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Nickel-Iron technology Off Grid Solar Power

Q15: Solving electrical problems?

(1) An MPPT problem

I am going through adding distilled water too often. The MPPT keeps adding 100% of current all the time as bulk, and never slows down the current to a trickle, when reaching float. So something is wrong.

I read about adding a cable to make the two or three MPPT's work together as one, but while this is possible now, it is not really necessary.

My MPPT boxes are NOT folding back the current as the voltage rises.

So as an experiment I removed 100 amps as a load, both bore pump and water pump, now my daily loads are

  • fridge per day (about) 20 amps
  • washing machine per day (about) 20 amps
  • LED lights per day (about) 5 amps
  • other 5 amps per day

    This is a total of about 50 amps per day.

    So with 60 amps coming in, the bank should be at float in one hour of charging,but the amps keep coming in all the day, for 5 hours, dumping 300 amp hours into the bank.

    So the result of all this is over charging and loss of electrolyte.

    Here is Zeus, because of the 35Volt panels in parallel give 16A, this makes 30 V bulk and 18 A going into batteries.

    Here is Trina, because of the 68Volt panels in series, and parallel gives 9A, this makes 28 V bulk and 22 A going into batteries.

    Adding these two chargers together we have 40 amps coming on at 9 am so far.

    The view of the laptop and the user volt settings. (H2 pipes removed)

    Not sure how to save the settings? do they save automatically on exit?

    The view of the userface for user defined settings of battery.

  • absorb is now 32V
  • float is 28 V
  • equalization in 30V

    Hoping this gives my MPPT boxes the chance to fold back the charging current.

    I quote from Victron, from experts:

    " There can be some conflict in the transition stages, from bulk to absorption and absorption to float. If one controller switches earlier than the others, they will not all contribute to power the system , at least not ideally. The one with higher voltage will dominate. But will not harm anything. When all controllers are in same state, there are no issues."

    So two or three MPTT's should work OK?

    "Each MPPT will behave according to the battery voltage it reads. And will work independently from each other. They will almost never be exactly in sync with each other, due to different voltage drops in cable lengths between MPPTs and battery bank. The different cable lenghts, will result in slightly different voltage readings, which in turn will give the MPPT different "instructions" on what to do." c should work OK?

    "Connect them together with a network cable. Use the VE.Can communication ports for the cable, and don't forget the VE.Can terminators. That is all! No pc configuration or any special settings needed ."

    So two or three MPTT's can be connected together, but how? no images and no ports do I see on my Mppt boxes?

    Something is wrong and I need help in understanding the user defined battery settings, Victron does not explain fully the process?

    Something is missing?

    What my system look like completed.

  • Five inverters
  • Three charger controllers (2 in operation)
  • H2 gas pipes to remove gas
  • Fans to assist air flow

    What my system needs is help, getting the charging process to fold back during float.

    Zeus is already on float at 11 am, and shows no current coming into battery. Seems working OK.

    Trina is o n bulk and has all current coming in. NOT OK :(

    So I restore Trina battery settings to default rotary user 2.

    This is the only thing that works??

    That means Trina uses a different voltage charging to Zeus. A lower one.

    Now I have both on float as they should be (its 11am and 60 amps is available- but not required), but the battery settings for Trina are not properly working, only when on default.

    Why is that? Maybe the MPPT Trina is a dud?

    Connected back all loads, so test the system under heavy 100 amp loads.

    See what happens in the day.

    It's noon, so I did some watering, and noticed the bore pump also switched on to fill the water tank. Both of these applicances used (water pump 18 amps) and bore pump (23 amps) a total of 41 amps, plus the fridge (4 amps) equals 45amps.

    The MPPT boxes are still on float, which it should be, because float means the battery bank is fully charged, and on a sunshine day I can get 60 amps from the solar panels.

    So when the water pump stopped, after 4 hours (takes only 110 amps to fill the tank); I was left with 27 amps going out, (fridge and bore still on), so Trina had 27 amps coming in. Zeus shows no amps coming in. Both on float.

    This is normal, batteries are fully charged, 27 amps going out and 27 amps going in.

    Is it possible to test the solar controller with more than 60 amps of load? Hmm? Not sure we can load the battery to more than 60 amps?

    Switched on 2 fans, all lights, water pump, bore pump, etc, and got a total load of over 45 amps. The voltage dropped to 24.6V.

    The solar chargers responded as follows:

  • Trina ( default setting 2) 30 amps : BULK
  • Zeus ( user defined) 30 amps : FLOAT

    This seems OK, so now let's see if Trina returns to FLOAT, now that I have reduced the loads once again.

    It's 2pm, getting wrong angles for solar incoming power, so I ran out extension leads and removed 50 amps load from battery bank. Now there is only 4 amps going out from fridge.

    Trina (under the default rotary 2 settings, not designed for Ni-Fe settings) has moved from bulk to adsorb and sending in 1 amp. OK this is normal

    Zeus, (under user defined settings for Ni-Fe) has moved from float to bulk, and dumping a massive 29 amps into the bank. This is NOT normal, going to overcharge my battery cells and remove too much water.

    Why doesn't Victron offer user defined instructions in infinite detail, so users understand what they are doing wrong?

    Trina is now at absorb, 30 minutes later, and Zeus is at float. The voltage is 28.6 which is higher for a Zeus float, (28.0 V). The rotary default setting does not define their voltages??

    I am confused by the lack of details,, and the lack of documentation, but things seem OK for now, except Trina is on a default setting. This means the default setting is a secondary for charging and Zeus is the primary MPPT setting set at 32V bulk charging, so one MPPT leads, the other MPPT follows.

    Hopefully I will figure out why Trina cannot be set to user defined, will try swapping it for a new MPPT.

    (2) Battery storage problems

    Another problem I noticed is the lack of battery amp/hr storage. One is supposed to have 500 amp/hrs of storage. In practice it's probably 400 amp hours.

    So if the battery was fully charged today with 28Volts by 2pm on float. When one runs a water pump for 2 hours, with a bore pump for 1 hour, this equates to 40 amps for water pump, (it consumes more amps as the invertor gets hotter) and 30 amps for the bore pump (inverter getting hot). This is around 70 amps, or about 85% fully charged battery. (70/500 as a percentage) So the battery voltage should be (assuming 28 V is 1 00%) 24V. I don't get this.

    If the charging is OFF, does the voltage drop to 24V? Hmm?

    In this case the voltage should drop to, 20.6V.

    This is what I got. The voltage is 21.8 V, the low voltage alarm is coming on the Inverter.

    The solution is to set the low alarm for the Inverter to 18 Volts.

    Of course lowering the bulk charge from 33 volts to 32 volts, is quite a drop in the battery storage capacity.

    All this documentation while helping me learn stuff, is left here so other readers can experience solving problems too.

    Next some solutions hopefully.

    Ni-Fe battery technology

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