Jay, Prepare to be even more impressed: https://www.youtube.com/watch?v=BQF4peNdtlY
Jason Szumlanski Principal Solar Designer | Florida Solar Design Group NABCEP Certified Solar Professional (PVIP) Florida State Certified Solar Contractor CVC56956 Florida Certified Electrical Contractor EC13013208 On Sat, Feb 22, 2025 at 6:20 PM Jay via RE-wrenches < [email protected]> wrote: > Hi Logan. > > I am super impressed with what the AIO can do. > > Question. What happens if something breaks inside. Is it field repairable? > > Thx > Jay > > On Feb 22, 2025, at 2:07 PM, William Bryce via RE-wrenches < > [email protected]> wrote: > > > Everyone wants to compare the AIO inverters to the older low > frequency inverters when it comes to the idle power draw. But everyone now > wants all the bells and whistles. > > Nothing is free, and if you take an older system then add up the charge > controllers draw, SCP monitoring system, Gateway device, and then add a > battery monitor to the mix you will find the Idle draw is much higher than > what the MFG says for the inverter alone. > > Feel free to check the math with a Schneider XW with 3 VH MPPT > controllers, a gateway, a SCP, and lithium batteries running closed loop. > Oh, the Schinder does not have any smart loads like most AIO do. > > My 2 cents. > > Logan > > > > On Sat, Feb 22, 2025 at 12:03 PM Jason Szumlanski via RE-wrenches < > [email protected]> wrote: > >> The voltage cliff is a real issue. Even though LFP batteries can be >> pretty deeply discharged without damage, for practical purposes we need to >> set the LBCO on the inverter at a relatively high voltage (or SOC) to avoid >> the steep part of the cliff altogether, rendering a good part of the >> capacity essentially useless. In situations where there is a readily >> available charging source at all times (auto-start generator or grid), >> there really should be a way to overcome this game of chicken between the >> battery protect mode and inverter LBCO. In the off-grid world, I don't >> consider that a bell & whistle, but more of a required feature. >> >> Maybe it's not so much an inverter issue as much as it is a needed >> battery feature. Imagine if there were a dry contact on a battery BMS that >> told it to stay on regardless of how it was feeling that day (subject to >> safety shutdowns, of course). Then you could force the battery to be alive >> with 48V DC connected when there is generator output voltage present, for >> example. Of course, there are risks with this simplistic example, like if >> the inverter/charger is faulted and cannot charge the battery. >> >> I think the right answer is closed-loop communications that can tell a >> BMS in protect mode to wake up because there is a charging source ready to >> go. If Midnite could implement this with AIO/Powerflo, it could be a very >> powerful selling point. On the other hand, maybe it's not that important as >> long as the inverter reliably reaches LBCO well before the battery goes >> into protect mode. That answer could be in closed loop communication logic >> where the BMS sends a warning to the inverter that it is about to shut >> down, so the inverter can stop inverting on the command of the battery, but >> keep the battery connected so a charging source will charge it. >> >> In other words, maybe it would be better for the battery to be in command >> of the inverter's LBCO rather than the inverter's own fuzzy logic. >> >> The parasitic draw issue does need to be addressed. I went through some >> calculations on some typical systems I have in the field. For example, one >> system has a 120kWh battery with four Sol-Ark 15Ks. I think the inverter >> manufacturers prefer "idle consumption" to the derogatory parasite >> comparison, but whatever you call it, let's assume 360W for four inverters. >> If the inverter LBCO is set at 12% and the protect mode is triggered at 2%, >> that gives us 33 hours until the battery reaches protect mode in theory. >> That is a substantial amount of time to get a charging source on the >> battery. But in practice, I have seen many batteries enter protect mode >> before a "properly" programmed inverter LBCO engages itself. >> >> That brings up another feature request. How about dropping the idle >> consumption of paralleled inverters and just keeping the primary inverter >> at full idle? >> >> >> Side note: I inherited a site where a Lithionics battery BMS is in >> control of the 2-wire start for a generator. In theory, this should work, >> but in practice, the owner often finds the BMS in protect mode with the >> generator not started. I haven't dug too deeply into this issue yet, but >> direct BMS control of the generator is another interesting option. But then >> you would want to build in all of the quiet time, charge percentage/voltage >> limits, exercise, and other logic that typically an inverter handles. This >> is an example of how a BMS is in control of the charging source, but it >> would be better if the BMS was telling the inverter what to do in terms of >> AGS and LBCO. >> >> Jason Szumlanski >> Principal Solar Designer | Florida Solar Design Group >> NABCEP Certified Solar Professional (PVIP) >> Florida State Certified Solar Contractor CVC56956 >> Florida Certified Electrical Contractor EC13013208 >> >> >> On Sat, Feb 22, 2025 at 11:17 AM Steve Higgins <[email protected]> >> wrote: >> >>> Hello all... >>> >>> The first issue is that inverter/charger parasitic loads have