June 21, 201610 yr 1 hour ago, The Terrible Triplett said: ... min of 4 x 200w 24v panels with average of 5.5 hours per day of good sunlight. That is just to recharge. I said it is JUST for recharge, if all is run off batteries, to power that specific load, roughly. Generator is to assist if one runs that scenario, to assist now and then. But, IF there is an increased daytime load, off course then the panels can be better specced to handle that load too, as the inverter, like maybe inverter type aircons, their fan option used at night to not use the batteries because of disciplined use. And adding irradiation figures, panels mounted at the optimum angle, the system can be a shining beacon of lean efficiency. Just adding more panels for a few days of really cloudy days, in my book, is a waste for in summer you over produce, unless you can sell it back to the utilities and make a ROI on your investment, or use it on the spot. So I thought, Nigeria, what has been written about solar there? Here is some info: http://www.ijetae.com/files/Volume3Issue6/IJETAE_0613_87.pdf And here: http://solargis.com/products/maps-and-gis-data/free/download/nigeria So depending on where our parents live, we can get really technical here, with figures to back it all up, or not.
June 21, 201610 yr 9 minutes ago, The Terrible Triplett said: I said it is JUST for recharge, if all is run off batteries, to power that specific load, roughly. Generator is to assist if one runs that scenario, to assist now and then. But, IF there is an increased daytime load, off course then the panels can be better specced to handle that load too, as the inverter, like maybe inverter type aircons, their fan option used at night to not use the batteries because of disciplined use. And adding irradiation figures, panels mounted at the optimum angle, the system can be a shining beacon of lean efficiency. Just adding more panels for a few days of really cloudy days, in my book, is a waste for in summer you over produce, unless you can sell it back to the utilities and make a ROI on your investment, or use it on the spot. So I thought, Nigeria, what has been written about solar there? Here is some info: http://www.ijetae.com/files/Volume3Issue6/IJETAE_0613_87.pdf And here: http://solargis.com/products/maps-and-gis-data/free/download/nigeria So depending on where our parents live, we can get really technical here, with figures to back it all up, or not. our system is specked for optimal summer usage, with shortfal in winter. At this stage I could actually benefit from more panels both in winter and in summer. Could install another aircon somewhere to justify it
June 21, 201610 yr 3 hours ago, Dejavus said: timer switch for switching the freezer and fridge off in the evening when the sun is down My system is too small to make it through the night, so I usually fall back to the grid at night. I've had power failures (grid) in the middle of the night, and once I forgot to buy electricity and CoCT had an outage so all the providers were down and there was nothing I could do. When that happens, I turn my freezer off, but not the fridge. The freezer can easily last until morning. It is speced to last 36 hours if you don't open it. A fridge is another animal though, they heat up way too quickly. I have an A++ rated fridge though, it uses maybe 0.3kwh over night. Anyway, so just make sure about this decision. It isn't always feasible to turn things off.
June 21, 201610 yr I swap back to Eskom at 95% SOC in winter, and 85% SOC in summer. Only power lights, computers (the NB ones), TV (with a Pi) and fridge during power outages. If Eskom fails late a night, system swaps automatically back to the inverter, and the powers the alarm also. Why? Panels are specced for daytime optimal use, and recharging batteries wastes my daytime savings - we work from home. Fridge, Bosch, runs 24/7 on solar, and lately the VoIP phones, routers, switch and all that have moved over. Using the batts a horse traded with Plonkster. My next move, when the ship comes in, is to go off-grid (bar the kitchen). Can run everything on 1 x 1300w inverter. Sums did not make sense, as most power is used at night, to go too far with panels daytime.
