What is going on with battery banks?

softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
Kept losing power due to low voltage shutdown early this morning. There are two 12 volt battery banks yielding 48 volts per bank. Each battery in the lower bank shows at least 12.1 volts. Each battery in the upper bank shows 11.6 or 11.7 volts. I disconnected the upper battery bank and that has solved the problem of the inverter shutdowns.

Feeling real crusty after hiking Colorado's toughest 4WD trail full of loose rock and going up to 11,500 feet. Then spent the night under the stars and discovering the zipper on the sleeping bag quit working. I'll check the specific gravity in each cell when I quit feeling like a barnacle.

Very odd thing? MATE says battery banks are at "78%". They drop to this level every night due to having both a fridge and a freezer. So the voltage wouldn't seem to be the issue. But yesterday was pretty cloudy.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    softdown said:
    There are two 12 volt battery banks yielding 48 volts per bank. Each battery in the lower bank shows at least 12.1 volts. Each battery in the upper bank shows 11.6 or 11.7 volts.

    Does this voltage discrepancy occur while the two battery strings are connected to each other in parallel?  If so, you have a wiring problem.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    Sometimes I confuse series and parallel. There are two 48 volt banks. Each bank has four 12 volt batteries. Every connection is done with 4/0 copper. I keep the connections pretty clean with baking soda.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • AguarancherAguarancher Solar Expert Posts: 315 ✭✭✭
    Maybe you could post a pic of your battery bank and buss bars.
  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    edited October 2015 #5
    Probably due to the cloudy weather yesterday. Would have hoped my batteries could handle one day of cloudy weather. They were able to handle two cloudy days prior to the upright freezer made in the late 60's. Time to get an Energy Star chest freezer. One battery does have SG averaging 1.12....lower than the rest. Though I wonder if water additions tend to stay at the top instead of circulating. Recently added water.

    Interesting world when a moderately sized freezer costs less than a moderately priced battery.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    softdown said:
    Sometimes I confuse series and parallel. There are two 48 volt banks. Each bank has four 12 volt batteries. Every connection is done with 4/0 copper. I keep the connections pretty clean with baking soda.

    First,  try thinking of Series connections as being serial (one is after another).

    Second,  you DO NOT want to have Baking Soda on any connections.  Clean connections,  and sand lightly with very fine sand paper,  clean again,  and then coat all connections lightly with Petroleum Jelly (even coating the mating surfaces of the lugs and battery terminals).

    A dilute Baking Soda solution can help keep the battery surfaces clean,  and after using it,  clean again with a clean cloth,  wetted with clean water.

    Third,  it is best to add water during the Absorb stage,  OR,  add water when the battery is fully-charged,  and do a short high-ish voltage Absorb.  Or,  perhaps add water just before your periodic EQ charge.

    It is not clear what you are saying when you note,  "One battery does have SG averaging 1.12....lower than the rest".   You cannot be saying that one string might be 1.265,  and the other is 0.065!!

    At some point,  a number of us do wish that you can buy some new batteries,  so you will have a better chance of learning on a set of batteries that have a known past,  and will not have been damaged/ruined by others.


    Good Luck,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    I've been using 8Ds since late 2010....they simply are not as evil as some would have you believe. Not going to replace them until it makes sense.

    Why do Americans seem to often think that everybody can buy anything when things may be inconvenient? Credit card debt grows each month.

    I said that one battery has SG averaging 1.12....lower than the rest. That is not a complex statement. That battery did have a small 12 volt load on it. Complicated by a significantly cloudy day.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • AguarancherAguarancher Solar Expert Posts: 315 ✭✭✭
    edited October 2015 #8
    softdown said:
    I've been using 8Ds since late 2010....they simply are not as evil as some would have you believe. Not going to replace them until it makes sense.

