Jump to content

Gnome

Members
  • Posts

    703
  • Joined

  • Last visited

  • Days Won

    21

Everything posted by Gnome

  1. I don't say you were idiotic. I said putting a neutral to earth MOV that has a line to neutral voltage would be idiotic. In other words. If you put a MOV with a clamping voltage of 400v between neutral and earth, that would be stupid. Yes, that is why you would size the neutral to earth as close to 0v, in terms of a clamping device. Meaning you'd put a clamping device there with something low like 35v, 50v, etc.
  2. Doing customs yourself is probably not that crazy. Half the time I need to correct the customs declarations made by couriers anyway. There is a handy schedule from SARS, so I assume it is just about matching the stuff and filling out the form. What was the cost to have it shipped by sea? I've already DIYed a battery a long time ago now, it seems to hold up pretty well. Hasn't really aged tbh. I was looking at the options should I need to replace it or build another for family members. But for my family we just opted to buy a pre-built unit.
  3. Chint is perfectly fine. I'd take it over "Onesto" any day. But for the budget friendly option I just use Schneider Electric. It is quite a job to replace an old DB with a newer format one. I'm not a "professional" but it took two days for this little panel. Some of it because the wiring wasn't complaint to begin with so I had to run new wires, but still removing that old one and putting the new panel in is a mission.
  4. Earth and neutral should be close to 0v. You wouldn't size a clamping device between earth and neutral for your peak to peak voltage. That would be idiotic and pointless. "Harmonics" whatever that means (fairly broad term) is not a factor for an MOV. The expected peak to peak voltage is the only thing that matters. If by harmonics you mean that the wave form is not sinusoidal, that is irrelevant because of peak to peak sizing for MOVs. If you mean high frequency noise, MOVs only clamp up to a certain frequency given the response time of the device (PTCs are used for shorter time spans). Either way neither are of concern.
  5. Live and neutral are ~120v in respect to earth. This is done to simplify the electronics. If the MOV was connected in a way that assumes neutral is truly neutral in respect to earth it would blow it up.
  6. But what I mean to say is, how did you know when it got here and then what? Do you show up at the harbour? Sharing is caring, tell the story More details is better, start to finish if you can, hehe I'm looking at Lithium cells; I'm for sure not buying them with air freight, that just doesn't make sense. I buy stuff from overseas multiple times a week and have yet to be told I need an importers code. But maybe with sea freight things might be different. Either way it is insanely easy to get one of those codes. I just don't want to be bothered with admin if I don't need to be
  7. What was the clearance process like? How does it work?
  8. Except that a 5kW inverter can run a 5kW load and a 5kW battery certainly cannot run a 5kW load for any appreciable amount of time (ie. no more than a few seconds). Not because it will run out of energy but because the amount of amps pulled by the inverter will be too high for the battery. Energy is only one aspect of buying a battery pack. Generally the battery manufacturer will provide a voltage for "float" and "bulk" and you can just set those and not connect the communications also. I run my battery without any communication between the inverter and BMS and my inverter is just to use the same voltage for bulk and float and run it constantly at that voltage. I calculated the voltage to give me 3.4v per cell. But you should follow the manufacturer guidelines on what voltage they recommend.
  9. Coming back almost a year later and my battery is still going strong. With all the load shedding we've had it, it has gone through quite a number of cycles. We still run this thing like there is no load shedding (when there is). Making food in the microwave, making tea with kettle, coffee with Nespresso machine, running my 3d printer, home entertainment system + TV, etc. Even with a 4 hour load shedding and TV for the full duration + kettle, microwave etc. we aren't really cycling the battery *that* much so I'm likely not putting it through the most stressful life. Voltage difference between the cells are sitting at around 0.02mv across the battery, so the cells are actually performing really well in that respect. Really the only problems are everything around us, cell towers in my area don't even run on backup anymore, they just straight up die now. My ISP is starting to struggle too with their UPSs dying. You can't really live in isolation I guess, so it is a bit frustrating when you loose internet during a 4 hour load shedding.
  10. I haven't read all the responses but nobody should ever run a Lithium battery pack without a BMS. Deep discharge and overcharge can both cause a fire and would be trivial to have happen on a Lithium battery pack. However what is being discussed here is not removing the BMS but removing communication between the inverter and the BMS. At least that is how I'm reading it. So the inverter is basically dumb and just constantly running at a given voltage. Which is completely fine. No BMS would be a BMS if it didn't have a mechanism to disconnect the battery to prevent the various safety scenarios. In other words, the BMS doesn't even need the battery to be connected to anything to enter a fault protection mode.
  11. Gnome

