After two previous generations of my Solar Power Supply receiving positive feedback on here and YouTube, I thought it would be time to share with you my third generation design.

Much like the previous version, this design improves from the second with a higher capacity battery bank, a more efficient charge controller, better electrical safety in terms of fuse implementation, more outputs and digital displays that show you just how much power is being generated and consumed.

So whether your after a solar power station yourself or are just interested in what's new this time around please read on...

Step 1: What do you need your system to do?

The first thing to plan is to work out what you will be wanting to power from your system, as mentioned in my previous Instructable, the whole of your house would be nice but seriously expensive and definately not portable. My system will only power small items such as an LCD TV, a couple of 12V energy efficient lightbulbs, a free-to-air receiver, a CD player and radio and to charge mobile phones and other miscellaneous items.

With your power intentions in mind it's important to now figure out the prices for each of the components, I wanted the best of the best so I settled for a top of the range PS-30M 30 Amp Morningstar Charge contoller from Sunstore.co.uk at £198.00 or $315. http://www.sunstore.co.uk/Morningstar-Prostar-30M-Solar-Charge-Controller-with-LCD-Display.html
This charge controller uses Pulse Width Modulation (PWM) to float charge the batteries once fully charged to maintain them whilst incorporating an LCD display to show the battery voltage and solar input current.
For the batteries I went for two Trojan T-105's, being six volts a piece to total 12 volts at 225Ah, this meant that the storage capacity of this bank would be huge, enough to power high drain devices for many hours.

With my two previous generations I used Maplin Electronics and Ebay to source all of my components but this time money wasn't as much as an object so I ended up splashing the cash on a multitude of sites.

The main items to power from the system are then used to calculate just how much power is needed and generated. The LCD TV and receiver draw 2.2 Amps DC on 12 volt, energy efficient lighting draws just under 1 Amp for a 12 watt bulb whilst the phone/GPS chargers draw very little power. Using the TV for say, 3 hours a day max would equal 6.6Ah consumed, lighting used for 4-5 hours a night would consume roughly 4Ah while all the charging of portable devices would be around 2Ah while pumps for air-beds wouldnt run for long so maybe only consuming around 1Ah, totalling 13.6Ah. Deep Cycle batteries shouldn't be discharged below 50% of their rated capacity, the smaller the discharge cycle, the longer the battery will last, therefore a battery of 30Ah would suffice. The UK receives on average 6 hours of sunlight per day during summer, which is the time of year we go camping, the main reason for building this system, therefore replacing 13.6Ah into a battery would take a 50W solar panel roughly 5 hours to recharge.

(Watts = Voltage x Amps)
(Average solar panel voltage at max power = 17 Volts)
(50 watts/17 volts = 2.94 Amps)

It's easier to draw power from a battery than to replace, requiring usually 10% more power to recharge than what was consumed, therefore:
(14Ah / 2.94 Amps = 4.76 hours of direct sunlight)
In a real world situation this will never happen due to too many different factors such as;
Solar panel shading,
Overcast conditions,
Battery temperature,
Size of wiring,
Other losses.

Therefore it's safer to use a larger battery bank, where power can be used up repeatedly if weather conditions the day after aren't suitable for efficient solar charging to completely recharge the battery. My 225 amp hours is way overkill but it's better to have more power than required.

