Battery Maintenance - De Sulfation

13

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation
    BB. wrote: »
    Just to make an updated post:



    I hope that if KnowledgeSponge gets some information from the Chemistry Professor, or some other data points on sulfation/desulfators, I will be interested to read the posts.

    -Bill

    as would i for if he has an answer or info that benefits us on the subject of sulfation then i'm all ears and i'll even act like i'm from missouri and ask that you show me.:-)
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    BB. wrote: »
    I hope that if KnowledgeSponge gets some information from the Chemistry Professor, or some other data points on sulfation/desulfators, I will be interested to read the posts.

    Ummmm..... seriously, I have my doubts that the Chemistry Professor is even going to waste the time to comment on it. This is a question for a Battery Engineer, not a Chemistry Professor. And frankly, every Battery Engineer I've ever talked to about battery desulfators has told me exactly what I posted earlier - your battery charger is the desulfator.

    Professors have a PhD, typically. When you look at this, BS - we all know what that means. MS = More of the Same. PhD = Piled Higher and Deeper.

    So basically, even if a Chemistry Professor did comment on it you wouldn't be able to understand what he said. Engineers tend to provide answers like, "No - it don't work".
    --
    Chris
  • TiminatorTiminator Solar Expert Posts: 32
    Re: Battery Maintenance - De Sulfation
    ChrisOlson wrote: »
    Ummmm..... seriously, I have my doubts that the Chemistry Professor is even going to waste the time to comment on it. This is a question for a Battery Engineer, not a Chemistry Professor. And frankly, every Battery Engineer I've ever talked to about battery desulfators has told me exactly what I posted earlier - your battery charger is the desulfator.

    Professors have a PhD, typically. When you look at this, BS - we all know what that means. MS = More of the Same. PhD = Piled Higher and Deeper.

    So basically, even if a Chemistry Professor did comment on it you wouldn't be able to understand what he said. Engineers tend to provide answers like, "No - it don't work".
    --
    Chris


    I was going to write that same thing regarding "Professors" at a University. I couldn't figure out how to word it so it didn't sound like what I really thought about them vs. a private sector scientist.
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Battery Maintenance - De Sulfation

    Again... Yes, batteries have been around for 100+ years and a single chemistry prof is probably not going to change a 100 years of experience by battery/material engineers/scientists...

    But, more information should not hurt either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Battery Maintenance - De Sulfation

    Is a " Battery Engineer " some kind of a special certification ??, or is some title you give Bob today instead of building maintenance ?? I once posted a E-mail I received from the Interstate Batteries Engineering Department total BS and a " Battery Engineer " without a clue trying to explain why they list their Absorb voltage 1 volt above their Bulk Voltage.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Maintenance - De Sulfation
    Is a " Battery Engineer " some kind of a special certification ??, or is some title you give Bob today instead of building maintenance ?? I once posted a E-mail I received from the Interstate Batteries Engineering Department total BS and a " Battery Engineer " without a clue trying to explain why they list their Absorb voltage 1 volt above their Bulk Voltage.

    You can be an electrical (or electro-chemical) engineer specializing in battery design.
    But you don't have to be good at it. ;)
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Battery Maintenance - De Sulfation

    How did poor Bob (or boB?) get pulled into this... He did not even post in this thread (that I am aware of)...

    Just trying to be nice and keep things on subject.

    I find that people with experience and who pay attention can be very helpful when trying to find problems. Three Decades ago, a couple of experienced final test guys (where I used to work) running disk drive tests notices some strange behavior by 4 disc drives (out of thousands that they had tested). The tests "passed" easily but the minor errors were not of a "known" pattern. The guys brought it to us engineers (in the magnetics department) and we found that there was (most likely) serious magnetic particle contamination inside the HDA (the sealed hard disc assembly).

    We could not even get an engineer at the manufacturer (Control Data) to even answer the phone (we were a "small" company). We made a video tape of our investigation and conclusions and just FEDex'ed to the engineering department.

    Somebody received the tape and not knowing what else to do--Played the tape. Then called over more engineers, then managers, then facility head. Then shut down the line, recalled recent products and completely scrubbed their mfg. line of contamination.

    I used to talk with our assembly folks all the the time about the problems they saw... And made hundreds of changes to our products and documentation (at multiple companies) based on their experiences.

