Solar panel and controller issue. - Page 1
Forum section: electronics / general

author: snipersquad100
author_rank: Frequent Contributor
timestamp: January 23, 2015, 06:33:18 pm
content: I got two 175watt 36v solar panels, will they work on a 12v battery bank via the charge controller pictured.Thanks

author: snipersquad100
author_rank: Frequent Contributor
timestamp: January 23, 2015, 06:34:57 pm
content: I also be connecting a 400w wind turbine.

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 06:50:52 pm
content: What is your question?

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 07:03:52 pm
content: Not enough info on the controller. What is the max input voltage?It does not look like an MPPT controller so even if it will tolerate the possible 40+V from your panels (unlikely), it will be very inefficient.Connecting a 400W wind turbine as well? No, not likely. Do you have a diversion load and controller?If you're serious about using your panels and turbine to any reasonable efficiency - you'll want 2 controllers.With a 12V nominal battery banks, you'll want MPPT controllers.

author: snipersquad100
author_rank: Frequent Contributor
timestamp: January 23, 2015, 07:31:58 pm
content: All the info I got on the controller is in the pics, I got it 2nd hand.So if I get a mppt charge controller would I be able to use the panels and the turbine on a 12v battery bank?What mppt CC do you recommend.thanks

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 07:45:25 pm
content: What size is the battery bank? This is very important. As is very common you seem to going about this backwards. TO design and commission a solar system you need to know your needs first and then design a system to fit. If you try and buy a couple of panels and a wind generator and then ask what can you do with it, you will usually be disappointed.The things needed to know to design a system:Where do you live?What energy requirements in kWH are you trying to support?Is this a critical need? Or is it just a hobby system? Or is it meant to reduce the cost of some current use?These are just the starting questions. You need to consider where the panels will be mounted to be sure there isn't any shadowing. DO you have a place to put the batteries? Do you have a backup generator if needed?You give so little detail and don't even give a proper question to answer.

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 08:00:15 pm
content: I agree with Lightages.As far as MPPT controllers, Midnite Solar, Outback, Morningstar and Schneider Electric are the quality brands.For a small system as your propose, I'd recommend theMidnite Solar KidYou'd need one for your 2 panels and another one for your wind turbine.Though Lightages points about defining your loads, etc first are spot on.

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 08:10:30 pm
content: I am a solar energy system designer and installer in Chile. I have been living on solar energy almost exclusively for 5 years continuously. I cannot even guess what the OP is asking!

author: snipersquad100
author_rank: Frequent Contributor
timestamp: January 23, 2015, 08:22:29 pm
content: I just want to know if the 36v pannels will work on the charge controller as its rated 12vdc 300w, or do i have to use12v pannels. The battery bank is 12v 1575amp hours. this is just for hobby intrested im not depending on it lighting myhouse, I just want it to give me 30amps at 12v for as long as possible.

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 09:07:58 pm
content: You can use a PWM controller with any panel whose VOC does not exceed the maximum rated voltage input that it allows. Note that 12V is the nominal battery voltage it is designed for and not the maximum voltage input.But the higher the panel voltage is above the charge voltage the less efficient the system will be.With a PWM controller designed for a 12V system the the most wattage you could hope to get under even the best conditions (cold temps, direct sun) from each of those panels would be around 75watts (assume about 15V bulk charge voltage at 5A). The exact number will depend on the charge voltages the controller is designed to use and the state of charge of the battery. With the right MPPT controller you could approach the panels maximum 175Watt output.I highly doubt you'd get 30 amps out of that controller even if you had the optimal PV array or wind turbine. More specifications from the controller are needed to be more specific.

author: snipersquad100
author_rank: Frequent Contributor
timestamp: January 23, 2015, 09:36:42 pm
content: Ok thanks mtdocBrand named Mppt controllers are pretty expensive for what I want to use it for, Its just for fun.I've seen some cheap mppt's on ebay but with bad reviews. I think I'll wire it all up and see what happens.

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 09:46:14 pm
content: Quote from: snipersquad100 on January 23, 2015, 09:36:42 pmYes, quality charge controllers are not cheap. Like most things, you get what you pay for. I have heard reports thatthis Chinese knock offworks reasonably well. But caveat emptor. I think there's a youtube video teardown of it.QuoteOk but be prepared for a puff of magic smoke.

author: G7PSK
author_rank: Super Contributor
timestamp: January 23, 2015, 10:11:54 pm
content: It states clearly on the lable 12 Volts DC solar input. So 36 Volts will surely let the smoke out.

