This cannot be normal battery charging

FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
This is a recurring theme with me and my system....but tell me, is this the way it works for you??

My charging day today.

At 7am the voltage read 12.0 and I turned the generator on and it charged at maximum 900 watts for about 2 hours then the current dropped off to about 200 watts while maintaining my setting of 15.0 volts. The generator  ran for another 1.5 hours while my wife washed. The lowest of my six cells read 1.215 (cell beside was 1.225). Turned the generator off and the system said it was floating. However, my float setting is 15.0

The solar came on strong but the system was only drawing about 300 watts from the sun (much more available)
This went on until 1pm when I had gained only 1.4kwh in solar and the cell read 1.210
At 330 it was still only drawing a small portion of solar available but maintaining 15.0 volts. Total was 2.2 kwh and the cell reading was 1.220 (other cells 1.240)
I started an EQ cycle because I was pissed at missing all that sun. And the Charge controllers were showing things like "Bat Full". Again, current draw was very small but voltage was high...I think...I had to go out for a couple of hours. EQ setting is 16.0
At 530 the solar total was 2.5 kwh and the good cells were at 1.245, the lower cell was not read. I started the genny again and current draw was low.
At 730 the genny had run for 2 hours but charging at very low watts..SG readings were 1.235 for the low cell, 1.250 for the higher.

This was a total sun day. To my thinking my two charging batteries should have nicely become fully charged....the high voltage while drawing low current is a mystery and seems to suggest sulphation???
I run EQ a lot..because otherwise the batteries never get up to NEAR full, never FULL.
This bank is 2 years old and I am only running 2 batteries as one of my 4 is out of commission due to a bad cell.

My settings are abnormal because that is what Surette is telling me I should try...
Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
12 volt Flojet water pump
off grid summer home in northern Ontario

Comments

  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    what are your settings?
    Have you checked the voltages at the batteries and compared them with the chargers? Are they the same? how about the connections, all of them, are they tight have they been cleaned lately?

    I had a similar issue and it turned out to be a slightly loose connection....comments were about  'high resistance' and you can get that from a loose connection...

    the cook calls.... Dinner....
    hth
     
    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
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭

    Freewilley,

    There can be a bit of a challenge with multiple charge sources,  sharing a charge stage (like Absorb and EQ) which has the charge voltage regulated.  The situation can be compounded if each charge source does not have its own RTS.  Variations in CC calibration,  differing voltage drops in cables connecting CCs to batteries,  etc can make two CCs,  for example,  share the charging duties poorly.   With two OB CCs,  you can often see one CC say " Bat Full "  or similar when that another CC or charger is holding the battery voltage above its voltage setpoint.   This will waste any charge contribution that the CC stating Bat Full might have been able to make.

    Low battery charge current with fairly high charge voltage would generally mean that,  on average,  the battery has become fairly well-charged.

    A relatively large variation in SG readings between all of the cells of a battery bank,  IS an indication that an EQ is probably in order  (as you had been doing,  later in the day).

    Checking battery cable,   CC to battery,  and Inverter cable connections has been covered previously,  in another Discussion.   Generally,  these drops can be measured with a MulitMeter that has fairly long leads (when necessary).

    From that other Discussion,  know that when you were running two parallel strings of batteries,  you had done long,  hard EQs.   You will probably need to EQ for some number of additional hours on this single string.

    On the positive side,  it does appear that your lowest cell in this battery IS responding   --  increased SG readings.  SO,  to me,  this is a good sign.

    You did mention,  that at 7:00 AM,  the battery voltage was 12 V.   Knowing the approximate battery temperature,  loads at that time,  and approximate loads that had been on the battery for the preceding few hours might help one guess an approximate SOC.  Your Surrette batteries have a Temperature Coefficient of -- 0.005 volts per cell, per degree C change from the Reference temperature of 25C.  If your batteries were about 15 C at 7 AM,  this would equate to about 0.3 V higher reading than if they were at the reference temp (25C).  This would make a significant difference in guessed SOC.   SO,  battery voltage alone,  even for a Rested battery is not the only indication of approximate SOC.

