Where do I start with solar? - Page 1
Forum section: electronics / general

author: paulca
author_rank: Super Contributor
timestamp: December 12, 2017, 06:57:18 pm
content: I've been thinking about having a go at solar, just initially as a play thing, but I have to start somewhere.I have been tempted to just go for a cheap chinese panel, but I've done that road before and it often ends up with a repurchase of a more proper item.I don't really have anywhere outdoors to put a panel. I have a sky light and in calm weather I could put it out that for a while, but most likely any small panel I get will end up in my man cave room window. The curtains are 99% of the time closed, so there is definately room for a 1m square panel behind the curtains. It's south facing, and I expect I won't get very high efficiency behind double glazing. But it is what it is.It seems that most of the "kits" out there immediately assume a lead acid 12V battery. Do I really need to go down that route primarily? Or can I start with something else? Maybe 18650s or something less arcaic, expensive, heavy and unreliable than an LA.I'm not looking to spend a fortune, I'd think £50 for a first end-to-end set up and is it too optimistic to expect 20-50W from that money?Just a first foot on the ladder type thing. If I can charge my USB devices and battery devices etc. from it that would be enough to play with.I hope to be moving house next autumn to somewhere with a garden, probably a garage and maybe a shed, but right now I'm in an appartment with no outdoor space (except my car parking space).

author: Belrmar
author_rank: Regular Contributor
timestamp: December 12, 2017, 10:46:13 pm
content: i would recommend you to use a lead acid battery , yes is not as energy dense as a li-ion battery but they are cheap AF and eviromentally speaking they are much better (basically almost 100% recyclable). also using a lead acid battery grants you the opportunity of only having to use a cheap pwm charger from ebay instead of a complex battery balancer.Talking about the energy you wold get....expect the worse as the windows of your house are no low iron and the ammount of light comming from a window is greatly reduced but for testing is good enough

author: metrologist
author_rank: Super Contributor
timestamp: December 12, 2017, 11:34:23 pm
content: I got a 100W Chinese panel for $96 USD shipped and it works great!I also bought one of those Li-ION solar charge controllers (you'll find the black or white plastic with blue labeling) and tried it with a 96WHr Li-ION laptop battery pack and it sucked. Maybe I could power a few USB devices, but I really did not have much else that would work well enough off the nominal voltage. I also found that the SCC would not dump the full power from the panel into my load.I bought the exact same controller for LA battery and it works great! It will dump the full juice into my load and I currently use it with a 12V - 120V inverter to run my 42V Li-ION ebike charger and to charge other USB devices.Adam Welch did a review of a MPPT SCC that had a programable setting and he said it worked great! I am considering that one so I can charge my ebike batteries direct from the SCC.

author: paulca
author_rank: Super Contributor
timestamp: December 14, 2017, 07:59:36 am
content: What do you think of these?http://www.ebay.co.uk/itm/like/252951999615?ul_noapp=trueOr...https://www.ebay.co.uk/itm/50w-Solar-Panel-10A-Charger-Controller-Brackets-6m-cable-for-12v-Battery/361537187409?hash=item542d4bae51:g:SIAAAOSw6oBXFSKQ

author: metrologist
author_rank: Super Contributor
timestamp: December 14, 2017, 05:11:13 pm
content: the 20W system has the same kind of controller that I am using. Both of these are for lead acid battery technology. Polycrystalline panels are the second tier common panel with decent efficiency. Monocrystalline panels are superior. I have the former from Newpowa.You should look into your region solar rating and figure out how much energy to expect, and then work out which battery will work with your system and needs.

author: paulca
author_rank: Super Contributor
timestamp: December 14, 2017, 08:11:45 pm
content: Quote from: metrologist on December 14, 2017, 05:11:13 pmI was going to ask about the battery size. Lead Acids are not in any way cheap here. £60 gets me a 40Ah car battery.If the battery was too big, does it not just mean it won't get fully charged during the day or is there more to it?

author: Seekonk
author_rank: Super Contributor
timestamp: December 14, 2017, 08:47:15 pm
content: C/10 is generally suggested. Since this is an electronics board I would think you would want to build something. I have 2KW of panels and I control them with an arduino. Total elecrtronics cost in my setup is only about $20. I usually tell people who want to use a 100W panel to just give up and wait becuse there is not much you can do with that much power. It sounds like 20W is really your limit space wise and I would use a couple old lap top batteries with a BMS board. Grab a couple 2596 regulators for your USB and Li pack. These can be made into power point controllers with just the addition of a few parts. Lead acid batteries suck. If you use one, just buy a new one for your car and use the old one for solar.

