Batt voltage looks good but no power

Offgrider9
Offgrider9 Registered Users Posts: 7
Disclaimer: Not really new to solar but new to forum and new to off-grid living...

I bought an off-grid home back in March that had an old, neglected PV system. I upgraded the modules, combiner box, charge controller, and batteries. The batts, Vented Pb-Acid Crown 395 Ah, are about 6 months old. They had been working fine, albeit under-performing according to my expectations in terms of days of autonomy, until 2 days ago. Suddenly, in the middle of the day the power in the house went out; the SW4024 had faulted due to over-current (according to LCD display on inverter). Since then, the inverter will only power the house if the sun is shining on the array or the genny is running. The batteries are contributing nothing.

This is a 24V battery system, all loads are running on 120/240. I do not have any instrumentation with which to measure SG but I do have a clamp-on meter as well as a Bogart Engr wall-mounted meter.

The battery voltage climbs healthily during charging either from the solar or the genset and seems to come to rest at about 26v. But when the sun goes down and/or the genny stops, the inverter shuts off and the power goes out. Basically, under load the batteries fail to produce any current.

The old battery bank that I replaced with the new Crowns was performing ok for a while but eventually the same thing happened with those. We would see a rapid rise in battery voltage as soon as the sun came up on the array. Then a rapid decline in voltage as soon as the sun went down. Battery storage capacity has left the building. I am apparently a very good destroyer of batteries despite the fact I do keep an eye on the water level, equalize them about once a month, have low voltage shut-off points set on the inverter, and have set the charge points on the controller according to all the literature I read on proper battery use.

I know enough to be quite dangerous but I really need to learn more to get past the point of being dangerous and delve into the realm of being useful. Any help along these lines is greatly appreciated. I apologize for redundancy if any threads have been posted about this in the past; please direct me to those.

Thanks!

Eric

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batt voltage looks good but no power

    Welcome to the forum.

    If you can't look inside your batteries (i.e. measure SG) you will never know for sure, but "Voltage not holding" is a sign of dead (sulphated) batteries.
    It is also a sign of loose wiring or far too short of an Absorb time.

    Let's just check the numbers to see what should be happening:
    1440 Watt array (just the 12 KD120's) should be capable of 46 peak charge Amps on a 24 Volt system, barely a 6.5% rate on a 700 Amp hour battery bank.
    I'm not sure the Canadian Solar 280's will work well with the Kyoceras as they should be around 30 Vmp I think and the KD's are 17.5-ish. I see no viable multiples there so maybe I've got the specs wrong. If they would it would max out that 80 Amp controller.

    You really do need to check that specific gravity. It's the only way to know what shape the batteries are in.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    More or less, the things that pop into mind:

    1) poor electrical connections (dirty, loose, corroded). When charging (or under load) use a volt meter set to 2 volt full scale and measure the voltage drop across each connection.
    2) open/shorted cells... If you can, measure the voltage of each cell--Look for differences, cells much higher or low voltage than the mates.
    3) Battery was under charged---Very common, battery never quite gets back to 90-100% state of charge a couple times a week. Instead, the average SOC goes from 100% to 90% to 70% to 50% to 30% towards 0% over time... The longer a battery operates (or sits unused) at less than full charge, the faster is sulfates (the soft fluffy sulfates turn into a hard black crystal that never participates in the charge/discharge cycle again--And reduces the amount of sulfuric acid in the electrolyte (from 1.265 full charge to 1.200 full charge to near 1.100 full charge--near dead or pure water).

    You need to get a good quality hydrometer and start measuring the temperature corrected Specific Gravity of each cell--Then start trying to charge the battery back to full charge.

    What are your set points on the battery charger and how long does the battery sit at "absorb" voltage (around 29 volts or so for a 24 volt battery bank)? You need a high enough voltage held for 2-6 hours to fully recharge the battery battery bank. Without measuring the Specific Gravity (or resting voltage--3+ hours of no charging/discharging current), you do not really know the state of charge of the battery.

