Discrepancy in charging behavior: Midnite Classic 150 and Outback FX3648

2twisty2twisty Solar Expert Posts: 199 ✭✭✭
I've had a strange problem for a while now:  When I'm running my generator to charge my batteries, it's behavior is rather drastically different from my Classic 150 when charging from solar.

My Classic will decide that the batteries are at float LONG LONG LONG before my generator will.  All the setpoints are the same for float voltage, absorb voltage, absorb time.  So I would think that if the classic decided that the batteries are full, why would the FX when supplied from the generator say that it's still putting 2200W into the batteries, while the Classic says that it's Over Volts? 

I thought perhaps there could be a need to adjust the voltage offset, so I started taking measurements and got some bizarre results.




My cables from the FX to the batteries are all 4/O.  The cable from the Classic is 4AWG to the distribution block shown.  From my understanding, that 4AWG can carry 80+A at 48V nominal, and I'm not putting even a third of that through the cable, s voltage loss should be minimal.

When the generator is running and the FX is charging, if I measure DC Volts at the distribution block, I get 65ish volts (way too high for absorb, right? that's more like an EQ charge?) and when I measure right at the posts of the FX itself, I get 165VDC.  Yes, that's 1 hundred sixty-five.

So when I move down the cable about 24" to the dist block, I get 100 volts less?  That's strange.  Sounds like something may be wrong with the FX....

Anyway, back to the original issue.  Since both devices are set the same, why (unless it's broken) would my FX want to continue charging for a whole lot longer?  The classic uses End Amps.  Could my End Amps be too high?  My SG readings are rather low when the Classic says they are at float.

There are many variables here and I think that's where my problem lies.  Variables compounding each other.  Please help me figure this out.

Comments

  • EstragonEstragon Registered Users Posts: 4,303 ✭✭✭✭✭
    How big is the bank, and what do you have end amps set to?

    Do you have RTS temp compensation on fx/classic?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    Looks like my end amps was high.

    Bank is 416 ah. It was somehow set to 6.8. I lowered it to 4, rebooted the classic and it went into bulk.

    I had to leave to take my wife TO the ER, so updates will have to wait until tomorrow.
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    I also hadn't rebooted the Classic in a while.  I used to have it reboot nightly, but due to a bug (feature?) in the firmware, it caused AUX2 to go high on the reboot -- and that's the signal I use to autostart my generator.  So every night my generator would start and I'd have to come out of bed and override it....so yeah..I turned off the reboot.  

    I might turn it back on again though.  There have been a couple firmware updates since I last messed with it,  I'll report back once I get to float with the new settings and measure SG.
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    Well, poo.  After charging with the generator until the FX decided it was done, the SGs are still low.  In the 1.235 - 1.250 range.  I just spot checked a few cells across the bank to see.  The numbers are better than before, but still VERY low.

    I'm running a solar EQ now. Hopefully it can bring them up some, but I'm thinking that I'm headed into the "killed a set of batteries" territory.

    This explains some of the other things I've been seeing, like a power cut last month due to LVD.   Time to start budgeting! 

    I think this was mostly due to the fact that I overfilled my cells and the overflowed, causing a loss of acid.  I talk about it in my YouTube video about filling your batteries.

    I'm gonna start a new thread on a related topic.


  • BB.BB. Super Moderators, Administrators Posts: 29,825 admin
    What voltage during charging are you measuring at the battery bank (middle of the day bulk/absorb, not float. Also what is the genset charging voltage for the bank)?

    Do the measurements with a known good DMM (new battery). double check the meter on your car battery to get an idea if the meter is sane.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    OK. I'll have to get that data later.  I'm running an EQ now to see if that will bring SGs up.  I will measure tomorrow during bulk.
  • BB.BB. Super Moderators, Administrators Posts: 29,825 admin
    What EQ voltage and current are you running now?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    Due to a dusty sky, I am using the FX and the genset to do the EQ. The FX's EQ voltage is 61.2  I didn't find an amperage setting.

    It hasn't even started the EQ yet.  FX says the voltage is only a 57.4 and it's still putting 2100 W into the batteries. I'm not sure how to interpret that.
  • westbranchwestbranch Solar Expert Posts: 5,176 ✭✭✭✭
    It's telling you the batts are in poor shape at this time..

