**The DIY Solar Battery Charger: A Worthwhile Project?**

As I rummaged through my storage, I stumbled upon a few solar panels that had been lying idle for quite some time. Being the curious individual I am, I decided to explore ways to utilize them as power sources for my projects. However, due to the nature of solar panels, directly connecting them to projects wasn't feasible. This is because their output voltage and current fluctuate constantly due to varying solar radiation levels.

**The Commercial Solution: A Worthwhile Investment?**

I came across a commercial solar charger that boasted impressive features such as overcharge, over-discharge, and overcurrent protection, as well as a 5-volt boosted output. While this product seemed like a great solution, I couldn't help but feel that the cost was a bit steep for my budget.

**The DIY Solution: A Cost-Effective Alternative**

I decided to take matters into my own hands and design a custom solar charger that would meet all my requirements. This involved creating a schematic with an overcharge/over-discharge and overcurrent protection, as well as a 5-volt boosted output. I also added a boost component to increase the voltage to a suitable level.

**The PCB Design: A Challenging but Rewarding Process**

I designed the printed circuit board (PCB) using a gerber file that I exported from my CAD software. This involved arranging all the components in a logical and functional order, creating traces, and turning the top and bottom layer into a ground top layer. Once complete, I ordered the PCBs and components from JLCPCB, which arrived after a few days.

**The Soldering Process: A Time-Consuming but Rewarding Experience**

Soldering the teeny-tiny components to the PCB proved to be a challenging task, but with patience and practice, I managed to complete it in around 2 hours. The feeling of accomplishment was immense when I saw all the components securely attached.

**The Efficiency Test: A Disappointing but Not Surprising Result**

I connected my lipo battery to the board and measured the efficiency of the boost converter, which turned out to be around 81 percent. However, when I tested the solar panel with an MPPT voltage of 18 volts, the efficiency was a disappointing 62 percent.

**The Verdict: A Worthwhile DIY Project**

While the DIY project took time and effort, I'm pleased with the result. The board now features all the important missing functions of commercial products, including overcharge/over-discharge protection, overcurrent protection, and a 5-volt boosted output. While it may not be perfect, I believe that this DIY solution is worth the investment for those who are willing to put in the time and effort.

What do you think? Let me know in the comments below!