June 21, 201610 yr 3 hours ago, The Terrible Triplett said: Just adding more panels for a few days of really cloudy days, in my book, is a waste for in summer you over produce, unless you can sell it back to the utilities and make a ROI on your investment, or use it on the spot. Glad it's in your book In my book where I am now running 80-90% of the time on solar/batteries with a small bank. Adding more panels would mean I can run my loads later and keep the bank floating longer when the sun starts to set and the PV wattage of my current array size drops off too much to be really usable, where having more panels just gives me more wattage to start my dependence on the bank later giving me more usable power at night or lower SOC usage. I'm even thinking of adding a string on the other side of the roof to give me more usable solar power in summer times. My end goal with the PV is to be able to run my base load (with me not at home) The same with your logic of only running a small inverter. We have explained a lot of times now that not everyone is happy with just powering the bare basics. I'm happy with running heat(winter) during the day or an aircon and the kettle knowing it will be free and it won't trip because of a small sized inverter. This kind of setup also covers me for future price hikes by Eskom making it too expensive to run all these "luxary/comfort" items. When I eventually get more panels I will be able to have the maid do the ironing while the washing machine is working in the background. And as stated earlier coming back from a week away to a rotten freezer is a big motivator for running a system like this. My end goal with the PV is to be able to run my base load (with me not at home (30-250w at peaks) even when the weather is cloudy. Currently this takes my SOC down to 80-85% during the night time giving me basically 3 nights of running with bad cloudy days before I reach 50% and then it can fall back to Eskom as a last resort
June 21, 201610 yr 1 minute ago, viper_za said: We have explained a lot of times now that not everyone is happy with just powering the bare basics. Yes, you guys have. And I keep on contra posting for I have explained a few times now that not everyone is happy, or can afford, to jump in and power their entire house overnight. We ALL know there are a few tricks in going solar. It is not cheap. That mistakes are made and that SWAMBO gets involved. When newbies arrive here, asking good questions, asking for help / advice, the answer is not necessarily and every time: Axpert. 48v battery bank. Lots of panels. What are their requirements, level of expertise? Do we even bother to want to know that? You can start small, you can do it in stages and you can take some time learning, you can use Axpert, you can use Victron, you can use 24v or 48v. I don't think you guys realise how intimidating, for newbies, some of the system here can be, the time and frustration some of them took to get operational, that is lost. And we are oblivious to the unfortunate arrogance we sometimes display here when we do not agree with each other on what we have decided to buy. We are losing good solid posters with lots more experiences to share, because of this BS. We want more people here, we will only get that by sharing our knowledge and experiences, kindly and humbly, that the next guys has less drama with fewer mistakes, even if he/she has 1 x 20w panel and 2 small batteries to start with. Do you hear what I am saying Viper?
June 21, 201610 yr To add onto this @Dejavus running a load on a 48v vs 24v bank gives you less amp draw on the batteries and giving you more room to cycle, another reason to rather opt for 48v
June 21, 201610 yr 5 minutes ago, viper_za said: To add onto this @Dejavus running a load on a 48v vs 24v bank gives you less amp draw on the batteries and giving you more room to cycle, another reason to rather opt for 48v Yes, valid point but I stand by what I said before. If the usage is low as per the calcs, the jury being out on the saving benefit over the lifetime of the batteries versus 48v costing double and double the replacement cost in 5-10 years (depending on use) versus 24v, all on a budget. So no, I stand by that for such a small load, go max 24v, save some money for it is a new system and the batts may get hammered due to abuse, time will tell. Or maybe they last 10 years with ease. Dejavus has to make the final call now, he now knows he has options, with maths backing his decision either way, that just needs to be checked very carefully, for I did it in a hurry.