    Using the voltage cutoff on an inverter (or low voltage disconnect) is a bit tough... Battery voltage is a combination of state of charge, temperature and current (amount and direction)--Using a voltage set point can be inaccurate (many inverters cutoff at ~21 volts--That is a dead and damaged battery. A better set point is around 23 to 24 volts--But even that is only a rough guess as to battery capacity and load response.

    It sounds like the battery is toast--Basically sulfated. Very little capacity--Load drain the battery almost immediately and charging appears to fully charge the battery very quickly.

    Here are a couple Battery Faq's:

    Battery FAQ
    www.batteryfaq.org

    Do you have a volt meter (clamp meter may have DMM functions). And is the current clamp meter is a DC capable current meter (most are AC only)?

    What is your solar array configuration (series/parallel)? Roughly, where is the system installed? Good sun (no shadows) all day long?

    How many Watt*Hours/Amp*Hours per day do you normally use?

    Have you considered a Battery Monitor (Victron is another good brand).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batt voltage looks good but no power

    Bill, I just have to point out that as a diagnostic tool battery monitors aren't much help because they rely on being set-up and programmed correctly at the start. Adding one to a system that is not new, much less dysfunctional, isn't going to give you any usable info.

    First step to fixing an off-grid system is always: find out what shape the batteries are in, and fix them if needed/possible. Then figure out how they got there and correct that problem.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    Disclaimer: Not really new to solar but new to forum and new to off-grid living...


    The battery voltage climbs healthily during charging either from the solar or the genset and seems to come to rest at about 26v. But when the sun goes down and/or the genny stops, the inverter shuts off and the power goes out. Basically, under load the batteries fail to produce any current.

    The old battery bank that I replaced with the new Crowns was performing ok for a while but eventually the same thing happened with those. We would see a rapid rise in battery voltage as soon as the sun came up on the array. Then a rapid decline in voltage as soon as the sun went down. Battery storage capacity has left the building. I am apparently a very good destroyer of batteries despite the fact I do keep an eye on the water level, equalize them about once a month, have low voltage shut-off points set on the inverter, and have set the charge points on the controller according to all the literature I read on proper battery use.

    I know enough to be quite dangerous but I really need to learn more to get past the point of being dangerous and delve into the realm of being useful. Any help along these lines is greatly appreciated. I apologize for redundancy if any threads have been posted about this in the past; please direct me to those.

    Thanks!

    Eric

    Where are you measuring the battery voltage? At the battery terminals themselves or at the CC? Are you just reading the built-in voltage display of your CC?

    Where did you get the idea that 26 volts during the charge cycle is a good endpoint?

    While you are charging, for typical Trojan batteries, the voltages should get to about 29 volts during the Absorb stage of charging and not drop back to a Float voltage of ~ 26.4 until the batteries are essentially fully charged.

    The recommended voltage for Equalize is around 31 volts, if you can get that high while staying within the current limits.

    It looks like what you are doing is chronically undercharging your batteries, causing them to continuously lose capacity until they are essentially dead. Even a battery with no useful capacity left will let you get up to 26 volts during charging, but will not really be accepting current or developing capacity.

    Now that all of the discussion of voltage is done, since you are using vented cells, you MUST measure the Specific Gravity (SG) with a temperature compensated hydrometer (or manually apply a temperature correction.) Fully charged SG will vary by battery type, but will generally be in the area of 1.250 to 1.270 (consult the literature from Crown for accurate numbers on your batteries.)
    (To the extent that it is useful at all, the only voltage indication which is meaningful without calibration against SG measurements for your batteries, is the resting voltage. The batteries should be neither charged nor discharged for three or four hours before making that measurement. You are relying on expensive equipment (ammeter and battery meter) which are not suited to this particular job rather than getting the inexpensive (as low as $10) tool that is critical.)

    I think you will find your SG to be much lower than that, indicating that your batteries are essentially boat anchors already. (Although use of lead for boat anchors is not environmentally sound.)