author: metrologist
author_rank: Super Contributor
timestamp: December 14, 2017, 10:11:43 pm
content: This is just my thought process on a small solar system.You would rather pick a sealed lead acid battery unless you put them outside (and you will need adeep cyclebattery). The controllers you linked will not work with Lithium cells.Generally start with what power demands will be on the solar system. If just wanting USB power to charge a phone, for example, that is probably just about 10Wh per day (assuming 2.5Ah cell battery @ 3.7 nominal volts).Then, figure about 5 days storage capacity and introduce efficiency factors/system losses, and a battery margin, so about 80% efficient and ~20% margin. I'm getting about 78Wh/day. A 12V 7Ah SLA battery would work (and so would a quality laptop battery, with the right solar charge controller).Now determine the insolation rating to ensure enough panel to charge the battery in a day, including charging efficiency. Let's just pick a nice round number like 2. Take 78Wh/2, divide by 85% charging efficiency, so a 50W panel should work.I'm using a 15AH lead acid motorcycle battery with my 100W panel, because that is what I had. I should be able to use a 40Ah SLA at some point (my average insolation is 5.5), or I'll get a boost MPPT solar charger for my e-bike batteries.

author: paulca
author_rank: Super Contributor
timestamp: December 15, 2017, 08:18:22 am
content: Quote from: Seekonk on December 14, 2017, 08:47:15 pmThanks. I like this approach. I only just discovered that 18650 cells are expensive, but brand new laptop batteries are not and contain 6 18650s. They may not be top of the range regards peak current etc, but I'm not sure I care yet. £8 for a 6 cell Toshiba battery. So I have an experimental 3s2p setup including balance lead, in the post.For charging it, I could just use the Accucel 6 directly connected to the solar, it will take 11-18V on input, then buck or boost for the battery. The downside is it requires attention, in that it won't auto start charging without you pressing buttons. I have seen people using them on Youtube. I'm not too sure how suitable they are regarding MPPT and what not, but it seems comfortable with a whole range of voltages regardless of what it's charging. I charged two 3s lipo batteries in series (25.2V) from an 11.6V supply for example.It might give me "Iteration 1" though. I'm starting to apply methodologies we use in software in work to my hobby projects to prevent scope creep meaning things never get finished and there is always something else to order. "Iteration 1" would be successful if I can charge my phone from a solar panel charged battery, for example. Iteration 2 would advance based on feedback from Iteration 1 as to what is most important to do next. Most likely an automatic interaction free charger.I have an off the shelf regulator with a USB outlet and while it gets hot charging an eCigarette at 1.6Amps it works. (I think it's s dicky little surface mount regulator, I'm probably torturing it, but hey, it was about £2). Runs off a standard XT60 LiPo plug and while they are not everyone's cup of tea they are great up to 60A and what I will be fitting to my 18650 pack.On space. It's a BIG window. Probably about 6 foot square. So even a 1m square or 1x1.5m panel. There are cupboards and fridges across the front of it anyway, so blocking the lower half of it with a solar panel is perfectly acceptable and the panel can lean back against those cupboards.

author: Seekonk
author_rank: Super Contributor
timestamp: December 15, 2017, 07:54:50 pm
content: It is fairly easy to modify any buck converter into a pseudo MPPT controller with just a few added common parts. Technically it is called MPPC (constant panel voltage). Power point only changes with temperature and since inside that won't change much. Many of the MPPT chips are actually MPPC with a temperature sensor. BMS boards take care of all the charging requirements.

author: metrologist
author_rank: Super Contributor
timestamp: December 15, 2017, 08:00:02 pm
content: Thanks! I had not come across MPPC.http://www.linear.com/solutions/4545

author: fourtytwo42
author_rank: Super Contributor
timestamp: December 16, 2017, 08:51:41 am
content: Quote from: Seekonk on December 15, 2017, 07:54:50 pmWhile this may be true enough for very small systems it is not true of large array's (several hundred watts up) because the MPP also varies with power output and shading, considerable loss of efficiency would be incured by trying to operate the array at a fixed voltage even if temperature compansated.

