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| Q21: Victron Smart Solar MPPT Remove the old Blue Solar MPPT and replacing with the new Smart Solar MPPT. The updating of firmware was tedious. I have three MPPT connected so far. Will in future connect FIVE MPPT boxes. And keep current under 100 amps, averaging 60 amps. Getting the Smart Solar MPPT to join my existing network to the Battery Smart sensor took some time, but I figured it out. Had to look up Victron manual for how to connect and set up existing network. Had trouble getting them all to sychronize. When you create network in Smart Battery sensor, only create one network. When you go to VE connect in each MMPT controller and click join existing network, do not click "leave network", use the back button instead, and on the main screen of the MPTT you see in the top right corner a icon network button.Than all is good. It's 11:00 am and all my MPPT controllers are on FLOAT. Amazing. The monitor says 95% SOC and the voltage is 28.8 V, and the incoming current is zero, the water pump loads etc are removing 10 amps, but the float current is not keeping up. No matter for now, some success, I think?
At the moment we have 21 Volt, 70% SOC and drained 100 amps from our batteries. The voltage is hard to read for SOC, as loading batteries causes them to drop to 20% SOC and under loading them causes them to rise to 70% SOC. So you never really know how much power you have left in practice, only in theory.
Today we used 100 Amps last night, and I had to write the battery capacity to 200 amp/hr, reducing the SOC to 33%. For some reason 100 amp/hr or thereabouts is all the useful storage my bank has. I notice we have 7 amps coming in as sunshine, and when I turn off the water pump and bore pump, the voltage rises to 28 V, but when turn on bore pump (20 amps) and water pump (18 amps) the voltage drops within a minute to around 19 volts, meaning my inverters fail, the storage is dead flat. So this means my batteries only hold about 150 amp hours, under load, or 200 amp hrs with no load. Not real good for a manufactured 500 amp/hr battery bank? What puzzles me is it takes so long to charge 150 amps? Under a condition of 60 amps coming in, the float should be reached in just 3 hours. (this is 180 amps, less efficiency factor).
Wow nice info from Victron Forum people. Today I have :-
Convert these to amps in and amps out, divide by 24 volts and we have in theory(excluding efficiency):-
My yesterday deepst discharge was 137 amps My last discharge was 9 amps so for tonight, I should have at least 300 amps for night, in theory I have 433 amps, so why does my voltage drop to 19 volts under the water pump load in the morning, as 18 amps? especially since I only remove 100 amps overnight? Yesterday things went well, used 4000 watts to charge the batteries. Correct. However today the voltage is 23 right down to 19 when under load of 18 amps from the water pump. How did we lose all that 400 amps, overnight we used 100 amps, and today with 300 amps remaining the voltage cannot handle a load of 18 amps, and so drops to 19v? Something is not right here? I clear history and start again. Will move all major loads to mains, (bore and water pumps - 40 amps) and test how long to float my batteri es and how many amps? Today I have :-
This is I used 70 amps last night but the batteries got charged 416 amps. So today with all major loads still removed, I want to see if tonight I use another 70 amps and it only takes a few minutes to charge again? Have cleared history again, so we wait and see if my batteries reach float really fast. At the moment it is 8 am, the amps coming in is 8, batteries still gurgle on 29 V, and all MPPT's are on bulk, so we see how long it takes to fully charge the overnight use of 70 amps. I topped up the water again, 125 ml per cell, NOT sure if my batteries are still overcharging? The loss of water is slowing down, but still happens? I notice a trend in the Mppt history max volt and min volt over time eg Trina
Seems like every second day my batteries reach 19V, dead flat? It's 8:30, 60 amps coming in, 25 amps gone into batteries charged, according to monitor, that 40% charging efficiency?? Not sure? Monitor has an efficiency set at 80% at the moment. Cell voltages are 1.4 V per cell. It's 9:00 am, 31.7 V and 70 amps coming in, charged 900 watts, that is (900/24= 37 amps) Batteries still on bulk, but I only used 70 amps last night? And have replaced already half of what I used last night? It's 9:05 am, 31.9 V and 68 Amps coming in the Mppt's all on ABSORB, have charged 1300 watts or 50 Amps, so this seems OK, for last night, ie Absorb state. The total available amps coming in is already trailing off. So it really only took the panels 1 hr to reach Absorb state, and in theory this is about 80% SOC. Now let's see how long it takes to reach FLOAT, with only 3 amps of load on the batteries, 240 V (135W) fridge, 24 volt water pumps and 24 volt computer extractor fans. All major loads (40 amps - the water pump and bore pump) turned off, for now. By 10 am, batteries reach float, total charge was 3000 W or 125 amps.