June 21, 201610 yr I see the 24V question as this: Can I get away with it. It is always better to go 48V if you can, even if it means buying cheap batteries in round one because you are an armgat (Afrikaans for poor-ass, just to help out the international guys). You will buy many batteries in your life. If you do it right, you will only buy one inverter every 15 years or so. Buy the right inverter so it will last 15 years :-) (Of course, I think the jury is still out on whether you ought to buy an Axpert if you want it to go 15 years with it, but that is all part of the homework). For myself, I went 24V, and I did buy the smaller inverter, but my charge controller... that's a 12/24/36/48 model. Ready for a future upgrade... :-)
June 21, 201610 yr 42 minutes ago, plonkster said: I did buy the smaller inverter, but my charge controller... that's a 12/24/36/48 model. Ready for a future upgrade... :-) Amen brother ... we can chop and change, always improving, and the older stuff, sell it for a profit or keep on using elsewhere. So when are you selling your Multiplus?
June 21, 201610 yr 40 minutes ago, plonkster said: even if it means buying cheap batteries in round one Not if you get Trojans ... I suspect getting good batts at a good price quickly in Nigeria, could be a wee bit of an issue. There are some financial troubles there, with the oil pipes being blown up.
June 21, 201610 yr 1 hour ago, The Terrible Triplett said: If the usage is low as per the calcs, the jury being out on the saving benefit over the lifetime of the batteries versus 48v costing double and double the replacement cost in 5-10 years (depending on use) versus 24v, all on a budget. This is true, but... If you have a load lets say 250w and you need to run that for 24hours it does not matter what system you have 24v or 48v you will need the same "amount" of batteries to run this load. You are also going to gain a few AH more on the 48v system thanks to Peukert’s Law. The 24v will need double the AH capacity to provide the same 1 day of backup as the 48v system 9 hours ago, The Terrible Triplett said: The sums for a 24v system with 2 days backup - no sun - you would need: For 50% DOD: 450ah bank - 8 x 225ah T105RE's batteries or 4 x 370ah Trojan.For 20% DOD: 1480ah bank - 16 x 370ah L16RE-B. For a 48v system, 20% DOD, you also need 16 x 370ah for a 740ah bank, or 24 x 225ah batteries - not a CHANCE!!! You said it yourself earlier
June 21, 201610 yr 1 hour ago, viper_za said: This is true, but... If you have a load lets say 250w and you need to run that for 24hours it does not matter what system you have 24v or 48v you will need the same "amount" of batteries to run this load. You are also going to gain a few AH more on the 48v system thanks to Peukert’s Law. The 24v will need double the AH capacity to provide the same 1 day of backup as the 48v system To some degree... You might loose 2-5% in-efficiency when using 24V over 48V. Using the load, in Watt, a 48V/100A battery bank is the same as 24V/200A, and they'll cost about the same. Though, looking at this supplier, the 48V/100Ah bank will be R500 cheaper than the 24V/200Ah bank: http://www.bonanzatech.co.za/index.php?id_category=540&controller=category The 24V system will require thicker cables as well. On the flipside, a 24V inverter will be cheaper for the same 48V model. So you save here, loose / spend there. Higher loads will just run better on higher volts battery bank
June 21, 201610 yr 2 hours ago, The Terrible Triplett said: getting good batts at a good price quickly in Nigeria, could be a wee bit of an issue. From my experience in Namibia... you might be surprised. You may find that not only do they have more choice... it might even be cheaper too.
June 22, 201610 yr Author From my experience in Namibia... you might be surprised. You may find that not only do they have more choice... it might even be cheaper too. As far as batteries go, I can get a trojan 105 12v 205ah @ equivalent of 4,587.15 ZAR or a US battery 2000 6v 125ah for 2,866.80 ZAR and that is due to the unstable economy mainly the forex issues. How does these compare to SA prices. Sent from my LG-H850 using Tapatalk
June 22, 201610 yr 39 minutes ago, Dejavus said: As far as batteries go, I can get a trojan 105 12v 205ah @ equivalent of 4,587.15 ZAR or a US battery 2000 6v 125ah for 2,866.80 ZAR and that is due to the unstable economy mainly the forex issues. How does these compare to SA prices. Sent from my LG-H850 using Tapatalk A Trojan T105RE (6V, 225Ah) goes for just under 3k ZAR. If you can get the 12V equivalent (aka equivalent to 2 x T105) for under 6k it's a good deal. My comments also derive from discovering that Lead Crystal batteries that sell for over 8k in SA can be had in other African countries for around 5... I can actually drive to a neighbouring country, buy the batteries there, come back, and still come in cheaper even with the added transport cost :-) Someone is seriously screwing us over in SA.