    You may be able to at least partially rescue them with a long term regime of Absorb and Equalize charging at much higher voltages than you are using now, but that may best be done by moving the batteries to a place were you have POCO power, or else planning to devote several weeks of solar PV charging to the task.

    If you carefully read advice on the battery voltage settings you need, it appears that either you read some really bad sources or else you misinterpreted what you read. It is also possible that there is a high resistance in the wiring between your CC and your battery bank, causing the voltage seen at the CC during charge to be much higher than the voltage at the battery terminals.

    Since your PV will only charge the batteries for a limited number of hours each day, you do not have enough hours in a day at the Float setting to properly charge your batteries, even if you did not discharge them each night.
    SMA SB 3000, old BP panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    Not necessarily as a diagnostic for a failing set of batteries--But it does make it easier to answer how many AH a day is consumed and how many AH a day are replaced (when the bank is working OK)... And make it a bit more obvious if a battery is being deficit charged over time.

    Also, for people that are not comfortable using a hydrometer--A battery monitor can make it easier for non-technical spouse/kids/guests to understand the battery state of charge (as well for sealed batteries where SG cannot be measured).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Offgrider9
    Offgrider9 Registered Users Posts: 7
    Re: Batt voltage looks good but no power

    Cariboocoot,
    To clarify, the volts and amps of two Can modules in series matches up pretty closely with four of the Kyo's in series. All mods are combined on breakers in a Midnite box on the roof before going to the MX80. I'm pretty confident that side of the system is fine. Taking care of the batteries is my weak spot.

    BB,
    I think all three of your ideas: electrical connections, shorted cells, and undercharging, have occurred or are occurring.

    It seems what I need to do is repair all battery connections - a couple are admittedly not very secure and I have tested lower voltages at these batteries (about 5.7v), apply anti-corrosion gel, clean tops of batts to make sure no electrolyte is present as some has spilled over during charging and has been sitting on the tops of the batts maybe providing a short-circuit path, get my hands on something to measure SG, and then give the bank a good charging.

    So, is there still hope or am I looking at a probable bank replacement...again?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    Probably bank replacement... Since they are fork lift batteries, perhaps you can find a local dealer and see if they can recover/repair the batteries for you (don't know if possible or not).

    Shorted/open/weak cells could be replaced (in some batteries)--Assuming the other cells still have some life left in them.

    What is the battery configuration? 2x 12 volt batteries in series and 4 parallel strings or what?

    I am not a big fan of paralleled battery strings (one string with large AH cells is my ideal--perhaps 2-3 parallel strings is serviceable--4 or more parallel strings require some effort to ensure everything is OK).

    Basically, if you have parallel strings of batteries--You can use your DC Clamp Meter to see what strings are accepting charge and which are supplying load--That is your first hint at one or more weak connections or failing cells (shorted cell will take most of the current, over charging cells in the string, under charging the rest of the parallel strings--Open cell will simply stop passing current in the string--and series cells will eventually self discharge, other parallel strings will carry the loads).

    Similar with using a volt meter to measure cell/battery voltages... Readings taken once a week or with high or low (compared to the rest) will point to places to look for problems.

    It may be possible that you can break the bank into batteries/cells and figure out which are good vs bad--And build out a lower capacity bank to get your system up and running--And then address the next set of issues (charging/loading and how your charging cycles are going).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Offgrider9
    Offgrider9 Registered Users Posts: 7
    Re: Batt voltage looks good but no power

    Boat anchors! ...That's a good one. You made me laugh and cry at the same time.

    I was referring to 26v as resting, an hour after charging stops. I had set EQ volts at 29 on CC per Outback's MX80 installation manual but decided, 2 days ago to change that to 30...and am considering increasing that to 31. But I really do need to consult the Crown manual instead of Outback. I do have a clamp-on VOM that can measure DC amps and have been using that to measure voltage at the batt terminals.