    Why do Americans seem to often think that everybody can buy anything when things may be inconvenient?
    Some people trip over dollars to pick up dimes.
    If you are really looking for help-advise, list your batteries 1 through 8 and the specific gravity for each cell of each battery. It's really not a good idea to take 12V off one battery in a string, but I think you already know that.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Are you 'side tapping' individual batteries in a 48v (4x12v  in series) bank?
     
    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
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    edited October 2015 #10
    Soft, low voltage events are a big wake up call, that things are really wrong.

    Batteries, series and or parallel, doenst matter which, as soon as you combine more than one battery or cell, you have to take special care to ensure that each sub battery and cell are intially and at all times subsequently maintained balanced at more or less exactly the same terminal voltage, SOC and SG.

    Why? because, charge setpoints apply to the whole bank and thus individual cells and batteries will only be properly charged if all the sub batteries are in a similar state. Sub batteries that are not charged properly... sulphate and die rapdily. And, on the discharge side of it, the weak cells will hit zero SOC earlier than the stronger cells. If you are lucky, enough sub batteries will hit zero at the same time and the overall terminal voltage will drop enough to hit the LVD and the system shuts down to (maybe) try to protect your setup ((however note that inverter LVD rarely and tend not to be designed to protect the bank, just the inverter, so by the time the inverter shuts down the damage is already done.)). If you are unlucky the one weak cell will then reverse charge, causing profound chemical damage to that cell or cells.

    So.. What do do? Simple, you need to test all your batteries to determine which ones are similar, and group the like ones together into usable banks. Say you have half of your 8 batteries with similar capacity, then make a bank of them, and use them alone, or using a battery switch or similar. And, if you still have some variance, then you need to cycle the bank in a safe SOC band. For most people that will be in the upper realm, because lead tolerates overcharge (way) better then undercharge. Then, youll need to do ongoing testing, and stand ready with a steady supply of spare cells. With the aim of maintaining a group of similar health batteries in your bank. Or you can do what most do, and buy a matched set of new cells ;)

    To repeat , you cant series or parallel batterys that are in quite different states of health, or charge, or internal resistance. Doing that you will be recycing that lead very very soon.

    Then, on the load front. If your night time loads are such that your SOC goes to 75% overnight everyday, then it stands to reason, or at least is pretty likely that protracted less than perfect weather, you are going to have to be ready with the genset. Keeping the SOC above 50% is really important for the long term health of the batterries.

    And lastly BTW, with that eratic bank of yours the last thing id be doing is relying on the FNDC's idea of SOC. So be careful how you estimate SOC.




    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    What was the slight 12 volt charge on the lowest battery? Was "experimenting" with a small de-sulfator on that battery. Decided that this simple de-sulfator needs to be used in conjunction with a 24/7 battery charger.

    In short....I think the combination of cloudy weather and the de-sulfator brought down the voltage on one bank.

    Though still a bit mystified by an inverter shutdown at a "78% SOC". One bank was about 78%. The other bank? Lower....

    It is curious to see people howl when voltages drop below 12 overnight. It happens.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    edited October 2015 #12
    softdown said:

    Though still a bit mystified by an inverter shutdown at a "78% SOC". One bank was about 78%. The other bank? Lower....

    It is curious to see people howl when voltages drop below 12 overnight. It happens.

    Your the only one I see posting with a problem. Every night before I go to bed I check my system's soc and do whats necessary to make sure I have enough power to make it through the night. If you want to go below 50%, then go for it. It's your credit card.

    I assume you have a FNdc, without proper calibration it'll never be accurate, even then things change, batteries age and the temperature changes. The first thing you have to do is get your batteries to 100% charge based on the SG readings from your hydrometer. The charge efficiency setting of FLA batteries is between 82 - 88% ( that you have to set and adjust until you know the setting, it may take 10 or more cycles of adjusting it based on the hydrometer readings and the amp hrs returned, if your showing 100% before you really are you lower it, if your showing 100% and accumulating amp hrs, you raise it ) Once you get to 100% then pull the cat5 cable on the hub and reset it.

