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Tacet

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  1. Hi all, I hope my searching skills didn't let me down, but I can't find the answer to what is probably an easy question. If I have a Sunsynk 12 kW hybrid inverter, how does it handle the balance between battery charging and load (assuming night, so no solar)? If my load is 10 kW, does that mean that I have only 2 kW left for battery charging? I'm trying to see what a realistic maximum constant power load is, taking loadshedding's recharge requirements into consideration. Thanks!
  2. Yep, that is the concept I use at home (my personal install is a Victron Multiplus II - works extremely well). Most telco sites, though, has too little roof space to supply even close to the full load from solar. The loads are usually connected to the batteries via an LVD that is controlled by the rectifier. Under normal operation the LVD will be closed. The batteries themselves are a fair range: 2 V VRLA, 12 V VRLA, lithium...
  3. Some perspective - most operators are preparing for >15 kW loads for each mobile site when 5G comes. I've seen small 19", 5U rectifiers that can do more than 20 kW. I see pros and cons to mixing on the AC side or on the DC side. Mixing on the AC side: As you say, it may well be cheaper. Extra conversion step - extra losses and extra things that can break. A really nice pro - on a site with multiple small rectifiers, a single solar installation can benefit all the rectifiers as well as ancillary equipment such as aircons. I don't think you'll be able to keep the inverters up if the mains fail, unless the solar installation/yield is larger than the site load. Mixing on the DC side: Simpler equipment, but a more difficult solution. You don't have to worry about the AC side at all. No backfeeding issues, no anti-islanding required. In case of an AC fail, the solar will still contribute. Thanks for the inputs, people! You're making me rethink my stance on mixing on the AC side - there are more benefits than I realized.
  4. That's certainly the easiest solution, but not very efficient. Instead of a single DC-DC conversion you now have DC-AC-DC. Also, inverters tend to be more expensive than charge controllers, so it makes the ROI a more dubious deal. I try to keep work and forum separate, but this question piqued my curiosity, which is why I brought it here. The industry is telecoms, so the main reason for operating at DC is to keep the equipment permanently on batteries. A rectifier will typically be used to supply either multiple DBs or equipment racks, so in most cases you won't pull 625 A to a single load. And yes, paralleled 150 mm2 or 185 mm2 cables does happen. In some places busbars are used between the battery cabinets and the rectifiers. For high power solutions we prefer a UPS solution to carry the load until the site's EPS kicks in. Unfortunately some of the equipment manufacturers are totally happy to have 18 kW devices that can only operate on 48 Vdc.
  5. System sizes are scalable - I'm looking at systems from 2 kW to 30 kW. I'm not worried about wire sizes - it is easy enough to bring your PV down to the charge controller at e.g. 250 V, and to install your charge controller next to the rectifier. I don't think it is quite that easy. If you simply parallel them and the output voltages are not exactly the same, the load will draw from the highest output voltage. If that is rectifier, then the solar charge controller will idle. If the charge controller tries to keep its output e.g. 0.01 V higher than that of the rectifier, the load will be supplied first by the charge controller and then by the rectifier. We often parallel rectifier systems for redundancy purposes. Even if the two rectifiers are from the same supplier, same model, in the same room (thus the same temperature) with the same configurations, you often see the load shift between the rectifiers under normal operating conditions. Those minute differences between temperature readings and output voltages makes a difference. Add battery charging to the mix: you want the existing rectifier to control the battery charge voltage and to limit the charge current if necessary. You still want to use your available solar energy to provide the load and charge the battery, but you don't want to overcharge the battery. The best idea of how to do this I have at the moment is to configure the charge controller independent of the rectifier, but with a float of e.g. 0.01 V higher than that of the rectifier. There may be times when the temperature compensation inaccuracies pushes the rectifier voltage higher than the charge controller voltage; it will be interesting to see how often that happens.
  6. A device that takes as input either 3-phase or single phase AC, and rectifies it to -48 V DC. On the DC side it will usually connect to both load and batteries, and the user will be able to set the float voltage as required by the batteries. The rectifier can do temperature compensation and is able to limit the charge current to the batteries.