    After reading all the feedback, I'd have to say that I've been undercharging the bank; a little less each time. I get decent sun on the array for charging but probably not enough to get back to 100% SOC each day, especially given the load usage in the house throughout the day.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    So, is there still hope or am I looking at a probable bank replacement...again?

    That is a matter of how low they've been for how long. The lower the longer the less hope for recovery.
  • Offgrider9
    Offgrider9 Registered Users Posts: 7
    Re: Batt voltage looks good but no power
    BB. wrote: »
    Basically, if you have parallel strings of batteries--You can use your DC Clamp Meter to see what strings are accepting charge and which are supplying load--That is your first hint at one or more weak connections or failing cells (shorted cell will take most of the current, over charging cells in the string, under charging the rest of the parallel strings--Open cell will simply stop passing current in the string--and series cells will eventually self discharge, other parallel strings will carry the loads).

    Similar with using a volt meter to measure cell/battery voltages... Readings taken once a week or with high or low (compared to the rest) will point to places to look for problems.

    It is possible that you can break the bank into batteries/cells and figure out which are good vs bad--And build out a lower capacity bank to get your system up and running--And then address the next set of issues (charging/loading and how your charging cycles are going).

    -Bill

    I would have no idea how to build out a lower capacity bank; not without some training.

    Can you clarify how to check which cells are accepting charge and which are supplying load? Is that just a matter of clamping on the meter, during the day when there's charge current available from the array and loads on at the house, and looking at polarity variation between the different cables connecting the batteries in the bank?

    Where should I look to buy a hydrometer or refractometer? Or is that an obvious question...Wind-Sun...duh.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    I don't have an off grid system--So I cannot tell you what hydrometers out there are the best right now... Refractometers have their own issues and probably would not be the best starting point right now.

    A good floating bulb hydrometer is a start (ones with integrated thermometers may be a bit more tricky to use). And a glass with distilled water so you rinse it out after taking readings (dried gunk can cause the float to stick). And a good flat surface/shelf with sides to prevent they hydrometer rolling off onto the floor (very common).

    One way would be to use a large 6 volt or 12 volt automotive charger (back in civilization with utility power--Or at your place with a genest--sized to power your battery charger, not a large 12 kW genset that will suck down 1-2 gallons of fuel per hour) and you can charge smaller blocks of batteries/cells. More or less, you are looking for batteries that will accept charging current at a reasonably high rate for hours on end until the battery is full...

    A 400 AH "cell" will take about 200 AH * 1.20 = ~240 AH to recharge from 50% to 100%... For example if you have a 40 amp charger, that would take about 6 hours minimum to fully recharge (realistically, probably about 4-6 hours to reach ~80-90% state of charge and another 2-6 hours to reach 100% SOC as the charging current tappers down to ~1-2% of bank capacity or ~4-8 amps of charging current at ~14.5 or 29 volts--whatever bank voltage you are charging at). Note that doing this for 4-8 batteries will take a lot of generator run time trying to recover the batteries (if possible).

    But this is all a guess until you get a hydrometer (try a local automotive store or battery distributor and see if you can get one there--even if it is not the best). And start seeing what the batteries are really at right now.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Batt voltage looks good but no power

    I would run over to O'Rielly's auto parts(Grass Valley, CA) and buy a hydrometer that looks like this;


    Attachment not found.

    Picture should be a link, I'd recomend ordering one from our sponser but you need info quickly. remove the foam prtecting the inner glass from the outer glass. Buy a couple gallons of distilled water, wash out the hydrometer a couple times before using and between testing each cell. I have purchased a couple of these and they mirror my higher quality hydrometer very closely. Be careful the inner glass 'float' is made of very thin glass and breaks easily. When you done wash out the tube a few times and let drip. I put mine in an empty gallon jug and leave it there until the next use, the bottom of the bulb fits closly to the top of the jug.
    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.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    Cariboocoot,
    To clarify, the volts and amps of two Can modules in series matches up pretty closely with four of the Kyo's in series. All mods are combined on breakers in a Midnite box on the roof before going to the MX80. I'm pretty confident that side of the system is fine. Taking care of the batteries is my weak spot.

