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Nickel-Iron technology Off Grid Solar Power

Q10: Off Grid - Make over

After a make over with new solar panels, before removing the blankets, I adjust to a user defined voltage charging:-

Conecting to each MPTT, under battery setting, user defined,I changed the charging parameters to :

  • bulk-absorb 33.0 volts
  • float 29.5 volts
  • equalization 32.0 v

    Showing you how to adjust voltage numbers...

    Wire the leads into the MPTT boxes.

    Than remove blankets, and let the sunshine charging begin.

    Wow. Nice, the 60 amps, I need as a minimum for our 500 Amp /hr system.

    At 60 amps, and 5 hours, I should get 300 Amp/hours, almost one day to charge fully from 60% to 100%.

    I do have a third MPPT, so need to charge even more, say to maximum of 90 amps.

    But you always get less than maximum, cloudy, overcast and rainy weather.

    Now let's get some wires to the house.

    Next I weld, bolt and make C channel beam to the house wall (7 metres away) for the holding and delivery of three 1.5mm2 twin and earth cables, and one 6mm2 twin electrical lighting wire. These four cables fit inside a 32mm orange conduit pipe, that sits inside the C channel to the house. Safer to do it this way, than underground, also cheaper option.

    Once you get your pipe lengths OK, the tricky bit is feeding the cable into the conduit, also elbows and junction box at end, that breaks down to a single conduit pipe leading off to a power point.

    Estimating the length of wire is hard, the pipes consume more than you think they do.

    Under the house showing partial completion. Notice the four cables inside the 32mm conduit break down to three 25mm conduit cables later.

    Two 25mm conduit pipes is pictured.

    The orange conduit is left unpainted to visualize an off grid system. Notice the C channel steel carries the cable over from Power House. Remember off grid means your 240V supply has nothing to do with mains power or mains power. It means off grid, all your mains wiring and mains powerpoints are redundant. Eventually you can ask the power company to disconnect you from the mains.

    Had trouble with water pump fuse keeps tripping. The pump runs on 516W, and 20Amps the current battery voltage is 26V. I had to change the fuse to 50Amps, and notice for a brief second the in rush current of the pump is a fraction over 27Amps, so the inductive loading is tripping the 30Amp fuse.

    The system so far, will have 5 Inverters up the wall, three rated at 930W and two rated at 560W. Each one has its own single powerpoint. Why so many? Cheaper than single larger one, and more redundancy, robust design. If one Inverter fails, the system has functional running. Three 1.5mm2 wires goes to the house, and two 1.5mm2 wires remain in the power house.

  • One 930W is for a 240V fridge.
  • One 930W is for kitchen appliances.
  • One 930W is shared daytime to washing machine, and night time to TV and fan.
  • One 930W is for water pump.
  • One 930W is for bore pump.

    In theory the system is designed to remove 5 units of power daily, while the storage is 15 units of power. This allows 2 days of backup.

    Close up of the user define MPPT voltage values.

  • Absorption voltage = 33V
  • Float voltage = 29.5V
  • Equalization voltage = 32V

    The two in series makes 64VDC, the two in parallel makes 2.5Amps at 7:00 AM. The MPPT turns this into 26V @ 6 amps. So Trina is running OK.

    The system so far, with future expansion for 5 inverters and 3 MPPT controllers.

    The default settings on each Victron Inverter.

    Noticed a black sludge over my electrolyte cap.

    What is causing this? Is it a problem?

    Hopefully my friend David Bartlett, from Iron Core Batteries, can help me out, with advice.

    David from Iron Core Batteries Australia, says my system is fine.

  • Adding a third string is OK
  • Carbon in the water is normal.

    "Some say" the carbon is placed into small bins in the plates along with the active nickel anhydride chemical to promote better conductivity. So the carbon leaches out for a while, and might reduce the chemistry efficiency of your battery over the years.

    "Some say" the KOH has a tremendous affinity to react with CO2 in the air, producing Carbon in the water. Nobody knows the exact chemcial reactions , in total.

    So this is the best regarding the carbon residue. After about 8 to 10 years, the KOH eventually pulls so much carbon from the air, that the electrolye is too sluggish to function properly, and one needs to drain out the KOH and sludge and immediately fill the cell with fresh KOH solution again.

  • David says to watch the night time loads.

    So everything is working so far satisfactorily.

    Next some details in wiring up more inverters, and getting the powerpoints into the house, as well as finishing touches.

    Ni-Fe battery technology

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