Cell voltages are 1.43 V per cell. Two say 1.42 V per cell, and one at -ve end says 1.44 V. I will change the monitor charge efficiency to 65%, and will see. So on a daily load of just 70 to 100 amps, all day, the batteries are working fine. They show 400 Amp/hr of storage, and the bulk time (1 hr) absorb time (1 hr) and float time (+ rest of sunshine) is all perfectly normal. We did not lose any power storage over night, all the remaining 300+ amps was there and it only took 2 hours to place the consumed (70 amps) current back again. I will leave this for another day to confirm everything is fine for such small loads, than later try this again for bigger loads.
Graph from : SOURCE Why is my cell voltage only 1.43 at Float, and not 1.6 V per cell? Why didn't it rise during charging? from 1.40 to 1.43 V isn't much? I will check this tonight. Last night, consumed 65 amps, 1900 watts or 1900/24= 79 amps, the batteries got 3200 watts or 3200/24= 133 amps. So the efficiency of charging is 79/133 = 59% The SOC is 400-79/400 = 80%, the monitor records 86%. The voltages of each cell at this SOC is 1.31 and 1.32 near -ve end. They say to change electrolyte if the specific gravity falls below 1.19 Will need to check this, and whether my KOH solution is spoiled by over heating the batteries, and over charging them. I might place a constant 20 amp load on the batteries, turn off all incoming current from solar panels, and test how many hours to run the batteries to 19 Volt, ie: 20% SOC? The monitor can measure the amps discharged, so I will get an idea of my battery storage and voltage drop. The current voltage is 26V, the amps should be 300A or so. And the cell voltage is 1.31 V. Draining 20 amps per hour, the water pump should take 15 hours to run until battery empty. Yeah right? I will be happy to run the water pump for 4 hours, so we will see. The cell voltage is only 1.3, not 1.5 or 1.6, so I suspect I should be 50% charged? Hmm? It's 6:20 am, panels on float because they are switched off, voltage is 25, amps draining at constant 22 amps, only the water pump is running. I will run the batteries down to 19 V. It's 6:27 am, Voltage is 24.9, cell voltage is 1.29 V, with 22A leaving battery.. Moniter says I have drained 100/24= 4 amp/hr so far. It's 6:45 am Voltage is 24.0, cell voltage is 1.28, with 22A leaving battery, the monitor says I have used 300/24= 12 amp/hr so far. It's 7:30 am Voltage is 23.0, cell voltage is 1.27, with 22A leaving battery, the monitor says I have used 600/24= 25 amp/hr so far. Voltage drops with constant 22A load..
Inverter no longer runs pump. So on no load, battery recovers to 23V and 1.30 V per cell. So the total amp/hr used in my batteries is 1100/24=45 Amps The monitor says I used 50 amps, + 117 from last night, makes my useful amp storage as 167 Amp/hr. Funny when you switch off solar panels, they assume FLOAT stage, and when you switch them onto the batteries again, they still assume FLOAT stage. Hence last night my little batteries went into 19V from sunset. So I removed all the loads off them. Today things should charge normally, in BULK, and charge into FLOAT. I need a hydrometer to verify that my electrolyte gravity, ie: chemistry (KOH and nickel hydroxide). They say to change electrolyte if the specific gravity falls below 1.19. So I suspect I may have to change the battery electrolyte, seems stange do this only after two years of use. Arn't they still under warrenty? I have tried really hard looking after them, and from my inexperience, have not done things as properly as I could have. My understanding is you replace the electrolyte solution, and you respectively get a new 500Amp/hr battery back again ! So I am quitely hopeful, all things will turn out good, and this helps other readers about Ni-Fe as a really good technology. I have read on forums of others replacing dead cells? What is a dead cell in Ni-Fe ? No such thing, unless it wasn't manufactured correctly to begin with? You can't hurt these batteries, well looks like I can, and did? We will see... Today 23V, 8:00am, 40 amps used, both pumps on, charged 9800 w and used 2700 watts This means 400 amp/hr went in, and 112 amps went out of battery. Weird isn't it, cell voltage doesn't rise above 1.43 but 400 amps went in, or I suspect, boiled all the water, and chemicals away.
Next we look at the battery hydrometer tests.
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