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Thread: All-in-One LiIon and Solar Powered Ground Station in a case

  1. #1
    Navigator Arxangel's Avatar
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    All-in-One LiIon and Solar Powered Ground Station in a case




    Well, I think this is LONG overdue given how many FPV planes I have, and also the fact that pretty much all of them could fall into the long range category! Since I am not planning on giving up long range flights, I decided to end my suffering and finally build a dedicated ground station that would have everything I need for those planes in one case, and I will no longer need to spend an hour before every flight unpacking stuff, arranging them, connecting cables, antennas, etc., those of you that also fly long range should know what I am talking about!





    My plan is to stuff everything needed for such flights in a single case, so that when I am about to go flying I would take only one case with me, and a chosen plane, or two, but they would all work with the same ground station. Some of the things that it will need to be in there are a monitor, a tablet (in my case a Windows one, as I prefer to work with Mission Planner), possibly a second monitor/goggles, the antenna tracker, a tripod for the tracker, Taranis radio, antennas, LiIon battery, a charger, 5v USB outputs to allow smartphones and other electronics to be powered, as well as a few 12v outputs just in case, in addition to powering everything else that is built in! The antenna tracker will probably have a battery of its own as it doesn't really consume all that much and I would like to have no wire running between the case and the tracker. Video will be transferred via a wireless link. The ground station itself will also be solar powered. I will get a 50W foldable solar panel that would fit perfectly within the folding table I keep in my car at all times, and will connect it to the ground station every time I use it, with the hopes that I will never have to connect the battery to a proper charger... but we will see how this is going to go!


    The build log as well as a full parts list can be found in my blog: ArxangelRC.blogspot.com




    STAGE 1


    Right, all projects need to start somewhere, and since a LiIon battery is something I have not had contact with until now, I decided to start there so I can have time to properly test it and assess its viability for this project. This would also allow me to familiarize myself with this type of battery and would allow me to figure out ways to use them elsewhere! Also, a LiIon pack would weight less for the same capacity compared to a LiPo battery, and with all the stuff I want to cram into this case I would welcome every chance to save some weight. I know, it is not critical for this ground station to be light as a feather as I will only need to transport it from my house to my car... 20-30 meters, but still... you never know where you might need to take it at some point!





    OK, enough babbling and lets get this show on the road! So, for a first try I didn't want to spend money on high quality cells, like what you can buy from NKON, since there was a real chance that I could destroy them, so I decided to go a cheaper route and ordered 2x replacement laptop batteries off of eBay. Each battery has 6 LiIon cells in it, so I ended up with 12 cells, which should have been 2600mAh each... though I never really expected that to be true, and they didn't disappoint - after cycling them on my MC3000 charger a few times it turned out that they are actually around the 2000mAh mark, but since this was only a test pack, I didn't really care.





    About two years ago I did play for a bit with two LiIon cells, but back then I soldered them together with a regular soldering iron, and since I didn't know that excessive heat could damage them... that is what happened, and they ended up having a lot less capacity than they should have. This time around I wanted to avoid taking a chance with a regular soldering iron, so I decided to invest in a proper spot welder. As luck would have it, Banggood had recently stocked one pretty acceptable model, price wise, and after some quick research I decided that it would be perfect for my needs, although given how quickly LiIon batteries are taking over... everything... I just might have some more work for it after all! Along with the spot welder I also got some pure nickel strips to allow me to put the pack together.





    Right, so at this point I had almost everything I needed to be able to build my pack. The last missing thing is a BMS board. This board basically takes care of cell balance during charging, and also acts to protect the battery from being overcharged or overdischarged. I got one for a 3S battery, because that is the voltage I would need for my ground station. The convenience with these boards is that you need only connect two power cables to the battery, and start charging it, the BMS will take care of the balancing and will cut off the charge when the pre-programmed max charge voltage has been reached! A disadvantage is that the balance action is very weak, and when you are charging and discharging the battery quickly, the BMS will not be able to cope up with the balancing, and over time the cells will become out of balance, which is one of the major reasons why LiIon packs fail! That is why I will also solder an additional balance cable to this pack, so that I can monitor the cells' balance with my charger, and balance them if needed to keep the pack healthy!


    OK, so now that I have everything needed, it is time to start assembling the pack. Since I have 12 cells and I need a 3S battery, I will be able to make a 3S4P pack. The 4P means that I will have 4x 3S packs in parallel, thus increasing the capacity of the whole battery. In this case it will be 4x 2000mAh 3S packs in parallel, which equals 1x 8000mAh 3S pack. After I decided on the configuration it was time to put my brand new spot welder to work! I was very pleasantly surprised how easy it is to work with one of these, and guess what... there are no unpleasant fumes to worry about. Assembling the whole pack literally took a few minutes, and I did have some fun watching the sparks fly around during the welding process! This was a refreshingly enjoyable experience!





    Now that I had a completed and working battery pack, it was time to put on the BMS board. Looking at the instructions it was easy to solder the main power cables and the balance wires to their proper places. Initially I was surprised why I couldn't get a voltage reading from the BMS board, but as it turns out it is disabled by default and needs to have some current put through it to activate it, which I did by measuring between both ends of the board with a multi-meter set to continuity. After that it worked perfectly. It is interesting to note that when the battery is being charged slow, the BMS does a pretty good job of balancing the cells.





    With the battery pack now complete, and since I want this ground station to be solar powered, it was time to turn my attention to that part of the project! To that end I also purchased a 10W solar panel for this test pack, and a dedicated LiIon solar charge controller that is super small and compact, and is actually properly programmed to handle 3S LiIon batteries. Soldering connectors to these items was quick and easy, and my connector of choice here is XT30, because I would never see currents over 30A, so there is no point in using a larger connector. I also added a watt meter between the solar panel and the charge controller, because I want to be able to monitor how much current is coming in. I will also put one between the battery pack and all the gear, so I would know what voltage the pack is at, and how much current everything is pulling.











    Now that everything has been assembled, welded and soldered, it was time to start testing this new system. Here in Sofia the pollution in the air is so thick that even outside in direct sunlight it will not do the full 10W... it achieves somewhere around 8W. I will have to test it outside the city where the air is cleaner, but if it turns out that this is not the problem, thеn I guess this is just how much the panel is able to give! In any case it should be OK for my test purposes.





    So far the BMS is working great and at these lower currents that the solar panel is able to give, it is doing a good job balancing the cells! We will see how it will perform with the 50W solar panel, as it will able to give around 2.5A of current. The solar charge controller actually stops charging the battery at around 4.1v per cell, which is perfect because that is how I wanted it to be, so I can increase the life span of this pack. I will also not be discharging it below 3v per cell in line with that same goal. The battery itself is able to give quite high currents and it gets only slightly warm. I am sometimes using it to charge my large 6S packs, and it does pretty well when I pull 60-65W out of it for a prolonged period. I am pretty happy with how things are progressing so far, so stay tuned, more is to come!






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    Navigator Beerwiser's Avatar
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    Very nice so far, looking forward to the build since I like my long range too.
    "You get what you put in, and people get what they deserve"
    Kid Rock

  9. #9
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    Very professional!

    I need me one of them spot welders.. I made the mistake of trying to convert a 3S to 2S by removing one of the cells... yeah now I can't solder them back together!

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    All-in-One LiIon and Solar Powered Ground Station in a case

    Hi,
    Just wondering, how do you plan to use the battery while charging ? Since the current setup does not permit that, so you either charging or powering up the ground station.....

    In my last setup I used an SLA battery with a picoUPS board, no solar but can charge and use GS simultaneously....


    Sent from my iPad using Tapatalk Pro

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