  7. Hi all, I'd like to pick a few brains, to see what the possibilities are. The company I work for have a few DC rectifiers supplying -48 V to various battery banks and equipment. We're unlikely to go for solar as we don't really have enough roof space. However, I'm curious about the concept: how would you supplement an existing rectifier with solar? The rectifiers are reasonably good at what they do, so you'd want the rectifier to retain control over the float voltage, temperature compensation, charge current limiting, LVD control, etc. Simplest way: install hybrid AC/solar rectifier systems. Various manufacturers make them, and they will do the job perfectly. But replacing is expensive - supplementing should in theory be much cheaper. Slightly less simple way: grid-tie inverters on the AC side. However, that feels like you're simply adding unnecessary conversion losses and an additional layer of equipment. The solution is readily available even in the retail market. More efficient and cost effective way: supplement on the DC side at -48 V. I've never seen solutions designed to do this, though. I'm not even sure if it possible to do it without communication between the rectifier and the solar regulator, especially if it comes to charge current limiting. Any thoughts, solutions, ideas?... I'm guessing that my preferred way is a pipedream. If it was possible you'd probably see it punted widely as a way to easily increase solar capacity on the DC side, irrespective of what equipment is already installed.
  8. Oh, the diagnosis is pretty easy. The key issue in that installation is the installer.
  9. Agreed. I'm not an installer, and for me my installation was mostly a fun DIY project. But my Victron installation looks neater, is certainly safer, and has been working for months now. It doesn't cost much homework to realize that you really do want a GX. As for battery compatibility - as long as the battery can put out 48 V there's no reason for it not to work. I'm using Narada lithiums that can't speak to Victron at all, and it works. The drawback of not having communication is that you have very dodgy SoC readings (Victron think that mine is at 85% when it is fully charged), but that doesn't stop the inverter from inverting.
  10. @Pietvis - sorry for the slow reply, I don't browse the forums that often. The NPFC should have a little pinhole with a reset button behind it. IIRC it is to the right of the RJ45 sockets. It is pretty simple - you press and hold the buttons for a few moments. The status lights will cycle, and then the battery will switch off. Pressing the button again will swith the battery on again. I've found mine to be pretty finicky when connected to a Victron 150/75 MPPT - if there's no solar/inverter input to the MPPT the batteries tends to see the MPPT as a short and go into protection mode. That usually happens if Eskom is down at night. Then I just disconnect the MPPT, and reconnect it later when the sun is up or when Eskom is back.
  11. There doesn't really seem to be much in the line of standard DB sizes, especially when looking at older DBs. I eventually got frustrated with my old DB and replaced it with a Hager board from Livecopper. The electrician asked me roughly R1800 to install the new DB. He enlarged the hole in the wall, did the plastering and rewiring, but I supplied all components. His work wasn't the best ever (I ended up shaking plaster out of the circuit breakers), but I felt that it was pretty cheap.
  12. My father's is ticking along really nicely - I'm keeping the grid breaker on for those occasional inrushes and for when the oven, kettle and geyser are on simultaneously - but other than that they don't really use much from the grid. Mine took a bit longer - I'm not going to climb onto my double storey's roof, so had someone install the panels for me. They did that this Tuesday.
  13. In my opinion Lithium's most important advantage - lack of fault current. Not having to worry about whether the busbars are too close to each other is so convenient. Excluding some more trunking, this is the only stuff that will be on the wall. Still to be done: Finish both systems Get CoCs for both houses Install smaller geyser elements (my little duplex has a 200 l geyser with a 4 kW element, crazy!) Install 25 A contactors to control geysers Install Sonoffs to control geyser contactors Have a Raspberry PI monitor the Venus to see when the battery is fully charged in the morning, and then switch the geyser on.
  14. My father and I are both installing Victron systems in PTA. His is functional, but needs quite a bit of tidying up, while mine will hopefully be connected in an almost tidy state. A few random pics. Decided to mount the charge controller to the battery cabinet - wanted to keep all the DC in there and minimize the number of devices on the wall.
  15. Indeed, there is nothing inherently "better" to 48 V than 24 V. 48 V has the advantage of thinner battery/MPPT cables and lower rated switchgear, but higher voltages mean more cells in series in the VRLA string, thus higher probability of eventual cell imbalances. If your system is already designed for 24 V you're not going to save on cable cost by switching to 48 V, so why bother? Mmm, is there any advantage in terms of inverter efficiency in having a higher DC voltage?
  16. They give an equalization charge voltage of 56.0 V-57.6 V, but not a bulk charge value. Have you asked your supplier for the manual? They should be able to provide it. Otherwise, I think Averge is bringing Leoch in; they might be willing to assist if your supplier can't.
  17. Do you have the user manual for the battery? I have a very old manual, so I'm not even sure if it is for the same generation of Leoch, but the float values I have are 53.5 - 54.4.
