Low morning Batt. voltage

wespowespo Registered Users Posts: 20
Hi All,
I have been noticing that my battery voltage in the morning has been getting consistently lower with the same or similiar amount of nightly draw.

I have a 440 AH AGM 24 volt bank consisting of 4 - Clean Amoura (brazilian made) 220AH, 12 volt batteries. We cycle the bank somewhat hard and the meter usually reads about 65% in the mornings.

I have noticed the voltage drop over the past month or 2 from ~23.5 volts under a few amps load to ~ 22.0 volts under a similiar, or same load. Is this an indication of a problem...age... sulfation..???

The bank recovers to >24 volts as soon as the panels start charging around 8am, and is usually full charge and floating (27.2v) by 1pm.

Thanks for the help.
Bill
«1

Comments

  • mike95490mike95490 Solar Expert Posts: 8,610 ✭✭✭✭✭
    Re: Low morning Batt. voltage

    Does your meter read 65% full or 65% discharged ? Is it configured right?

    Just because you hit float, you may not be spending enough time in absorb.

    What and how, is your charge controller programmed, do you have battery temperature sensor ?

    With AGM, you can't equalize, but with decreasing voltage as you describe, it's a classic case of deficit charging. You could be your own government! Ease up on the loads for a day, run the genset, take a load off the batteries, or risk severe damage, if not too late.

    Maybe you've overcharged the batteries, and are boiling them dry, bummer if that happened.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    The meter is a trimetric 2020 and reads 65% full. I have 1080 w of PV with an FM60 charge control set to bulk 28.8...absorb 1 hour, and float 27.2. This is as close an estimate as I could get for the data provided with these batteries. I don't have a BTS, but live in the tropics with a very steady 75-85 degree temp.

    They have been in service going on 3 years now.

    I do notice when in absorb (28.8V) that the batteries make a small gurgling sound....bad with AGM??? This stops when in float.

    During the day, the voltages stay above 24.0 even with the fridge, toaster, and fans going....about 60 amp draw on meter.

    Could old age be showing..???..

    Gracias
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Low morning Batt. voltage

    What have you got for a charging system?

    If you haven't been able to put about 44 Amps of current into these batteries for charging they have probably become sulphated. As this happens, the actual Amp/hr capacity of the batteries goes down, down, down leading to the state you describe: it may charge up to "proper" voltage but the batteries no longer have sufficient capacity to see you through the night.

    Unfortunately with AGM's you can't stick a hydrometer in and see what's going on with each cell and you usually don't try to "equalize" them either.
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    You are correct in that I have not been able to charge at 44amps...but have been able to charge at around 20 for most of the battery life and recently (with the addition of 2 more 180 watt panels) have increased that to over 30amps. The batteries were steady until about 1 month ago when I noticed the voltage drops in the AM. last night was the worst and the voltage got as low as 20.0...according to the trimetric...20.3 on the charge control.

    I thought 5% of the AH capacity was sufficient for charging??

    Does the gurgling sound when at 28.8 volts and through absorb mean anything significant??

    Thanks.
    Bill
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Low morning Batt. voltage

    Increase you absorb time to the maximum the charger allows ... your Trimetric is showing your not replacing all the energy your using, so more needs to be put back into the battery bank or over time you will just flat out kill the battery's. You need to see greater than 100% for a few days

    You can do soft Equalize on AGMs, typically that 15V vs 16V for flooded .. for now I would suggest you raise your bulk charge to 30V for a week, increase the absorb to 4+ hours and if you can back off on the loads until you get the battery bank fully recharged

    During the charging keep a close eye on the battery's, warm is OK, hot for AGM's would indicate your to aggressive on the soft EQ
  • BB.BB. Super Moderators, Administrators Posts: 30,049 admin
    Re: Low morning Batt. voltage

    Does the battery monitor consitently show near 100% charge at least several times per week?

    The bubbling in the batteries is probably indicating that one or more of them are pretty much at 100% charge. Generally, much "bubbling" will overheat/overpressure the battery and cause venting. Also, the catalyst (platinum or similar) in the battery caps appear to have a definite life--and "lots of bubbling" will erode the catalyst and cause early failure (and, the battery will vent with no catalyst to cause recombination of the gases).

    It is possible with parallel strings that you have on battery with a failed cell (short or open) that has "suddenly" reduced your capacity to 50%. Also the string with a shorted cell will overcharge the other "good cells". And, if most of the current is going into a good string (open cell)--your bank is now 1/2 your assumed capacity. Higher currents, deeper cycling, etc.

    And if you have a shorted cell--it is possible for one string to be "overcharged" while the other is undercharged (on string is 24 VDC nominal and the other is 22 VDC nominal).

    Measure voltages across each battery (during different phases, charging, discharging, and resting)--see if battery voltages are near equal.