June 22, 201610 yr T105's are in SA, about R 2 300.00 T105RE's about R 2 600.00 - 1600 cycles at 50% DOD L16RE-B are about R 4 833.04 - 1600 cycles at 50% DOD Namibia is quite a ways removed from Nigeria, Namibia does not have terrorist plaguing the oil industry. But maybe because of the oil there is a super dooper industry for batteries. I have no idea. Lets hope there is. Cables: I suggested 35mm2 or 50mm2 by default, irrespective of the system volts, so the cables do not cost more. Going this way, you do it once and never look back.And at R95.00 per meter for 50mm2 square, that is not expensive for the peace of mind. @viper_za20% DOD with 2 days backup is, well, very nice, but also costly. 50% DOD with 2 days backup, gives you roughly +-25% DOD per day. And less we forger, there are some utilities still available, so use that, it is cheaper than solar, and then you don't need to run at night unless there is power outages. Last comment on this matter: Define your loads and power needs and then fit the battery configuration to support those needs.Negatives: If a 12 volt battery cell fails, you know immediately for nothing runs at 10 volts. If a 48 volt battery cell fails, the system can still work at 46 volts, the bad cell causing problems in the bank i.e. overheating / fire/discharge other parallel strings, etc..If you have 4 x 12V batteries, it's easier to keep them happy in series (@48V) than in parallel (@12V), even though you have the same number of Watt-hours available. We are talking 4 x 6v batteries in series for 24v, or 8 x 6v batteries in series ... so it is not an issue, keeping either happy. An idea: 24 Volts is pretty common and many of the 12 volt switches/breakers/fuses will work at 24 volts too.You can get a lot of 12 Volt stuff off the shelf from the shops. A good dividing line: If the battery bank is >800 AH, look at going to the next higher voltage. If your loads are around 1,200 to 2,000 Watts maximum, a 12 volt bank is usually fine. If your loads are 1,200 to 2,400 to 4,000 Watts, a 24 volt battery bank is usually a better choice. If your loads are 4,800 or larger, you should be working with a 48 volt battery banks only.Thus a good rule of thumb is 12v increments for every 1000 to 1200 watt increment in require peak power. Case sample: Taking 300 Watts and multiply it by say 8 hours you get 2.4 kW hours - for there are utilities available, not 100% off grid. So if we target 2.4 kW hours and factor in the inverter conversion efficiency and consumption we get 2.8 kW hours per day. Not an onerous amount of power to supply. This can be done reasonably on a 24 Volt system, as it is about 117 Amp hours @ 24 Volts used. That would be a 468 Amp hour battery bank. Parallel strings of four batteries for 440 Amp hours @ 24 Volts. If not or you think consumption may be higher you have to make the decision of whether to go with 24 Volts or take the leap to 48. It's right on the threshold - I agree. If you go with 440 Amp hours @ 24 Volts the solar should look like this: 44 Amps * 24 Volts / 0.77 = 1371 Watt array, round up to the nearest available size. That would be minimum. You could go up to 2X that if the weather is not all that co-operative. If you go up to 440 Amp hours @ 48 Volts the minimum array size doubles. Conclusion: The choice of system Voltage is based mainly on how much power you use. The more Watt hours per day, the better off you are going up in system Voltage rather than increase the Amp hour capacity of the battery bank. This is to keep the current manageable. We agree on this. For instance, using the 10% peak charge rate and a 60 Amp controller you get numbers like this: 12 Volt system, 600 Amp hours of battery = 3600 Watt hours maximum 24 Volt system, 600 Amp hours of battery = 7200 Watt hours maximum 48 Volt system, 600 Amp hours of battery = 14,400 Watt hours maximum We agree on this too. To try to store 14,400 Watt hours of capacity on a 12 Volt system would require a 2400 Amp hour battery bank. That would want a charge rate of 240 Amps, which would require four 60 Amp controllers (or three 80 Amp ones). We agree on this too, madness. The other factor is the maximum power. If you need to supply 1200 Watts peak or less, a 12 Volt system can handle that. But as the maximum peak Wattage goes up so does the Amperage, and a 12 Volt system starts to get unmanageable current levels when you pass the 2 kW mark. Agreed again! So, it all comes right back to: What is the peak load, what is the load and for how long must it be powered? That is the right way to determine between 12v/24v and 48v - not by quoting Pheukerts law, some saving, comparing cheap batteries or using an assumed 1000w power draw. Common guys, I am trying really here to get back to facts and good advice, than personal preference because that is what we have and believe in.