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 10:31:15 pm
content: Quote from: G7PSK on January 23, 2015, 10:11:54 pmI suspect that's Chinglish labelling. No charge controller designed to charge a 12V nominal battery would have a maximum rated input voltage of 12V. Is it designed to charge a lower voltage battery only? I don't think so since it says "battery input 12V" - which by the way is another nonsense spec - "battery input" is not a normal charge controller specification and nonsensible unless it is also has a load output.But it's true that assuming this is a PWM controller, it's very unlikely it will tolerate the possible input voltages from those panels.Any charge controller needs the following specifications available for any reasonable ability to determine PV panel (or wind or hydro) input and battery bank size:Maximum input voltageMaximum output amps.Nominal system battery voltage(s)Charging voltages - 1 for each stage if it's a 3 stage charger.The numbers given on the OPs chargers front label are close to useless.

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 11:01:58 pm
content: 1575Ah batteries? OK, first of all you need a minimum of 5% of their rated capacity to charger them correctly. With 350W worth of panels you will get about 30 amps, best case. 5% of 1575Ah is closer 80 amps. Not even close. You cannot charge your battery bank with this. They will not get their electrolyte mixed properly and will die from sulfation. The maximum, absolute maximum, battery bank you could support is 600Ah at 12 volts. But this is only theoretical. In practice it will be much less. Try to use the panels you have for your battery bank and they will die.Second. The panels are rated 43.6 volts open circuit. Use them in serial and that will be close to 90 volts. That will kill that charge controller for sure. I am also sure it will not stand up to even the 30 volts. Also the thing is rated at 300W but you want to hook up 350W. It is simple, not enough capacity for those panels, never mind the batteries.So to do what you want, there are three options.1. Use the panels you have and cut down the batteries and buy another charge controller2. Buy more panels, buy another charge controller, and use the batteries you have3. Use the charge controller you have, use one panel perhaps, and cut down on the batteries.Now you say you want 30 amps at 12 volts for as long as you can get. 1575/30 is around 52 hours. BUT. Batteries should never be discharged below 50% charged or they stop working at all very quickly. Actually you should try to always keep them above 70% if you can. So best case is you get 25 hours, worst case (best battery lifetime) you will get 15 hours.To keep these batteries working properly you should have in reality more like 2000W worth of panels and a charge controller or two controllers that can handle at least 160 amps. But you live in England. Because of the amount of sun you get in a day you need probably more like 4000W of panels to charge those batteries correctly. I have not even counted the inefficiency of the charger and other things.This is why people get discouraged with solar energy. The newcomers always set an arbitrary goal and then their jaws drop when they see the equipment needed and price. It is always best to look at your real energy consumption, try to remove any consumption that is just luxury, then find more efficient devices appliances and equipment, and then see what you can live on. Then you design the solar system to match. Conservation is the way to go first. Solar is not a cheap investment, money or time.I think this gives you starting point to think about what you really want to do.

author: mtdoc
author_rank: Super Contributor
timestamp: January 23, 2015, 11:17:23 pm
content: Whoa 1575 AH battery bank! I missed that. Yeah more panels is an understatement..Are you sure that's right snipersquad? That's an awfully large battery bank for a hobby project "just for fun"

author: eneuro
author_rank: Super Contributor
timestamp: May 24, 2016, 11:12:27 pm
content: Hello, I've small 10W solar panel with 0.5A short circuit and about 23Voc, which I use to charge 7AH 12V gel battery.Of course I need battery overvoltage protection, so I've designed such circuit using.. only 12V zenner diodes, optocoupler, mosfet, diodes to protect solar panel from battery at night.Nowadays, in summer I geat easy 0.5A short circuit and this battery is charged in sunshine easy-I use it to make cell phone calls and as stand by for old Siemens cell phone, and it works-I've never charged my phone room wall socket, since I've made 4.15VDC voltage regulator to exchange with flammable Lion oryginal cell phone batteryHowever, looking into this answer:Quote from: mtdoc on January 23, 2015, 07:03:52 pm... assuming I can track sun (I've my solar panel perpendicular to sun most of the daylight), how much more efficient can be controller using MPPT, instead of my solid state battery limiter, which doesn't draw any current when fully charged battery left at floating voltages between 13.5V-13.9V?Quote from: mtdoc on January 23, 2015, 07:03:52 pmWhy I might want MPPT controller, when I can track sun and I have my pannel perpendicular to the sun, which means that this panel can see Sun most of the day?I've just managed to choos all elements for this small PCB to source-without any MPUs (microcontrollers, etc) just analog circuit can take care of 12V battery to limit its voltage to floating 13.5V-13.8V even in the middle of the day at full Sun.Why I might want MPPT -maybe for winter days?I've also bigger ~66W 1.2m x 0.6m pannels, which will be connected in series to create ~250 VDC under nominal load, so maybe some kind of MPPT will be needed, but to charge small battery like 7AH using 10W solar panel it looks like simply solid state battery limiter should work at good Sun light conditions like in the summerI see no reason by something like this, which looks like simply battery limiter, etc , which costs more than 66W 1.2m x 0.6m solar panel, by make a few PCBs 1 in x 1 in (2.5cm x 2.5 cm) which should protect 12V battery, tooColeman 7 Amp Solar Charge Controller with Rings by Sunforce - 60012https://www.batterystuff.com/largerimage.html?id=566