I already had my solar panels from my previous solar power supplies consisting of two AKT 80 Watt solar panels, one BP 80 Watt solar panel and four BP 12 Watt panels totalling a theoretical 290 watts. All of my panels were sourced from eBay over the years.
You said that &quot;I wanted the best of the best so I settled for a top of the range PS-30M 30&quot;. Why didn't you go with an MPPT controller (https://en.wikipedia.org/wiki/Maximum_power_point_tracking)? They'll harvest up to 33% more energy from your panels over a PWM controller.&nbsp; Looks like a fun project though and I know what you mean about &quot;admire my baby&quot; as I have several projects of this nature although you've taken yours to a nice finished case and all.&nbsp; Mine never seem to make it past the its working great stage but don't get the fit and finish job you've so nicely done with this unit.&nbsp; Also with that box venting issue, you might consider a small say 20 to 40mm 12v fan and about 5 diodes in series to drop the voltage to the fan.&nbsp; It will run very slowly except during peak charge voltage time when the batteries start to gas at the end of the absorb cycle and use almost no energy (about 250mw w/80mm fan).&nbsp; You can always put a manual over-ride switch (SPDT) on the fan to remove the diodes and run full speed when you want extra venting and turn off the fan altogether for storage or when you just don't have a need for venting.&nbsp; The fan will turn so slow most of the time that you won't hear it operating.&nbsp; I use a similar setup for one of my whole house battery banks that is kept inside my garage (1300amp/hrs@12v).&nbsp; It is vented to the outside using a clothes dryer venting kit modified with an 80mm 12v fan (computer case fan).&nbsp; This way there is about zero risk of gasses building up and exploding.<br> <br> Cool Toy ......... enjoy<br> <br>
Hello there, <br> <br>I just wanted a reasonable PWM controller as the energy increase using an MPPT controller isn't always as good as advertised. Sure if I had the funds to allow for a MPPT charge controller then fair enough, but my current PWM is fine for my needs, it beats my previous shunt style on-off regulators used in my previous supplies. <br> <br>Thanks for the comment, <br>Lewis
Nicely done. <br>How much are you using the AC inverter? The crazy thing about AC is, of course, 99% of the time it gets converted to DC for use in the device. It would be easy enough to add a few DC-DC converters to replace wall-worts and other external AC adapters. Items that plug directly into an AC outlet would need to have their warranties voided by removing/bypassing their internal power supplies... but I'd think that would be more efficient overall? Maybe not. Plus, sometimes it's just nice to plug stuff into an AC outlet and not worry about it.
Thanks :) <br> <br>I don't use the inverter that much as I know how inefficient converting DC-AC to DC again. That's why I have the three dc output plugs as I prefer to use DC over the inverter whether it's for charging phones, headsets, cameras, powering tv's, lighting, clocks or fans to name a few. <br> <br>Thanks for the comment, <br>Lewis
Oh, I love the wooden case you built for this! I have a small system I built when I lived in NM, and it's in an ammo box and an old steamer trunk I lined and vented. It works, but yours sure is prettier!
Thanks for the feedback it means a lot :) <br>Lewis
Perhaps you have made a little &quot;slip- up&quot; in your instruction regarding lead acid battery maintenance. To check charge status, a HYDROMETER is used to test SPECIFIC GRAVITY, NOT A hygrometer.
Aha, so I did, maybe I wanted to measure the humidity of the batteries though ;), <br>Thanks for alerting me, <br>Lewis
Acid based batteries with vent caps can release hydrogen gas while charging. These are not like the sealed batteries used in UPSes and flashlights. <br> <br>Storing your batteries inside while charging can create a real explosion hazard. <br> <br>
Yeah I know that they do, but only two batteries releasing a little hydrogen gas that floats as it's lighter than air in a well ventilated room in reality wont pose much danger, trust me I know enough about the hazards and risk assessment as I've just finished a three year course on risk management and assessment at university.
Very nice system. <br> <br>Clearly this is something that has evolved over time. <br> <br>What would you say your total investment is ? <br> <br>Doesn't seem necessary to keep the battery right there in your living room. Seems like that could be kept out of the way like in closet, garage or basement &amp; then only have the control unit in your living room. Looking at the setup i'm thinking thats more for vanity than practicality. I'm thinking you like having it all front and center so you can admire your &quot;baby&quot; and show off the system to your friends. Absolutly nothing wrong with that. ;) <br> <br>Nice job.
