May 26, 201610 yr 10 hours ago, Manie said: What is the difference between solar only and the sbu ? Now that I see this in the broad light of day. You have two setting from two different programs - Program 1 (Load source priority) and Program 16 (Charge source priority). Let's deal with Program 16 There are 4 options for battery charging Solar with utility being used if solar is not available (CSO) Utility with solar being used if utility is not available (CUT) Solar and utility used at the same time. The inverter prioritises solar and if solar cannot meet the max charging rate stipulated in Program 2 it augments it with AC power quite nifty in my opinion. (SNU) Solar only the batteries are charged from the panels. It will NOT use utility to charge batteries even if utility is available. Now Program 1 (load priority) which give so much trouble. UTI - Utility This is perfect if you are using the inverter as UPS with no panels. When Eskom goes down the inverter seamlessly switches to battery. SBU - Load is prioritised first solar then battery and then when the voltage drops below the threshold in Program 12 goes to Eskom. SOL - Load is prioritised so that solar and battery are utilised during daylight and utility when solar is not available. This setting is not ideal in that there is a fair amount of switching as daylight fades and at day break.
May 26, 201610 yr 11 hours ago, The Terrible Triplett said: 2) If the MPPT operates at +-100% capacity consistently, the heat it can generate can become a problem. Well, two things really. If you have a decent controller, it should already be designed with sufficient margin to operate at 100% all of the time. But if you don't trust it to do that, then oversize the controller as well. With an oversize controller, you set a maximum current that is lower than the capacity of the controller, but is in line with 10%-15% of your battery Amp-hour rating. If you already have the controller (built into your Axpert), and you are worried about running it at full capacity for long periods, you may have to willingly downsize it a bit by setting a lower maximum. I'm assuming that can be done.
May 26, 201610 yr I have NO problem running the separate Victron Controllers at full capacity ... but I would think twice if it is one unit with the heat buildup of the inverter in same box, fans or no fans, for they can stop working at the most inopportune moment, causing a very annoying moment when a R25 fan causes a few thousand rand worth damaged equipment.
May 26, 201610 yr 22 minutes ago, The Terrible Triplett said: when a R25 fan causes a few thousand rand worth damaged equipment Once again, properly designed equipment have a temperature sensor, which controls the fan and possibly also backs down on power. Interestingly I found no temperature sensor in the Microcare MPPT. The fan is turned on by one of the io pins on the microcontroller, I can only assume it detects certain known conditions and turns the fan on (or maybe the microcontroller has an internal temperature sensor, like some atmel chips do). I remember it would turn the fan on early morning and late afternoon under what I would consider low power conditions, I can only assume there must have been some rationale behind it. I have half-a-mind to rewire the fan if I ever reuse this unit and add a temperature sensor, because I cannot remember it ever getting warm even when operating at 90% capacity. It has such a decent heat sink on the back, black anodised aluminium, that I can hardly imagine it will have any trouble running at full tilt, even without a fan. On the WRND there is a temperature sensor and a fan connection on every buck converter (the 120A unit has 4 parallel buck converters). Only the fan connection on the last board is used. I have no idea if they back-off the power, or only turn on the fan, and if the temperature sensors are synchronised in a manner so that any hot unit will signal the fan (which may be connected to a different unit) to turn on. Might be something to look at. From what I've read, the Axpert is aware of (and acts on) the temperature inside the case. Perhaps we should ask @Coulomb if he knows what would happen if the fan fails :-) Edit: Quick look at the data sheet. While some PIC microcontrollers do have internal temperature sensors (like the PIC16 range), the Pic18F26 used in the MC charge controller appears not to have one :-)
May 26, 201610 yr To be frank, where you're considering different orientations (to get a better power spread), I'd spend a little more and add a separate controller :-)
May 26, 201610 yr Jip. Victron, SMA, Morningstar and Outback etc all have online calculators, taking all factors into consideration for ones specific panels, temps etc, warning you of potential problems. On my 45amp Morningstar, I can add up to 1550w according to calcs (5 x 310w in series). So what diffs does it make to add one more? For I am pretty sure there is a safety margin but quite frankly, does one want to dabble with warranties and all that? And all that where you can reduce your load to fit the panels mounted / load powered so that you then have excess power. If you are already are as efficient as can be, panels just just not enough, as you say, rather focus the effort by considering adding more panels at different orientations using separate controller/s, for a lot is wasted on a fixed structure ito early mornings, when it is cool, and late afternoons.
