5 hrs bulk, 2hrs in absorb. In mid summer about 5hrs float. In winter I wouldn't get to Vabs on solar alone from 50%SOC. EQ roughly every two months with SG check.

Current varies with sun - tends to be around 30a in bulk. I adjust sometimes, for example I might increase Vabs for shorter or a run of dull days. Mine are US Battery L16s.

As others have said, although this is working for me, it might not for you. I'm replacing 8yr old boat GC batteries this year that had quite different charging and use (abuse) pattern.

Like Macgivor says, it's a bit like a marriage. Every situation is different.

Using the system 1 in my signature, which I've been watching very closely for the last 2 months since a controller change, with a daily DOD of ~ 40%, the bulk charge is completed by 10 am with a maximum current of 25-30 amps, absorbtion takes about 1.5 hours and ends on current below 2%, then float (absorption is set for 3 hours). The daily power is between 2.5 & 2.7 Kwh with loads, primarily the refrigerator during charging, on a cloud free day, during overcast days the process takes an additional 3 hours to reach float, tropical climate 17°N, never needed a generator. So very different with no low sun during winter to contend with, array is sized to cover cloudy periods, plan to double the array, and go with 48v in the near future. Would this system work at 40° from the equator? probably not during winter months, especially with cloudy periods.
Settings, bulk 29.6v, absorbtion 28.9v, float 27v, recharge 25v, EQ 31.8v....×2 for 48V.....59.2v,  57.8v, 54v, 50v and 63.6v, these settings work with the system / battery I currently have and may not work for others, so basically irelevant to another system /battery.