    Hubble AM-2 SOC

    It is legit scary that OP is an installer. With that said, you typically charge the batteries up to a certain point to get all cells up to the same voltage. Then you back off a bit and you'll see a slight "dip" in SOC. Pumping the voltage back up will needlessly shorten the life of the battery. Probably the OP installed the inverter with a "float" charge setting != "bulk" charge setting. Or in my case I only charge up to ~3.4v per cell and then keep it there, I never bother to get the cells up to 3.65v per cell because that last 4% (per my BMS) isn't worth the absurd amount of extra wear it has on batteries. My configuration is LiFEPO₄ so the voltages and charge strategy is best not to be applied to a hubble product.
  12. Yeah, I've seen it happen with portable generators and suicide plugs. Someone I know had this happen in their complex recently. Also haven't personally seen it with inverters.
  13. https://www.victronenergy.com/inverters/inverter-rs-48-6000-230v-smart But I guess I know nothing Of all the inverter companies they are the most honest with their specifications. But looking at their "maximum efficiency" then looking at their stated max outputs it becomes quickly obvious that they applied those at the most ideal circumstances. I'm not going to argue with you, it is going to go back and forth. The reality is they aren't that efficient. I have a ton of electronics experience and I actually have the equipment to test it, specifically a professional level load tester which I've used to test few of inverters. SunSynk and Axpert types so far. They aren't nearly as efficient as they claim while on battery. Not nearly. As for the efficiency and design of computer power supplies, again an area I have a lot of knowledge in, specifically calculating loads for data centers and being intimately involved in technology specifications, selections and de-ratings (hint hint, for the biggest data center owner in the world). Including how the designs look and how they compare to inverters to a lot of respects. But what is the point in arguing with someone that knows best. This is also why I know that de-ratings need to be applied to the equipment without exception and using the values you have in the public data sheet, specifically the maximum stated efficiency, is pretty far off the mark. Unless ofc you are a bakkie brigade installer as we call them, then YOLO. The maximum stated efficiency and most enthusiastic values why not.
  14. For Eskom yes. If you back feed you could output any frequency you want while there is load shedding.
  15. Hahaha. I know it seems naive to assume that, but coming from electronic engineering side of this, let me tell you that a lot of these ratings inform customer buying. So they always take the most enthusiastic value. They'll typically give the efficiency rating the data sheet at the most optimistic ambient temperature with the most ideal input battery voltage with the most ideal load percentage. Those 3 components together can cause an enormous shift in efficiency. You can actually see this, for example, from the Victron inverters where they have a crazy efficiency rating but when you look at the actual data closely you'll notice they use a very high input voltage and very rapidly derate based on temperature. If you want a really good example of this that is REALLY moving fast, take a look at computer power supplies. They are years ahead of inverters, they are using GAN FETs and have really incredible efficiency ratings and even more impressive claims. When the devices are actually tested you realise that the maximum rating rarely applies and when it does apply it is for an incredible narrow band. Unfortunately I don't see a good amount of independent reviews where the efficiency claims are tested and an efficiency graph is generated. Before this kind of testing became common place with computers the manufacturer outright lied, all of them without exception. And even now that it is very tightly controlled by specifications they still only claim the best they can achieve which is very far off from worst case. Inverters are not special, they operate on a lot of the same principles and have all the same constraints and have most of the same common components. And since people buy using that single value, it is important to give the most optimistic value there or you are hurting your company when the competitors are all doing it. This is true for all electronics, they all work like this.
  16. Rarely will customers have a continuous load of X watts. The two data points of concern are Continuous load in watts over a period p Maximum load in watts during that period for duration d. Your battery kWh specification informs 1 for the period p. The battery continuous rating informs 2 for the duration d. Unless d <= battery maximum rating duration you need to use the battery continuous rating. Last but not least, as with ANY installation you derate your equipment by some well established efficiency factor (not even just electronics, every aspect of building design incorporates this, AC, fresh air fans, etc.). In the case of inverters 85% is a fairly typical efficiency rating, so your actual load calculations should incorporate that amount. Thus the customer load can be taken as 1.15 * rating of 1 and 2
  17. What do you consider continuous? Also have you actually setup your inverter to be inline with the maximum draw of the battery? So if you install a system for a customer, do you set it up to keep it within the specification of the battery? Or do you just put it all together and walk away hoping the customer doesn't ever have someone say running a 5kW load for 10 minutes during their load shedding?