    When there is heavy current flowing (charging or discharging) set you meter on low voltage DC scale and check for voltage drops across wires and connections--see if there is a high resistance point (higher voltage drop) someplace (bad wire, loose connection, corrosion, etc.).

    5% rate of charge is a good minimum current to ensure everything works well... However you also need to now your daily Amp*Hour (or Watt*Hour) taken by your loads and provided by your panels.

    If your loads AH>charging AH -- your system is going to die (pretty quickly). It does not sound like you have excessive loads vs solar panels based on what you have said so far.

    It is possible that at 3 years, you have one (or more) batteries beginning to fail and it is affecting your whole system (65% state of charge (daily?) cycling is pretty substantial--you may just be seeing normal wear and tear).

    The above are my guesses--I cannot tell what, for sure, may be happening.

    -another "Bill"
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Low morning Batt. voltage

    One of the reasons I shoot for 10% charge rate is that most of us draw off the batteries at the same time as we are charging. If the batteries want 20 Amps for 5% rate and the panels only produce 20 Amps and at the same time you're using 10 Amps - the effective charge rate is only 10 Amps; 2.5%

    Chronic under-charging has a bad habit of not showing symptoms until it's too late. You may have been bringing the voltage up to Absorb level, but not keeping it there long enough as Solar Guppy has said. And as Bill mention, if a plate has shorted out ... I've been there, done that, bought the replacement batteries. :cry:

    Run through a charge cycle, shut everything down, let the batteries sit (preferably over-night) check each one's 'resting' voltage.
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    Thanks for the good info. Here are the stats:

    Tri2020 shows 100% most every day.
    AH used sunset 'til morning charging = 85AH average
    AH made daily average = 150AH average (on FM60)

    I don't feel any heat at all on the batteries (or wires)when charging...even when bubbling. The connections are all solid with no corrosion.
    I will check the voltages on each cell with the DMM. If I contact the battery terminals individually will that give me an accurate reading of each battery...or do I need to disconnect them all???

    I can increase the absorb time to max...problem is I am not home from 9-3 to be able to check the battery temps. Is that critical at the absorb voltage of 28.8??
    I can increase the bulk to 30V this weekend and stay around to check batt. temps. Anything specific I should look for...warming, gassing, sounds. should I monitor with a DMM in addition to the Trimetric?

    Bill
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Low morning Batt. voltage

    after it is shown that the batteries received a full charge you might try to disconnect them and allow them to sit for a few hours and check the voltages of the batteries individually. this could reveal a bad cell in one of the batteries and what you described here,
    "I do notice when in absorb (28.8V) that the batteries make a small gurgling sound....bad with AGM??? This stops when in float." could happen as a result of one cell going bad for it sounds like it may be gassing. if all of the voltages show to be good then i suggest load testing to see if the batteries are up to snuff. contact the battery manufacturer for advice and procedures too. do not up the voltage to your agms unless it is ok with the manufacturer.
  • PhotowhitPhotowhit Solar Expert Posts: 5,105 ✭✭✭✭
    Re: Low morning Batt. voltage

    IMHO

    The Trimetric is a programed measuring device, the 65% charge in the morning with a voltage reading of 23-5 to 22 volts(understanding that it has a load) looks to me like the capacity that you plugged into the meter when you setup the system no longer represents the current capacity of the battery.

    I'd disconnect all loads and charging in the morning and see what voltage your batteries level out at (I don't know how long this will take with AGM Batteries)

    I don't deal with AGM batteries, but others here do, my guess is if they don't come above 24 volts, you've lost considerable amount of the batteries capacity and should look into a new set of batteries.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Super Moderators, Administrators Posts: 30,049 admin
    Re: Low morning Batt. voltage

    There is voltage under load / under charge (battery voltages should be pretty close to the same under stress conditions). If the battery voltage don't match to within 0.010-0.100 volts or less--you may have problems. If they differ by 1.000 volt or more--definitely there are issues.

    If you let the batteries set with no current flow (no loads, no charge) for ~3 hours or more--the voltage will represent the current state of charge.

    If you don't have a shunt on each battery string (probably nobody does)--you should get a DC Clamp type Amp Meter.

    Or--my cheap and dirty method--find the longest stretch of cable in each string (say the 2' cable from positive battery terminal to the common bus bar point where your loads and chargers connect--both cables should be the same diameter and same length--they will then have similar resistance).

    Set a DVM to 2 volt or 200mV full scale and measure the voltage drop across each cable (under "heavy load" for your system--either charging or discharging). If both cables have 0.100 volt drop--then the current is probably roughly balanced. If one cable shows a 0.150 volt drop and the other shows less than 0.075 volt drop--then the two banks may not be sharing current equally).

