I would like to make a more reliable nightlight for my daughter. I was using cheap solar string lights but they just don't last long enough or get enough sun on that side of the house.

So I've started with 2 sets of cheap solar led string lights, one with 10 led's and a 300mah 1.2v AA battery and the other with 20 LED's and a 300mah 1.2v AAA.

My question is if they were cut off at the solar panel, could they then be powered from a 5v 350ma ex-phone charger? Series or parallel?

Would also like to use one of the panels for as a daylight switch if anyone could explain how that works and if its pretty basic with the parts I will now have spare.

  • \$\begingroup\$ Do you have any links to the mention items? \$\endgroup\$
    – Jason Han
    Aug 5, 2017 at 5:12
  • \$\begingroup\$ Use one of the panels to drive a relay... \$\endgroup\$
    – Solar Mike
    Aug 5, 2017 at 6:08
  • \$\begingroup\$ No sorry no links, don't even have the boxes. I can take pics of the two boards and panels if that helps. \$\endgroup\$
    – Shayne
    Aug 5, 2017 at 6:23
  • \$\begingroup\$ A photo would help answer some questions, perhaps. More likely, it would just cause more questions still, though. What I might do is to carefully check to see if there are just two conductors leaving the circuit in order to drive the string, or if it is more complicated. If that simple, I'd cut them at that point and use a variable power supply and slowly increase the voltage, monitoring the current, until I observed the right intensity. Then I'd mark down those readings. From there I could design the rest. \$\endgroup\$
    – jonk
    Aug 5, 2017 at 11:34

1 Answer 1


If you're going to use a 5V power supply, you will need something to limit the current, or you will fry the LEDs. That could be as simple as a resistor. Use a separate resistor for each string. The value of the resistor will determine how bright the LEDs will be. Something in the tens or hundreds of ohms would be sensible.

Solar lamps use a dedicated chip to control everything. All the time the solar panel is delivering a measurable current, they charge the battery. When that current drops too low, they turn on the LEDs. Making your own equivalent is not simple.


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