# LED lights wired in series will not light

I have a pack of simple LED lights that I planned on wiring in my boat for cabin lights.

I installed and wired them all in a simple series circuit. Power supply connected to switch, switch connected to positive side of first LED and negative to positive of the remaining LEDs and so on, then connected to ground.

None of the lights will work.

When I test each individual light with a 12V source they work fine but when I wire 2 or more in series they will not pass voltage through the LED to light the next light.

What am I doing wrong?

• What is the forward voltage of each LED? You need to provide at least the forward voltage times the number of LEDs in series for them to light. You also need to limit the current so that they don't burn out. Commented Apr 17, 2017 at 13:01
• Do you have a N x 12V supply for N strings? Wrong? you did not spec LEDs, number of LEDs and supply spec! Commented Apr 17, 2017 at 13:07
• They are 12v LEDs. I have a total of 6 LEDs i'm trying to wire in series. So you're telling me I need a 72 volt power supply to light all 6 LEDs in series? Commented Apr 17, 2017 at 13:15
• Welcome to the site. Please quickly realise that this is not a free design house, homework-answering service or an on-line technical encyclopedia, copied out to you on demand. People will help you take the next step if your question contains all the details and shows you've done as much as you possibly could on your own. Please either revise your question showing details of work and findings so far or delete it if you find Internet searches give you your answer anyway. Again, a warm welcome to the site. Commented Apr 17, 2017 at 13:18
• You can run 6Sx12=72V or 3S2P =36V @ 2x Irated or 2S3P @ 24V @ 3xI or 6P at 12V with 6xI but do not daisy chain more than 2 . Also most ledstrips ad design with 9V threshold and rated at 12V or 14.2V for watt rating so you can increase V+ by 20% max but wire and supply must have ampacity to work well. Commented Apr 17, 2017 at 19:10

I think you are using 12v LED lights. Accordingly, when you connect many LED lights in series, the 12v is going to be divided equally among the LED lights. Thus, if you have 2 LED lights, 6v for each one. If you have 3 LED lights, 4v for each one.

In your case, you should connect them in parallel to get the job done.

Finally, remember that for resistors in series, the current is the same for each resistor, and for resistors in parallel, the voltage is the same for each one.

• These answers are supposition and guesses. The OP's question is missing lots of the detail. Commented Apr 17, 2017 at 13:21
• Yes they are definitely 12v LED lights. I was trying to not have to run so much wire in a small tub rail but it sounds like i'll have to run the extra wire to create a parallel circuit for each light? Commented Apr 17, 2017 at 13:29
• @Chad S. Yes sure. To connect the LED lights in parallel, connect the '+' of the battery to the '+' of the first LED lights, then from the latter to the '+' of the second LED light and so forth. Do the same connection for '-'. Commented Apr 17, 2017 at 22:15
• Ended up running them them in parallel and they work great. Thanks. Commented Apr 18, 2017 at 13:19

If they individually work on 12V without immediately blowing up, they are probably LEDs with built in resistors designed to operate at a higher voltage. If that voltage is 12V you can not connect them in series.

Verify they are actually 12V LEDS, and if they are, wire them up in parallel.

simulate this circuit – Schematic created using CircuitLab

• They are definitely 12v LEDs. Commented Apr 17, 2017 at 13:16
• @ChadS. Then you need to run a double wire and solder the LEDs across them. Commented Apr 17, 2017 at 13:21
• I"m sorry but i'm not sure what you mean by needing to run a double wire? Commented Apr 17, 2017 at 13:22
• @ChadS. see my edit Commented Apr 17, 2017 at 13:24
• I'm not seeing your edit sorry Commented Apr 17, 2017 at 13:27

If they work one at a time perfectly witj 12 volts, either wire them all in pallel, or leave in series, and multiply the number of lights times 12...then get on amazon and get a step up converter, one with adequate max voltage that either meets or exceeds the sum you jist came up with, as well as current capacity.

You can run 6Sx12=72V or 3S2P =36V @ 2x Irated or 2S3P @ 24V @ 3xI or 6P at 12V with 6xI but do not daisy chain more than 2 .

Also most 12V led-strips are designed with 9V threshold and rated at 12V or 14.2V for watt rating so you can increase V+ by 20% max but wire and supply must have ampacity to work well. Confirm with valid specs.

6S means 6 in series 2P means 2 strings in parallel .

Regarding using standard 12V lights (such as MR16) in series, it sounds right to use a higher voltage, but it might (will?) cause problems. I have a 36V electric bike which I made some lighting for. Initially I used three 12V MR16 spotlights in series. It worked fine for a while, but then I had a failure. It may have been a one-off, so I replaced it. Eventually, another failure. I came to the conclusion that, although the bulbs are rated at 12V, they have chip inside to either step down the voltage or regulate the current and they didn't work in series. I suspect one ended up going over voltage and failing.

The solution in my case was to buy a stepdown converter and to run them in parallel at 12V. Since then I have had zero failures of bulbs.

Two other things not mentioned: if in series to a higher voltage, one blows, they all go out and with standard led 12V bulbs, there are no issues about which way they are attached to DC as they rectify the current and work happily either way round on DC.

So, in a nutshell, do what others here recommend and go parallel.