    No professors involved at all. Just people who payed attention and asked questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Battery Maintenance - De Sulfation
    BB. wrote: »
    How did poor Bob (or boB?) get pulled into this... He did not even post in this thread (that I am aware of)...

    Just trying to be nice and keep things on subject.

    I find that people with experience and who pay attention can be very helpful when trying to find problems. Three Decades ago, a couple of experienced final test guys (where I used to work) running disk drive tests notices some strange behavior by 4 disc drives (out of thousands that they had tested). The tests "passed" easily but the minor errors were not of a "known" pattern. The guys brought it to us engineers (in the magnetics department) and we found that there was (most likely) serious magnetic particle contamination inside the HDA (the sealed hard disc assembly).

    We could not even get an engineer at the manufacturer (Control Data) to even answer the phone (we were a "small" company). We made a video tape of our investigation and conclusions and just FEDex'ed to the engineering department.

    Somebody received the tape and not knowing what else to do--Played the tape. Then called over more engineers, then managers, then facility head. Then shut down the line, recalled recent products and completely scrubbed their mfg. line of contamination.

    I used to talk with our assembly folks all the the time about the problems they saw... And made hundreds of changes to our products and documentation (at multiple companies) based on their experiences.

    No professors involved at all. Just people who payed attention and asked questions.

    -Bill
    You got the Wrong BOB, the BOB I am talking about Is the Engineer that use to be at our Plant that was assigned to do all the jobs that no one else would. How many Bob's am I responsible for ? You can change it to Tom if you want.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Maintenance - De Sulfation

    Bill;

    You know I used to be the guy in the middle in that sort of operation: this doesn't work, tell us why and who's fault it is. Then listen to them deny responsibility. Oh yeah; fun job. Not.

    Blackcherry was referring to a generic "Bob", not a specific one. Like "Bob's yer Uncle". :D
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Battery Maintenance - De Sulfation

    I am sorry BC4. Misread your post.

    I used to be that engineer that would do the jobs that others thought were "beneath them". I enjoyed the challenges and learned a lot (and I did get into trouble on occasion too :blush:).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    I once posted a E-mail I received from the Interstate Batteries Engineering Department total BS and a " Battery Engineer " without a clue trying to explain why they list their Absorb voltage 1 volt above their Bulk Voltage.

    So did he tell you that's because the specs for the U-series batteries are designed for an industrial constant-current IUIa profile charger? Those chargers actually have a voltage setting for the constant-current bulk charge stage.
    --
    Chris
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Battery Maintenance - De Sulfation
    ChrisOlson wrote: »
    So did he tell you that's because the specs for the U-series batteries are designed for an industrial constant-current IUIa profile charger? Those chargers actually have a voltage setting for the constant-current bulk charge stage.
    --
    Chris
    No he didn't tell me that , because that not how it's listed. It's on a chart as two separate items. Bulk, 14.4 Volts and Absorb 15.5 volts. It's the same old game, move the shell with the pea under it till everyone loses track. You and I can create a new charge regimen today and someone would copy and paste it somewhere and swear it is a fact.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Maintenance - De Sulfation

    What's really weird is that for years now I've noticed the batteries seem to perform better when charged with solar than with the built-in charger; they seem to 'like' being brought up slowly with V & I until maximum current is reached, then pushed up to the Absorb Voltage, then have the current back off while V is maintained. (As opposed to the charger that hits them with full current to begin with.)

    Since I don't have a bloody great big testing lab here I can't get this phenomenon nailed down. Anyone else seen this curious behaviour?
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    No he didn't tell me that , because that not how it's listed. It's on a chart as two separate items. Bulk, 14.4 Volts and Absorb 15.5 volts. It's the same old game, move the shell with the pea under it till everyone loses track. You and I can create a new charge regimen today and someone would copy and paste it somewhere and swear it is a fact.

    Yeah, I know what you mean. Those are the same specs for our UL-16's in our boat if you extrapolate them to 24V system - 28.8 Bulk and 31.0 Absorb. That's what I set our PowerTech shore charger to and it works great. What it does is charge at C/5 until the voltage reaches 28.8, then switches to C/10 until the voltage reaches Absorb. Then it switches to the constant voltage absorb stage. I got the finish set at 31.2 volts.
    --
    Chris
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    What's really weird is that for years now I've noticed the batteries seem to perform better when charged with solar than with the built-in charger;

    'coot - Oh, I've DEFINITELY noticed that too. I think the slower charging lets the chemical reactions take place at a more reasonable speed. If you look at how a battery works, it's probably no different than the difference in capacity between the 2hr and 20 hr dicharge rates. You get better performance from the battery at the 20hr rate. That has to work in reverse too.