    Good that you are getting guidance from Surrette.   AND,  glad to see  your high voltage settings.   In addition to allowing shorter Solar days to provide more battery charging,  the high Absorb voltage settings will extend the length of the Bulk stage.   This will provide longer charge time before the point that voltage regulation begins.   During Bulk,  there should be no real issues with your two CCs providing all of the charge power available from your PV arrays.   This is a good thing.

    Had noticed in another Discussion that you are going to,  or have already ordered enough RTSes for each CC and the Inverter/charger to have its own.   This should help.

    AND,  once again,  you should really manually temperature compensate your EQ voltage,  as the CCs (at least)  do not do this on their own ...   at least the MX does not,  and believe that the FM does not either.

    And so on.    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.
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    At those low of SG, and the relatively quick charging (a couple of hours)--I am really worried your battery bank is having problems (sounds sulfated, or other problems like poor electrical connections, too small/long of cable connections from charger to battery bank, or something else).

    This is a 12 volt battery bank with 4x 6 volt at 428 AH batteries? Presently 2x 6 volt batteries for a 428 AH battery bank. Nominally 10% rate of charge for solar and 10-20% rate of charge for genset (or genset+solar).

    With the charging you are doing (and equalization) the high cell(s) should be pretty close to 1.265 (or even a bit higher). But if the cells are bubbling pretty good--at 1.250 SG (temperature corrected)--Then that is the new "full charge".

    Measure the voltage across each battery as you are charging--What is the voltage across each? The battery with the high voltage is limiting your charging current. If it is the battery with the high SG--You could try clipping a resister (or even other load, if you can find some 6 VDC light bulbs) across the good battery to let some extra charging current through the low battery.

    If it is the low SG battery with high charging current--Then it sounds like you have a high resistance cell (sulfation, failed cell grid?). Also check the voltage drop across each cable connection and length of cable (you could have internal cable corrosion under the insulation).

    Do you have a 6 volt AC battery charger that you can keep the old batteries charged (when running genset/lots of sun)? Of your two batteries you cut out of the bank, is one of those still "good"? Can you replace the battery with low SG with the extra battery?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    thanks guys, you sure are patient with me and my batteries.
    the connections are not loose.
    I do not have a 6 volt charger. 
    Bill, one of the cut out batteries IS good. I planned to cycle it in the bank, but now I think I should have a new fourth bat next week.
    Are you saying that the rate of charge can be higher for a combo with the genset? What I have in my head is the max charge at 1100 watts for 2 batts and 2200 for the four. Can it be higher if it is not just a solar source?
    I have been over the cable length before and it is ok.

    Vic, when you talk about the low cell, you may be thinking of my bad battery which is not being used, it is dead to me....can you explain more about manual temp compensating on EQ cycle???? First time I heard of that. I do measure temps with my Hydrometer and also with a candy thermometer.
    And I am soon to get my RTS and on a sidenote I talked with another off-gridder I know and she was surprised to hear she also needs more RTS...and she has been on solar for 10 years....


    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    Even more weirdness.
    For the first time ever, last night WHILE the generator was running, my sewage macerator pump kicked on and the power went off from the inverter. It started back up again in 10 seconds, of course pump was on and kicked off again. Second time, it started up by itself and ran fine. Not sure if pump was still running..
    First question...if you start feeding power into a system that has passed low cutoff, does the inverter start up automatically? I thought I would have to charge up the bank and then try to start the inverter manually...but apparently not?

    Just now, without the generator running, the system fell below the cutoff when the genny was not running and shut down. When I started it up again, with the pump unplugged of course, I was watching the CC battery voltage and it briefly flashed 10.5 and moved quickly to 11.5, which is where I expect it to be with the pump running (the pump pulls about 1200 watts).

    What is really weird about both outages is the battery bank was not low when it occurred. The voltage was 12.5 and SG confirms this.
    The pump runs about 5 plus times a day and certainly ran several times between these two outages (with much lower juice in the bank) without crashing.
    There were no other significant power drains on the system the second time...the first time there might have been another 1000 watt draw, not sure as I was in the shower....

    Please share your thoughts on this brand new issue which is just not explainable when I review the history of my system over the past 8 years....except for the possibility that my pump motor was malfunctioning and drew too much juice when this happened...but only twice (so far).