    BB,
    I think all three of your ideas: electrical connections, shorted cells, and undercharging, have occurred or are occurring.

    It seems what I need to do is repair all battery connections - a couple are admittedly not very secure and I have tested lower voltages at these batteries (about 5.7v), apply anti-corrosion gel, clean tops of batts to make sure no electrolyte is present as some has spilled over during charging and has been sitting on the tops of the batts maybe providing a short-circuit path, get my hands on something to measure SG, and then give the bank a good charging.

    So, is there still hope or am I looking at a probable bank replacement...again?

    I can think of only two likely reasons for electrolyte "spilling" during charging.
    1. You filled a cell too full when it was cold and as the battery warmed up during heavy charging, the expanding electrolyte, also full of gas bubbles, increased its volume and overflowed, or
    2. You were charging very heavily while some cells were at their gassing voltage and the rapid "boiling" forced some acid mist out the cap and it re-condensed on top of the battery.

    When you have a 24 volt battery bank made up of 4 six-volt batteries in series, the same charging current will flow through all of them and the voltage at the CC will be the sum of their individual voltages.
    If one battery in the string reads 5.7 volts (essentially dead), it can reduce the voltage of the string so that when the CC is applying 29 volts to the string, some of the cells are getting much a much higher voltage than is appropriate. Those cells will be warming up and also generating hydrogen and oxygen bubbles, losing electrolyte. If some batteries require much more water at refill time than others do, this is a bad sign.

    The main reason for Equalization is to force current through the already charged cells to supply charging current to the cells which for some reason are not fully charged yet. But this must be done in a controlled way when some batteries are very low so that you do not overgas the "good" cells.
    Also, if a cell has lost essentially all of its capacity as the result of sulfation, both its voltage and its SG will be low and no amount of recharging will restore them to normal.
    With series cells, if one or more go bad and you do not notice it and correct the situation, it can lead the rest of the cells into premature failure.

    FLA batteries can take a lot of abuse of some types, and if you are very lucky they can survive for awhile with little or no attention, but to get full life out of them you have to watch them carefully and not just rely on the inverter and the CC to do the right thing. :-)
    SMA SB 3000, old BP panels.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    So, is there still hope or am I looking at a probable bank replacement...again?

    Goofy thing is, you might return them and plead ignorance and since they are under warranty, they may be covered. Sometimes, even abused, warranties are honored for assorted reasons....

    ...worth a try.

    BTW, those hydrometers are in stock, and they are open 8am to 8 pm Sunday at 121 Olympia Park Road - Grass Valley, CA, just since I had the web site open, they're even cheaper than here in mid Missouri!
    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.
  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    Re: Batt voltage looks good but no power

    This is the one I use, but it does take a bit of getting used to using it. There is a thread on suggested usage of a hydrometer. http://www.solar-electric.com/brtecoprhy.html
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Batt voltage looks good but no power

    I'm with Photowhit, time IS a wastin'. Go out today and get that Hydrometer. If there is a close neighbor, try borrowing one NOW.

    Look for Crown's Battery Manual (or similar name) for EXACT charging parameters.

    For almost all FLA batteries(ones with removeable caps), EQ should be around 31 V. Be sure that you are using a Battery Temp Sensor attached midway down a battery near the center of the bank.

    Make certain that the charge voltages are set correctly on each charge source, and generally, each charge source needs its own BTS, although OB Inverters and CCs can share one if you have the correct giblets, and use the correct ports for them.

    For now, increase the Absorb voltage on the CC, and would recommend increasing Absorb times to HOURS and HOURs. Little to loose at this point.

    Most of this has been covered by others. Good Luck. Two Hydrometers or three is a good thing. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    You can cut down the Absorb voltage/time once your batteries are up to 100% and working well again...

    To a degree, watch your water consumption. Perhaps you need to add water every couple months.

    If you are adding a lot of water every month cut back on the absorb time/voltage.