    It ain't easy and it ain't bean bag.




  • PhotowhitPhotowhit Solar Expert Posts: 5,729 ✭✭✭✭✭
    edited October 2015 #13

    You got 4-5 years out of 8D's, I'd be happy and limp along and plan to replace them soon.

    Of course you could just keep letting the inverter shut down, spoil some food...

    "Why waste the food" go ahead and eat it...It costs money why not, Does it make sense?

    FWIW I suspect you knew before buying and old upright freezer they are less efficient than chest types... and I would guess late 60's aren't as well thought out.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    >It is curious to see people howl when voltages drop below 12 overnight. It happens.

    Not in my world it doesnt. Or at least not more than a half dozen times a year.

    Did you read my post? All your answers are in there, and what others are telling you.

    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • Dave AngeliniDave Angelini Solar Expert Posts: 6,090 ✭✭✭✭✭
    Not in my world or the 81 + homes offgrid that are looking for my advice.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • softdownsoftdown Solar Expert Posts: 3,597 ✭✭✭✭
    FWIW....the temp rose 2 degrees in the freezer compartment of the fridge. As of now....I'm still not sure what happened that morning.

    I inherited the upright freezer that was a gift from me to my folks a long time ago. Some things have sentimental value to me. It is a high quality freezer....but was made when energy was ultra cheap.

    A few people have been a tiny bit of a snot in this thread. Pretty rare on this board.

    Photowhit said:

    You got 4-5 years out of 8D's, I'd be happy and limp along and plan to replace them soon.

    Of course you could just keep letting the inverter shut down, spoil some food...

    "Why waste the food" go ahead and eat it...It costs money why not, Does it make sense?

    FWIW I suspect you knew before buying and old upright freezer they are less efficient than chest types... and I would guess late 60's aren't as well thought out.


    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    PWs point, (in case it wasnt abundantly clear) (which it was)(or wasnt not)(i mean... was not not clear)(blimey...you get what im tryn to say), was that a freezer costs hundreds of bucks, and RE system costs thousands of bucks. Hence the cheaper path is ALWAYS energy conservation.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    edited October 2015 #18
    Why don;t you try some $29 battery HA01  balancers from ebay, you will need 3 per 48 volt string, you can;t make things worse at this point I am battling the same issue, undercharged and overcharged batteries in the string. I will be testing the results of these units shortly.
    http://www.ebay.com/itm/251906187493?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,090 ✭✭✭✭✭
    Here is a cheering thought from a pessimist, things can always get worse!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Dave, if you and i lived on the same planet, i suspect we'd get along just fine.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • dgd911dgd911 Registered Users Posts: 3
    The baking soda on battery terminals intrigued me. I keep a couple of kg packets of baking soda near my FLAs as a safety in case acid gets spilled (along with powder fire extinguisher and leathery acid proof gloves, face mask etc..).
    So is the baking soda on terminal and wire lugs a common practice in the terminal/lug cleaning process?
    I have never heard of this before, my cleaning tool is a stiff brush or even a wire brush, chisel, for hard deposits
    then the coating in petroleum jelly method
    Seems the last thing I would want near my FLAs is baking soda
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    I don't clean using baking soda. I keep 2 boxes right handy to the batteries in case of an emergency such as a spill on my body. Call me paranoid but FLA's have vent holes. Even small amounts of baking soda getting inside a cell will neutralize a small amount of acid. I use small wire brushes and scrapers to clean the terminals and the copper straps I use as interconnects. Then I use red lacquer to coat the terminals. I find that works great as a preventative measure and is less messy than petroleum jelly.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • AguarancherAguarancher Solar Expert Posts: 315 ✭✭✭
    I use baking soda. I mix in a small jar with water to make a thick slurry then apply with an acid brush. Rinse off with water when finished. Never had a problem. Never had a need to use it on my battery bank though.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,090 ✭✭✭✭✭
    I don't clean using baking soda. I keep 2 boxes right handy to the batteries in case of an emergency such as a spill on my body. Call me paranoid but FLA's have vent holes. Even small amounts of baking soda getting inside a cell will neutralize a small amount of acid. I use small wire brushes and scrapers to clean the terminals and the copper straps I use as interconnects. Then I use red lacquer to coat the terminals. I find that works great as a preventative measure and is less messy than petroleum jelly.
    yes same here, never have used anything since the late 70's working in remote Telcom at HP up in the Big Basin area (Silicon valley) where the earth station was.
    An old guy taught me then to not put anything but clean shiny metal in all battery connections. Wipe them down with clean rags and water every other month and there should never be  a need for anything else on a battery. I think many people mess up there batteries by overfilling them and then doing an EQ.  Once you start the corrosion process you are screwed until you replace it all.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭
    edited October 2015 #25
    I don't clean using baking soda. I keep 2 boxes right handy to the batteries in case of an emergency such as a spill on my body. Call me paranoid but FLA's have vent holes. Even small amounts of baking soda getting inside a cell will neutralize a small amount of acid. I use small wire brushes and scrapers to clean the terminals and the copper straps I use as interconnects. Then I use red lacquer to coat the terminals. I find that works great as a preventative measure and is less messy than petroleum jelly.