author: rhb
author_rank: Super Contributor
timestamp: December 18, 2017, 12:28:14 am
content: You might just setup a PV panel and use it to run LED lights during the day. Harbor Freight sells a 100 watt 4 panel array for $150 in the US. That's enough to run 7-8 1500 lumen LED lamps. Great for daytime lighting for detail work. That is about to become my first experiment. No battery. A battery to store charge adds about $80 and has only a 5-7 year life vs the 15-20 for a good PV array. Life of HF array and battery as yet unknown.Solatube and others make skylights with reflective tubes, but they are expensive and also require roof penetrations. A PV array and LED lights is a more convenient version that costs less and can't cause a roof leak.

author: Someone
author_rank: Super Contributor
timestamp: December 18, 2017, 01:53:48 am
content: Quote from: rhb on December 18, 2017, 12:28:14 amIt may not be cost effective for everyone but running LED lamps during the day where lighting is needed can result in lower overall energy use than letting light through the windows (due to heat loss/gain through the windows).

author: kathy45
author_rank: Newbie
timestamp: December 26, 2017, 07:05:57 am
content: This looks to be more complicated than I thought. Interdot, the fridge does work when reaching next to the inverter. I have no other items joined to the inverter. Pouching, I made another cable to check if the lead was indeed the case.

author: paulca
author_rank: Super Contributor
timestamp: December 30, 2017, 10:56:13 pm
content: Quote from: Seekonk on December 15, 2017, 07:54:50 pmIf only this was true. I've been searching around BMS boards and to be honest I haven't found a single review of one that actually works.I know the single cells 1S BMS boards work fine, but it's when you move to 2S to 7S that things come apart. I've seen reviews of boards that just don't work period, boards which are sold as charging BMSs, but are just protection boards, boards which will not cut out to over 4.3v+ per cell, boards that let the voltage drop to 2v per cell and the better ones still appear to use a resistive drain on the high cells to drain them down to the low cells for balancing and can't keep up with a sensible charge rate.I am still to find a multicell BMS which supports:Proper cc/cv chargeProper active cell balancing, or at least cross-cell balance charging.Proper cut out voltagesSupports discharge AND chargeI can find a dozen Lithium chargers which support all of the above, but they don't typically like being in the circuit with the load and don't like being charge/discharge controllers, so they would need relay switching between charge and discharge. All of which makes them fairly useless with solar.I watched lots of Adam Welsh's videos and Julian Lett videos and I don't think between them they have found a reliable multi-cell BMS. The best they seem to have come up with are Frankenstein devices with BMS to resistive balance the cells, a 12.6V cc/cv charge module to feed it and a boost converter to bump the 12V supply up. I'm not sure this could be connected to a solar charge controller, I'm pretty sure it couldn't as it would be trying to sense a battery not a charger board.I don't even think they showed this set up under proper test, regards the BMS balancing cells or the proper cut off voltage of 12.6V (for 3S).The Adam Welsh videos on Lithium solar charge controllers didn't seem to go well either. I don't think he found a reliable lithium charger which didn't float charge and ended up using a "Gell lead acid" mode and a 7 series pack to match the voltage of a 24V gell LA.

author: paulca
author_rank: Super Contributor
timestamp: December 30, 2017, 11:52:06 pm
content: As always once you say you can't find something on a forum, the very next web search turns up 3 of them.This one here, reviewed by Adam Welch supports Lithium and can have their float voltage configured well below peak charge voltage meaning the cells should not remain trickle charging all day but will get a break. I'm not sure how they would fair if there was a constant but small load as it will discharge to float voltage and then the controller will start trying to maintain that voltage on the cells "floating them" but at least it won't try and float it at 4.2V per cell!https://www.ebay.co.uk/itm/391950642450?var=660913082749Here's a bit of a basic question. The solar charge controllers I have looked at don't seem to support fixed current charging. They seem rated for a maximum charge current and if there is solar power available will pump that current into the battery. So if I buy a 10A SCC and give it enough panel to provide 10A, it will charge the battery at 10A.This would suggest that I need to match panel, scc and battery in ascending order of rating. For example:8A panel -> 10A SCC -> 12A max charge current battery.If I'm doing initial tests with small batteries I would assume I can get away with a small panel.2A panel -> 10A SCC -> 3A max charge battery.Does that work? If I up the battery capacity I could then up the panel to a maximum of 10A on that SCC.Given my 18650 pack I made is 3S2P, 2600mAh cells making it 5.2Ah, that has an absolutely maximum charge current of 5.2A and I'd prefer to run it at 2.6A. Converted to watts that's 2.6A * 12.6V = 32.7W - efficiency and margin.That would make my max panel size 32W or something like this:https://www.ebay.co.uk/itm/222373840601Alternatively as I will be running it indoors and it isn't 100% efficeient anyway, I could aim for the 50W panel and be lucky to get more than 2.6A but know I'll never get more than 5.2A.Does any of that make sense?