    If you don't add any water for 2-6 months, crank up the voltage/time again.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Offgrider9
    Offgrider9 Registered Users Posts: 7
    Re: Batt voltage looks good but no power
    inetdog wrote: »
    FLA batteries can take a lot of abuse of some types, and if you are very lucky they can survive for awhile with little or no attention, but to get full life out of them you have to watch them carefully and not just rely on the inverter and the CC to do the right thing. :-)

    My problem was that I assumed the batts could take a lot more abuse than turned out to be the case. I was relying heavily on my Xantrex (inv) and Outback (cc) team to do all the work and thought for me. Expensive mistake.

    I bought me a hydrometer at the local auto parts store this a.m., as well as some terminal upgrades, anti-corrosion gel, acid neutralizing/removal spray, and a few other goodies for my long-overdue battery care package.

    The batts are all cleaned up, all connections are tight, corrosion-free, and gelled up. Probably too little, too late but it makes me feel better anyway. So, the SG numbers are:
    1200, 1200, 1180, 1200
    1150, 1125, 1125, 1150

    I still need to connect a BTS. Kind of thought that was optional...

    Whether or not this bank is wasted, I really need to get educated on, not only how to take care of the batteries, but also, and maybe more importantly, how to properly monitor the batteries. I think that's how I ended up here in the first place. I have a Bogart Trimetric but I don't think it's reliable. I need a good battery monitor.

    Thanks for all the insight guys!
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    Here is a quick Rolls document on taking SG readings:
    Charged    Specific Gravity
    100%    1.265-1.275
    75%    1.225-1.235
    50%    1.190-1.200
    25%    1.155-1.165
    0%    1.120-1.130
    

    Your cells are (roughly) between 50% and dead... I assume you have more readings than posted here (more cells to reach 24 volts).

    The Trimetric has lot of people who like it very much--But the programming is a bit confusing for many.

    Most (all/some?) battery monitors reset back to 100% SOC based on some setting (like holding 29 volts for > 3 hours or such)--If you do not reach the reset point, the meters will drift over time/use.

    Obviously, the actual battery capacity varies over time (and temperature) too--The meters cannot estimate actual capacity changes over time.

    The temperature sensor is nice for batteries that are in wide ranges of operating temperatures (like an uninsulated cabin. And/or where the charge controllers are in one room and the battery bank is somewhere else. In some cases, the remote battery temperature sensor is much more accurate than the on-board sensor (such as the MorningStar 15 MPPT controller really needs the remote battery temp sensor or it will over estimate the battery temperature--and slow down the charging rate/lower the target voltage).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batt voltage looks good but no power

    Try matching the battery strings with similar SG readings (all the near 1.200 in one string and all the 1.1xx in another--if you can).

    And get the batteries charging (if they will take a charge) with relatively high charging voltage to get maximum current in the batteries.

    If the cells get warm/hot, the cells bubble, and the SG does not rise--Then there is not much you can do... As long as the SG continues to rise, they are taking a charge.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • paulskirocks
    paulskirocks Solar Expert Posts: 84 ✭✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    I have a Bogart Trimetric but I don't think it's reliable. I need a good battery monitor.

    Did you make sure to program it for the proper "charged" set point voltage and "battery capacity" amp hours?
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Batt voltage looks good but no power
    Offgrider9 wrote: »
    I have a Bogart Trimetric but I don't think it's reliable. I need a good battery monitor.

    The trimetric is a good monitor.

    A battery monitor is often compared to the gas gauge in your car, but that is not a good analogy.

    The gas gauge in your car actually measures the amount of gas in your tank. A battery monitor doesn't measure anything. It is more like the odometer in your car. The odometer counts miles and the battery monitor counts ampHours.

    Suppose you have a car that gets about 25 mpg and has a 15 gallon gas tank. Suppose also that your gas gauge does not work. What do you do? You use your odometer. For example: After a fill up you drive 150 miles and you expect that you have used 6 gallons and have 9 gallons remaining in your tank.