author: suicidaleggroll
author_rank: Super Contributor
timestamp: May 24, 2016, 11:59:06 pm
content: Quote from: eneuro on May 24, 2016, 11:12:27 pmEasy - grab a big power potentiometer, adjustable load, or a set of power resistors and go measure the I/V curve for your panel, covering the whole range between short circuit and open voltage.Now, multiply I*V to get power, and plot that against voltage. You should get something that looks like this (obviously with different x and y scales, but a similar shape):See how peaky that power curve is?Now, measure your battery voltage during a typical charging cycle during the day, see where on that curve you fall. Unless your battery justhappensto be charging at the voltage at which you'll get maximum power from your particular panel, you'll be throwing away your panel's potential. It could be 10% of its potential, it could be 80%, it's easy to measure and check.An MPPT will run the panel at whatever I/V combination results in the maximum power, and then it uses a DC/DC converter to step whatever voltage that happens to be down to feed your battery. With an MPPT you'llalwaysget the maximum power possible from your panel, regardless of sun/cloud conditions, ambient temperature, or your battery's voltage.It makes sense that a decent MPPT costs more than the panel, because without it, you'd probably need to buy a panel 2-3x as large to get the same amount of power out of it in the real world.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 25, 2016, 07:00:29 pm
content: Be careful with those BP charge controllers, they tend to leak electrons all over the place.On serious note, been playing around with solar myself. One thing to keep in mind is whatever capacity you want, double it. You want 100w, get 200w of panels, you want 100AH of battery, get 200AH etc I find a 30w panel gives me about 15w, and you don't want to run batteries at capacity. So in general the bigger the better. The small system I built is for camping, so it's to charge stuff like flashlight batteries, camera battery, phone battery, run 12v lights in the tent etc, so I went with 2x 30w panels in parallel and 14.4ah of battery. I'm working on improving that setup so I have a voltage display and low voltage cut off and since my controller does not float the panel or use a common ground I can't measure the voltage or current easily so will ditch it and build my own, should be a fun project for a noob as I never made a PSU before. Will add a 350w pure sine inverter too. (obviously would not be able to run that at capacity for long but good for a small air mattress pump or something)

author: Flipflop
author_rank: Contributor
timestamp: May 25, 2016, 08:49:35 pm
content: Julian Illett has made some very interesting solar charge controllers using Arduino. I'm thinking of making my own sometime but, at the moment I'm using a fairly cheap Chinese PWM unit with an LCD display.

author: eneuro
author_rank: Super Contributor
timestamp: May 25, 2016, 09:17:21 pm
content: Quote from: suicidaleggroll on May 24, 2016, 11:59:06 pmI've found those P/V curves for example in decent intro there:All About Maximum Power Point Tracking (MPPT) Solar Charge Controllershttp://www.solar-electric.com/mppt-solar-charge-controllers.html/However, what about not search for those power peaks, but approximate this P/V curve based on a few measurements based on available light conditions using photodiode or photoresistors and "hardcode" in MPU flash memory?I mean, cloudy day will change those P/V curves, so advantage of MPPT search will be that it will be able to find those changed Vpeak where we have Ppeak, but if we were able predict those curves based on panel temperature and light conditions for family the same PV panels, we could try estimate based on light measurement ant PV panel temperature, so maybe avoid MPPT peak power search?Anyway, energy "lost" in less efficient battery charging without MPPT could be used to heat something eg. water using simple resistive load to better match solar panels in series with 12V battery sitting close to each solar panel.It looks like, we could have than one bigger MPPT like system for adjustable HV load, while still be able charging 12V batteries.If twenty 7Ah 12V batteries were used we have 240VDC and 1680 Wh of offgrid power available...I've 7 66W 36V 1.2m x 0.6m PV panels so in series in good sun conditions ~250VDC available under a few amps load, which gives less than 1kW, but I'm not looking for expensive huge PV arrays, while I want track the sun.We'll see how this solar panels grid will perform in summer in Europe with full sun trackingI'd like make my own cheap solid state 12 battery overvoltage limiters and instead of buy MPPTs, invest money in a few Ah 12 batteries to be able charge those batteries during the sunny days when PV power will not be used to power up some mechanical stuff directly from the sun

