Simple solar light setup

sunshineloversunshinelover Posts: 3Registered Users

Hi all,

I'm just starting out with solar. My first project is a stand alone light system for the kitchen.

My goal: To have a stand alone strip light run by solar & battery. I really want this. We have lots of storms where I live and there's always the threat of electricity going off for awhile. Also, I love the idea of being more independent. Here's what I have:

Renogy 30 watt mono solar panel, 12v 20 amp solar charge controller, 35ah 12 volt battery, 1.5 foot strip light (7.7 watts/foot, 12v).

I want this to be my main lighting in my kitchen. If it works out well, I won't even use the regular ceiling light anymore. I know the 30 watt panel probably won't charge the battery very fast, but it will live in the upper part of the kitchen window (inside the home) and it's the biggest wattage panel I could find that would fit.

My questions:

a) I want an on/off switch and have no idea where it should be wired in. If somebody could link to the correct switch on amazon I'd really appreciate it, plus tell me where to wire it in. Would the off/on switch be enough, in case of arcs or smoke, etc? I've been reading this forum and the smoke & arcs came up, which concerns me. The solar panel is connected to the charge controller with mc4's, which are difficult to disconnect, especially in a hurry.

b) Where would the fuses go? What amps, etc, do they need to be? Again, amazon link would be great.

c) The battery is a Mighty Max sealed lead acid battery. If it lives on top of the fridge inside my home, is there a danger of dangerous gas, etc.?

d) If I were to purchase a larger wattage solar panel, it wouldn't fit the window without the middle part of the window frame covering part of the panel. In your opinion, would that still charge the battery faster than just using the 30 watt one?

e) What is the correct order to disassemble my light setup if I want to do so? Ex: disconnect the solar panel first?

Thanks for any advice you can give me. I'm very excited to be getting started on my project.

Sunshinelover


Comments

  • BB.BB. Posts: 27,227Super Moderators admin
    edited April 11 #2
    Welcome to the forum SunShineLover.

    Here are some comments to start with... In solar (and electrical jobs), the details do matter. Please ask if something does not make sense to you.

    Hi all,

    I'm just starting out with solar. My first project is a stand alone light system for the kitchen.

    My goal: To have a stand alone strip light run by solar & battery. I really want this. We have lots of storms where I live and there's always the threat of electricity going off for awhile. Also, I love the idea of being more independent. Here's what I have:

    Renogy 30 watt mono solar panel, 12v 20 amp solar charge controller, 35ah 12 volt battery, 1.5 foot strip light (7.7 watts/foot, 12v).

    For a good working solar power system, "knowing your loads and needs" is the first step. For example, a quick design may look like:

    • 10 Watt strip light * 4 hours per day = 40 Watt*Hours per day
    Assuming you placed the panel on the outside of a south facing window (behind window glass can cut performance by upwards of 25 to 50% in a vertical position), then assuming you live in a reasonably sunny location, need backup power during the winter, perhaps:
    • 40 Watt*Hours per day load * 1/0.61 DC solar system eff * 1/2.0 hours per day sun = 33 Watt panel

    So--depending on your real usage (if less or more than 4 hours per day), this panel is close to meeting your needs (turn off light when not in use, etc.). If you tell us what major city you are in, is this a south facing window, etc., we can put in more details into the calculations.

    Regarding the battery power:

    • 12 volts * 35 AH * 1/10 Watt load = 42 hours of "run time" between charging (suggest max 50% discharge or 21 hours of run time between charging).

    Then there is sizing the charging to the battery bank. 5% to 13% rate of charge is typical. 5% for weekend/summer usage, 10%+ recommended for full time off grid usage:

    • 14.5 volts charging * 35 AH * 1/0.77 panel+controller derating * 0.05 rate of charge  = 33 Watt panel minimum
    • 14.5 volts charging * 35 AH * 1/0.77 panel+controller derating * 0.10 rate of charge = 66 Watt panel nominal

    Your system "should work" OK unless you live in a place with "dark and gloomy" winters.

    I want this to be my main lighting in my kitchen. If it works out well, I won't even use the regular ceiling light anymore. I know the 30 watt panel probably won't charge the battery very fast, but it will live in the upper part of the kitchen window (inside the home) and it's the biggest wattage panel I could find that would fit.

    My questions:

    a) I want an on/off switch and have no idea where it should be wired in. If somebody could link to the correct switch on amazon I'd really appreciate it, plus tell me where to wire it in. Would the off/on switch be enough, in case of arcs or smoke, etc? I've been reading this forum and the smoke & arcs came up, which concerns me. The solar panel is connected to the charge controller with mc4's, which are difficult to disconnect, especially in a hurry.

    It is very difficult to start and sustain an arc at 12 VDC... Slightly above 12 VDC is needed. 24 VDC+ -- That is a different matter.