    If you fill up the tank again you can, as above, use your odometer to estimate your gallons remaining.

    But what if you do not completely fill your tank. For example, starting from a full tank you drive 150 miles and then you add 3 gallons to your tank and then drive 100 miles and then add 4 gallons to your tank and drive 150 miles and then add 5 gallons to your tank and drive 100 miles. At this point you estimate that you have 7 gallons remaining in your tank, but that estimate is not too accurate because your mileage is not ever exactly 25 mpg. Mileage depends on many factors: how much idling, how fast you drive, how fast you accelerate, temperature, etc.

    So it is with your battery monitor. It counts ampHours in and out. It does not take into account the effect of temperature on battery capacity. It assumes that 1 amp for 100 hours is the same as 100 amps for 1 hour (its not the same...Peukert effect). It does not even know the ampHour capacity of your battery (other than what you tell it), and that capacity varies with age, temperture and sulfation of the battery.

    Your battery monitor works like the odometer... when you fill up the gas tank you reset the odometer. When you fill up your batteries the battery monitor is reset. Your battery monitor will reset itself when the batteries are full, but you have to program it to know when the batteries are full. Without a hydrometer or refractometer you don't know when your batteries are full.

    Over on the outback forum it is commonly written: "lie to your battery monitor and it will lie to you". In other words, have you programmed your trimetric properly?

    Bottom line: the longer its been since a complete charge, the less you can trust your battery monitor. And you can't trust it at all if its not set up correctly. That said, battery monitors are valuable tools in estimating your SOC, but you have to understand their limitations. You must have a hydrometer or refractometer, and then you and your monitor learn how to estimate your SOC without having to use the hydrometer every day.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Batt voltage looks good but no power

    A battery is made up of '2 volt' cells, so a 12 volt battery has 6 cells each with it's own electrolite. They don't share electrolite, so each cap has to be checked...

    You may be able to have these replaced 'gratis', worth a try.

    Battery temperature sensors while optional, and if your batteries are in the same area as your charge controller, aren't generally needed, they are needed when you equalize a battery.

    Some people setup their Trimetric using half of their battery capacity, this is generally accepted usable capacity of your battery bank. Even if you save this battery bank, it will be tricky to set up your trimetric as you will likely have reduced battery capacity. Don't give up on this valuable tool, you just will have to program it with a lower battery capacity.

    Before batteries go bad, they appear to be taking a charge quickly, this is because the battery capacity has been diminished and it take less time to reach capacity. So to try to save these they need to be equalized, I'd probably crank up the genny in the early morning and charge back through the inverter. I'm pretty sure the SW4024 will equalize, I think it's a little dip switch on the side of the unit, if not let the MX80 equalize and check the battery every hour or so, and check your specific gravity(SG) readings. you can just check a few single cells, when those cells quit increasing, start checking all the cells, if none of them increase for a couple hours, you've reach their max capacity. You will want to check each cell for water levels as the batteries will loose water during this...
    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.
  • Offgrider9
    Offgrider9 Registered Users Posts: 7
    Re: Batt voltage looks good but no power

    The trimetric was installed when I bought the house and I have not yet reprogrammed it. But that is now on my list of next steps; along with installing a BTS asap, re-checking SG with hydrometer, and possibly rearranging the batteries to match up the batts with similar SG readings. All great advice. Thank you guys!

    The batteries are performing OK now after removing all electrolyte from the tops and outsides of the batteries (electrolyte may have provided a short allowing voltage to drain), removing all corrosion at terminals and on cables & properly securing all cable & terminal connections (batteries were probably being starved for charging current as a result of increased resistance), applying a good amount of anti-corrosion gel to terminals (hadn't used this and was getting heavy deposits), reprogramming both the inverter and charge controller charge set points which were all a bit low, especially at the inverter, and immediately giving the bank a thorough charging from the genny.

    Will check SG levels when the current monsoon stops and report back. Thanks again everyone!!