June 22, 201610 yr 1 hour ago, plonkster said: A Trojan T105RE (6V, 225Ah) goes for just under 3k ZAR. If you can get the 12V equivalent (aka equivalent to 2 x T105) for under 6k it's a good deal. My comments also derive from discovering that Lead Crystal batteries that sell for over 8k in SA can be had in other African countries for around 5... I can actually drive to a neighbouring country, buy the batteries there, come back, and still come in cheaper even with the added transport cost :-) Someone is seriously screwing us over in SA. In which countries do you get lead crystals at that price? I will gladly go pickup batteries for anyone
June 22, 201610 yr Lead Crystals are expensive, currently i get 200ah lead crystal at a cost of R6000excl
June 22, 201610 yr 21 minutes ago, SilverNodashi said: which countries do you get lead crystals at that price? By now it is probably an old price, but I heard a rumour of them selling under 6k in Namibia.
June 22, 201610 yr 1 hour ago, The Terrible Triplett said: @viper_za20% DOD with 2 days backup is, well, very nice, but also costly. 50% DOD with 2 days backup, gives you roughly +-25% DOD per day. Quoted you on saying this, remember??? 22 hours ago, The Terrible Triplett said: The sums for a 24v system with 2 days backup - no sun - you would need: For 50% DOD: 450ah bank - 8 x 225ah T105RE's batteries or 4 x 370ah Trojan. For 20% DOD: 1480ah bank - 16 x 370ah L16RE-B. For a 48v system, 20% DOD, you also need 16 x 370ah for a 740ah bank, or 24 x 225ah batteries - not a CHANCE!!! Just a refresh then to point out that even you had the same amount of batteries for 24v and 48v at 20% I'll just add this as the real reason one does not go 48v is because it is/was just too expensive at the time of buying your equipment. Lower voltage systems are great when you convert your loads to run on the same DC voltage.
June 22, 201610 yr Viper, yes you did and yes I took the 20% DOD as a case sample. I also then said afterwards, once I realized that 50% DOD over 2 days is actually more than enough for 2 elderly disciplined users, with utilities still available at times. So thank you, it is all about the costs on a budget and if money is not an issue, then go bos. But it is also about 48v not necessarily the only choice, for it depends on a few factors, power needs being the most important one after costs. You can reduce your load, or you can decide not to ... that is between the person / their needs and or their financial status.
July 14, 20169 yr Author Hi again, I am at the final phase of this and have opted to double the battery bank to reduce the DOD to maximum of 25% I have done my calculation and they only really need to use battery for roughly about 10 hours. SO I am now buying 4 x 12v 205AH US battery and 6 x 200W mono panels. (I intend to add more later) Axpert 3000KVA MKS PLUS inverter supports (1500W PV array). IS there any special way to connect the panels to utilise the panels to the fullest. attached is the specs from the proposed panels. Thanks in advance.
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