    Unequal current sharing can be the result of the wiring/connections (if one string has 3' of wiring and the other has 8' of wiring--the batteries will not share currently equally--also if one battery string is close to the load/charger and there are jumper wires to the other string--that second string will have more series resistance and not share current properly).

    Some people will move batteries/switch parallel connections to help balance battery aging across the stings over time (sort of like rotating your tires--I don't do that either :roll: ).

    Anyway, my two cents worth.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Low morning Batt. voltage

    good thought bill as cables and or connections can go bad and cause batteries to go bad.
  • westbranchwestbranch Solar Expert Posts: 5,182 ✭✭✭✭
    Re: Low morning Batt. voltage

    without the Manufacturers specs we are only guessing. They should have something like this manual for your AGM's

    http://networkpower.exide.com/exidepdfs/Section_92.61_2009-04_Absolyte_GP_IO_Manual.pdf

    If you read through this manual you may find some relevant info that you can transpose to your AGMs

    HTH
    Eric
     
    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
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Low morning Batt. voltage

    The TM2020 will say what you programmed it to say. The % full is based on output versus input with the programmed charge efficiency loss put against input. When you operate over time at above 70% state of charge the charge efficiency is over optimistic as the charging above the 85-90% SOC is poorer efficiency. You can end up going in the red a little bit every day. AGM are pretty good from an overall recharge efficiency.

    TM2020 % full is a good relative indicator but not absolute.

    I think Guppy's suggestion is best. Give'um a good charge. Beside watching heat, watch for case end-side bulge. They will build up pressure at 14.5-15 vdc charge. You want to avoid venting if possible. A little bulge is okay. If you start to hear a high pitch squeal it means some venting and you should back down the charge rate.
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    Floating Voltage (V) 13,20 - 13,38 a 25ºC
    Voltage Equalization (V) 14,20 -14,40 a 25ºC
    Temperature Compensation -0,33 V for each 10ºC over de 25ºC
    +0,33 V for each 10ºC under de 25ºC

    These are the only specs I could get from the company for these batteries.

    Thanks for all the info here. I do believe this is a case of chronic undercharging. The first year of life for these guys was with a MSW inverter/charger that only kept them at 25.7 volts max.

    Once I got PV's, FM60, and MagnaSine PSW inverter, I was able to give them a more appropriate charge.

    I will follow SG's recommendations and see if I can squeak a few more miles out of these batts.

    One more question: During a good charging cycle, should you notice some heat on the battery casings? I have never felt any temp increase from ambient (usually ~80 degrees), nor have I noticed warm wires connections, etc.

    Thanks again.
    Bill
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Low morning Batt. voltage

    If you truly get the battery's 100% recharged from a discharged state, yes, the cases should be warm to the touch. Since they are not, this also indicates that there is not allot of energy going into the battery bank, as recharging is not 100% efficient and the loss is dissipated as heat!
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    SG,
    You are right about that! Changed the bulk to 30V and increased absorb to 4 hours on the FM60 today. All 4 of the cases are warm to very warm. It has been in absorb for 48mins so far...
    Is there a specific way to check the individual battery voltages???...other than disconnecting them all. The Trimetric reads a steady 28.7V now at about 18amps.

    Forgot to mention...these batteries each have one of those "eyes" you can look into to check if charged. 1 of mine is green...ish(kind of hard to tell)...the other 3 are black/empty. How accurate are these things..???

    Many thanks.
    Bill
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Low morning Batt. voltage
    wespo wrote: »
    Forgot to mention...these batteries each have one of those "eyes" you can look into to check if charged. 1 of mine is green...ish(kind of hard to tell)...the other 3 are black/empty. How accurate are these things..???

    Many thanks.
    Bill

    Not very. The "Delco Eye" as it used to be called only looks at one cell. Also, they "stick" worse than a hydrometer float. It is recommended that you 'rock' them gently after charging if the "eye" doesn't go green right away. We used to say "Red is dead, black is lack, green is keen." :p

    And are you sure these are AGM's? Something about that doesn't add up. Just because a battery is "sealed" doesn't mean it's an AGM. Or maybe this is something completely different that I've never encountered before. That's always a possibility.
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    Marc,
    you may be right. I got these from a company in PR that has since gone out of biz. They are a Brazilian made battery...supposedly AGM according to the PR Co., but who knows...their english was not good and my spanish is not technical. They are definitely VRLA sealed, but I can shake them and they sound liquid inside. A few posts back were the only specs i could get from the manufacturer after at least 8 no reply emails. They are clean moura batteries, 12CM220's. They have good weight for their size, but that eye has never been green. They did come with a 2 year warranty...but that has since expired.

    I have them on a heavy charge today as recommended...so I'm hoping for the best...time will tell.

    Thanks.


