Unexpected Behavior of my system.

Here is my system specs.  
120v system 2800watt MSW Inverter supplying most 120 volt outlets in my RV from my 520 AH LA batteries. Batteries are serial/parallel connected Crown 260AH 6v LA batteries.   Inverter connected to battery bank by 4/0 5' cables.
Solar side.   4 each 160w panels series connected to a 100/50 Victron MPPT controller.   35' of 10 gauge wire from panels to controller, 6 gauge wire of 12" from controller to 4/0 Battery cables.

When in full sun controller is putting out 33 amps,  My house is using about 11 amps to power everything plugged in most of the time.  Bogart shows about 22 amps going into the battery bank.  That seems to be right  33 - 11 is about 22 amps what is showing is going into the battery bank thru the Trimetric Shunt. 

What I don't understand is if I use the toaster (85 amps) the power from the controller goes down to almost nothing.  And around then the 50 amp breaker between the controller and Batteries (on the 12" 6 gauge wire) trips. 

All I can guess is the Inverter is trying to suck 85 amps out of the controller (which is a 50 amp controller)  And that blows the breaker?

Do i need something between the controller and inverter to prevent that?  If that is what is happening...


4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 

Comments

  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    What's the current rating of the CC?

    Is the breaker DC rated? Is it polarized (with load/line markings, or a "+" mark)?
    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
  • PhotowhitPhotowhit Posts: 4,706Solar Expert ✭✭✭✭
    I take it the inverter is on a separate breaker to the batteries?

    The system voltage may drop a bunch with a 800 watt load + 10-12% for inverter (800 watt ÷ 11 volts =) 70+ amp load.  My guess is it's wired in-correctly and the breaker is between the battery bank and the inverter. 

    This is the only potential for an over load. If the inverter was still working after then something else is wrong. Even with the system voltage dropping and 640 watts of array incoming, doubtful you could get to a sustained 50+ amp load to flip a proper DC breaker. 640 ÷ 11 = 58 amps, but it's doubtful you could get that wattage out of your array in the heat and it would take a while for the breaker to flip, likely longer than a toaster running. Check the connections to the breaker for good tight connections.

    I guess the voltage could drop even lower, I think the magnum has a pretty wide voltage range. (I believe they are the only inverters with a wide enough range for Nickel Iron batteries) but if they are dropping lower than 11 volts, I would worry about your battery health if they are 70% full (I think that was the percentage discussed in the previous thread.)
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • bigbillsdbigbillsd Posts: 18Registered Users ✭✭
    edited October 6 #4
    Estragon said:What's the current rating of the CC? Is the breaker DC rated? Is it polarized (with load/line markings, or a "+" mark)?
    The CC is rated for 50 amps.  Its a Victron 100/50.   I have two 50 amp DC breakers,  one on each of the cables coming from the CC.  They are not polarized and are probably not the best quality from China.  I have decided I am going to replace them with Bussman 187060F-03-1 60 amp surface mounts when I get home in a few weeks where i can receive them from NAWS. 

    Not sure the new breakers would prevent the tripping as the toaster was pulling 85 amps.  Only available from the batteries. 

    -Bill 
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
  • bigbillsdbigbillsd Posts: 18Registered Users ✭✭
    Photowhit said:
    I take it the inverter is on a separate breaker to the batteries?

    The system voltage may drop a bunch with a 800 watt load + 10-12% for inverter (800 watt ÷ 11 volts =) 70+ amp load.  My guess is it's wired in-correctly and the breaker is between the battery bank and the inverter. 

    This is the only potential for an over load. If the inverter was still working after then something else is wrong. Even with the system voltage dropping and 640 watts of array incoming, doubtful you could get to a sustained 50+ amp load to flip a proper DC breaker. 640 ÷ 11 = 58 amps, but it's doubtful you could get that wattage out of your array in the heat and it would take a while for the breaker to flip, likely longer than a toaster running. Check the connections to the breaker for good tight connections.

    I guess the voltage could drop even lower, I think the magnum has a pretty wide voltage range. (I believe they are the only inverters with a wide enough range for Nickel Iron batteries) but if they are dropping lower than 11 volts, I would worry about your battery health if they are 70% full (I think that was the percentage discussed in the previous thread.)
    The Inverter has a single 400 amp Fuse inline on the 4/0 cable to the battery positive lug.   The controller has two 12"  6 gauge cables, each wire goes thru a 50 amp breaker, then onto the lugs on the inverter to use the 4/0 cables over to the battery compartment.   After I trip that 50 A breaker coming from the CC the inverter is still working as normal.  Its just not seeing any current from the panels anymore.  You are correct the highest wattage I have seen the panels produce is just above 500 watts. 
    The batteries are 8 month old Crown 260 AH 6 volt's.  Wired Serial/Parallel giving use 520 AH.  They have been working well and babied, never discharged more than 30% and charged right back up.  Water is well maintained with a BWS. 

