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DIY laptop powerbank project

  • sheepish Top 10 Forum Poster Sunday, February 26, 2017 5:31 PM Reply

    A real MPPT decouples the battery from the panels.


    The cheap ones also decouple the battery when it's charged. They do the same job a bit slower, and in a different way. And cheaper.


    A decent MPPT can increase efficiency upto 40%  depending on climate and
    charge state of your batteries among many other to-be considered
    factors.


    The article I mentioned did say that amount of improvement can be seen in winter, when I'm unlikely to be camping, or bothering to set out solar panels. Also, to get that sort of improvement it has to be cold, and it doesn't get really cold here. The quote:


    You typically get a 20 to 45% power gain in winter and 10-15% in summer.
    Actual gain can vary widely depending weather, temperature, battery
    state of charge, and other factors.

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  • Ignatus Sunday, February 26, 2017 7:11 PM Reply


    @sheepish


    Alright, then I understand your summer-time camping situation and power requirements a little bit better now.


    I'm just concerened that many of the ultra cheap ones don't work properly.


    Also, just to clarify, you initially asked me what I think about DX's solar charge controllers and didn't specify if you meant MPPT or regular PWM devices.


    A good MPPT tracks the solar panel's power curve every few seconds and has many other features.


    I don't see see any of those features mentioned in detail with cheaper MPPT devices and would suspect that most of them might be more simple PWM devices wrongly labeled.


    I'm generally a very frugal person, but if I had to decide between investing $50-70 into a well designed and reviewed MPPT from a reputable brand that comes with a 1 year warranty versus a $20-30 device from DX... -I'd spent the extra moolah in a heartbeat!


    -Preferably from the rainforest website. - Can return it easily if it doesn't work properly and no need to wait a whole month to get it.


    Personally, I would want to own the most efficent and reliable charging-circuit available. Efficiency is the very reason for me building a powerbank from Lipo cells in the first place.


    Also, if I estimate that I've spent so far maybe $200 on my DIY Lipo powerbank and will spend another $250 or more on solar panels... penny-pinching on an MPPT (or in my case lipo charging device) doesn't make any sense to me. = Total project cost approx. $500.


    However, if I'd just be camping in an RV for a few weeks during the summer and wanted to go super low-budget and don't care abot bulk/weight then a 40Ah lead-acid battery, 80W -120W of good qualiity panel/s and a $30 MPPT is all that is needed.

    =Total project cost approx. $250.



    It all depends on one's personal needs.




    Regards,

    Ignatus

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    post edited by Ignatus on 2/27/2017 at 2:26 PM
  • sheepish Top 10 Forum Poster Sunday, February 26, 2017 7:27 PM Reply

    I'm just concerened that many of the ultra cheap ones don't work properly.


    I've just been having a look on a certain auction site. You're right, the cheap ones look dodgy! All claim MPPT (at too low a price) but don't have a heatsink on the back.


    I also came across lots of locally available MPPT solar controllers that will handle lead acid and lithium ion cells. They are a bit more expensive but it's nice to know they are available.


    However, if I'd just be camping in an RV for a few weeks during the
    summer and wanted to go super low-budget and don't care abot bulk/weight
    then a 40Ah lead-acid battery, 80W -120W of good qualiity panel/s and a
    $30 MPPT is all that is needed.


    That sounds very close to my situation, except my panels aren't good quality. They're free cosmetic rejects. Price of the controller is thus a bigger proportion of the total.

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  • Ignatus Sunday, February 26, 2017 8:08 PM Reply

    I also came across lots of locally available MPPT solar controllers that will handle lead acid and lithium ion cells.


    OoooH Ahhhh hmmmh..


    If the locally available MPPT controllers that are able to handle lithium cells, are available online, even if just to look at... - Would you please be so kind and share a link via private message?


    That is exactly what I haven't found so far. -A reasonably priced MPPT that can charge Lipos. There is one that I found that was for Lifepo4 cells only and the other one is a

    Genasun MPPT Controller For Lithium Batteries, but the smallest one costs a shocking $99

    That is were my frugal side kicks in and says NO WAY! :)


    Okay, after reading the specs, I'm slightly tempted to spend even this much.


    Electrolytic-Free, Ceramic Capacitors

    Electrical Efficiency:         96% - 99.85% typical     

    Tracking Efficiency:          99+% typical      

    MPPT Tracking Speed:    15Hz      

    Operating Consumption:  0.150mA (150uA)    

    10-Year Warranty



    .........A few seconds have passed since writing the ^^^ above /last sentence...


    then my frugal side kicks in and says:


    $99 for an MPPT? - Only if I dont find a more reasonably priced solution that handles my Lipos.




    Edit/Update:


    Alright, just like planned I'll continue to focus on completing the powerbank related tasks first.


    I've
    just seen that the Genasun MPPT mentioned to be compatibe with Lithium cells,
    but they are  referring to LiFeP04 and not regular LiPo cells.