author: rhb
author_rank: Super Contributor
timestamp: December 31, 2017, 01:43:17 am
content: For the level of sophistication you are seeking I suggest that you set up a sample panel, dump the output into a resistive load and measure voltage and current in situ. Then set about designing the charger and battery system. Of course, you may want to consider a tracking mount for the panel.In my case, I'm going for dead simple. A couple of 35 Ah gel cell lead-acid batteries, a 100 W Harbor Freight set of panels and charger and a small Harbor Freight gen set. All mounted on a hand truck fitted with BMX wheels for rough terrain and sporting a telescoping mast for a multiband inverted V dipole for HF and a vertical for 144 and 432 MHz bands. But before I actually build it, I'm going to characterize the PV panels myself. However, most of my effort will be on building the package and mounting the panels as a foldable array.

author: Seekonk
author_rank: Super Contributor
timestamp: December 31, 2017, 07:38:14 am
content: Quote from: paulca on December 30, 2017, 10:56:13 pmThis is a universal problem in solar with even flooded cells. Any active solar system never gets much out of bulk charge. For that reason I pull as much bulk power as I can directly from the panels instead of the battery. Still, everyone muddles through with how they are set up. Those multi stage charge routines only work when you are on vacation. Good enough for this application which appears to be pointless.

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2018, 06:29:34 pm
content: So I took the plunge and bought:EPEVER 10A Tracer MPPT charge controller50W Mono-crystalline panelYuasa 26Ah Deep Cycle 12V SLAThe panel comes with 5m cable, I have plenty of 14 AWG wire for the battery. The battery max charge current is 6.5A the panel short output is 3A, charge controller is 10A, so all in spec and could later take a 100W panel with the same battery.It's plenty to be playing with. The plan is to start small.

author: metrologist
author_rank: Super Contributor
timestamp: January 03, 2018, 08:32:15 pm
content: Quote from: paulca on December 30, 2017, 10:56:13 pmI recently received the boost MPPT CC that he reviewed and so far I've seen it shut off the current when the target voltage has been reached. I need to do some longer testing to see when/if it comes back on (and I will have forgotten if he mentioned it). That will not actually matter much to me as I plan to use it with a 100W 18V panel to charge 36V LiION e-bike packs that will be rotated quite often.Looks like you got a decent small system to experiment with.

author: paulca
author_rank: Super Contributor
timestamp: January 03, 2018, 09:02:50 pm
content: Quote from: metrologist on January 03, 2018, 08:32:15 pmI thought about the Lithium stuff. I decided to go with the SLA because they are generally considered standard, simple and safe. I can use it as a ballast to charge Lithium IONs or Lipo's under supervision. Summer evenings and weekends when I'm home during the day I can experiement with the Tracer and it's settings for the battery voltages via the software giving quite fine control that 'should' do lithium packs. Remains to be seen and doesn't solve the balance problem. The constant discharge balancers like Adam is using worry me somewhat, but if the cells are balanced it shouldn't in theory be drawing much current, except to power it's LCD etc.

author: paulca
author_rank: Super Contributor
timestamp: January 06, 2018, 09:07:30 pm
content: Basic wiring questions.I could just bare the ends of the solar panel wires and stick them into the charge controller, but I want to put a switch in there to kill the solar power without having to unwire it.I got some nice switches, they are DPDT.Two questions:1. Are there standards in the solar world for connectors, does it matter and would I be shunned for soldering a male and female XT60 onto the switch pins?2. Related to 1. I know I usually only need to switch either wire in a circuit but as the switches are dual and the XT60 sits so perfectly on the pins... is there any downside to switching both + and - of the panel, battery or load? I know it would then leave the components isolated and able to float voltage. Is keeping the ground/- connected preferred as it keeps the voltage of all components in sync? Or does it matter at all?I also have 10A fuses for each panel, battery, load, just in case.

