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Thread: Micro-Solar Setup : My First Experience w/Off-Grid Electricity

  1. #171
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    Good job. It's difficult but enjoyable, important work.
    Don't bring skittles to a gun fight.

  2. #172
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    2nd batch of batteries arrived today. Too late tonight, but tomorrow I'll get cracking on next steps "top balancing" as the next set isn't slated to arrive until mid-December.

    Also, finally broke down and decided to throw down the coin for a 50 amp MPPT solar charge controller which should be here day after tomorrow. That will support the three 210 watt panels I want to upgrade to, later this year or early next.

    This reflects a reconsidering of the strict observance of maintaining a purely 12v system, while preserving that option for future circumstances. More on that later.
    Last edited by bruss01; 11-21-2020 at 07:56 PM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  3. #173
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    First and second battery shipments undergoing "top balancing".

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    Here's Will Prouse explaining what it is, why it's beneficial, and how to do it.

    https://m.youtube.com/watch?v=x5ABvbbics8
    Last edited by bruss01; 11-21-2020 at 06:12 PM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  4. #174
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    Will has a VERY informative channel. LOTS of good info for everyone!!


    I donít have a low voltage charger besides a small one for 18650 and 14500 batteries so here is how I balance the batteries. I connect all of them in parellel just as you did, but I let them sit like that for about 48 hours. It is not as good as top balancing, but it is much better than doing nothing.


    For those that donít know what we are talking about, here is a brief explanation;


    The lithium batteries we are talking about are individual cells. It takes 4 of these cells wired in series to equal a 12 volt battery. Each of these cells has a working voltage range. This is typically about 2.5 volts minimum to about 3.7-4.2 volts maximum. So with 4 of these cells wired up in series, your 12 volt battery bank has a useful voltage range of 10 volts to about 14.8 volts. Anything above or below this range can damage the cells. When you get these cells, they are rarely ever balanced meaning they rarely ever are the exact same voltage. So each cell is at different states of charge. If you do not balance the cells then you run the risk of having one cell at a lower voltage than the rest, and thus since it will be at a lower voltage then the rest of the cells as it is being discharged, the overall capacity of your battery bank will be decreased. This is because once that one cell reaches 2.5 volts, the BMS will shut off the power in order to prevent damage, even if all of the other cells are sitting at say 2.8 volts when this happens. If the BMS does not shut off the power, the one cell voltage will drop below its design specification and it will end up being damaged.


    Lithium batteries have incredible capacity, incredible cycle life, and incredible power density, but at the expense of being fragile in some ways. Every battery type has its pros and cons. This is why research is so important to find out what battery chemistry is the best for your individual needs.
    Prepare for the worst, hope for the best

  5. #175
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    Still charging at 2.80 amps after running all afternoon and overnight, so there was a good bit of unfilled capacity in these despite all testing at 3.2v right out of the box. As Will explains, the discharge curve on these is so flat that just a voltage reading isn't a very good indication of what percentage of charge capacity is being used. Getting all the individual cells equally full before ganging them together in a battery will ensure that they're all using the greatest amount of their usable capacity from the outset. Otherwise it's like a herd, who can only travel at the speed of the slowest cow or calf... you have a straggler hindering the whole group.
    Last edited by bruss01; 11-22-2020 at 10:40 AM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  6. #176
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    Somewhat disappointing weekend. It seemed like everything took 3x longer than it should.

    I intended to install the hinges for the lid. That turned out to be a challenge in unexpected ways.

    First, upon determining to install the hinges, I discovered they were side-mount. But I don't have sides... ok, we fix that...

    I put a 5" section on one end by the terminals and charger. Actually looks ok. The bigger challenge was the far end by the inverter. Plywood in a thin segment that would allow full access to the inverter wouldn't be steadfast enough to support the weight of the lid. So I made the decision to go with aluminum for the hinge support. .this involved my first experience with Alumalloy, an aluminum brazing compound. It was a mixed experience and I'm not 100% satisfied with it but it feels solid despite the rookie assembly... so for now it goes into the build. Including time out for lunch and a trip to the hardware store (propane torch was insufficient at least how I was using it) this took the entire day sad to say.
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    I'd intended the L-shaped sections to run horizontal but the hinge will require clearancing the enclosure wall a bit. In retrospect i would have liked to run those top to bottom and T-boned the square tube where circumstances warranted... but I wasted a whole day getting this far and I've learned not to let the perfect be the enemy of the good. If the pics above seem confusing, it's likely because some of them are with the bracket mounted the wrong way.

    The Alumalloy was not as easy to work with as I anticipated. I wasn't having good results with the propane torch, so I ran to the store for a mapp gas torch. I finally did get it to work, though I melted a small bit of aluminum in the process (not a big deal). So I'm sure it was hot enough. Next time I'll pay more attention to surface prep. The pieces do seem very firmly bonded despite my rookie job of it.

    And for those who are interested, the Bits & Pieces for today include:
    3/4" aluminum square tube (12.25")
    1" aluminum "L" beam, 3 inches (2)
    Alumalloy, 1 stick
    Last edited by bruss01; 11-23-2020 at 05:35 PM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  7. #177
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    Other end.

    ETA - bloddy hell... I'm having fits wit photo posting. Forgive the irrelevant firearm pic.

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    Last edited by bruss01; 11-23-2020 at 01:04 AM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  8. #178
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    Got hinges in the box today, took about an hour and a half.

    Didn't realize going in that the box wall would need to be clearanced for the hinges, so I had to gouge out some grooves. That's an ugly piece of work but it's functional. Anyone going down this path, if you have a router and can do a nice job of it before assembling the box, it's worth your while. Maybe once it's painted it won't look quite so crude... maybe?

    Anyway, here are shots of the carnage.

    Hinges 8.jpg
    Hinges 7.jpg
    Hinges 6.jpg
    Hinges 5.jpg
    Hinges 4.jpg

    Bits & Pieces from today's episode:

    Bench Seat Hinge for Toy Chest- Lid Support Stay Hinge- Heavy Duty No Slam Safety Torsion Hinge
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    #10 pan head screws 1/2" (4)
    Last edited by bruss01; 11-24-2020 at 09:02 PM.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  9. #179
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    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

  10. #180
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    In other news - the LiFePO4 cells were still charging at 2.75 amps a full 48 hours after putting them on to top-balance at 3.6v... at this rate we'll be at it until Christmas. as they started at 2.96 amps two days ago.

    I've bumped up the voltage to 3.8v and saw the charging amps go up to 5... checked in a couple of hours by turning volts back down to 3.6 and saw only 2.33 amps current being drawn. I don't want to push it higher than 3.8 because once they get full, the are DONE and this is a case where more isn't better. I'll continue to check them every couple of hours this way... the initial 5 amp charging at 3.8 has dropped down to 4 amps presently, so we're making some good progress now.
    "The thing about smart people is they seem like crazy people to dumb people" - Stephen Hawking

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