Reddit reviews DROK DC-DC Buck Converter Module 90W Step Down Voltage Regulator Reducer Converter 4.5-60V to 1.2-30V 3A Adjustable Volt Transformer for Battery Golf Cart 48V to 24V

Last attempt at copy pasting the original comment.

Looking to add lights to your bike that run off the existing battery pack for way less than electric bike specific lights? Especially when electric bike specific lights, are typically lame, 1-4 LED dated looking Chinese lights.

I'm going to show you how I added 2 - 7 LED Ultrafire U-L2 bike lights to my bike for less than $100. Do not use these lights on the road, they are extremely bright, and rated at 4000 Lumens each.

You can, however, buy the converter, and some lower power bike lights, or a single light even for even less money.

The first thing you are going to need is the converter. Its $21. This thing will take just about any pack voltage in, and output anywhere between 1v and 30v. Adjustable with a screw. Handles up to 3A

Here's the link: http://www.amazon.com/dp/B00C9S5QNC/ref=sr_ph?ie=UTF8&qid=1450034772&sr=1&keywords=adjustable+step+down+converter

The next thing you are going to need is a light, these are the ones I used, they're $46. http://www.dx.com/p/ultrafire-u-l2-7-x-cree-xm-l2-t6-3-mode-4000lm-cool-white-bike-light-black-4-x-18650-241291#.Vm3Gr_krKUk

You are also going to need some things I assume you already have like solder, and a soldering iron. Maybe some heatshrink tubing to clean things up a bit. Maybe one of these so you can disconnect the lights.

http://www.amazon.com/LHI-2PCS-WRA0053-12awg-Silicon/dp/B012IQ7AJ2/ref=sr117?ie=UTF8&qid=1450035007&sr=8-17-spons&keywords=wire+connector+14ga&psc=1

So the little blue converter, has a green clip that comes out. You are going to need to splice into your battery's output cables, and run some new smaller cable out to the inputs of the green clips. Then you want to wire one end of the disconnect to the green clip, and the other to your lights.

I ended up just wiring both lights together, then into the disconnect, and then into the clips.

At this point you should have a disconnect coming out of the green clip, and the other going straight to your battery. The converter should not be attached to your clip yet. Plug the converter in, and measure voltage at the disconnect. Turn the CV screw on the converter until you get 7V. Now plug your light(s) in and you are good to go.

NOTES

If you run 14 Cree LEDs off this thing like I am you will be at the very end of the converters capability at 3A. It's going to get super hot, hot enough to melt plastic and potentially damage anything it touches. You will need to upgrade the cooling capacity. I attached an old intel heatsink I had with some zip ties, it keeps it cool enough that you can touch it and warm up your hands. This is only needed if you plan on running 14LEDS on high, for periods longer than a couple minutes. It has no problem with both on low, or 1 on high, 1 on low. If I had some thermal paste lying around I would have used it.

A COOL FEATURE

The ultrafire lights I have, have this cool feature of changing the color of the button on the back of them based on the voltage going in to them. They go from Green to Blue to Red to Flashing Red to let you know how much charge you have left in the packs they came with. You can set them up to change color with your battery pack. For example if my pack has a full charge at 58.4V, and I want the lights to turn red when I hit 48V I set it to like 7.4V at full charge so that at 48V it will put out 5.4V. These are estimates not exact numbers, you will have to math, if you cannot math I may or may not math for you at a later date.

Another note about that feature. Light output is not effected by input voltage into the light, and the higher the voltage you put into them the hotter the blue converter is gonna get.

Here's a video I did of the lights a while ago running them off the supplied battery packs. They typically only lasted for 45 minutes before the packs died, hooked to an ebike battery they last for as long as you want to ride. https://www.youtube.com/watch?v=mTMVEObSdxg

ah, forgot to discuss this part

So .... electronics is not a pair-matching game it's more of a ..... domination game :P

So, the 12volt regulator needs 12+ volts to regulate itself to 12V

so the battery has to be .....14+ volts

So the AC/DC majiggm can charge the battery it needs to have a higher voltage then the battery, something like 16+ volts

So, lets start with the battery, led acid battery may not be the best choice at all, they are bulky and heavy .... the only upside is that they are cheap, that is a 8 amp hour 12 v battery, meaning it can give 1 amper for 8 hours or 8 ampers for 1 hour

Here we we have a 12V 2 amp hour battery, connect them in-line (ones minus to ones plus) and you have a 24V 2 amp hour battery (which is the equivelant of a 12V 4 amp battery)
http://www.amazon.com/Tenergy-2000mAh-Battery-Leads-Airplanes/dp/B00408X4LU/ref=sr_1_1?s=hpc&ie=UTF8&qid=1406580248&sr=1-1&keywords=12v

It's a 2A circuit meaning it can run the amp for 2 hours without a problem.

you can take 4 batteries, take 2 and 2
connect each 2 in-line and then connect the pairs in paralell (+ to + amd - to - ) but thats expensive

alternatively you can take 2 led acid batteries, connect in-line and get a single 24V led acid battery which should be able to run it for 8 hours at a lower price, but thats heavy

So, money Vs. weight

About the charger

assuming you connect 2-4 batteries to make a 24V battery, you're gonna need to charge that battery with a higher voltage, regulating it doesn't matter much since, you have a regulator for the amp circuit and batteries are not picky

here is a fairly cheap one, with adjustable voltage

http://www.amazon.com/DROK-Adjustable-1-2V-30V-Converter-Regulator/dp/B00C9S5QNC/ref=sr_1_4?s=electronics&ie=UTF8&qid=1406580763&sr=1-4&keywords=30v


So to sum up

Regulator needs at least 14V

Batteries are hard to find in strange voltages, so I recomend 12+12 to make a 24V battery

the 24V battery needs a higher charging voltage so you can take any .... 26-30 V power supply with enough ampers to charge it


My advice if you wanna keep it cheap, find a smaller, cheap led acid battery and buy 2 of those
find a cheap 26-30 volt power supply to charge it with and you should be able to keep the cost very similiar

Did you see these on Amazon?

https://www.amazon.com/gp/product/B00XKKWSES/ref=ox_sc_sfl_title_19?ie=UTF8&psc=1&smid=A2OCOGC9B25845


https://www.amazon.com/gp/product/B00C9S5QNC/ref=ox_sc_sfl_title_2?ie=UTF8&psc=1&smid=AFHAE9RJVUMB