author: metrologist
author_rank: Super Contributor
timestamp: January 08, 2018, 04:01:16 pm
content: I'm using XT60 connectors on the output side since that is what my ebike batteries use. The solar side uses solar industry sealed connectors, but I am also considering using the XT60 connectors there as well for when I want to swap my boosting or SLA controllers. (I really want to get a second panel though)

author: paulca
author_rank: Super Contributor
timestamp: January 08, 2018, 08:38:59 pm
content: XT60s it is.Panel arrived. Looks lovely. Heavier than expected.Of course I had to play with it.... at 8 o'clock at night indoors. Slightly surprised it gave 8V open circuit under dim relaxed lighting and 12V when I pointed a 20W ceiling spot light at it. I even hooked up a 3W power LED knowing if the panel managed to produce more than 3W the LED as no more. The LED lit, but only just. Probably 0.1W.Still... indoors, 20W halogen spot light from the ceiling that isn't bad.It will be Saturday morning before I get to put it in actual sunlight, if we actually get any.Charge controller hasn't appeared yet and the seller has some negative feedback about tardy delivery, so I expect it's another "I'm not really relay ordering from China" idiot. Grrr. The battery hasn't arrived either and hasn't even been marked as despatched. I may have to message him with "WTF?". The battery was cheap as it was 1 year old stock and the seller says he will charge and test it before despatch. But it can't take a week to do that!

author: paulca
author_rank: Super Contributor
timestamp: January 09, 2018, 06:49:36 pm
content: Charge controller and battery arrived. Battery arrived with 12.38V so it's not broken. I don't have a load capable of capacity testing it properly, but I'm not that fussed as long as it does the job.Wired it up, partially anyway, and the charge controller powers up and while it says it's daylight due to indoor lighting, it obviously isn't getting enough to put anything into the battery.I'm not going to run it until the weekend when I'm present and it might take me a bit of time to trust it to run while I'm out at work.I have a metal cased fridge I don't use. I'm tempted to put the charge controller and battery inside it as some minimal fire protection. How worried should I be?

author: metrologist
author_rank: Super Contributor
timestamp: January 09, 2018, 07:05:34 pm
content: I have not taken any precautions with my batteries. One is for motorcycle and the other for a typical family car. Since they are wet cells, I would not put them in the house, but on the bench in the garage seems fine. The e-bike Li-ION batteries get moved around as shrink-wrapped battery packs would.I would not even worry about SLA - most backup power supplies use them, so just don't short it out.I used some automotive aux lights to test my system - something that would drain more than the system could output. I should run that all day to see what the system could actually cope with.

author: paulca
author_rank: Super Contributor
timestamp: January 09, 2018, 09:05:08 pm
content: I have got a 5A DC load I built, but it would take nearly 5 hours to drain the SLA (26Ah). I also have some 100W power resistors, but they are 1Ohm and 0.1Ohm, so that's what on 12V... The 1 Ohm would draw 12 amps / 144 watts. I might have two of them, in series they might make it, 6Amps, 72 watts shared between them. Still going to take 5 hours and not something I would leave unattended. The 0.1Ohm would make fire.Anyway, I wired a load up to it and it's charged it's first LIon pack (via a Turnigy charger mind).So... do I put the panel in the window and risk leaving it when I go to work? I'm thinking, no. I can't confirm the MPPT portion does not have a fault that will let smoke out while I'm at work. I don't want to come home to a broken in door and bill from the fire service (as it will set off the building wide fire alarm) ... or much worse.Saturday then. Which will give me time to discharge the SLA a bit and give the panel something to do Saturday morning.

author: mtdoc
author_rank: Super Contributor
timestamp: January 11, 2018, 04:35:10 am
content: Quote from: paulca on January 09, 2018, 06:49:36 pmWith a SLA battery you have nothing to worry about. No need for metal enclosure. Even with FLA batteries - you only have to worry about significant amounts of hydrogen gas venting during equalization and then it's only an issue if you have a large battery bank (> kWh worth). Large FLA battery banks require enclosures with venting to outside.Quote from: metrologist on January 09, 2018, 07:05:34 pmIn the house shouldn't be an issue unless you plan on spilling electrolyte on your carpet... Of course as above, a large FLA battery bank needs an enclosure and venting to the outdoors.