    If you haven't rebooted in a while you probably haven't updated the FW in a while, there was a new version posted about a month ago IIRC....  may be worth it  to update etc while you are at it...

    Also what is your minimum ABSORB time set to?  you may need to move it up to 3 to 4 hrs to get a good charge before doing an EQ if the SGs are that low ,1.235
     
    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
  • EstragonEstragon Registered Users Posts: 4,303 ✭✭✭✭✭
    Supposedly the bank is taking ~35a to get to EQ voltage. If it's taking a while, like hours, to get there, I don't think that's necessarily a bad thing. To me, that suggests the classic is ending absorb too soon and the bank is undercharged but still taking a charge (not completely sulfated).

    Still, earlier in the thead you saw some odd voltage readings from your FX. I would watch the charge/EQ closely and use SG and battery temp to tell me when to stop. To me, the first priority is to get batteries charged properly, and then to figure out what's going wrong.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 29,825 admin
    • P=V*I
    • I=P/V= 2,100 Watts / 57.4 Volts = ~36.6 Amps
    You are not even 100% charged at this point... You probably want the controller/charger to "hold" (absorb) for 2-6 hours, 2 if shallow discharge, 4-6 hours if deep discharged.

    For EQ charging, once the regular bulk/absorb charging is finished (tailing off to 1-2% rate of charge or 2-4 amps), then run your 61.2 volts EQ voltage. For EQ you are setting the voltage to get around 2.5% to 5% rate of charge and hold. Check SG every 30-60 minutes for all cells. Once all cells' EQ stops rising--Then that are your new 100% charged SG numbers (log temperature corrected SG for each cell--Pick one "pilot cell" to check your state of charge/SG every week or month to make sure you know what the battery is doing).
    • 416 AH battery bank * 0.13 rate of charge = 54 Amps highest "cost effective" solar rate of charge
    • 416 AH battery bank * 0.10 rate of charge = 42 Amps nominal "off grid" solar rate of charge
    • 416 AH battery bank * 0.05 rate of charge = 21 Amps minimum recommended solar charge/nominal equalization charge(weekend/seasonal solar)
    • 416 AH battery bank * 0.025 rate of charge = 10.5 Amps minimum EQ charge rate
    Note that even a 2.5% rate of charge into a full battery bank (i.e., EQ charging), can easily overheat the battery bank if kept up for 5-10+ hours (roughly 50% of the charging power goes into heating the bank). If the bank gets too hot (over ~110 to 120F, check with Mfg.), stop EQ for the day are resume the next day or so. This can take many hours or even a few days to get the SG high/to spec. in all cells.

    Make sure that the cells are no more than 1/2 full (plates are covered)--Filling cells to capacity then running high Absorb/EQ will generate gas and expand the electrolyte--leaving you with a mess on the tops of the cells and losing acid.

    If you are using a genset--You don't need to use your 8+ kW genset, you only need to pump (say max EQ of 21 amps * 61.2 volts=) 1,285 Watts into the battery bank--A smaller genset (more fuel efficient) genset can run this load.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,500 ✭✭✭✭✭
    If you overfilled cells and lost acid, you will never see 100% on a hydrometer.  Best you can do is to charge till SG stops rising, and that's your new full.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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

  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    Would there be any sense in obtaining some sulphuric acid ad adjusting the concentration back to standard?  My plan of action would be to charge until they won't go higher on both SG and voltage, then add enough concentrated H2SO4 to bring the cells back to 1.260 or so, then charge again.

    Would this have any benefit?

  • PhotowhitPhotowhit Solar Expert Posts: 5,041 ✭✭✭✭
    2twisty said:
    Would this have any benefit?
    In general, no. The sulfate is there affixed to the lead plates and hardened or sluffed off and sitting in the bottom of your battery. The idea in equalizing is to recombine or remove the hardened sulfates.

    Did we ask you how old the batteries are?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • PhotowhitPhotowhit Solar Expert Posts: 5,041 ✭✭✭✭
    Hope all went well with your wife and ER.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    String one is about 2.5 years old.  String 2 is 1.5.  String 1 is the one that is acting up the most.  I am operating only on string 2 at the moment.  

    Wife didn't go well at ER.  She's still in the hospital with kidney issues and dangerously high potassium levels.  :(
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