WEBVTTKind: captionsLanguage: enA while ago. I realized that I got quite a few solar panels laying aroundthat are not being used for anythingDue to the nature of solar panels, it is obviously not possible thoughTo directly connect them to projects and thus use them as power sourcesThey're constantly altering output voltage and current due to different solar radiations is the reason for thatBut feel free to watch my basics video about solar panels to better understand their working behaviourThe solution to this problem would be a circuit that uses a solar panel to charge up a Lipo or Lithium-Ion batteryWhich we can then use as a power source for our projectsBut that such a circuit actually exists was my initial questionWhile searching for it on eBay and the answer is yes such a circuit does apparently existThe only problem is that after I did a couple of tests with its I realized that it is not perfect for my applicationSo in this video, I'm going to ask the age-old question once againDoes it make sense to DIY such a solar battery charger, or should we just buy the commercial solution instead?Let's find outThis video is sponsored by JLCPCB whose service I utilize to order 10 PCB's for this projectFor only $2. They were produced in 24 hours and shipped to Germany in only three daysSo feel free to give JLCPCB a shot by uploading your gerber files todayFirst off, let's take a closer look at the Buy optionAt first sight, the board quality, as well as all the solder joints seem pretty decentThe only thing I subjectively disliked were the JST connectorsBut thankfully the board offers breakout points for the solar and battery connectionsThe main IC of the board is the CN3065constant current/constant voltage linear charger for single cell lithium ion and lithium polymer batteriesSay that three times fastAfter inspecting its pin description, as well as its detailed description in the data sheetsIt seemed like a suitable choice for small solar panelsthat deliver 4.4 volts to 6 voltsThankfully I got such solar panels laying aroundLike this 110 by 60 millimeter one that can do 6 volts and up to 1 watts. SoSo for testing purposes, I directly connected the solar panel to the PCBthrough two thin wires andAs you can see by shining light on the panel, the solar charger does react to it,which was a good signnext it was time to find a test battery which ultimately turned out to be a1200 milliamp-hour Lipo batteryBut right before I was done soldering it to the PCBI realized that the solar charger IC hereonly features an over-voltage protection during chargingBut misses and over-discharge protection and more importantly a short-circuit protectionThis is especially important since the battery voltage is simply bridged over to the SYS OUT JST connectorWhich means we could easily short the battery here if we make a mistakeSo to protect the Lipo for now,I added an additional protection circuit to itbefore hooking it up to the solar chargerAt this point I wanted to test the circuit setup outside but surpriseit is December and the sun did not feel like working with meAs an alternative I had to create my own sun with an LED panelAfter attaching the solar panel to its with duct tape and cranking up the brightnessThe charge LED turned on and the battery started charging move around to 27.5 milliampsAfter then measuring the input current at the solar panel sideas well as its voltage and the battery charge voltageI came to the conclusion that I was dealing with an efficiency of around 70% at the timeSince this circuit works in a linear fashion and does not utilizeMPPT for the solar cell, that is definitely acceptable andBecause the circuit had no problem reactivating the chargingwhile the solar radiation strength was oscillating a bitI have to say that the circuit is definitely usable for small projectsBut then again it got not sufficient protection features for the batteryNo boost converter to create stable 5V for your projectsand no MPPT feature for the solar panelSo naturally, those were the goals for my DIY solutionWhich is why I visited the website of Consonance Electronics nextWhich are in fact the manufacturers of the CN3065 ICThere I found out that they got a whole section with solar panel powered charger IC'sAfter comparing all of those, I decided on the CN3791Which works with a single cell as wellBut uses a switching technique which should guarantee a higher efficiency at higher input voltagesWorks with up to 28 volts solar panels charges with up to four amps and features MPPT functionalityAlong side its other features which were mentioned in the data sheets. It seemed like a perfect fit andLuckily, the IC was also easily availableSo I used the typical applications circuit of the data sheet as a referenceto create my own schematic with the Easy EDA softwareThe datasheet also provided guidelines for the capacitor selectionas well as the inductor, MOSFETs and diode selectionWhich was certainly helpful while creating the schematicthe only thing which I was uncertain about at this point were the resistors R8 and R9Which are used for setting the MPPT voltage but more about that laterOnce the solar charge IC schematic part was completeI simply opened up my old Lipo charge protect boost project and added the protect/boost components to my new Solar Charger schematic andThrough this simple addition. I added an overchargeover-discharge and over current protectionas well as a 5 volt boosted outputWhich means that all my goals for my DIY solution were fulfilledNext I clicked the convert to PCB buttonand started arranging all the components in a logical and functional orderAfter then creating all the traces and turning the top and bottom layer into a ground top layerThe boards did not look half badSo I exported the gerber files of itand then ordered the boards for pretty cheapJust like I mentioned it earlier from JLCPCBAlongside, I also ordered all the mandatory components for the board andafter waiting for a few daysI was not only greeted with a ton of components but also the PCBswhich made a good first impression under the microscopeThat means it was time to solder the teeny-tiny components to the PCBFor which I mainly utilized a soldering iron with a very fine tipas well as a bit of additional flux and solderThe whole process took me around 2 hoursand to my own surprise did not turn out that badly this timeAt least in my opinionAnyway, after soldering all the SMD componentsI added the through-hole components and just like thatMy DIY solution was complete, but did it work?To find that out. I firstly hooked up my lipo batterythis time though without the protection circuits andAfter flipping the power switch the output of the boarddelivered 5.13 volts. Perfect.Through the help of the USB constant loads and my lab bench power supply,I then calculated the efficiency of the boost converterwhich turned out to be at a maximum of 81 percentand features a maximum current draw of eight hundred and seventy milliampsAfterwards, I also tested all the protection features which worked just fineNow for the solar panel tests,I did not feel like working with such a tiny panelinstead I went with this 10 watt one,which features a maximum voltage of 21 volts,a maximum current of 0.61 amps and an MPPT voltage of 18 voltsThis voltage is important for our DIY boardSince the MPPT pin of the ICneeds to be at a voltage of 1.205 voltswhen those 18 volts are applied to the resistor networkSo after a bit of calculating I got the required resistor valuesand thus soldered them in place on the PCBOnce that was done. I hooked up my solar panelto the boards and positioned it very professionallynext to my LED panelAfter cranking up the brightness to the maximum.The circuits came to life and charged up the battery successfully andYes, you can charge it while outputting a constant 5 volts for your projectsbut after measuring the input power/output power, it seemed like the efficiency of the circuits was still a bit lacking to say the leastAs a result, I went outside in order to find some proper sunlightwhile monitoring a couple of important valuesBut no matter how much I tried I never got any decent resultsdue to inconsistent solar radiationBut what I can say from the outdoor test,is that the MPPT tracking seems to function correctlyeven though the set voltage seems to be a bit higher andLuckily, I was able to perform a successful indoor efficiency testlater on which turned out to be around 62 percentwhich was acceptable considering the terrible experiment conditionsSo all in all I'm pretty happy with my DIY solutionSince it adds all the important missing functions of the commercial productsWhile still being versatile due to its wide voltage input rangeThe only negative things are they spent time for soldering and the money aspects?But for me that is definitely worth it,which is why DIY is this time the winnerBut what do you think?Let me know in the comment section belowAs always, thanks for watching. Don't forget to Like, share, subscribeStay creative, and I will see you next time!