increased >>> exponentially in the past 20+ years. When the LBCO cuts out, the inverter >>> may shut off, but it does not remove itself or any other DC-connected >>> device from the battery. These devices still draw a parasitic load. In >>> the 1990s, the Trace SW would pull about .3 to .4 amps of current from the >>> battery when connected to it. Today, many manufacturers use cheaper >>> transformers, and the high-frequency inverters draw a much higher current. >>> Some of these all-in-one inverters draw 1-2 amps of current from battery >>> banks, just connected and not even turned on. >>> >>> What's important here is that the battery voltage is already very low >>> when you trigger an LBCO shutdown (it's not a disconnect). For a 48-volt >>> system, this is 44 to 47 volts, depending on where you set the LBCO. When a >>> Lithium battery is this low, the voltage dropoff is much higher. With a >>> lead battery, the voltage dropoff is much more linear, but with Lithium >>> chemistry, this voltage dropoff is more like a cliff. This is why it's >>> important for many of these Lithium systems to set the Battery cutouts a >>> bit higher so people have more time to fix the situation before the BMS >>> shuts down. Ideally, the customer should be educated not to >>> over-discharge the bank, which would help. Many of these customers want >>> turnkey systems that they don't want to think about but don't want to pay >>> for it or do the work that is required to maintain it. >>> >>> Now, if the battery had gone into "Protect" mode and the BMS had shut >>> down, the battery is outputting very little votlage... the inverter/charger >>> needs voltage to run. There used to be a line of inverters in the marine >>> and RV market that would do what we called "Dead Battery Restart". This >>> meant there was a parallel circuit in the power supply so that when you >>> supplied AC to the input, a secondary power supply bypassed the regular >>> battery power supply and would power up the inverter and allow the charger >>> to run. Most of the inverter manufacturers got rid of this circuitry >>> because it was not cheap, took up space on the boards, and was just another >>> circuit that could get damaged with generator/shore power surges. I don't >>> know of an inverter today with this dead battery restarting circuit. >>> >>> With this, you need to be very careful. If the customer has cratered the >>> battery voltage and drawn down the voltage so low that they have damaged >>> the cells, jumpstarting the battery can create a charging hazard, and that >>> could cause the cells to swell internally. If that happens, the battery >>> will get warmer and warmer under charge, and eventually, you could have a >>> cell rupture. This can happen quickly with Li-ion, but with LFP, it's much >>> harder to create this problem. Usually, in LFP, cells will swell a bit, and >>> the current interrupter on the individual cell will open up and drop that >>> string, and you will lose capacity. >>> >>> Like everything else, it's a race to the bottom on cost; this affects >>> quality and features... Everyone wants the "Bells & Whistles," but they >>> don't want to pay for it. >>> >>> Steve Higgins >>> >>> >>> On Sat, Feb 22, 2025 at 5:08 AM Jason Szumlanski via RE-wrenches < >>> [email protected]> wrote: >>> >>>> I have been thinking a lot recently about the reasons off-grid systems >>>> can shut down, and working on strategies to prevent these nuisances that >>>> require manual intervention. >>>> >>>> Ideally, a BMS should never shut down due to low voltage/SOC because a >>>> properly programmed inverter should reach it's cut off well before the BMS >>>> decides it needs to protect the battery, especially where there is closed >>>> loop communication. But let's say that happens, where the BMS does make the >>>> DC battery output go to zero. >>>> >>>> It seems to me like the inverter should be able to start a generator, >>>> and then signal to the BMS that a charging source is available. But I'm not >>>> aware of any system that actually does this. The inverter should be able to >>>> wake up the battery. I can see this being particularly possible where one >>>> manufacturer is writing the code (I'm thinking Midnite AIO/Powerflo). >>>> >>>> Of course, the inverter would have to have power in order to do that, >>>> so if it's nighttime and there is no PV, the inverter power would need to >>>> come from somewhere. I have two thoughts. First, someone could manually >>>> start the generator, waking up the inverter, but they would not have to >>>> reset the BMS if the inverter told it to wake up. The second way would be >>>> for the inverter to somehow close the 2-wire start circuit upon inverter >>>> shutdown, restoring power to the inverter automatically. >>>> >>>> If those are not options, an external NO relay powered by the inverter >>>> output could be added to the 2-wire start circuit, perhaps with a time >>>> delay to return to the NO position to allow the generator to remain powered >>>> until the inverter does it's thing and starts charging the batteries. >>>> >>>> Anyway, my question is whether any inverter/battery combination out >>>> there works in a way that the inverter tells the battery there is a >>>> charging source available to wake up the BMS and reconnect DC power. And if >>>> not, why? >>>> >>>> Jason Szumlanski >>>> Florida Solar Design Group >>>> >>>> >>>> >
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