Feedback please

SystemSystem Posts: 2,511 admin
I am new to this and solar power is now my hobby focus. I need some feedback on if I am really off base with my idea or not. Let me start by saying, this setup will only be for running a few low wattage lights outside every once in a while and running a few items during a blackout if needed, but luckily, that doesn't happen very often in my area, but it's nice to have something. Freezer would be the only thing I might run if power was out for a couple of days.
Here is what I currently have:
Cells to create a 60 watt, 18 volt panel.
Panel for the cells.
2 12 volt AGM 100 ah batteries @ 8 hour dischage rate (found these on a deal so I bought them)
1500 watt inverter
Solar Boost 2000E, 12 v 25 amp. (I probably over bought here but my thinking was for more panels in the future so it's an investment.)

From the things I am reading, it looks like I don't have enough panels to recharge both my batteries correctly but it does look like I could recharge one of them with the one panel. Does anyone have any feedback? Am I on the right track, or am I off? Does anyone have any suggestions on setup? My current plan is to keep the batteries at 12 volts but string the together and make sure to hook the inverter to a battery from the positive while taking the negative from the other battery. My plan for the panel, since this is a mobile setup was to set the panel in the backyard to charge and when bad weather really hits(aka hail) move it in till it passes. In this type of setup, would I need to ground the panel?

I appreciate any advice you can give me!

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Feedback please

    Welcome to the forum.

    You may be a bit optimistic about charging even one of those batteries with that panel. You might realistically expect 3 Amps from 60 Watts, and that's rather low even for 100 Amp hours. With good sun and light use it might work.

    As for back up power for the freezer ... Forget it. Refrigeration equipment is a big power user. It has high start-up demands, wants pure sine wave power, and will use significant Watt hours over time.

    Have you read all the warnings here about homemade panels? They are not only difficult to build, but inevitably fail. Sometimes dramatically.

    Sorry; this looks like a horrible load of bad news. :blush:

    To actually recharge those two batteries, btw, you'd need about 400 Watts of panel.
  • System2System2 Posts: 6,290 admin
    Re: Feedback please

    Thanks for the feedback. It's not horrible news, it's just a learning curve!

    I do know about the dangers of DIY panels, but I wanted to do one just to understand the internals. I learn better that way. I think I am doing as much as I can to limit issue though, I have glass/aluminum panel made for solar, and have been able to get the Dow encapsulant so I won't be using any wood or plastic backing. I'll have to rethink a few things, but this is what I needed, Thanks! I am sure I'll be asking more as I rethink and research a few more things.
  • BB.BB. Super Moderators, Administrators Posts: 28,607 admin
    Re: Feedback please

    The following are some cuts and pastes from an Everything Solar FAQ thread:

    Here is a nice thread that discusses building a smallish emergency power system:

    Emergency Power

    And here is another example by Mike90045 called the Solar Monolith:

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    Update pictures/information here.

    For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.

    Here is a nice thread with video from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Feedback please

    we generally recommend charging at a 5%-13% rate of battery capacity and at the minimum you would be looking at 5% x 200ah = 10a. many here state a 77% typical rate of return from a pv so this ups the current from the pv to about 13a needed. that's a far cry from the 3a or so your proposed diy pv could possibly provide in any case.
  • System2System2 Posts: 6,290 admin
    Re: Feedback please

    I am going to ask a stupid question, please bear with me. I've been reading the battery FAQ pages to learn, and I am trying to figure out if I would damage my batteries if I don't charge them with at least 10amps for both batteries or 5 amp for just one. Are the suggested min amps just a guideline? If I charge the battery slower, would it be a bad thing, or would the 3 amp panel not even charge a battery of this size? My plan is to not use it every day, but to use it occasionally so it would have a few days to a week to recharge to full capacity, at least that is my theory.
    Thanks!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Feedback please
    I am going to ask a stupid question, please bear with me. I've been reading the battery FAQ pages to learn, and I am trying to figure out if I would damage my batteries if I don't charge them with at least 10amps for both batteries or 5 amp for just one. Are the suggested min amps just a guideline? If I charge the battery slower, would it be a bad thing, or would the 3 amp panel not even charge a battery of this size? My plan is to not use it every day, but to use it occasionally so it would have a few days to a week to recharge to full capacity, at least that is my theory.
    Thanks!

    Not a stupid question at all.
    A battery that doesn't need 10 Amps isn't going to take 10 Amps; the Voltage will be high enough (and the internal resistance as well) that it will come up to charging Voltage quickly. Neither current nor Voltage is fixed in charging; both vary according to the state of charge of the battery and the stage of the battery charging. The 5%-13% is a peak current target, so that if the battery is well discharged there is enough power there to bring it up quickly, and still get through the Absorb cycle while there's daylight left.

    AGM's are even more lenient on this, as they aren't as apt to suffer from sulphation and don't have any electrolyte stratification problems. They can take more current or less, but are picky about Voltage.

    FLA's can be charged at a lower rate but risk both sulphation and stratification (especially the tall case batteries). This can be overcome by an occasional equalization charge. They are less picky about Voltage but more so about current.

    Curiously, deep cycle batteries do want to be cycled deeply at least once in a while. They don't like to be kept "floating forever". No battery, however, wants to be recharged over days: start the charging process and finish it.
  • BB.BB. Super Moderators, Administrators Posts: 28,607 admin
    Re: Feedback please

    For lead acid batteries, the tend to start to sulfate if kept below ~75% state of charge for more than a few hours. So, when your battery is discharged below ~75% state of charge, you should try to get back up above ~75% state of charge within a day (solar, genset, etc.)...

    The longer/deeper the battery is below 75% state of charge, the more capacity the battery will lose.

    Say you have a cabin with a minimum amount of solar panels (between 1% and 5% rate of charge). You can use the batteries and on Sunday AM before you take off, fire up the genset and recharge the battery bank back above 75% state of charge--turn off the genset and head on home--letting the solar array bring the battery bank back up to full charge.

    Charging a battery bank between 20% and 80-90% state of charge is fairly fuel efficient--and fairly quick. The last 10-20% charging will take 2-4 hours of gradually declining charging current--better suited to solar rather than a genset.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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