How to hook up a solar cell, charge controller, battery, several LEDs

Discussion in 'The Projects Forum' started by Coenobita, Apr 30, 2016.

  1. Coenobita

    Thread Starter New Member

    Apr 29, 2016
    2
    0
    I am working on an art project and I would like to create a simple solar driven lighting system. I have two six inch square panels and batteries salvaged from security lights. The two batteries are 6v 5.5 Ah. I have no other parts. I would like to light up 3 LEDs. I will wire in a light sensing switch and ideally the light is bright and long lasting.

    Help with part selection and schematics

    I am a blacksmith with lots of experience making things but not much with simple electronics. I am eager to learn! Thank you. Www.kinghorn.ca
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    The good news is that you should have plenty of panel area for just 3 LEDs. But you didn't say how long you need to light them, versus how long they see sunlight.

    Frankly if I was doing this, and depending on what you need, I'd hack one of those cheap solar lights you can get. A 6V battery is likely too much for one, but on the other hand it already has all the functions you need built in.

    Do you know anything about your panels? They are often described by the open circuit (no load) voltage and the short circuit current. They are probably adequate for charging a 6V battery, and all you need is a diode to block reverse current. That might be already built into the panels. What type of batteries do you have (lead acid, NiCad, etc.)?
     
  3. Coenobita

    Thread Starter New Member

    Apr 29, 2016
    2
    0
    Hello Wayneh,

    Thanks for responding.

    The batteries are lead acid and came with the solar panels. Otherwise there are no markings on the panels. I took the panel housing apart and there is no diode present. I will definitely get 4-5 hours of direct sunlight for charging.

    I would like my system to light up for 8 hours. Preferably with bright lights. I would rather learn how to do this rather then disassemble an off the shelf system so I have more control over what I am working with.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    Okay, well that means you need a light sensor circuit to produce the on/off function.

    Otherwise I believe you can get away with just a blocking diode between the panel and the battery. No fancy charge controller needed. Another option would be a shunt circuit to dump excess solar energy when the battery voltage is high enough. I can find that for you if you're interested. Use a Schottky type to minimize the voltage drop (and power loss) at the diode. The security lights, if you still have them, would likely have had the proper diodes in them somewhere. But anyway they are cheap and easy to find.

    There are tons of options for the light sensor switch circuit. I tend to use comparators for everything but I think you can get an even lower power option. Seems I've seen one here recently - I'll look around. Maybe someone else can chime in if they recall a low-power light sensor switch.
     
  5. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    I have recently built a LED lamp using a 5Ah lithium battery, a voltage booster, 2x 3W COB LEDs,
    and a steel lid from a storage tin.

    The booster module is a MT3608 module.

    LEDs are attached with no more nails compound, a generic variant.
    I have previously done tests with very hot LEDs but these dont get hot.

    The voltage is adjusted so the cooler doesnt heat up too much.

    Note batteries dont like deep discharge, though sealed batteries will survive it.
    Especially when they are recharged with high current, in fact they will loose capacity.
    First low current charging is required.

    Using a wifi speaker globe as diffuser the whole room is illuminated.

    Actually I can not say if the MT3608 modules are good for 6V.

    I tried with 12V battery and about 7 or 8 pcs were destroyed. Even after eliminating all ground loops, the chips were keep popping. I think only when the output voltage is 19v. When it is 12v same as input nothing happens.

    So I changed my LED circuits for the ant farm. I made a bridge, installed switches.

    I can power the booster either from 12V PC supply or the battery.
    Then the big red LED can be switched off.
    The white 10W chips are driven at 2 volts less to have longer battery life.
    Additional buck converter.

    I have some experience with deep discharging a lead battery. Its a sealed 12v 20Ah battery.
    Electronic charger so it freaks on a flat empty battery. Now I can bridge to 12v from PC! But never tried so far.

    For instance lithium charger modules some of them have deep discharge protection.
    You should have this to prolong battery life.
    I want to build deep discharge protection, just didnt find any time so far.
     
  6. Jesnil Trups

    New Member

    Jun 21, 2016
    1
    0
    Hello all,
    I think it will be better if you buy it from store, But you have already the equipment. So I have 1 suggestion that you have to gain some knowledge about the connections & the equipment. Recently I have bought a solar panel from solar galore & i had the same problem,so I called a electrician & connected it.
     
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