  18. I'm a bit late in chipping in here, but rather late than never. Regarding the Huawei ESM48100 - there are two versions around: the ESM48100A1 and the ESM48100B1. The ESM48100A1 has a very silly 50 A charge/discharge current limitation. If you exceed that, the battery will basically not put out any current or accept any current. It will reset itself a bit later. So basically - if you try to pull more than 2.4 kW from the battery, the battery will almost instantly drop the load. The ESM48100B1's charge/discharge current limit is 100 A.
  19. Unfortunately not. Its normally provided by the battery manufacturer, so you'll have to ask the local distributor. I know they are available for e.g. Narada, of which we have plenty in the country, so Dartcom should be able to source them. Basically "vent kit" is a really fancy name for a length of clear PVC pipe that goes over the venting nozzles.
  20. Well, I'm going lithium, so hydrogen isn't too high on my concern list. As for VRLA - even though they recombine etc., never a good idea to operate/keep them in an enclosed space without sufficient ventilation. Basically, make sure you have a happy marriage between Annex D of SANS 10108 and the batteries' emissions as per SANS 60896-21/22. And remember, you do get venting kits to make sure that it vents into a well ventilated space.
  21. I'm busy preparing for (hopefully) installing my MulitplusII this weekend. I have very limited space to install (living in a duplex), so I was thinking of installing the MultiplusII on the wall above the battery cabinet (lithium batteries). That will minimize cable length, keep everything together, and conserve precious space. But in the Multiplus's manual it states: Will installing it above the battery cabinet, with clearance of more than a meter between the battery and the inverter be acceptable? I understand the concern in case of flooded batteries, but most telcos have no issue with installing 4 strings of 190/200 Ah VRLAs directly below the rectifier. There shouldn't be sufficient hydrogen buildup to be a problem. And in the case of lithiums, I really don't see the reason for the prohibition. My main concern here is warranty - I don't want to do something that will negatively impact my warranty.
  22. I see that Hager gives DC tripping thresholds for most of their breakers on their website. Has anyone tried to get more information about their DC ratings? They're only giving their AC voltage ratings. These might make for a cheaper and simpler option for string protection if they're DC rated. The fact that they're listing DC thresholds at all is making me hold thumbs.
  23. Yep, which is why the room requirements for VRLA batteries is simpler than for flooded cell batteries. Dry-out is still the main reason for VRLA failure, though; as you said, the recombination is only effective up to a certain point. That's where flooded cells have the advantage - they're refilled with maintenance.
  24. @Sidewinder About terminology: VRLA - Valve Regulated Lead Acid. Simply means that it is sealed and hydrogen buildup is catered for via valves. Not meant to be topped up, so easy maintenance, but more limited lifespan than accessible cells. Easier to operate safely than open cells where hydrogen buildup has to be considered in the room design. You get VRLA batteries using all flavours of inner designs: AGM, Gel. You get them in 2 V blocks, 6 V blocks, 12 V blocks.... Flooded - you have access to the electrolyte, they're not sealed. More maintenance is possible. As with VRLA, you get flooded batteries that use AGM to contain the electrolyte, and you get flooded batteries that use Gel to contain the electrolyte. AGM - Absorbent Glass Mat. Battery electrolytes are kept in absorbent mats between the plates. Reduces the chances of acid spill, and offers a few other advantages in terms of performance and life expectancy. Most prevalent design on the market. AGM is a popular design for deep cycle batteries. Not all AGM batteries are deep cycle batteries. GEL - electrolytes are kept in a gel-like paste between the plates. Supposed to give more cycles due to less opportunity for hydrogen to escape, but will typically be more finicky in terms of float voltage, and will generally be able to give less current than a similar sized AGM. Regarding lithium - why do you really want the battery to speak to the inverter? The main reason would be to know the SoC, but why do you want to know that? It adds convenience, but personally I don't see it as a dealbreaker. My VRLA batteries can't tell me what their SoC is (with the exception of Northstar's ACE equipped batteries, though I've seen very few of them around), and the VRLA's silence has never bothered me. That said, my experience is in a pure DC environment, so my requirements might differ a bit. In theory the lithiums should give you much better cycle performance than most VRLA options, but the proof is in the pudding. I guess we'll have a better idea in a few years. About the 2 V cells - you do get unsealed 12 V blocks as well which you can top up when necessary, and they're generally cheaper than sealed options. But then you have to be careful of hydrogen leakage - that's why those old exchanges had dediacted battery rooms complying to fairly stringent ventilation requirements.
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