    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    It possible that the inverter will restart (I don't know)... But it does sound like your battery bank is getting pretty weak (high internal resistance or bad cabling/etc.--Or simply low SG on one or more cells).

    More or less, for solar I suggest 5% to 13% is a good range with 10% or more for full time off grid use (just based on battery charging--Still would need to talk about hours of sun and your daily loads, by season too). If you had all four batteries 6 volt @ 428 AH on solar with 10% rate of charge:
    • 2 * 428 AH battery bank * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,612 Watt array nominal
    So, your 1,400 Watt array is not bad... But also need to know how much power you use, and hours of sun per day... Just guessing: Inisk Ontario Canada with 55 degree tilt, fixed array:
    http://pvwatts.nrel.gov/pvwatts.php
    MonthSolar Radiation
    ( kWh / m2 / day )
    January2.76
    February4.41
    March5.92
    April5.92
    May4.71
    June4.52
    July3.90
    August3.92
    September2.72
    October2.11
    November1.45
    December2.08
    Annual3.70
    What is your hours of sun like? Your there in October--That is only 2.11 hours of sun average. If we assume that your full bank is running 25% discharge * 2 days (and 50% max discharge):
    • 2 * 428 AH * 12 volts * 0.85 inverter eff * 1/2 days storage * 0.50 max discharge = 2,183 WH per day (from battery bank)
    • 2,183 Watt*Hours per day * 1/0.52 off grid system eff * 1/2.11 hours of sun (October) = 1,990 Watt array to "break even" (in October)
    I have no idea about your daily power usage--But I can certainly see you needing to use the genset every so often to recharge during this time of year (with my many guesses).

    Lead Acid Batteries, I suggest that about 13% rate of charge (~8 Hour rate of charge) seems to be the maximum that would be recommended for charging without a remote battery temperature sensor (higher rates of charge, the batteries can overheat--But when equalizing a battery bank that is at ~100% full, even a 2.5% rate of charge over many hours can overheat a flooded cell lead acid battery bank too).

    With flooded cell batteries, below ~80% state of charge, they are actually quite efficient, and can take >20% (maybe even 25%) rate of charge without much issue... When the batteries are >90% state of charge, you are probably down in the 5% rate of charge area for "normal" charging anyway.

    What seems to work well for many people, is to let the battery bank get down towards 50% state of charge, and then use the genset (at 10% to 20%+ rate of charge) and bring the battery bank back up to ~80% state of charge (such as in the early morning), then let the solar panels finish the charging. If there is no sun, you can always run the genset the next day for 50% to 80% SoC charging.

    Where charging with a genset gets "expensive" (less fuel efficient) is trying to use your large genset+battery charger (sized for 10%++ charging) to take the battery bank from 80% to >90% state of charge--Most gasoline genset are not very fuel efficient when operated at less than 50% of rated load (i.e., the fuel flow is pretty flat from 50% to 0% rated load for gasoline/propane gensets).

    Anyway--Any of the above helpful?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    edited September 2016 #8
    I went and rode my bike for an hour and reread your post and realized my mind was foggy the first time.
    Now I have edited out some of my nonsense...

    Yes, this is stuff that I am familiar with (thanks to your many attempts to help me over the years) and thanks for taking the time to summarize it. For instance, this morning my lowest cell was 55% approx SOC and I am running the genny at 900 watts charging (could it be set higher?) while coffee runs and then wife does a couple loads of wash. Solar kicks in about 10 am until 4pm, minor power for a couple hours either side, but not much.

    Ok, so your math says that I can safely put in 1600 watts from my panels, I think...please confirm, maybe you are just telling me I can have another panel...somebody on the board did some math for me a couple of months ago and came up with 1100 max for 2 S550s. That is why I am setting my genny rate of charge at 900, to allow for a little solar as the morning goes on.
    Can you answer if the maximum charge going in can be higher when combining solar and gen charging? 
    That is what I get from your statement
    Nominally 10% rate of charge for solar and 10-20% rate of charge for genset (or genset+solar).

    That is really important to me so that I use the maximum charging from the genny. My Yamaha is more efficient when it is running at 2/3 capacity, so when I have lowered the limit when using just 2 batts I am wasting gas.