    Most fuses/breakers and switches are rated with (something like) 120 VAC and 24 VDC maximum working voltage.

    For a low voltage system, you are (most likely) fine with almost any off the shelf switch (you can use a normal house light switch--Possible that you will have to replace it every 5 years when used on low voltage DC--Not a big deal).

    Always wire to your loads... For example a 30 Watt panel is roughly (Imp=30Watts/17.5 volts Vmp=) 1.7 Amps... Use a 1.25x derating factor and 2.1 Amp Imp from panel. Design a 5 amp breaker/fuse/wiring system. You can use 14 AWG house wiring very nicely. Your 10 Watt load is (10w/12v=) 0.83 amp load--Using the same wiring and fuses (or the one 5 amp fuse for both controller+loads) would be fine.

    Your 20 amp controller is bigger than you need--If you ever decide to make a larger system--new wiring and fuses/breaker will be needed.

    b) Where would the fuses go? What amps, etc, do they need to be? Again, amazon link would be great.

    Fuses and breakers go "close to" the +12 volt battery connection. The battery is the source of "high current" (could be 50-100+ amps into a dead short). Fuses and breakers protect the wiring--You want a short circuit to always go through the fuse/breaker (why--Wire right off + terminal for a few inches or a foot, then fuse(s), then wire to loads/charging sources/etc.

    c) The battery is a Mighty Max sealed lead acid battery. If it lives on top of the fridge inside my home, is there a danger of dangerous gas, etc.?

    Always treat any battery with respect. For Sealed Lead Acid batteries, they generally do not gas unless you a) Over charge them or b) they get old and start to fail. So--It is best to put them where if something bad happens (split case and acidic electrolyte leaks out, and/or they gas), that nothing else will be damaged (i.e., not a sealed box next to an arcing switch).

    Heat wise--Lead Acid batteries work best at ~45F to 75F. On top of the refrigerator, the battery may run hot (from refrigerator coils on back). Not great for the battery (run at +18F or ~88F, the battery will have ~1/2 aging life--A 3 year battery may fail in 1.5 years). If your battery lasts 3-5 years, you are doing good.

    d) If I were to purchase a larger wattage solar panel, it wouldn't fit the window without the middle part of the window frame covering part of the panel. In your opinion, would that still charge the battery faster than just using the 30 watt one?

    Solar panels almost always lose 50% to 100% of output power if there is any shadow on the panel. Placing the panel outside the window (somehow) is a better solution. Watch for wind/rain damaging mounting. If you have lots of lightning storms--Placing anything metal with electrical leads "temporarily" outside a building is of questionable safety (lightning strike, wind blows panel off mount and hits somebody/something/etc.).

    e) What is the correct order to disassemble my light setup if I want to do so? Ex: disconnect the solar panel first?

    Connect the solar charge controller to the battery first, then connect the solar panel leads (unless it is dark outside). Many solar charge controller use the battery voltage/energy to figure out if they are connected to a 12 volt or 24 volt battery bank--And can be confused if connected to solar power first (not always, but a good rule to follow).

    Thanks for any advice you can give me. I'm very excited to be getting started on my project.

    Sunshinelover

    Good luck,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Posts: 2,056Registered Users ✭✭✭✭
    Something you may want to check is charge controller charging algorithm setting. Small controllers often have dip switches or other means of setting charging voltages and times. If there's a preset for AGM (assuming sealed = AGM), you'll want to set it to that. If no preset, set voltage on the lower end of whatever range offered (eg. 14.4v). Flooded lead acid setting (eg 14.8-15v) and especially auto-eq (15.5+) can damage the battery, and possibly the strip light.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • sunshineloversunshinelover Posts: 3Registered Users

    Thanks a bunch for the help so far, I really appreciate it.

    To answer your questions:

    The kitchen window faces East. What's nice about its location is that the house next door is white & it reflects the afternoon sun right back to the solar panel. I realize South facing is best, but this is what I have to work with at the moment. These are older windows so they might not be low-e. We live not far north of St Louis, so our winters are dark & gloomy.

    We aren't planning to stay in this house forever, so we aren't willing to put any holes in the walls. The solar setup will be inside the home. The battery will live on top of the fridge, but will be setting on a board. It doesn't get all that warm up there. However, you got me to thinking that maybe I should set it in some kind of a tray instead of just setting it up there like it is. That way if it leaks, the tray will catch it. The tray will not be metal, but may set on metal (extra protection from acid?).

    This is an experiment to see how things work out. I plan to "budget" my use of the lighting to fit the amount of energy the panel is able to produce to store in the battery. It may be that, later on, I might try a larger panel or get two of the same kind so they both fit in the two parts of the window so the battery will charge faster and I can use the light longer.