  18. You are going in circles. It cannot supply over 50A for a realistic load time period, so it cannot supply 5kW continuously.
  19. Yeah I assumed there was some fine print I'm missing, thanks for clearing that up It is more about the voltage than the frequency
  20. No. The efficiency is not 100% That is basic electronics theory, the specification states the maximum efficiency but that number is typically at a target of 80% load. So the standard electronics principle of add 10-15% applies. Thus you can take their efficiency and drop it by 10-15% and use that as a realistic number of the true efficiency of the inverter
  21. What do you mean by this? 50Hz default can really mean a lot of things, so it is down to the fine text of what that option entails. But I certainly would not want an inverter that would allow a frequency outside a pretty tight 50Hz ± 1 Hz band, or maybe up to 1.5Hz. But ultimately why I would not risk letting the inverter "auto-detect" is that if you have some idiot that back feeds at a different frequency, you would not want to have that influence your local installation. Smaller non-inverter generators are guilty of this, their frequencies vary wildly, it is actually insane how unstable they are. SA grid cannot and will never not operate outside 50 Hz. The turbines at power stations are directly coupled to the grid, so they are spinning at some multiple of the grid frequency. Turbines cannot spin at other frequencies, just like a full laundry machine can basically "crash" the drum at some slower and higher speeds. The turbine would explode. So they trip the turbine off-line if the grid frequency is outside the safe operating band. So we are well and truly stuck at 50Hz. I'm no expert at what the exact tolerance is, but if America & Russia is anything to go by, the safe tolerance is around 1Hz or so. And operating outside that frequency at load for any amount of time will very rapidly wear out the turbine mechanical components. Now I digress you may likely have all this theory already and I don't fully know what "50Hz by default" means, but I again wouldn't want to allow arbitrary grid frequency on an inverter or any kind of "auto-detect".
  22. Yes but the battery has a maximum discharge rate. I'm not sure why I need to spell this out, but let me do that then: A typical household with have loads that run for minutes to tens of minutes that push the load at near the 5kW limit (ie. hair dryer, kettle, etc.). A battery stating that it is rated for 50amps continuous would thus not be able to supply that load, regardless of how full the battery is or how many minutes you need it. Yes you need to calculate the number of runtime minutes you need, but before you can even get to that number you need to be able to meet the maximum short term load of the household. Although 5-10 minutes seems short, it is an eternity for a battery and you can't simply write that off as "peak". That would fall into its continuous load specification, unless they explicitly call out for how long it can handle a "peak" load. Peak loads are usually measured in seconds up to a minute. EDIT: Going even further with this, if you buy 2x of those batteries and indeed they can only supply 50 amps, that means even a 5kW inverter cannot truly supply 5kW continuously for even just for 30 minutes because at 5kW load, factoring in the realistic efficiency of 85%, we are sitting at a continuous load of 6kW for 30 minutes. At their nominal voltage of 51.2V that means it is roughly 117 amps. Thus to supply 5kW continuously for any real load length of time, you need 3 of these batteries, even if you just wanted to run that load for 10 minutes. UNLESS they have a chart that maps runtime to discharge rate that makes it possible to get more accurate on the what the continuous vs maximum load means. Since Peukert's law doesn't apply to Lithium batteries, runtime length is a walk in the park to calculate, you just simply take your load average for an hour or two and there you go. The challenge is if your load maximums within that hour can be met by the battery. And for that you can ignore capacity and only look at the continuous amp rating. Btw. any installer that doesn't take the above into account has no idea what they are doing and I would say 100% they don't have the knowledge required to be installing equipment for customers.
  23. Ok let me rephrase, how many batteries are required to run a 5kW load continuously, at 100% duty cycle until the battery is depleted. Runtime is trivial to calculate with Lithium batteries, so the calculation factor here is, what number of batteries do you need to meet the SunSynk inverter specifications of 5kW continuous load. EDIT: Exactly.
  24. @Powerforum Store Maybe you guys can answer some of the questions around the Sunsynk batteries (https://powerforum-store.co.za/collections/batterys/products/sunksynk-battery-lfp-wall-mount-5-12kwh-51-2v) How many batteries do you expect a customer to have to support the 5kW SunSynk inverter? What are the conditions of the installation in order for the warranty to be valid?
  25. Now I'm looking at just building my own battery again. It is just SO much cheaper for what you get, capacity wise. But obviously I can't install that for my parents. (too far away, warranty, possible problems and such comes at a price and probably worth the price) Sigh.
×
×
  • Create New...