    Regarding cleaning with a dilute solution of Baking Soda and water  --  this is a DILUTE solution,  about 1 tsp,  or a bit less of  soda per quart of water.  This is only used to clean the batteries  when all the vent caps are in place.  Then,  the battery tops are cleaned with water on a cloth,  rinsing it frequently ...  no muss,  no fuss.

    The cloth that is used for the WEAK soda cleaning is one a "Shop Rag",  that are red in color,  and are made in South Asia  (India,  Pakistan,  etc)  The red dye in these rags has a reverse Litmus function  --  turning from red,  to blue in the presence of acid.  EDIT:  This color-change is completely reversible over a period of years.    The red rags are kept in a plastic container continuously wetted by the dilute soda solution for a month or two,  until they are cleaned in water,  and the soda dose is renewed.   Some of these soda-laced cleaning cloths are  five or so years old <<. 

    The color-change indication is useful to me,  and can even indicate when the soda,  in solution, has become depleted.

    And,  regarding the Petroleum Jelly,  on clean terminals and lugs,  BEFORE mating them,  have always done this,  and the terminal protection seems to just last forever.   AND,  there appears to be NO ill effect from this compound between mating contacts.  In all probability,  the micro-rough contact areas simply displace the jelly as the connections are torqued.   This treatment literally seems to last forever,  without any corrosion.

    Have been doing the above for decades,  has always worked GREAT.   Just my experience,  and we all have our own methods,  and for those which work well,  seems to be little reason to change them.    Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Vic said:

    And,  regarding the Petroleum Jelly,  on clean terminals and lugs,  BEFORE mating them,  have always done this,  and the terminal protection seems to just last forever.   AND,  there appears to be NO ill effect from this compound between mating contacts.  In all probability,  the micro-rough contact areas simply displace the jelly as the connections are torqued.   This treatment literally seems to last forever,  without any corrosion.

    +1

    There are all sorts of commercial products for the terminals, but petroleum jelly works so well that I don't see what a commercial product could do better.

    Vic, that's interesting about the shop towels... I will try to find some.... where do you get yours?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • VicVic Solar Expert Posts: 3,136 ✭✭✭✭

    Hi vtMaps,

    These red-colored shop rags,  that are about 12" on a side, are often available at Home Depot,  in bags of about 20 - 25 ea.   Have seen them in Auto Supply houses,   including,  NAPA stores.   Some of these rags are quite red, and others,  tend toward pink,  but they all seem to have this reversible (over hundreds of cycles,  or more)  color change nature.

    FWIW.   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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