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LED string lights with 18560 and 2 2.5w 5v solar panels

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  • LED string lights with 18560 and 2 2.5w 5v solar panels

    I'd like to have a solar powered light string using the panel as on at duck off at dawn.

    I have two 5v 2.5w solar panels in parallel.

    One 18650 battery, 2500mAh.

    I have a string of 12 LED lights 1 watt per bulb.

    I'd like to use a TP4056 module with protection for charging.

    I'm thinking of something similar to the attached Capture.PNG.

    I've done some simpler stuff but I'm not a transistor guy. I don't think the 9013 in the schematic will handle the 12x1w bulbs.

    Any recommendation on the design and if the 9013 will work or another that will?

    TIA
    Attached Files

  • #2
    What will your high voltage and low voltage cutout be for the 18650? Are you limiting current to the LEDs?

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    • #3
      4.2v is the high. It appears that the TP4056 and the 18650 I'll be using both have a low voltage cutoff at 2.5v seems too low to me but I'm not sure what I can do about that. The TP4056 I'm looking at states: "Battery Over Discharge Protection Voltage: DC2.5V, Battery Over Current Protection Current: 3A"

      Sorry but I'm a newb at some of this.

      Comment


      • #4
        Originally posted by RichJacot View Post
        4.2v is the high. It appears that the TP4056 and the 18650 I'll be using both have a low voltage cutoff at 2.5v seems too low to me but I'm not sure what I can do about that. The TP4056 I'm looking at states: "Battery Over Discharge Protection Voltage: DC2.5V, Battery Over Current Protection Current: 3A"
        ......
        I don't know what a TP4056 is but those voltages are the maximun you would want to take a NMC 18650 and unless you can reduce the high voltage and increase the low voltage you will wear out the 18650 in less than 500 cycles. The battery overcurrent protection is not what I was asking about. I was wondering if you had any way like is found in most LED drivers to limit the current going to the LEDs. There is a sweet spot with most LEDs below their maximum current where they become the most efficient. That would be the ideal current to get the most light out of your LEDs and use as little of your battery. That part is simple physics and that should be your starting point.

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        • #5
          I do not have a way to limit the current other than what is stated in the TP4056 spec sheet (listed above). Nor do I have a way to increase the low voltage cutoff. I do agree that 2.5v is too low. I would ideally want the low voltage cutoff to be in the 3.5v-3.7v range. I'm open to suggestions on how to accomplish this...

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          • #6
            Originally posted by RichJacot View Post
            ......... I do agree that 2.5v is too low. I would ideally want the low voltage cutoff to be in the 3.5v-3.7v range. I'm open to suggestions on how to accomplish this...
            Get a programmable charge controller. The. Problem most likely will be they are more expensive. I don't know if the cost would be worth the tradeoff of longer battery life for a single cell.
            Once you do the math or run a few cycles on your setup you may find you need more cells.

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            • #7
              Adding another cell would be a pretty easy addition. i.e. additional battery holder and TP4056 charge module.

              I still need help to know if the diagram is acceptable and a transistor that will handle the string of LEDs I mentioned.

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              • #8
                Originally posted by RichJacot View Post
                .....

                I still need help to know if the diagram is acceptable and a transistor that will handle the string of LEDs I mentioned.
                Sorry, I am not a transistor guy. I was only looking at the issue of the physics of the LED draw and the battery charge and discharge limits and the effect those would have on battery life.

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                • #9
                  Don't get me wrong. Thank you! All is helpful and welcome as I'm new a tinkering with this stuff.

                  Hopefully a transistor guy will notice the thread.

                  Comment


                  • #10
                    A transistor can handle the current for LED's. But you have to design a circuit to accomplish that. Many transistors will work, and many more will not.

                    a 2N9013 ( forget it, I can't locate a data sheet now. gotta run)
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

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                    • #11
                      I looked at it a while ago and any circuit gets a little complicated quick. Things are quite easy when only dealing with 15ma. A TL431 could be used to detect a low voltage and switch a PNP transistor on the high side. A transistor has a current gain. That transistor base will see about 1.5ma from that 2.2K resistor. If the transistor has a gain of 100 that is 15ma, reasonable for a LED. The transistor acts as the dropping resistor and won't supply more current than that. What is the forward voltage of your LED? These demonstrator circuits are generally junk and not made to be bigger. With such a low voltage there are a lot less design options.

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