author: eneuro
author_rank: Super Contributor
timestamp: May 25, 2016, 09:23:07 pm
content: Quote from: Flipflop on May 25, 2016, 08:49:35 pmLCD display is not needed for each charged 12V battery controller-I think-red LED diode should be fine to show when it is fully charged at floating 13.5V-13.8V voltage...which means mosfet is turned off, so... we can powerup LED diode-during charging mosfet will bypass LED indicator and it should work without any MPUs involved on small footprint PCB

author: suicidaleggroll
author_rank: Super Contributor
timestamp: May 25, 2016, 10:52:35 pm
content: Quote from: eneuro on May 25, 2016, 09:17:21 pmThat's an option too, but it's significantly more time consuming to measure your panel's performance under every combination of solar incidence and ambient temperature, build up a reference table, then pull in light and temperature sensors into your MCU to index that reference table, etc., and it'sstillnot as good as just developing a simple MPPT that will adapt to whatever you throw at it. Either way, yes, you can target a specific pre-computed voltage and use PWM to drive it, and there are controllers that do that. They are cheaper than MPPT and they aren't as good, but they're still better than just plugging the panel straight into the battery like you're doing now.Quote from: eneuro on May 25, 2016, 09:17:21 pmI'm not sure what you mean. How are you planning on extracting this extra power you don't get without an MPPT, without an MPPT? By that I mean, if an MPPT would give you 10W, but by plugging straight into the battery you're only getting 4W, how are you planning on extracting that additional 6W from the panel to run a power resistor without using an MPPT? And if you do use an MPPT to extract the additional 6W, why wouldn't you just feed all 10W into the battery with it?

author: Flipflop
author_rank: Contributor
timestamp: May 26, 2016, 12:09:42 pm
content: Quote from: eneuro on May 25, 2016, 09:23:07 pmIt has the LCD because you can change the settings for battery type, float voltage and load control. The whole controllers current consumption is less than 10mA. It is only a PWM unit but, better than nothing!

author: eneuro
author_rank: Super Contributor
timestamp: May 26, 2016, 02:34:30 pm
content: Quote from: suicidaleggroll on May 25, 2016, 10:52:35 pmBecause of, using sun tracking mechanical module which will help see PV panel the sun perpendicular to its surface for amost all day will give me more overall power than MPPT connected to fixed PV solar, I guessWhen my goal is keep battery in full charge and It doesn't matter if it will be charged within 5h or 10h, than MPPT might be useless for me, but real sun mechanical tracking system will do the job better.Lets look at the numbers: fixed panel flat in horizontal position and sun at 45 deg angle above horizon-this panle will see in full sun ONLY cos(45 deg) ~0.71 of available sun power in comparision to my looking directly into the sun (perpendicular), so input power looses are 30%.MPPT is not "perpetum mobile" and can't give back this lost sun power due to its fixed position and even if it had 99.9% efficiency in searching for MPPTI've made quick approximation of P/V using linear and cosinus function on normalized P/Pmp and V/Vocand now by passing to this C/C++ function:Quotesolar panel basic parameters I can estimate this P/V curve using additionally Voc adjust for temperature and solar irradiation by using reference PV panel for sensing Voc and Isc at given day sky cloud conditionsWith reference panel not connected to battery it looks like we can estimate sun irradiation by measurement of reference PV short circuit current: I=Isc*k (with a few experiments find coefficient k)and Voc, which can be also estimated: Voc=Vst +B(T-25*C) , where B~ -100mV/*C as start point.Additionally, Voc~Vmp*k , where 0.7<k<0.8, so such quick estimation based on measured sun irriadiance and PV panel temperature should get decent approximation of P/V curve without any MPPT dynamic searching, which in cloudy day can create oscilations.It can be input to PWM in DC/DC, but sometimes ripple and 20kHz+ sound crap created by those modules is not acceptable and simple solid state charging of battery without any MPPT can be usefull, so instead of MPTT... mechanical sun tracker should help recompensate for less efficient solar PV battery chargingAnyway, for those looking for MPPT algorithms there are some hints:Maximum Power Point Tracking Algorithms for Photovoltaic Applicationshttp://lib.tkk.fi/Dipl/2010/urn100399.pdf