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    post edited by Ignatus on 2/27/2017 at 2:23 PM
  • sheepish Top 10 Forum Poster Monday, February 27, 2017 4:07 AM Reply
    I haven't found detailed specs yet, just a list of products and prices, so don't know if it's just LiFePO4 or Li-ion. Without tax it's about US$75. The same shop sells 4 cell LiFePO4 batteries from 40 Ah to 400 Ah. Expensive!
    Remembering 30 years.
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  • Ignatus Monday, February 27, 2017 2:19 PM Reply


    @sheepish


    Grrr, could kick myself.

    For just $2,20 more per cell, I found today Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) 18650 shaped cells.


    LG 18650HG2 , 3000mAh , 3.6V , 20A max discharge rate and upto 2000 life-cycles!!!

    Well, maybe the next DIY powerbank gets some of those.


    Anyhow, I just could’nt stop and done lots more reading on solar charging.

    A simple decision has been made:

    Depending on whether I use one or two solar panels, I will either connect the panel/s to a buck or boost converter with CV & CC feature, set it to something reasonable and from there to an ordinary Lipo charger or BMS.


    In regard to your MPPT question:

    After educating myself more, I agree with you and MPPTs seems like a waste of cash for most smaller solar setups.

    Needed are at least two panels in series with just a single 12V battery, or a setup that consists of 3 or more panels in series charging a 24V battery , 5 or more panels in series charging a 48V system etc. …

    Basically, if the panel systems voltage is way higher than the battery system that you want to charge (and maybe even has some panels in parallel), only then splurting on a good quality MPPT from a reputable manufacturer might be justified. - At least that is my opinion.



    In tune with the ultra low-budget, summer-time boondocking spirit:

    a.) for a budget of around $30 choose any regular PWM that has many good reviews.

    -Or preferably DIY one from scratch!  (top notch commercial PWMs can cost upwards of $100)

    Here some good info on how different PWMs are designed/operate including a schematic for a DIY PWM:

    https://ludens.cl/Electron/solarreg/Solarr~1.htm



    If you don’t mind manually disconnecting

    b.) SKU: 358336


    A solution for less than $3? Super Low-tech solution?

    c.) a few chunky diodes in series would do the trick too!


    I really hate that all my posts turn out so freaking long, but I’m always at a loss as to how I could  bring my points across without being specific & elaborative or sounding too rude if I cut it short.

    I was under the impression that nobody writes as detailed and extensive in forum posts or blogs as I do.

    Hurray! -I was wrong!

    Meet the sunshine specialist: Solar Bob


    He writes 100 million-trillion-gazillion word long, blog posts about RV solar panel systems.

    All the solar power knowledge that he gathered over 15 years of his RV solar life.

    So, be prepared to read & die in agony :


    https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/


    Enjoy ,

    Ignatus

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    post edited by Ignatus on 2/27/2017 at 2:22 PM
  • sheepish Top 10 Forum Poster Tuesday, February 28, 2017 4:44 AM Reply

    You don't actually need to keep PMing me. I'm already firmly subscribed to this thread.


    After educating myself more, I agree with you and MPPTs seems like a waste of cash for most smaller solar setups.


    Considering the price of genuine MPPT controllers, yes. Also, it seems the efficiency of a typical MPPT controller's buck conversion may be quite low for small systems. It looks like DX's claimed MPPT controllers are not.


    If you hit enter or space at the end of a link, it links automatically. I've already seen a reference to that guy by someone who was amazed by how much he rambles.

    Remembering 30 years.
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  • Ignatus Tuesday, February 28, 2017 11:31 AM Reply

    Oh, damn it! No way!


    I'm really sorry.


    Seriously, I've had no idea that adding an > a t <  sign in front of a name creates a PM... and I always silently wondered how people send each other PMs here on DX since I could never find that feature button.


    How embarrassing.


    -If I would have known that, I would never have put so many <a t > signs with peoples' names in all my posts!


    Sorry Sheepish and everyone!



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  • ozOzo Top 10 Forum Poster Tuesday, February 28, 2017 1:22 PM Reply

    Heheh, this forum has a bunch of idiosyncrasies that relatively few know about, some I'm sure are intentional, others, well... let's say the IT team here do a very good job of making it appear that they are not as good at programming as they most likely are! We have for instance discovered at least 4 different ways of typing an SKU number that automatically turn it into an autolink like this: SKU: 358336.

    Were you aware btw, that  clicking on the number and clicking on the little red arrow after it bring up two different pages? Perhaps also you hadn't noticed that besides the @usernaim function, there is a forum rules compliant means of sending a PPM (private pm) that only the two parties are privy to (apart from the IT team, no doubt). But I'm starting to ramble so... another time.

    Worldwide 4G bands list:
    http://en.wikipedia.org/
    wiki/List_of_LTE_networks
    Worldwide 3G bands list:
    https://en.wikipedia.org/
    wiki/List_of_UMTS_networks
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    post edited by ozOzo on 2/28/2017 at 1:27 PM
  • sheepish Top 10 Forum Poster Tuesday, February 28, 2017 2:38 PM Reply

    -If I would have known that, I would never have put so many <a t > signs with peoples' names in all my posts!


    LOL. I just thought you were being friendly.

    Remembering 30 years.
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