    I do run the generator regularly at this time of year (12 days and we are gone till May when we have 4 times the solar) so that does a lot of charging and taking power needs out of the equation.
    Your average sun times look good but averages for a hybrid system are not totally useful because on a cloudy day the generator adds a lot of juice, both in taking the load off the system and charging the batts...On a sunny day in May-July I take in 8kwh, if my bank was larger then that would be higher due to the lowering of current in afternoon.
    A note on Gen usage and buying gas...when I started out I followed conventional wisdom and had a large propane fridge. Of course it lightened the battery load BUT took propane every day, sun or cloud. When I went to electric I saved about $250 per season in propane costs I figure. That buys a lot of gas for the generator! And got us a WAAAAAY better fridge experience on many levels. So I no longer mind using my gennie...

    Going back to this shutdown...I checked all connections and all are tight and clean. I checked SOC when this happened last night and all cells were at least 80% charged. I checked voltages at the battery posts and they agree with the CC voltages and with each other.
    The light (in my head) went on and I plugged my pump into my kill-a-watt meter so I will see the maximum draw when the next shutdown occurs. I think the pump has to be the issue....I manually ran it and it drew a max of 1083 watts and all was fine...I think it is drawing much more on occasion and that causes the drop in Voltage but the meter will tell me that over the next few days. If not, then it is a block in the system somewhere...

    I am very grateful for your time. THANKS!


    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    For the genset, just using some math to estimate your "ideal" maximum loading/charging current. Can you confirm it is a 3,500 Watt inverter genset? All I could find was the ef3000 family with ~2,800 Watt/VA rated continuous output):
    • 2,800 VA * 0.80 derating (for long gen life) * 0.9 inverter eff * 0.9 typical PF at full load * 1/14.5 volts charging = 125 Amps @ 12 VDC maximum from genset
    • 2,800 VA * 0.80 genset derating * 0.9 PF from inverter charger = 2,160 Watts maximum @ 120 Volts output for charging
    For your 2x batteries at this time:
    • 428 AH * 0.10 rate of charge = 42.8 amps "nominal rate of charge"
    • 428 AH * 0.20 rate of charge = 85.6 amps "more or less maximum rate of charge" (to ~80-85% or less State of charge, battery bank should naturally reduce charging current after that point--and genset will be running less output power to charging load--Just watch battery bank temperature and that you are not "bubbling the battery bank too much"--cut DC charging voltage a bit if bank is getting too hot or too much bubbling). With genset, charge to 80-85% SOC, let solar finish--Fully charge battery bank (>90% SOC) when closing up for season. Keep solar panels and charge controller connected (assuming you trust charging system to float battery bank properly--you can use minimum float voltage for your batteries for winter--Don't want to gas the batteries and expose plates over winter when nobody is there to check water levels). Normally all loads should be turned off during winter (avoid discharging bank when no sun/snow on panels).
    85.6 Amps charging would be around:
    • 85.6 amps * 14.5 volts charging * 1/0.90 inverter eff * 1/0.90 PF =  1,532 VA
    • 85.6 amps * 14.5 volts charging * 1/0.90 inverter eff= 1,379 Watts
    VA or Watts--Depending on which you are measuring (above is a lot of guessing--But should be close enough for your needs).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    That is my genny, but this version has the "boost" feature which handles up to 3500 watts load for a short time. Your math is correct for it.
    No worry about max on genny, the most that my inverter will allow is charging at 1700 watts and that is at the Mate, so the inefficiency of the inverter charge would take that down by 10% (I do not think that is my setting, I think that is built in somehow, anyone who knows different can let me know). So that is what I use for 4 batts, and why I do not worry about overcharging when the bank 4 batts.

    So you are saying that with the two batts I could charge at 1379 total? I will up my gen charging if that is the case. It is also just about the highest number I see ever coming to my panels. I will up that allowable charging from my panels then...right now I am limiting it through the CC to about 900 watts. If the max is as high as 1379 I can remove that restriction...