May 26, 201610 yr 19 hours ago, Chris Hobson said: Hi Warren I have 12 x 250W panels and max produced 3300W on cool day with some cloud. I was led to believe that so long as you did not exceed the max voltage of the MPPT you were safe. The inverter draws the power it needs. So if the panels are producing more than +- 3000W then the inverter limits itself to that. The advantage of more than 3000W of panels can be demonstrated by the following scenario. Say it is a cloudy day and you can only produce 2000W from 3000W of panels. If you had 3750W of panels you could now produce 2500W. If the sun was shining brightly you would still be limited to +-3000W. That is how it was explained to me. When I wanted to install an Imeon the initial proposed install had 18 x 250W panels i.e. 4500W of PV for a 3kW inverter. This makes sense as the inverter draws the current from the panels rather than the panels "pushing" the current into the inverter. I will confirm that what I want to do is possible before I launch into the unknown. Mike SuperDIY and others do any of you have practical experience in this matter? Chris, you are spot on, electricity is drawn, not pushed. As long as you stay below the maximum input voltage you should be safe. The inverter will only draw what is required. As you've mentioned, you have had first hand experience where your panels produced 3300W and your inverter is still running today.
May 26, 201610 yr 17 hours ago, Manie said: What will happen if your batteries is full and you load is half of your solor? Sent from my SM-G920F using Tapatalk Nothing, the inverter will draw only what it needs from the panels.
May 26, 201610 yr 17 hours ago, The Terrible Triplett said: What still konfusses me is when the batteries are full, inverter operating at max the panels and controller can provide so zero goes into / out of batteries as per BMV, yet the batts are not damaged. You are confusing me now when you say: "so zero goes into / out of batteries as per BMV, yet the batts are not damaged." Read your statement again... Zero goes into / out of the batteries, yet the batteries are NOT damaged
May 26, 201610 yr Good point SuperDIY .. late night typo. What I meant to say was i.e. batteries are fully charge, 25amps at 32v coming in via the controller whilst inverter is humming away happily, that the batteries are not damaged with such a huge current going through / over / skipping across them.
May 26, 201610 yr 7 hours ago, The Terrible Triplett said: ..., that the batteries are not damaged with such a huge current going through / over / skipping across them. The skipping over happens in the inverter. It doesn't go into and out of the battery at all; the Victron saying zero current into/out of the battery is not lying. There isn't even much clever happening in the inverter to make this happen, it's basically Kirchoff's law (currents into a node must sum to zero). Well ok, the clever part is the solar controller supplying just enough current to balance the load. After that, nothing flows to the battery automatically (in accordance with Kirchoff's law). If you like, the battery is in parallel with the solar charger output and the inverter's DC input; it isn't actually or nationally in series between these elements.
May 27, 201610 yr Coulomb, if you only knew HOW many people I have asked this question to! Battery manufacturers, solar people and manufacturers, in the last 6 years! None could say with confidence what happens. Most either did not know or leaned towards battery damage. At which point I asked: But then all solar systems are damaging batteries for all will charge and power loads at max ability of array? Normally that is when the conversation stopped. Which brings me to the 2nd part of the conversation. Same scenario i.e 25amps at 32v coming in (24v system) via the controller whilst inverter is humming away happily BUT this time the batteries are NOT fully charged. Lets assume they are 50% DOD. What happens then? How does the batteries not get damaged with the controller giving all it can from the array to power inverter and charge the batteries?
May 27, 201610 yr Hi Coulomb Do you know of anyone in Oz who has oversized their PV array with the PIP/Axpert? I am getting mixed response from the supplier in SA. This may be due to them wanting to sell me a second unit. Chris
May 27, 201610 yr 58 minutes ago, The Terrible Triplett said: Same scenario i.e 25amps at 32v coming in (24v system) via the controller whilst inverter is humming away happily BUT this time the batteries are NOT fully charged. Lets assume they are 50% DOD. What happens then? How does the batteries not get damaged with the controller giving all it can from the array to power inverter and charge the batteries? It's simply arithmetic, and a fork in the road. Ye olde electrons arrive down the cable (lets use conventional flow, so it would be a dearth of electrons that arrive there instead) at the positive pole of the battery, and it finds itself faced with two roads diverging (in a yellow wood), and it picks the one less impeded (apologies to Robert Frost). It can either go into the battery, or it can jump onto this other red cable that's going off to the inverter... if there is space. If there is no space on that road, I might be forced to go via the battery instead... that might be the path of least resistance. So, if you have a charge controller pumping away at 20% of the battery's Ah rating (which is too high), but the inverter is sucking up half of that current, then for half of the electrons arriving at the positive pole, it's less effort to skip the battery and continue on to the inverter instead (and pass go, and collect R200... :-P), so only the other half goes into the battery, leaving the battery with only a 10%-of-rating charge, which is perfectly safe. If something goes wrong, and the inverter shuts down, you risk damaging the battery of course, for now all of the current would have to stampede through the battery instead. When your charge controller and inverter are interconnected however, we can adjust the maximum current so that the remainder (after subtracting the bit the inverter sucks off) is always within limits. And this is what the Axpert does of course. You could of course also do this with other equipment, where such interconnection is allowed, for example, with a Victron inverter and MPPT in hub-1 mode. So now to expand on what Coulomb said, for the Axpert this fork in the road is inside the case of the inverter. When things are properly balanced, all (or almost all) electrons takes the "breede weg" via the inverter and skip the battery.