    You also have to realize that industrial IUIa constant-current chargers that hit batteries with big current at the beginning of bulk are designed for efficiency and least charging time. But they make up for the rapid chemical reactions that have to take place with the constant-current finish stage. And our RE chargers can't do that.
    --
    Chris
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation

    chris,
    that's how i understand it to be for most batteries too, but concorde states they want their batteries fast charged as opposed to a slow one. i never understood why they believe faster is better, but i've had good luck with slow charging them too. they are a higher efficiency battery and they reflect it in a slow charge so i am at a loss to understand their advice on fast charging.

    for those not equating the term fast charging, it means a high ah charge rate.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    niel wrote: »
    chris,
    that's how i understand it to be for most batteries too, but concorde states they want their batteries fast charged as opposed to a slow one.

    Neil, I'm pretty sure that's because of battery temp. I have lots and lots of data here logged with my Classics that conclusively proves that fast high voltage charging yields a cooler running battery than long extended absorb times at lower voltages. Being heat is the second killer of batteries behind sulfation, I'll just bet that Concorde has taken the same approach that most industrial battery and charger manufacturers have taken - get the job done and shut the charger off. Don't drag it out and subject the battery to constantly rising internal temps over long periods of times.
    --
    Chris
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation

    I concur with the slow charge thoughts that 'Coot has.
    '
    A question that pops into mind is , Has anyone done a comparison of the watts used in both strategies, IUIa vs a 'regular 3 stage' solar charge?

    I'm wondering if they total to about the same over a full charge?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Battery Maintenance - De Sulfation

    For anyone interested, here are a couple papers that folks have posted over the last couple of years that go into battery contruction and usage
    BB. wrote: »
    Add from Stephendv (Oct 20, 2011; -Bill:
    stephendv wrote: »
    ... Victron has authored a great paper that covers some interesting material on charging forklift batts: http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf

    From Mike90045,

    A nice 54 page book on batteries--even includes a Battery 101 primer (series/parallel connections, etc.): (see attachment at bottom of post)
    mike90045 wrote: »
    Only if your battery stays below 70% charged for more than 24 hours. The lead sulphate crystals will harden, and not dissolve during discharge. This is called sulphation.

    Say you loose 1% capacity each episode, and one episode a week. In a year, you have 50% degradation of your battery. That's what insufficient charging gets you.

    See attached battery file for in depth explanation.

    Sulfation - Formation of lead sulfate crystals on the plates of a lead-acid
    battery.

    Added 3/5/2012: Here is a nice thread on why I/we suggest not paralleling batteries if it can be avoided:

    Series rule of thumb


    See below for DOE Paper attachment.

    -Bill

    Attachment not found.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation

    chris,
    i'm not sure that holds water as a slow charge does not produce as much heat and is able to dissipate some of the heat produced before more is made. a fast charge builds heat at a faster rate and it doesn't escape as fast as it should amplifying the problem. now i may be reading you wrong here as i'm reading that you are saying why concorde insists on a fast charge. if this is not the case and you agree with a slow charge then we are on the same page with my still being in the dark as to why they want fast charges.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    niel wrote: »
    chris,
    i'm not sure that holds water as a slow charge does not produce as much heat and is able to dissipate some of the heat produced before more is made. a fast charge builds heat at a faster rate and it doesn't escape as fast as it should amplifying the problem.

    Not according to the logs in my Classics. When we get a good day our system will charge our bank at 170 amps and I've seen it reach 200-220 amps on an exceptional day. When we get those days and the bank bulks really fast, then absorbs for 2.5 hours before dropping to float, the peak battery temps are usually around 5°C lower than when we don't get enough power to do that.

    On the other days what happens is that we only get enough incoming for about a C/15 charge rate during bulk. The bank might reach absorb voltage of 62.0 for brief periods. But it don't stay in absorb and drops out to Bulk MPPT most of the time, running at 56-58 volts. It can sometimes spend 6-8 hours in that state. Every single time the battery temperatures elevate to 30C, even with my cooling fan blowing in the battery cases on a 70°F ambient day.