    Oh, and the 1379 is at the batteries, correct? That would mean I would up the limit on the genny charging by 10% (which is where I am reading it at the Mate)? So I would set it at about 1500 watts (the mate does set it in amps, of course)

    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    The 1,379 Watts is based on a Kill-a-Watt type meter plugged into the Genset's AC output.

    I would guess that you can measure the charging current through the Mate? If not, at some point you should some sort of DC shunt+meter or a DC current clamp DMM so you can measure directly.

    More or less, you want to keep the batteries happy. Above 13% rate of charge, you just want to make sure they are not getting too hot, and are not gassing too much.

     Typically, if your heavy charging current is less than 80% SOC, you can shove a lot of current into a flooded cell battery bank without issue. It when the batteries are over ~80% SOC that they become less efficient (and more of your charging energy is turned into gassing and heat).

    For solar power systems, those run all the time without people present--So we try to keep the system "safe" and not run them on the edge (high charging current, high charging voltage).

    When you are there because you are running a manual genset--You are keeping a close eye on the system and probably only running the genset for a couple of hours (from 50% to 80% state of charge)--Much less chance of over heating the battery bank and causing damage (or worse).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    I should add--Sometimes the setting units are confusing with inverter-charger stuff... You may set the charging current in DC Amps (at 12 volts for your system)... But you may set the maximum input current (from the genset) in AC Amps @ ~120 VAC.

    10 amps at 120 VAC can give you (very roughly) around 80 amps at 12 VDC... So understand what units and where they apply when programming your inverter-charger.

    My maximum 120 AC wattage is to give you ~85.6 amps of 12 vdc charging current. If you can measure the DC current flowing into the battery bank--That is the number you want to control.

    Note that many inverters have both a maximum AC input current and a maximum DC current adjustment/set-point.

    The inverter's AC input max current is usually the max current available from the genset (say 20 amps @ 120 VAC for easy round numbers). That is what it will take from the AC genset to BOTH charge your battery bank and run any AC loads around the home.

    The neat thing is that if you start running more AC loads (microwave for example), the inverter-charger (I think, I do not know the details of your inverter-charger) will cut back on the DC charging current until the microwave turns off--Then the inverter-charger will increase DC charging current again...

    So, make sure you are "adjusting" the correct value(s) here.

    Of course, if you run your AC loads directly from the AC genset and not through the inverter-charger--then the load shedding will not function as I have described (inverter-chargers only support load shedding if you draw your AC power from the inverter-charger directly).

    If you set the AC input current to your inverter-charger--Then the inverter cannot "pass through" the power from the genset to your household AC loads pass what you have programmed max current for the genset (say you programmed 10 amps maximum on AC input current--Then any AC loads on the inverter-charger will cause the charger section to cut back on DC charging current).

    Does that make sense?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    It totally makes sense and makes my world better.
    My generator does run through the inverter. It is limited through the mate to 2700 watts total, but I am not concerned that it is too high as it never charges higher than 1700, so it only draws more when we have power needs on the AC panel..these typically are 1000 watts for no more than 10 minutes at a time (dishwasher cycling, coffee dripping, microwave, hair dryer). So it rarely sees any continuous draw over 2200.
    And you are right that I run the generator only when the state of charge is 50-70% so that is safe on that end. If the generator IS run when solar is producing, the generator input cycles right down to a couple hundred watts or less, no issue there.
    I cannot measure the DC input, what I can see is the Mate which tells me how much is charging and how much inverting.

    I am wondering about why my charger is limited to 1700 watts from the gennie. I looked up the spec and it is rated at 125 amps DC continuous....maybe I have a setting limiting that? I would increase that to 2400 if I can see how, but only use that on my full 4 batt bank, of course.

    I know I threw a bunch of things at you, but what do you think of this from earlier post
    Oh, and the 1379 is at the batteries, correct? That would mean I would up the limit on the genny charging by 10% (which is where I am reading it at the Mate)? So I would set it at about 1500 watts 
    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    I have not looked at the detailed spec's and manual for your Outback VFX2812... But, ignoring losses:
    • 125 Amps * 13.6 "float" = 1,700 Watts
    So, somewhere around 1,700 Watts maximum sounds about right (there are lots of possible limits, current, power transfer, temperature, etc.)--So, in general, all sounds about right.