May 27, 201610 yr Cool!!! If I find that R200 note ... sy gat, dis MYNE!!! 2 minutes ago, plonkster said: If something goes wrong, and the inverter shuts down, you risk damaging the battery of course, It takes a separate charge controller a minute of two to adjust ... so I do not see this as a problem. Jip, I have dunnit. Switched off the inverter under the above circumstances to see what happens.
May 27, 201610 yr 1 minute ago, The Terrible Triplett said: It takes a separate charge controller a minute of two to adjust ... so I do not see this as a problem. No no no... imagine that the battery is severely depleted, so that dumping all that current into it does NOT raise it to absorbtion voltage. If you told the charge controller to push say 50 amps into your 200Ah battery, it will do that while in bulk mode, at least until it hits the absorption voltage... only then will it back down. This is probably not too big a problem on the small wussy residential banks we use... those lift their voltage very quickly... but you have to at least apply your mind to the problem and understand the risks, init? :-)
May 27, 201610 yr I think we are talking cross purposes Plonkster. Separate charge controller is meant to be non Voltronic, like mine, CC is separate from inverter. So no idea what this means " ... dumping all that current into it does NOT raise it to absorption voltage ... ". Who on earth would do that, and if the controller does that, replace it, it is damaged.
May 28, 201610 yr My setup seems to be similar to you TTT where i have a separate Charge Controller and it has limited feedback (battery voltage) as to where the amps that it produces is going to. (inverter, battery or combination). So i have to assume worst case scenario and that is i have no load on my inverter and the full PV array capacity is going to bulk charge my battery bank. US 125 XC battery spec sheet says that my bulk charge should be a constant current of 10% of C20 rating which works out to 24 Amps. My 1.8 Kw array can produce 37 amps so i have a potential problem that i could be charging my batteries at 15% of C20 rating. On the other hand my tiny Optima 55Ah, 12Volt, yellowtop deep cycle batteries has no current limit on bulk charge as long as the battery temperature remains below 51.7 oC. (Amazingly this battery has a cold cranking capability of 750 Amps)
May 28, 201610 yr Carl: Can you not set the charge controllers MAX charging current... ? Pg 21 of manual... mx60_pv_mppt.pdf
May 28, 201610 yr Yes thanks Mark, i can set the Max. charging current on the Outback but then i would be limiting my potential energy yield from the array.
May 28, 201610 yr For me - protecting the battery bank comes first... you may limit yield but that is the price to be paid. Maybe 25A is a compromise! better than 37A
May 28, 201610 yr Agreed Mark but I am finishing off an ancient old set of golf cart batteries bought at scrap value. I discharge them 100% every night. (have been doing that for over 1 year now) On the next battery bank i will match it to my array capacity as i hate wasting energy.
May 28, 201610 yr Therein boys and girls, you always need to match the battery bank with the controller with the array, or you lose something along the line. Camel, I would not worry if I was you. The 15% charge rate will not be sustained, actually I don't think it would cause a problem because: a)) you always have a load on b)) If there is no load and batts are flat, a condition that is not the norm, the controller will sense the batts requirements and adjust accordingly .i.e the 15% charge rate is the exception, not the norm. c)) You have a lekker equalisation period IF the is 15% charge rate coming in for off-grid, as you do, I think 15% is borderline ok. If I had that, I would be have been happy.
May 28, 201610 yr 24 minutes ago, The Terrible Triplett said: Therein boys and girls, you always need to match the battery bank with the controller with the array, or you lose something along the line You keep saying this and this is not true for the Axpert boys, the thing has enough settings to be safe by having a limit on your charging current and still be able to use the rest of your PV to carry the load
May 28, 201610 yr Viper: In your sig you have : "1800w (6x 300w Renesola Virtus II 2x3strings)" Is this 2x 3 panel strings?
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