Thanks for doing the R/R/ temp testing.  I have a little temperature gauge that was made to keep track of computer core testing....and I am going to temporarily mount it on my Cafe' bike and see how hot it gets when I am riding.  I have it mounted to the battery box/rear fender combination that I made - but it is not as beefy as the stock rear fender.

When you get into your testing.....I really need some recommendations on what LED's I could use to improve on the tail light on my Cafe bike.  It has a bunch of tiny LED's that really aren't bright enough to be functional in the daylight (pretty typical of the cheap LED lights), and I would really like to improve on the light output.  To keep me safe I added an LED emergency light under the fender to function as the brake light.

No socket....it is the light I showed it the photographs.  It is hardwired and does both the running and brake light - but is very dim on both.  It is the kind of light that if you are staring at it from 20 feet in the sunlight..you are not sure if the thing is ON or not.

I would like to remove those tiny LED's and use some larger 1 or 1.5 watt LED's in their place.  I can solder, make a mounting board, etc., and I am looking for recommendations on what kind of LED to buy.

chzeckmate wrote on 10/11/15 at 20:32:05:

You're going to want SMDs for the best viewing angles.  I have two sets of three red ones for running lights and they are bright as f#@k.  They're cheap and efficient.  My setup cost me less than $6.00.  Got them from EPO in Houston....I love that place!

Here's what they look like on my bike at night.  In this video they seem about as bright as the taillight but in the day you can tell they are brighter than the tail light.
https://www.youtube.com/watch?v=8VR87qsmD24

chzeck, they do make T1's with a 90 degree viewing angle and up to 8,000 mc or so (in red). Replacing the current leds with high power substitutes is gonna be the easiest solution. reason being that the little pads are not set up for the spacing of SMD type LEDS.
If you want to just pull the original LEDs and put slightly larger and brighter ones in (that use the same voltage so the device works the same), I'd recommend these.
https://www.superbrightleds.com/moreinfo/through-hole/5mm-red-led-30-degree-v...

If you want the exact same size, just brighter...use these.
https://www.superbrightleds.com/moreinfo/through-hole/red-3mm-led-45-degree-v...

Since the pc board that the LEDs are mounted to has a circuit on it to limit voltage for the running light and allows full voltage for the brake function, you dont want to play around too much with higher wattage. You cant know how much the circuit will take, or if it will work properly if you substitute drastically different LEDs.

Personally, I would scrap the led pc board entirely. I'd put three 2 watt LEDs on a piece of prototype breadboarding from Radio Shack and wire the middle one to the running light wire and the 2 outside ones to the brake light wire.
Or just use a plain piece of plastic (pvc, acrylic, whatever) about 1/8" thick and the same shape as the original board and epoxy the three new high power LEDs in place. It's not like they will ever burn out. Then just solder directly to the LEDs.

Three of these would out perform the original board by a huge margin. They can be glued to a plastic base and use 26 ga wire to connect them to your running light/brake light wires.
https://www.superbrightleds.com/moreinfo/high-powered/cree-xrc-series-1-watt-...

What do you believe is the power (lm) of the bulbs that come in the cheap lights like this?



The tail light I have is small, so the pre-wired 12V LED's most likely are too big.  My turn signals have a pair of 1.5 watt -  70lm LED's in each one and they are plenty bright....so for the tail light I most likely can get by with a brightness of about 50 lm, I would like about 100 lm for the brake light.  

This looks like a good possibility for the tail light.  They are 10lm each, and it would take 5 of them wired in series to work with the 12v, and the size is small at 7.5mm square, and they look easy to solder.  If I have room I could get 10 of them mounted in two series circuits.
https://www.superbrightleds.com/moreinfo/through-hole/5mm-red-high-flux-led-9...

For the brake light.....

These might work at 21 lm and it would take 4 in series to work at 12V.  They are tiny at 5mm square and one reviewer said they are hard to solder leads to.
https://www.superbrightleds.com/moreinfo/surface-mount-smd/pure-white-5050-sm...

Yea.....I don't know nothing about LED's.  I listed 2 different ones as I thought I would need a different brightness for the running light and the brake light.  Now after watching a YouTube video I believe I can use the same LED and run both the running and brake lights through the same LED, and get different light output (brighness) by placing a resistor in the power coming from the running light, and run the brakes lights straight (or through a resister with less resistance).

I also believe I have to run enough LEDs in series to reduce the voltage on each LED down to it's operating voltage (or use a resistor to step the voltage down).

Dave wrote on 10/16/15 at 12:17:10: I also believe I have to run enough LEDs in series to reduce the voltage on each LED down to it's operating voltage (or use a resistor to step the voltage down).

Running LEDs in series distributes the voltage load over more components evenly. This reduces waste power to heat.

For instance, if the bike is generating 12VDC (it won't be, it will be higher than that in real life that's why you need regulation instead of resistors) you have 12VDC to spread out in the circuit. If you used one LED and one resistor, those two components would be forced to use all that voltage (Kirchhoff's circuit laws).

White LEDs only need somewhere between 2.8 and 3.4 volts (varies with manufacture) to operate at FULL POWER. So because our power source is much higher than 3 volts (we got 12 and higher) we can run more LEDS in series to match that closer and use the available voltage more efficiently. But you need to leave a little overhead for the device you are using to regulate the current.

Assuming a 3V LED, what is often common in 12V applications is to run 3 of them in series for a total forward voltage (Vf) of 9 volts. This leaves 3 volts left over for use with your current regulation device.

Resistors don't regulate voltage, they regulate current. The amount of current they pass is proportional to the amount of voltage running through them. Because available voltage can swing in automotive applications, its best to use a current regulator of sorts. The easiest get-up-and-go would be a linear regulator.

You will not be happy if you don't use a current regulator. Especially if you are trying to make your lights change intensity by opening up another circuit through them.

Also, LEDs will change their forward voltage based on the temperature they are currently at. As they get hotter (like when they are turned on), their forward voltage drops. This drop in forward voltage will cause them to want to pull more current (diode magic). Now you have an already hot LED trying to get itself hotter even faster. You are now experiencing thermal runaway and will drastically hurt your LEDs lifespan. Again, you need to use a form of current regulator.