    From what I have been reading there isn't something else needed between the controller and batteries to keep the inverter from trying to pull 85 amps from the controller?   Like a big diode device?  

    Scratching my Head over in ABQ...  -Bill


    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
  • mike95490mike95490 Posts: 7,913Solar Expert ✭✭✭✭
    I let my inverter pull from the charge controllers all the time, in the daytime.  Otherwise, it's wasted power, not getting used.
    Wire everything to the battery bus, let the electrons go where they will
    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 ,

  • bigbillsdbigbillsd Posts: 18Registered Users ✭✭
    mike95490 said:
    I let my inverter pull from the charge controllers all the time, in the daytime.  Otherwise, it's wasted power, not getting used.
    Wire everything to the battery bus, let the electrons go where they will
    That's how I originally thought it should work, but after that breaker trips I am starting to wonder what I am not understanding. 
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    Most DC rated breakers I've seen are polarized. The line terminal is for the battery, load for the controller. It may seem wrong that the load is the charge controller, as in normal operation, the battery is the load. In a fault (controller fails shorted) though, the short is the load, and the battery is the current source.

    This is why I asked about the breaker and controller. A polarized DC rated breaker, properly installed, really shouldn't be opening from the toaster load IMHO.

    Replacing the breaker is probably a good idea. Being suspect in the first place, and having opened under load at least once, it may have arc damage and be prone to heating in normal operation.
    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. Posts: 27,904Super Moderators, Administrators admin
    Your solar array + MPPT charge controller can output upwards of 50 Amps on a clear/cool day with a good size load on the battery bank (and/or if battery bank is significantly discharged).

    For US/North America circuit breakers, I use a 1/0.80 (1.25x) derating factor for continuous loads. Circuit breakers are designed to break at 100% load (may take minutes to hours), and not break at 80% or less load...

    For a 50 amp branch circuit, I would design the wiring and breaker for: 50 amps * 1.25 NEC derating for continuous current = 62.5 amps

    And I would "round up" to the next standard size (i.e., 75 or 80 breaker+wire rating).

    To confirm what was typed above... The electrons will flow from where they are sourced (battery bank, charge controller, etc.) to the load(s) (AC inverter, other DC loads).

    When you run heavy DC loads, the charge controller should be the "first source" of energy (i.e., you want the controller outputting 50 amps, if there is enough sun, and 35 amps from the battery bank... Vs zero from the charge controller and 85 amps from the battery bank (battery bank should only supply all current at night/during bad weather).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bigbillsdbigbillsd Posts: 18Registered Users ✭✭
    Thanks for your explanations.   I used these inexpensive breakers from Amazon.  https://amzn.to/2ylTJG7   Probably should not have in hindsight.  The company says they are non polarized.  I thought that was odd.
    Controller input from panels is on the top as pictured and battery to the bottom right.    The one that trips is the bottom one on the battery side.  -Bill
     
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
  • BB.BB. Posts: 27,904Super Moderators, Administrators admin
    Another point to ponder...

    This is an RV? And you have the RV "house battery negative bus" grounded to the frame of the RV? Correct?

    If so, then you should not have any circuit breakers in the Negative wiring.

    First, it is not needed. With a negative to ground bonded power system, the negative wiring never gets above zero volts (maybe a few tenths of volt). So there is never any worry about a negative to ground short circuit (no breaker needed).

    The other reason to not use a breaker in the negative wiring (and code does not allow you to put breakers/fuses in ground bonded neutral power systems like North American home wiring)--If the negative breaker trips from over current, it does not shut off power to the devices (loads). But leaves than at +bus voltage (or +120/240 VAC for house wiring) and sets a trap for somebody working on the system (breaker off, must be no voltage in the system).

    For certain power systems (large ships, floating or isolated power systems), they do put breakers in the +/- (or the two outputs)--But they use "ganged breakers" that if one side trips, the other breaker is turned off at the same time (like the 2 pole 240 VAC breakers we use in North America).

    So, at the very least, you will save money on breakers... You will only need 1/2 the number as you only use them in your + Busing.

    Newer DC breakers (at least those NEC/UL/NRTL rated) are supposed not to have polarity (designed to break current flow in either direction). And many "unknown" certified breakers are designed to not interrupt very large amounts of current.

    For example, North American Home breakers are rated to 10,000 Amps Interrupt Current. That is the estimated/designed maximum current from a pole top transformer and down lead to the home.

    When doing a "real engineering" design system, you need to look at the amount of current available in the case of a dead short.... A 12 volt battery bank for off grid solar can output a 1,000 Amps or more into a dead short. But the wiring resistance may limit the real short circuit current... (12 volts/1,000 amps=0.012 Ohms of wiring resistance--That is pretty low resistance/heavy copper wiring).