    Bill
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Low morning Batt. voltage

    normally one should never exceed the max battery voltage listed for any agm or any vrla battery for that matter as you can't add lost water. your batteries may be on their last leg so what you do with them may be a non-issue. you will need to save for new batteries soon as i don't believe these may be reliable. i'm no doctor though and can't say how long they have to live.:roll:
  • mike95490mike95490 Solar Expert Posts: 8,610 ✭✭✭✭✭
    Re: Low morning Batt. voltage
    wespo wrote: »
    I have them on a heavy charge today as recommended.

    nearly full AGM should not be on a "heavy" charge. Do it slowly, once you vent, you loose capacity. When they are "full" they will start gassing and venting very quickly. 115F was the max for flooded cells, I think AGM would be even lower.

    Either way, I think they are likely toast. Either sulphated, or boiled dry.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Low morning Batt. voltage

    A charge indicator 'eye' requires a flooded cell to work. They are not AGM batteries which do not have the excess electrolyte to operate an 'eye'.

    They are 'maintanance free' batteries. These batteries have similar requirements on preventing venting that AGM do but do not have the starved electrolyte soaked glass mat.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Low morning Batt. voltage

    that's my thoughts too rc, but it's still sealed as far as we know with little chance of adding water. maybe they are from delco and they list a way to add it?
  • mike95490mike95490 Solar Expert Posts: 8,610 ✭✭✭✭✭
    Re: Low morning Batt. voltage

    Many of the "no maintance" batteries have caps, but they don't look like caps, it's a whole panel (or 2) flush with the top of the battery case. I use an offical "paint can lid lifter" (broad with a little lip on it) to pry the ones on my truck off.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Low morning Batt. voltage

    Many have the top cap cover ultrasonically melt sealed. Takes quite a bit effort to pry them apart.
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    These do have a whole panel across the top. It looks like it MAY be removeable. What I have found over the weekend was one of the batteries (of the 4) was a full volt different than the others. I got these reading with the DMM:

    Under PV charge (28.8V): Batt 1&2 are a string..3&4 another string

    Battery 1 - 14.48V
    Battery 2 - 14.37V
    Battery 3 - 14.32V
    Battery 4 - 13.33V

    No charge/no load

    Battery1 - 12.71
    Battery2 - 12.55
    battery3 - 12.33
    Battery4 - 12.03

    After night of use

    battery1 - 12.33
    battery2 - 12.20
    battery3 - 11.88
    battery4 - 9.97

    Think it's worth prying the top off for learning purposes...looks like I'll need to get another batt. bank. regerdless. I do have those tools pictured...

    Do you recommend a particular type of battery if they may be sitting idle for 5 or 6 months?? They would still be connected to the PV's and CC during this time.

    Thanks...learn more every day...

    Bill
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Low morning Batt. voltage

    What do you mean by "sitting idle for 5 or 6 months"? If you mean completely disconnected and not hooked to any type of charger at all, you'll need AGM's. Real ones. :p Their self-discharge rate is minimal compared to a flooded cell. If they can be left alone and kept charged by solar panels then the flooded cells will be okay (especially if your charge controller can manage an "auto equalize" cycle once a month).
  • wespowespo Registered Users Posts: 20
    Re: Low morning Batt. voltage

    'Coot,
    I mean connected to the PV's and CC. I have a FM60 which is capable of delivering an equalize charge every set # of days. I am currently searching for new batteries, and would like to go with either "real" AGMs...which I can't find here...or more likely FLA's. I don't have much experience with testing, water addition, etc. but am learning.
    What do you think about opening up the "bad" VRLA I have now to see what is going on inside?? Anything specific I should look for to indicate what caused the failure??

    Bill
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Low morning Batt. voltage

    You could try prying open the VRLA's - especially the 'low' one. See if you need to add distilled water and bring the electrolyte level up. Try an equalization charge. Chances are it's toast, though.

    Nothing wrong with flooded cells, and they tend to be less expensive per Amp/hr than AGM's.

    With a new set, you should charge and equalize them before putting them into use. Then measure their Specific Gravity to start with. That will give you a "base" number to evaluate future SG readings. Hopefully you can get some "true" deep cycles and the manufacturer will supply actual "20hr" Amp/hr rating and the correct voltages for Absorb/Float/Equalize. Otherwise you're 'hunting in the dark' and are likely to come away with the same problem you've got now.

    If you can keep them connected to the array while you're gone there should be no trouble. I leave ours hooked up over the evil, dark, cold Cariboo winters and in Spring they're ready to go. (Except the one that suffered a collapsed plate this year. ARGH! :grr )
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Low morning Batt. voltage

    yes, that 4th one is shot imo. 1 and 2 are still good to use for something with number 3 shaky, but still some life left i suspect.
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