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On 12V applications like mobile homes, RV, sheds, Tiny houses it might be nice to have a lot of light with low powerusage and easy to mount. Recently a very nice LED-panel on Ebay caught my eye, it looked something like the included photo.

Now these LED panels are available in a large varieties, both circular,
square or rectangle, starting at 3 Watts up to 30 Watts or even higher. Most of these panels are from China and are pretty cheap. A driver is included that work on AC from 100 to 240 Volts, so it works worldwide.

Step 1: Measure the Driver (in Use)

To test I used an average 15W panel (8″ round) and I am wondering if
it’s possible to convert LED panels to 12 Volt instead of regular AC-grid.

On the driver it reads: Output 48-58Vdc at 300mA, so that gives about the 15 Watts.

The measured output (with the panel attached) of the driver was 48Vdc indeed but the current was a bit less, about 260mA.

Step 2: Disconnect the Driver

The driver can be openend with a screw-driver, it’s simply clicked together with the small PCB in the middle.
The wires can be removed from the board with a soldering-iron. It should be unnecessary to say to leave the driver disconnected of the mains. But if your driver won’t open easily or you want to get the panel disconnected real quick, just use a wire-cutter of pliers and cut the wire.

I disconnected the wires with the soldering iron, and that leaves a nice, clean driver behind.
That also keeps the wires at maximum length, but still seem a bit short, so I extend them just a little bit with some cable, but that is not really relevant for the project.

Step 3: Step-up to a Higher Voltage

To optain 48V (in this case) from a 12V source is relatively easy
with the right DC-DC converter, a step-up converter, since we need to higher with the output voltage.

One of my favorite shops on Ebay chivazhu sells these (under $10) and much more electronics.

This inverter can convert from input-range 10-32V to and output-range of 35-60V. This all with a maximum power of 120Watts, it’s recommended to add cooling when exceeding 80W, but since we need only 15W, it should not really be a problem.

Step 4: Reconnect

Get the DC-DC converter and connect it to you 12 Volt lines on the
input-side, watch the polarity. Without connecting the LED panel measure the output. The factory-default maybe lower or higher than the desired 48Vdc for our panel. Adjust the ouput of the inverter if needed to approx. 48 Volts. Then disconnect the 12V Volt input and connect the panel.

Step 5: Test It

Put the 12 Volts back on and enjoy your 15W LED panel.

Step 6: Measurements

With the new connection made to the panel, it’s good to measure things in the end process:

Output voltage: 48V (as set on the DC-DC converter)

Output current: 250mA (as it was before with the driver)

Input voltage: 12V (bit higher since it’s a battery but the output remains stable)

Input current: 1.2A ( as expected)
The input current is a lot higher than the output current to the LED Panel.

Ohm’s law defines: Voltage x Current = Power, so 48V x 0.26A = 12.48W (just a bit lower than the promised 15W). That same power must goes in, so 12.8V (actual battery output) x 1.2A = 15.36W.

The fact that the input power is higher than the output power has to do with the efficiency of the DC-DC converter, which is now calculated as nearly 82%, not bad.

Final thoughts

The output voltage of different driver varies on output power, these drivers are usually constant-current outputs, that means the generate a maximum amount of current for the LED-panel, very different from the output of the DC-DC inverter, that could handle 5A or more. This can easily damage your LED’s in the panel or worse. Measure the output voltage with the panel connected is the best way to go.

A driver of a 12W panel shows 25-42Volt/300mA, so always measure the output voltage first (with the panel attached) before you connect a fixed voltage.

Some more work

Put the DC-DC inverter in an enclosure !

Use fuses, never connect directly to the battery.

More on www.tinyoffgridliving.com

<p>This instructable is NOT correct for anyone not experienced with leds. You cannot use a DC DC boost converter to properly power an LED array. You ideally need a DC powered constant current driver that has a boost output voltage similar to the original driver. I am certain you destroyed that LED fixture and simply didn't include that information in the instructable as a lesson learnt.</p>
<p>This is cool and a nice write up, but you could make it much more reliable using a boost converter that incorporates current limiting. Using an adjustable voltage only supply greatly increases the risk of LED failure. As the junction temperature increases, the forward voltage drop of the LED's decrease. This will cause an increase in current flow that generates more heating which could lead to a &quot;thermal runaway&quot; and the destruction of the panel. Likewise, if you have a single diode fail in a multi diode panel, the increased current flow can cause a domino effect destroying the remaining good junctions. Here is a <a rel="nofollow">module</a><a rel="nofollow"> </a>that would work well for your project. Thanks.</p>
<p>Hi, </p><p>Thanks for your comment.</p><p>I tend to disagree on the failure part however.</p><p>To use a variable voltage I added the posibility to use it as a dimmer, in case the light becomes to bright for my bathroom.</p><p>If a single diode fails, much more will be disconnected because of the failure, In the panel there are 100+ diodes with a voltage of approx 2V a pieces, so at least 24 must be in series to reach 48V, if one gets broken, it will shut down at least 23 more, and the other series will continue on 48V, where if I used a constant current out put the voltage would have gone up, leading to total failure of the panel.</p><p>Either way, I will toss out the panel anyhow, but I think mine is the safest solution.</p>
<p>You are correct that if a multiple parallel string configuration suffered an open circuit failure in one of the strings it would increase the current flow in the other strings, and probably lead to total failure. But open circuit failures almost never happen. The common failure mode for an LED is a shorted junction. Open circuit failures rarely happen and are usually mechanical failures of the die bond. Try hooking a single LED to a nine-volt battery until it fails then measure the junction with an Ohm meter. Good luck!</p>
<p>Thanks for your suggestion, it was interesting. </p><p>So I burned a couple of LED's, one with 3..7V Lithium, one with a 9Volt battery, and one with a 12V power supply. The only difference was the speed of failure. The Ohm meter however gave the same result every time, no short circuit all burned out (open circuit). </p>
<p>Your right! That was a crappy test. Sorry you had to sacrifice some LED's I went out and blew a bunch up and they failed open too. I used too be able to reliably introduce a short failure mode with the battery trick, but materials and construction must have evolved over the years. For your application that uses lots of smaller diodes in strings, I aggree constant voltage power works well if carefully adjusted for worst case operation. If you decide to pursue newer high power LED technology in the future, say a single string of 15 1 Watt LED's constant current is the only way too go.</p>
<p>Nicely done. Thanks for sharing this!</p>
Thank you

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