LED panels (on 12Vdc – step-down)
Rebuilding drivers for LED panels raised some more questions than we anticipated up front, so obviously more explaination is nessecary. Just to be complete in our examples we split this into 2-parts, stepping-down (the native LED voltage is lower than the 12Vdc supply) and stepping-up (the native LED-voltage is higher than the 12Vdc supply).
Step up or step down ?
We decided to split our earlier story into two parts, some panels need a lower voltage to work on that 12Vdc, so we step-down from 12V to a lower voltage, this is mainly on the small 3-4 Watt panel. This changes if you feel you should use a 24Vdc solar setup.
LED panels step-down
The smaller LED-panels use a voltage lower than 12Vdc, so we need a step-down converter, this only applies to the 3-4 Watt smallest panels, they are about 7.5 – 12 Volt depending on the manufactorer. Below is a list of panels we rebuild back to 12Vdc, but actual values will depend on brand and supplier, so please measure voltages before and after rebuilds. Very small DC-DC inverters in both step-down and step-up are available on for example Ebay. It is also possible to have multiple LED-panels on the same inverter als long as power requirements are met. Most buck converters are 1or 2 Amps so it’s easy to hook-up up to 4 panels at once.
- 3 Watts (usually 15 LED’s at 0.2 Watts): 7.5 Volts, 9.5 Volts
- 4 Watts : 12.7 Volts, 12.8 Volts
- 6 Watts : 19.3 Volts
- 9 Watts : 19.6 Volts
- 12 Watts : never rebuild
- 15 Watts : 48 Volts x 260 mA = 12.36 Watts
- 20 Watts : never rebuild
- 25 Watts : 56 Volts (True 18 Watts)
In the future we try to add information to the list to get it as complete as we can, if more than one voltage is mentioned it’s a different brand.
Now it’s nice to look at these guidelines, but please remember the one who measures his LED panel in working conditions with 85-265Vac adapter is king, and works a lot safer. Most suppliers use 0.2 Watt LED’s, so 15 pieces for 3 Watt panels, upto 75 pieces in their 15 Watt panels. On the biggest panels it seems to vary, 90 or 120 LED’s in the so callad 24 or 25 Watt panels. However math tells us you might just have 18 Watt output.
The 4-Watt panel is a tricky one, but since our 12-Volt solar will be higher than 12.7-Volt or 12.8-Volt we measured, sometimes we still use a step-down inverter just to make sure it stays working and doesn’t burn. Just to be sure that these 4-Watt panels always get the right voltage we can combine both stepping up and stepping down in one modified driver. First let’s go up from 12-Volt to 18-Volt, just to go from there back to 12.7 or 12.8-Volts.
So Stepping-down with less than 1″x0.75″ surface on the PCB ( Printed Circuit Board).
PCB Step-down 1″ x 0.75″
This small inverter can be stored anywhere, handles upto 28Volt input and 3Amps max. more than enough for multiple LED Panels.
The rest of the LED panels use mote than 12Vdc in native mode, so we have to step-up the voltage to connect those panels to regular 12Vdc.
Part 2: Stepping up