author: paulca
author_rank: Super Contributor
timestamp: January 14, 2018, 09:32:58 am
content: I have solar power! Woohoo!Put the panel in the window yesterday, but it was the darkest, wettest, miserable of days. The CC did register charging, but 0.0A.This morning however it's blue skies (for now) and the sun isn't up above the houses across the street and I have registered my first amps to battery, 0.1A.Will see how far that gets when the sun is up properly before the weather closes in later again.EDIT: And when the sun came out from the behind the houses I have 1.1Amps. Oddly the charge controller has not switched to PPT mode, it's sitting at 14V, the max power point of the panel is 17V. I read this about the Tracer, at low power levels it remains in PWM mode and just sustains a charge voltage for the battery. Maybe if the sun comes up out of the horizon haze it will improve.I'm not expecting the full panel 50W behind a window, but 25W would be nice to see in direct sun light. Any more would be a bonus.

author: paulca
author_rank: Super Contributor
timestamp: January 17, 2018, 09:28:41 pm
content: Our weather sucks. There has been virtually no sun this week. I started with a battery voltage of 12.2V and I now have a voltage of 12.6V. I've taken no load off it. I have also taken to switching the battery off at night and back on in the morning to save the little the charge controller is pulling.I did manage to get it all fused and switched up properly. Makes me feel a bit safer leaving it unattended.I bought an RS485 to USB adapter and played with it's software, but I want to log the data. So in the post is a MAX485 board and another ESP8266. It can send it's data to my existing data logging set up (originally for home heating but now generic enough that it will accept any data over the network). It will create RRA archives and graphs for the panel volts/amp/power and battery/volts/amps.I also plan to sleep the ESP overnight, once the panel voltage drops below 5V or so it can deep sleep and wake up periodically to check for dawn. It will be running of the charge controllers RS485 5V.Interestingly(?) I was going to add a "light level" sensor to my data logging system, but monitoring panel power seems a lot easier than messing about with calibrating LDRs.

author: bazza
author_rank: Contributor
timestamp: April 02, 2018, 12:29:54 am
content: * 40w 12v ebay panel ( make your own stand out of wood ).* 10 A pwm or mppt charge controller ( EPSOLAR or EPEVER brands are decent if going Chinese)* ~20 Ah to ~30 Ah 12v AGM lead acid battery* loads of common ( cheap) elecrical cable stripped for use in solar (running off the regulator's load terminals)* several lovely DC-DC step-up and step-down DC-DC converters on ebay to run lots of DC gadgets of varying voltages* several spring lever terminal blocks on ebay, so you can hook up several 12v items at once* automotive fuses for safety, or din-rail mounted circuit breakers if you wish* cigarette lighter sockets ( plug in cheap cigarette plug USB chargers into these )* not forgetting a bunch of 2.1mm x 5.5 mm screw- down plugs and sockets* not forgetting universal laptop plug sets 2.1mm available on ebay, which will help you in your quest to hook up a bunch of stuff to any DC gadget with a removable ac adapter plug ( in conjunction with the Dc-Dc converter with correct voltage dialled in)Years of fun. Best education is to learn by doing.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 19, 2018, 09:03:08 pm
content: I found that Croation one:https://www.ebay.de/itm/Solarmodul-Photovoltaik-SolarPanel-300W-24V-Monokristalline-wohnmobil-hause/253647307997?hash=item3b0e8ec4dd:g:RJ0AAOSwbA5bCDaPHow about that?

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 26, 2018, 06:55:01 pm
content: If you want to do a solar project for fun but that still has utility value, look at building a portable solar power pack for camping or emergency. I did this so I can play around with solar. Basically it's a box with a battery, charge controller and inverter, and a separate folding panel that plugs in. A microcontroller (basically at atmega running arduino code) monitors the voltage so if it goes too low it cuts power to not drain battery too much. There is also a LCD. I can console in with a laptop to adjust calibration etc too.Now using it for my shed until I get a proper setup and roof top panels. It's surprisingly hard to buy big solar panels here due to shipping cost. I have not found a source yet where I don't need to take out a 2nd mortgage for the shipping. I may end up having to build my own. Just not sure what materials to use, as I only know how to work with wood and expansion/contraction would probably crack the glass.