Thanks :) <br> <br>This is the third version of my solar power supply, and if I do say so myself, the best one yet. <br> <br>If I built this version from scratch without using parts from my older ones I would say that it would cost me around &Acirc;&pound;1000 ($1600). But seeing as I used my existing radio, solar panels and inverter I'd say that it cost me around &Acirc;&pound;550 ($880)? <br> <br>It's for pure practicality that the battery sits next to the unit as running heavy grade DC cables from one room to another would not only be expensive but the voltage sag at the end of such a cable run wouldn't be worth considering. As you say, I like to admire my 'baby' whilst using it as a handy but heavy, bedside table ;), <br> <br>Thanks for the comment, <br>Lewis
How many AH are those batteries? They look huge. <br> <br>You should be able to run quite a bit more off your system. I used to have a 27&quot; CRT running off my 45 watt system.
Hey there, <br> <br>The batteries are rated at 225Ah, tonnes of power available for whenever I need it. <br> <br>Thanks for the comment, <br>Lewis
Very impressive. <br>Congratulations. <br> <br>Shouldn't the the battery container be vented ?... (maybe I'm making a fool of myself by asking such a question &acirc;€&brvbar;&Acirc;&nbsp;but then again &acirc;€&brvbar; :D <br>
Ah whoops, forgot to mention about that :). Yeah the battery container has to be vented and I achieved it simply by drilling some 20mm holes in the back of the container in a line, one of which the main power wires come out of. <br> <br>If I discharge the system quite a bit during the night, upon reaching full charge the next day it is normal to hear the batteries bubbling and gassing when they approach full charge. <br> <br>Compared to the sealed maintenance free batteries used in my previous designs these batteries require occasional topping-up of distilled water whilst more than occasional battery monitoring with a hygrometer is critical not not allow the specific gravity to fall too low. Just remember to wear eye protection when dealing with sulphuric battery acid :). <br> <br>
thank you !&hellip;<br>have nice sunny day :)
<p>Hi Lewis. I am currently doing a portable solar power supply.</p><p>Here is my question. Do I need to connect a circuit breaker between the battery and solar charge controller. For me to switch off if it is not in used? Or the solar charge controller will auto switch off when it is not in used or it will run for 24 hours??</p><p>Thank you.</p>
<p>The solar charge control unit will balance and discharge the power so battery's will not get over charged, you do not need a switch between solar panels and a charge control unit. That is its function, to divert and control the power going into the battery's</p><p>.http://www.eagleready.org/solar/wiring.html</p>
<p>You should go to inplix webpage if you want to learn how to build it yourself.</p>
<p>wow! This system is pretty awesome! Just wondering if you might know how I might disconnect my tied in home roof system from the grid and go direct into my home, in the event of ? Blackout, or terrorism? I'm new at this but want to prep for the worst. Thank you for any info you can give.</p>
<p>Did you build something less fancy gadget? Like without stereo and some those stuff. I'm try find instructable that simple something recharge power tool. and power up the light. Something for off the grid. I'm plan going off grid. Last thing I want keep going back home to recharge all battery for my power tools</p>
<p>Oh, I love the wooden case you built for this! I have a small system I built when I lived in NM, and it's in an ammo box and an old steamer trunk I lined and vented. It works, but yours sure is prettier!</p>
<p>Solar Power Supply was totally unknown for me. I visit a site https://www.indiegogo.com/projects/solar-250kw-mobile-power-station here i first seen this topic but thanks to you shared details on that.</p>
<p>Acid based batteries with vent caps can release hydrogen gas while charging.</p>
<p>Acid based batteries with vent caps can release hydrogen gas while charging.</p>
<p>Why did you use a 50A fuse on the Negative of the battery box?</p>
<p>Doesn't seem necessary to keep the battery right there in your living room. Seems like that could be kept out of the way like in closet, garage or basement &amp; then only have the control unit in your living room.</p>
<p>Great instructable! I've learned a lot and seem to be developing a passion for efficient renewable resources. </p><p>I'd like to suggest more efficient solar cells for version 4? Basically stick a glass ball over the solar cells and focus the light, like in the link below. Possibly miniaturize the whole power supply? ;-)<br></p><p><a href="http://www.indiegogo.com/projects/rawlemon-solar-devices" rel="nofollow">http://www.indiegogo.com/projects/rawlemon-solar-devices</a></p><p>Keep up the great science! </p><p>M</p>

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