    My 1,379 Watt estimate was on the 120 VAC line of the genset (assuming the inverter is, roughly, 81% overall efficiency and you are charging at 14.5 volts--average).

    From looking at the programming manual (assuming I have the correct one):
    http://www.outbackpower.com/downloads/documents/Make_the_Power/fx_vfx_series/fx_series_programing_manual.pdf

    You would set the AAC input (genset) to, roughly:
    • 2,700 Watts / 120 VAC = 22.5 AAC (that is the maximum power from the generator)
    For the charger subsection, Outback also uses the AAC (amps AC) as its control point--So, roughly:
    • 88.5 amps * 14.5 volts * 1/0.9 charger eff * 1/0.9 charger PF = 1,584 VA
    • 1,584 VA / 120 VAC = 13.2 Amps AAC (AC2/GEN/LIMIT)
    So, you would set the VFX to 13.2 Amps (AAC) to limit the DC charging current to approximately 88.5 amps (guessing on my part the derating factors).

    It is a bit confusing--But they are doing these (particular) limits on the AC 120 VAC line in--So, in this case, you have to convert the DC current @ 12 VDC to AC current at 120 VAC to enter into the VFX controller's memory.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    So back to my inverter crash issue...
    It has not happened again...yet. I am monitoring that pump with my meter, and it typically draws 943 to 1083 watts. BUT I noted that at least once it went as high as 1500. hmmm?...maybe hitting some solids? Sorry.

    one thing I adjusted was the low voltage cutoff, lowering to 10.2. If I am monitoring the system, is there any reason why I cannot go even lower? What are the dangers to the components (I understand that you do not want the system drawing down the batteries for more than a few seconds), if any?
    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    How are you monitoring your power? A kill-a-Watt type meter is usually sampling about once per second--They do a very poor job of logging peak power/current/voltage/etc. It is not unusual for an induction motor to draw upwards of 5x normal operating current when starting (assuming the AC power source is capable).

    The low voltage cutoff is really there to help protect the AC inverter... They are constant power type devices--Power=Voltage*Current. If the voltage drops, the current rises--And that can overheat/fuse the internals of the inverter. So, I would not try to drop the batter cutoff below mfg. standard setting.

    Are you seeing 10.2 volts at the battery or the AC inverter's DC power input? Do you have heavy enough/short enough cables that you get less than 0.5 volts (recommended) drop from battery to DC input terminals at full load?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    edited October 2016 #17
    Well, if the cables were wrong, I think that would have shown up before this...they were actually longer for 6 years and I shortened them 2 years ago. The interconnections are 4 awg. From the inverter they are 5 feet max. They are 4/0.
    I did see a low of 9.9 on my MX summary screen before it woke up one morning after the cut out. This morning it says the low was 11.2 yesterday. So I think I am less than .5 drop...under full load I think the voltage would have been less than 11.7 yesterday at some point. I often can see 11.4 at the mate at a heavy load (1200 watts). So 11.2 is nothing unusual or low under a big load..
    I am only using the kill a watt. I do not have anything else, beside the MX display.
    I will boost the low cut off back to 10.5 then.

    Still no crash of the system since Wednesday night....I have been running the genny a bit more and doing some EQ since. The bank is healthier, reading 12.2 this am at daybreak, before anything turned on (just the fridge and micro draws overnight).
    That is a very good number with 2 batts in the bank, a typical number when I have 4 batts online.
    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
  • FreewilleyFreewilley Solar Expert Posts: 223 ✭✭
    Well, I postponed moving low voltage cutoff back to 10.5....and I am wondering if I should.
    I am seeing a daily low voltage from yesterday of 10.1
    So I guess I would still be seeing crashes if I move it back up.
    Hopefully I will be soon back to 4 versus 2 batts and this will not be an issue. It makes me wonder though as I have regularly used just one string of my bank (to EQ) and never seen a crash before.
    And about 4-5 years ago my batts were much weaker than this current set.
    Mate, VFX 2812, FM 60 & MX 60, 2 Full River AGM 400 6v, 1400 watt Solar Array, Yamaha 3000iSEB inverter gen
    12 volt Flojet water pump
    off grid summer home in northern Ontario
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