    Not your brand/model of breaker (I do not know what it is)... But here is an example of what a spec. sheet can look like. Here is a Bussman marine breaker, similar to yours, specification (Northern Arizona Wind & Sun--shameless plug for our host):

    https://www.solar-electric.com/mrcb-200-amp-marine-circuit-breaker.html

    And the spec. sheet:

    https://www.solar-electric.com/lib/wind-sun/Bussmann-MRCB.pdf

    Interrupt Rating: Main Breaker Protection Interrupt Rating (5,[email protected] 14Vdc, 3,[email protected] 28Vdc and 1,[email protected] 48Vdc).

    And from the graph, it will (almost?) trip at ~150 to ~600+ seconds at 100% rated current at 70F (there is a + tolerance band too).

    Since these are thermal breakers (rather than magnetic current trip), they also have a temperature trip curve... 150% to 50% of rated current (from -50F to +250F, including the "tolerance band"). It is much easier to design with a bit of margin of error/conservative (i.e., fudge factor with 1.25x heavier wire and breaker larger than expected current) than to run much of this stuff "at rating" and assume that everything is OK.

    We are very used to plugging stuff into our home and everything works... But most of those items draw much less current than the circuit's rated capacity. But when we put loads on the system that are at the very margins of rated capacity, we hit problems...

    For example, I take care of a small apartment building with electric hot water. The elements draw around 20 amps @ 240 VAC. They were built ~60 years ago, and the breaker panel had 20 amps breakers and 14 AWG wiring.

    Not sure why, but the NEC table lists 20 Amps as OK for 14 AWG in the table but has a footnote that says not to use more than 15 amp breaker on 14 AWG wire... Anyway, 50-60 years later, on occasion a breaker will false trip for the water heater. And eventually, the false trip happens more and more often. I had the electrician pull out the 14 AWG wire (wiring looked fine, no signs of overheating), and replace it with 10 AWG wiring and a  30 Amp breaker (20 amps * 1.25 NEC derate = 25 amps). 12 AWG is limited to 20 amps, so I needed 10 AWG. Needed another breaker, so uprate to 30 amps. Now, no more false trips, and no more failing breakers over time (I hope). Interestingly, there are 4 units and only one unit had this problems where I needed to replace the 20 amp breaker....

    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

    -Bill "that boring engineer that types too much and still makes mistakes" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Posts: 2,840Registered Users ✭✭✭✭✭
    I think the reason they're not polarized is they're designed with lower voltage/current interrupt capabilty, which is okay for many marine or car audio applications, but not ideal for connection to big battery banks.

    Breakers like the midnite ones sold by NAWS have arc chutes or whatever to handle higher current interrupts without blowing to bits
    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. Posts: 27,904Super Moderators, Administrators admin
    Here is the Midnite Breaker Spec. Sheet (made by Carling Switch?):

    https://s2.solacity.com/docs/Midnite/Carling_F_Series.pdf.pagespeed.ce.0FVFif0Y8O.pdf
    Maximum Interrupting Capacity 50,000 amps @ 125VDC
    More information here:

    https://www.solacity.com/product/midnite-solar-mnedc250/

    Breaker installed correctly and reverse polarity:



    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Posts: 27,904Super Moderators, Administrators admin
    Some more AC/DC breaker videos:



    The "Amazon" breaker is here:

    https://www.youtube.com/watch?annotation_id=annotation_3580510729&feature=iv&src_vid=S0diAeysxVo&v=WTA-TQ14XAo

    Midnite's Breaker basics:



    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Posts: 27,904Super Moderators, Administrators admin
    Oh, I forgot to add why to never install a breaker/switch/fuse in the ground/return of a ground reference power system...

    Especially, in the olden days, we had lots of ground reference communications interfaces (RS 232 was very common). Typically, these comm signals were referenced to ground/DC negative power lead. If you popped the DC negative power lead with a breaker, then the "ground reference" inside the communications device would "see" voltage and current on the ground lines and typically pop a trace on a connected device.

    Grounds that were "hot" (or at least not near zero volts) between two grounds (in a data center, telephone central office, etc.), we would see lots of Wyse Terminals with blown RS 232 comm ports (the ground trace was fused).

    There are some solar communication systems (controller to inverter to combo device/laptop, etc.) that could be damaged by "lifted" DC negative connections back to the battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bigbillsdbigbillsd Posts: 18Registered Users ✭✭
    Very interesting.   I finally found a 60 amp breaker locally,  at a sportsman warehouse of all places, it was for a trolling motor.  I replaced that and the next day the 50 amp cheapo breaker on the negative side tripped.  I went back, bought another one and installed it.  When I get back home I will just wire that direct, and also buy a bussman that has a button to trip the breaker.  The ones I could find locally did not have that feature,  just the lever that pops out when tripped to allow a reset.  -Bill
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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