    And what's more, the SG of our batteries never gets above 1.240-1.245 on those long drawn-out days. On the good day it will be at least 1.255-1.260 at the end of absorb.

    I don't know how many people have ever actually logged it. But the Classic logs all this stuff once every 2 seconds if you're using the Status Panel on a PC. And I have almost 2 years worth of data showing the above every single time.

    If you search the forum you might find one of the graphs I posted when I put in and was testing our East/West solar on a single controller with the south facing section. I think the battery temp trend line was in that graph - it's one of the things I religiously log. There may be some misconceptions, different batteries may be different, or whatever. But I got hard data on it on our Surrettes that low voltage long charge times do not work and excessively heat up batteries.
    --
    Chris
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation

    that may be so for your surrettes, but higher voltage is not allowed for agm batteries as it degrades the battery.

    i do know fast charging nicds and such are not as efficient as a slower charge and a loss of efficiency does not make for a better charge. maybe i'm wrong on the flas or agms as it wouldn't be the first time i was wrong on something, but i'm not following how it is so.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Maintenance - De Sulfation

    I think inetdog could confirm that there is something of a lag in applying a given amount of power to a mass and how its temperature rises over time (not well-expressed). We usually see this with fuses/breakers where current above the rated limit still takes time before it has any physical effect.

    Blast! What is the term? Thermal inertia? Thermal cycling? It's like with warming rooms in different ways: heat a radiator up way above desired room temperature and then wait for the heat to affect all the air vs. in-floor heating maintaining a lower but constant temp all the time.

    I'm thinking applying the power quickly not only pushes the temp up but gets the charging done before critical temp is reached and then the battery immediately starts cooling down again. So there would be a balance here between enough current to charge rapidly without incurring temperatures that would be damaging and applying insufficient current for a long time that would 'slow cook' the plates.

    (Should have remembered to buy that Naprosyn yesterday.)
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    niel wrote: »
    that may be so for your surrettes, but higher voltage is not allowed for agm batteries as it degrades the battery.

    Whoa! Definitely not for AGM's! You'll burn up a AGM with the kind of voltages I use on my Surrettes. I'm talking flooded batteries.
    --
    Chris
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation

    chris , your data really supports doing a gen powered BULK in the AM if it is a poor PV day &/or you did a large depletion the day before.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation
    westbranch wrote: »
    chris , your data really supports doing a gen powered BULK in the AM if it is a poor PV day &/or you did a large depletion the day before.

    I know, but even on a bad day we get pretty good power here - it's been a LONG time since we produced less than 15 kWh in a day. I got the auto gen start voltage-based triggers set so the inverter takes care of that by itself if it's ever needed. We just don't use the gen for battery charging only maybe a dozen times or so in the winter when the inverter will start it after several really bad days. Otherwise the only thing we use the gen for is Load/Gen Support when the inverter overloads.

    I DID make some adjustments to my Classic's AUX Waste Not mode to actually hold the voltage lower on those "bad" days by bringing the water heaters online sooner. I set the voltage offsets lower so it works the system at 54-56 volts instead of 56-58. That keeps the batts cooler and makes better use of my RE power.

    I know - not the thing that most folks would do. But our system is set up a bit different than most folks.
    --
    Chris
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Battery Maintenance - De Sulfation
    I think inetdog could confirm that there is something of a lag in applying a given amount of power to a mass and how its temperature rises over time (not well-expressed). We usually see this with fuses/breakers where current above the rated limit still takes time before it has any physical effect.

    Blast! What is the term? Thermal inertia? Thermal cycling? It's like with warming rooms in different ways: heat a radiator up way above desired room temperature and then wait for the heat to affect all the air vs. in-floor heating maintaining a lower but constant temp all the time.

    I'm thinking applying the power quickly not only pushes the temp up but gets the charging done before critical temp is reached and then the battery immediately starts cooling down again. So there would be a balance here between enough current to charge rapidly without incurring temperatures that would be damaging and applying insufficient current for a long time that would 'slow cook' the plates.

    (Should have remembered to buy that Naprosyn yesterday.)