    I've tried for so long to get answers to my questions. It's great to find a board with kind people to help. In our area, I can't find anybody at all that knows anything about solar. I did find an electrician, but he only knew about the electrical part. I think, between the two of us, we fried the charge controller LOL! It was only after he helped me wire the components together that I read about the need for correct disconnection of components (hence my question above). I'm waiting for my new charge controller to arrive.

    Thanks so much!

    Sunshinelover

  • EstragonEstragon Posts: 2,056Registered Users ✭✭✭✭
    Leaking of a sealed battery is unlikely, but not impossible. Most plastics stand up well to battery acid, so a cheap plastic tray or tub should work well to contain the battery. I like to keep batteries and connections well away from metal, and to secure things well to minimize the chance of an accidental short.

    Many (most?) electricians have limited experience with DC systems. Some may have a bit if working with entry control systems, burgler/fire alarms, etc., but generally don't. For example, to an AC electrician, black is the live or "hot" conductor, white is neutral, generally at ground potential. A DC system will most often have the black wire at ground. Getting confused and reversing polarity can let the magic smoke out of DC gear.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Posts: 27,227Super Moderators admin
    And, realistically, ditch the solar panel and just use AC power to recharge... It costs next to nothing. For example:
    • 10 Watts * 5 hours per day * 30 days per month * 1kWH/1,000WH * $0.15 per kWH =  $0.225 per Month electrical costs
    Depending on system efficiency, it can get upwards to $0.50 per month electrical costs for battery backed kitchen light. And you can have 4-8 days of of backup (without AC mains for 5 hours per night)...

    Regarding your location... If St Louis Mo, vertical mounted window (excluding window glass):

    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Saint Louis MO
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a vertical surface:
    Jan Feb Mar Apr May Jun
    2.47
     
    2.47
     
    2.52
     
    2.27
     
    1.99
     
    1.92
     
    Jul Aug Sep Oct Nov Dec
    2.01
     
    2.26
     
    2.76
     
    2.98
     
    2.46
     
    2.35
     
    And notice during the summer, your solar collection may actually be worse in an East facing vertical window.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sunshineloversunshinelover Posts: 3Registered Users

    BB: Well, the solar insolation figures aren't very encouraging. Bummer. Thanks for the link, it's an awesome site!

    I agree that using AC power to recharge the battery would be the best way. However, that wouldn't help me at all if the power was off for any great length of time (say, a couple of weeks). This project is a learning experience & the way to get my feet wet as far as solar. I want to experiment with this and learn as much as I can, just to see what my little system can do in its location & learn how to assemble stuff. There's a reason I'm starting small, with inexpensive components LOL

    Someday, when we find the right property, we plan to be off grid, so I really need to learn this stuff. In the future, I'm sure the panels will either be placed outside at the correct angle, or be inside some kind of sheltered area, out of the elements as much as possible. No need to figure out those fine details at the moment.

    Estragon: Yep, the charge controller is programmable & I'll watch out for the settings. TY for the advice about the leakage & plastic. I purchased a plastic dishpan yesterday to set the battery in.

    Thank you sincerely for all the advice so far. I really appreciate it.

  • BB.BB. Posts: 27,227Super Moderators admin
    Sorry. :'(

    As with real-estate, solar energy depends on location, location, location.

    We spend a lot of time here trying to set realistic expectations about solar and battery powered systems.

    Longer term--I would suggest that you look at your entire living situation and figure out what you need to have for 3 days and 2 weeks survival. Basically, setup for camping. The suggestion I use is:
    • You are dead:
    • 3 minutes without air
    • 3 hours without shelter (if you live in an extreme climate)
    • 3 days without water
    • 3 weeks without food
    • Prescriptions--Typically 1 month with 1 week to refill (sometimes 3 months at a time).

    Tent, sleeping bag, water equipment (filters, sterilization tablets, fuel+stove for boiling water, etc.), cooking stove, dried/canned food. Water and soap for cleaning, place for doing your business, etc.

    Ideally, you want a gallon of water per day per person. That quickly adds up if you have a family and no water heater in unit to drain if needed.

    3 days supplies. You can wait until emergency folks can respond.

    3 weeks--No water in apartment, can't use toilet, no water storage, lugging water/stuff up stairs, etc.... Cities have have been known to turn off fresh water if sewage plants are shutdown (or local sewage pumping failed). Turn off electricity to whole neighborhoods if one part has issues, etc.

    For lighting, LED flashlights and head lamps are a great start (headlamps free your hands for working, and always point light to point of interest). A small AAA 3 level flash light can run 50+ hours on one battery.

    Get a pack of AA and/or AAA batteries, and you will have years of useful lighting (and 5-10 years between needing to replace batteries in closet).

    Get a small solar panel plus AA+AAA charger and use Eneloop rechargeable batteries, and some small solar systems will charge cell phones too.

    -Bill

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