LED lights series or paralel

[AndyAndyAndy]

I have barebone wirring harness where behind rectifier/regulator are no lights, horn, turn signals.... nothing. If I want to add LED light like the ones on the image (1 front, 1 rear, 1 switch), should I wire them in series or paralel?

 

[jmaack]

series can and will work. I usually wire all lights in parallel.

 

[karl]

series can and will work.

Yes. If your definition of work is loose.

If you wire two 12 volt lights in series, you need 24v to drive them to their full potential.

But at only the current required for one bulb.

Wire two 12v lights in parallel, and it only requires 12v, but draws twice the current.

Make sense?


For the OP's problem, wiring 3 led lights off 12v, in series, is probably not a good idea, as 4v at each light is no good.

 

[mindymogul]

In laymans terms Series = 1/2 brightness for LED, incondescent, or Halogen lights. Parallel is best option and less load on the circuit.

 

[jmaack]

Yes. If your definition of work is loose.

If you wire two 12 volt lights in series, you need 24v to drive them to their full potential.

But at only the current required for one bulb.

Wire two 12v lights in parallel, and it only requires 12v, but draws twice the current.

Make sense?


For the OP's problem, wiring 3 led lights off 12v, in series, is probably not a good idea, as 4v at each light is no good.

this is true. however since a majority of led either will or will not work only if correct voltage is used being an led they will still drive. but like you said they will each be powered lower until you reach the point where it just physically won't turn on.

 

[65ShelbyClone]

In other words, they have to be wired in parallel if you want them to work properly.

The red tail light is simple enough that it probably just has a current-limiting resistor in series with the LEDs in it. The LED fog lights probably have some circuitry inside that either steps the voltage up or down or limits current with PWM or something. I have several sets and they make a high frequency whine when they're on and do strange things when the voltage drops too low(like pull tons of current and put out very poor light). They need a full 12-14v to work properly.

 

[itsid]

Parallel is best option and less load on the circuit.

that's unfortunately false...
parallel increases current and thus load...

anywhoooo..
12V light needs to be wired parallel on a 12V system (no matter if battery or through a 12V regulated & rectified alternator)

BUT here's the point...

For the OP's problem, wiring 3 led lights off 12v, in series, is probably not a good idea, as 4v at each light is no good.

3leds at 12V is actually nice...
a common [white] LED has a voltage drop of around 4V each (3.6 ish) and that'd work out just nicely then.. with just a tiny resistor.
'lights' is what may crack that pot... depending on the internal setup of the individual LEDs in a light.

many (mostly cheap ones) LED lights you buy off amazon as 12V .. do not necessarily need 12V to run at full power..
in fact most actually have a voltage dropping resistor inline to keep the LEDs alive from that "overvoltage" of 12V.
if you remove those you more often than not end up with a setup that requires either 4 or 8 volts

And that's where you can adjust to your needs...
a 4V requirement and a small resistor to step up to a 6V and you can wire the two sets in series w/o any issue (and w/o loosing brightness)
even an 8V light can be wired in series with a 4V rear for example without any additional resistor.
but to know for sure you'd need to take a look inside.

count the actual LEDs and how they're wired up (parallel, series, sp-grid-array?)

So if you want to do some extra math... and a bit of soldering...
you can very likely wire them in series after you modified them.
(BONUS improved power consumption by 100% brightness LEDs)

'sid

 

[karl]

3leds at 12V is actually nice...

Yes, totally, I did not want to go that deep into driver circuits, kirchhoff's 2nd law, or individual component leds.

Just generalized the 12v LED light unit together, as a "bulb".

Thanks for explaining things clearer that I can, The connection between my brain and keyboard can be impeded at times.

 

[AndyAndyAndy]

I don't have original wiring diagram, but this is my setup.

Green background is what I'm going to add to the wiring. Does it look OK? Maybe some fuse somewhere, what rating would be the best? Should I place it right before light switch?

 

[karl]

I don't have original wiring diagram, but this is my setup.

Green background is what I'm going to add to the wiring. Does it look OK? Maybe some fuse somewhere, what rating would be the best? Should I place it right before light switch?

Looks right.

Do you know how much power the engine stator produces? Or more important, how much DC power out the rectifier?

How much power does each light require?

Im guessing around 18w for the head light, 6 watts tail, 2 amps?

So a 3 or 5 amp fuse sounds about right.

Volts * amps = Watts

Watts/ amps= Volts

 

[itsid]

keep in mind that you need to factor in switcing loads.
it's not as bad as with an incandescent lamp (which can draw upwards of 20Amps when cold for a brief period)
but still.. some setups have a rather high switching current

a lazy fuse might be what you want here..
ideally the mfg hints you towards the correct size though.

I personally would fuse the power early in the system (close to the rectifier) with a 5 or 10Amp just to catch shorts.
then each light individually with as small as possible to catch the light failing..
that way a taillight failure doesn't kills your headlights and vice versa
(sometimes life chews one's ankles...and you want that extra bit of visibility to not get hit by a truck )

just saying.

 

[madprofessor]

The fuse Sid speaks of should be the very first thing you wire up, but should be 2 of them. In your diagram the power comes from a CDI, whatever that is, I'll just pretend it's like a battery.
At the first wire intersection, that power splits up and goes 2 different directions. That's where you should fuse it, with each direction getting it's own fuse. No idea what your power requirements are for either direction, and I doubt you have a decade box. If you do I want to buy it for a backup. You'd have to just figure out what size fuses would be best.
Note: Little pushbutton circuit breakers the size of a matchbox can be had from Amazon, and resetting a breaker is a lot faster and way cheaper than replacing fuses. I put a pair of 30 amp ones on a commercial dishwasher in place of OEM 240 volt 30 amp fuses that would heat up and finally blow. At $5 each, and hard to find. Breaker solved problem, worked ever since. Do an Amazon search for breakers and find any rating you want.

 

[itsid]

In your diagram the power comes from a CDI, whatever that is, I'll just pretend it's like a battery.

nono.. the CDI sucks power from the same battery it's not a source at all.
(capacitor discharge ignition) the CDI stores a tiny amount of the DC power in an internal capacitor (hence it's connected to the battery and rectifier)
and then 'on command' discharges that into the ignition coil, allowing said coil to draw a short burst of rather impressive currents.
it also shorts the coil against ground once you want to kill the engine.
more sophisticated units can then limit the rpm by controlling the spark to cut out above a certain value etc..
in any case.. it's nothing like a battery at all.

Also:
I do NOT recommend AC fuses for DC systems! (especially not ac circuit breakers!)
quite a bit of a difference, and you can no longer rely on the actual values any longer.
16Amps @ 220V AC is something very different from 16Amps @ 12V DC
(has something to do with how the internal wire heats up to it's breaking point under different voltages and current direction.)
In the end.. you will never know at what amperage it'll actually blow in your system (which is kind of a bad idea IMHO)
if you step away from mfg intended usage (voltage and type of current in this case)

So circuit breakers... Not really a good idea
unless you find one that's specifically made for DC and meant to be used at about your voltage (say <30V in case of a 12V system)

'sid

 

[madprofessor]

Absolutely correct about AC and DC. Maybe I'm assuming too much, that is, that everybody would load test a breaker before deciding on the right rating.
The breaker is still a good idea, I got the idea long ago from some car's headlights having a little breaker under the hood separate from the other lights' power.
To load test a breaker for DC you have to put a clamp-around meter (ammeter) on the power, and start adding things to load it up until it blows. Then you know.