    I will give it a try. The term thermal inertia is a good one, as is the old standard "heat capacity". There is a direct linear relationship between the amount of energy you put into a system as heat and the temperature rise of the system assuming that there is no heat loss during that same time.
    If you are losing heat as soon as the battery gets above the surrounding temperature, then you will not reach as high a peak temperature with slow heating as with a fast heat pulse.
    But this all assumes that either all or a fixed proportion of the energy being put into the battery heats it. It does not.
    Most, hopefully, of the energy goes into chemical energy which can be converted back to electrical energy. Some of it, near the end of the process, goes into breaking water up into hydrogen and oxygen. That specific part is not going to necessarily heat the battery either. But there is electrical resistance which does heat the battery and there is some energy loss in the electrolysis reaction too, since you put energy in to split the H and O out of the water but get some of it back and turned to heat when the H and H or the O and O combine to make H2 and O2.

    I do not have a good explanation at the moment for why the slow charge seems to produce higher battery temperatures. Except to observe that the longer time spent in the high voltage, low efficiency part of the charging cycle (last part of Absorb and high current Float) the more energy will be converted into heat.
    SMA SB 3000, old BP panels.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Maintenance - De Sulfation
    inetdog wrote: »
    I do not have a good explanation at the moment for why the slow charge seems to produce higher battery temperatures. Except to observe that the longer time spent in the high voltage, low efficiency part of the charging cycle (last part of Absorb and high current Float) the more energy will be converted into heat.

    I think it is not the rate but the time: as you said for the applied energy only part of it produces heat. At the beginning of the charge cycle a greater percentage of the applied energy goes into restoring the charge and less of it becomes heat. The closer the battery gets to a charged state the more this proportion changes; a higher percentage of the applied energy becomes heat than restores charge. So we get the seeming paradox of the rapid, high current charge actually putting less heat into the battery than the slow, low current charge. No doubt there is an ideal balance between the two dependent ion the particular battery's efficiency.

    I would suspect that an AGM because it has less mass not only heats faster but dissipates heat more readily and the net result is that it is less affected by heating over-all. Heats up quickly but does not get to dangerous levels before charging is done and can cool off. Like searing a thin steak as opposed to slow-cooking a thick roast: got to get the temperature right for either or you ruin the meat!

    Marc "There I go reverse-engineering again" B. ;)
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Battery Maintenance - De Sulfation
    inetdog wrote: »
    I do not have a good explanation at the moment for why the slow charge seems to produce higher battery temperatures. Except to observe that the longer time spent in the high voltage, low efficiency part of the charging cycle (last part of Absorb and high current Float) the more energy will be converted into heat.

    I can confirm that my batteries heat up faster at higher charge rates in bulk mode. And I have an explanation for this. First, the resistive heat loss is proportional to square root of the current, which producs much more heat at faster charge. Second, this is much less time for the heat to dissipate.

    Of course, if you heat up the battery to levels seriously above ambient, the heat dissipation will speed up, but that's a totally different question.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Battery Maintenance - De Sulfation

    As Steve (Higgins) from Surrette pointed out, the industry has pretty much adopted the IUIa charging profile for industrial batteries because it's more efficient than voltage-based charging. More efficient means it gets the job done with less heat and torture to the battery. That is what I sort of try to simulate except that I have no way to do the finish stage except via a manual EQ cycle, which should actually be done at constant current but my controllers can't do that.

    Whatever the deal is, our batteries have been really happy with the way they've been treated, based on my service intervals and the fact that I load test each one with my Sun AVR to test them for capacity when they get serviced. If I was doing something wrong it would've shown up by now because I've been treating them this way for going on a year and a half.

    But I should mention too, that I don't use a set absorb time all year. I was messing with generators here a bit ago and on a whim sampled some random cells to see how they're doing. We had three really bad days in a row here and the bank was at an operating voltage of 47.1V this morning @ 1.9 kW load, which is getting below 60% SOC. Really nice sun and wind for a change and they were absorbing at noon. My random checks showed 1.255 at 1 hour 40 minutes absorb (on the Classic's counter) so I shortened the absorb time to 2 hours now for summer.

    This is an example of how, when batteries get absorbed more often (every 3-4 days instead of 7-10) that they don't seem to need the full absorb time to get the SG up. That's what I think, anyway. And as I always figure, the hydrometer is the only tool that tells the real story. But shortening the absorb time for summer (and more frequent cycling) will keep the batt temps down too.
    --
    Chris
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