author: mtdoc
author_rank: Super Contributor
timestamp: July 26, 2018, 07:50:46 pm
content: Don’t try to build your own PV panels unless it’s just for fun and educational. You will not produce anything even close to the cheapest commercially produced panels. Many have tried and failed.As far a buying single large panels on the cheap, trySolar Blvd.. Fedex shipping on individual panels in the US is $30 and I believe it’s the same for at least some parts of Canada (Vancouver, BC for example).

author: metrologist
author_rank: Super Contributor
timestamp: July 26, 2018, 08:00:34 pm
content: I just jumped in with no objective. A 100W panel and a few charge controllers for different applications.I've been thinking of small systems as this, such as to take my fish/reptile tanks off-grid. The reptile tanks are ideal because they really only need to run when the sun is out (to recreate the sun with artificial lights and heat), the fish tanks need some heat and circulation during the night, however, and the battery makes it not worth it in the long run, unless just for experimentation.The one application that has paid back the most is the MPPT controller set up to charge my e-bike. I cannot quantify that, but the payback is not just an obscure financial calculation, but the objective enjoyment that all that power and acceleration I'm experiencing is basically free - after paying for the system, of course.Let me run a number... that system cost $130. @ $0.20/kWh, it will be 650kWh to break even. The e-bike uses about 160Wh to go 5 miles, with some assist, so about 4000 charges or 20,000 miles to break even. I'm going to need more tires.

author: Seekonk
author_rank: Super Contributor
timestamp: July 27, 2018, 04:15:34 pm
content: It is hard to do anything with solar with less than 500W. One of the best paybacks is heating water for those who have water tanks. This is supplemental heating which means that almost 100% of potential PV energy is used. That is a far better payback than oter uses for PV. For $340 you can get two 280W panels out the door locally. $10 to build a little controller and you have a system that out performs a heat pump water heater in payback. Plus you have a little system to provide power in an outage. Yes, most wall warts work fine on 60V DC. This laptop right now is. I'm off grid and get all my hot water from excess PV that would normally be just wasted. People with solar are the greatest energy wasters in the world. A working system usually requires that by design.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 27, 2018, 10:57:55 pm
content: Quote from: mtdoc on July 26, 2018, 07:50:46 pmGreat Scott noted that there are a few times where DIY solar panels make sense - small panels where the cost per watt is high and panels that have to be unusual dimensions.I would like to see someone do a "DIY or Buy" for MPPT controllers. In my experience, the cheap ones are not very good so DIY should easily win, especially after someone makes open source code for it.

author: mtdoc
author_rank: Super Contributor
timestamp: July 28, 2018, 12:47:34 am
content: Quote from: NiHaoMike on July 27, 2018, 10:57:55 pmYeah it cost him 140 Euros in materials and 8 hours labor to produce a 100W panel- about twice the cost of a commercial panel. Worse, the durability is highly suspect which has been the case with other DIYers.QuoteThat’s probably true for the low power ones. There’s been low power Arduino MPPT plans and code around on the interwebs for years now. But where MPPT really makes a difference is with higher power systems ( say > 500W or so). In that case, best to stay away from the cheap ones and DIY unless you really know power electronics well.

author: Scrts
author_rank: Frequent Contributor
timestamp: July 28, 2018, 06:55:24 pm
content: Just wondering: did anyone make any analysis on where it's worth getting the solar system in terms or earth latitude? I understand that equator countries will obviously be good, but where is the cut-off line? Where statistically there's less sun for the system to be effective enough and pay off in reasonable amount of time?

author: mtdoc
author_rank: Super Contributor
timestamp: July 28, 2018, 07:09:04 pm
content: There’s no latitude cut off. It is situational dependent. Obviously there will be huge seasonality issues, but even in Alaska and nothern Canada there are situations where solar PV makes sense - especially if grid power is unavailable or prohibitively expensive.If you’re asking about adding solar to a locale that already has reliable grid power, then payback time will depend on local solar insolation (not just latitude dependent), how much grid power costs, how much space one has to install how large of an array, how much it will cost to do the installation, etc, etc.

author: Seekonk
author_rank: Super Contributor
timestamp: July 28, 2018, 07:28:26 pm
content: There is a $5 72V buck converter that I love because it is very easy to modify to stand alone and or be controlled by a uno etc as a charger. I have several in parallel in my system with 60V grid tie panels. Saves a lot of effort and searching for parts. Nice when you want to supplement a 12V PWM system with grid tie panels.