How to add 12V lights to your ebike without a DC-DC converter

Anyone who rides an electric bicycle at night knows the importance of good ebike lights. Not only do they help you see obstacles in the road, but they make you more visible to distracted drivers. In addition to the obvious safety feature of electric bicycle lights, they can also add some fun style and customization to your ebike.

Fortunately for ebike riders everywhere, there are thousands of bright yet inexpensive LED lights out there. Unfortunately, most of them either require their own batteries or run on 12V DC.

Common bicycle lights that are powered by AA batteries aren’t a great option for ebikes. They require replacing batteries every few weeks or months, they are rarely sealed well which often leads to corroded batteries, and they often come with cheap mounts that break off when they become aged and brittle. They are also almost always “be seen” lights instead of “seeing” lights, meaning they are better for letting cars see you than for lighting up the road in front of you.

Some bicycle or ebike lights come with their own small rechargeable batteries and are powerful enough to be “seeing” lights, actually illuminating the road and obstacles in the distance. However, the convenience of not replacing batteries is negated by the frustration of remembering to recharge the light’s battery with a separate charger every few days. This is more of a hassle for some people than others. I once reviewed a pretty good one, but I simply don’t use those types of lights anymore because they have so many disadvantages.

I much prefer lights that are powered by the main battery pack on my ebike. The only cheap, button-cell battery light I regularly use is this one, mounted on the back of my helmet, and usually only when riding on faster roads with lots of car traffic. For less than $1.50, I can put up with my helmet tail light occasionally dying on me.

When it comes to my main ebike lights though, I only use lights that are powered by my ebike’s battery. Ebike lights that are powered by the main battery have a ton of advantages:

• No batteries to change out
• No separate charger required
• As long as your ebike has battery left, your lights will always work
• They are usually cheaper (I’ll show you some great cheap ones below)
• MANY more options; you’re not limited to dinky little bicycle lights
• Higher quality and brighter lights meant for automotive use

To be fair, there is one central disadvantage of ebike lights that are powered by the ebike battery: namely that they consume some of your battery and thus cut into your range. For most lights though, this will cause a tiny impact that you’ll never actually feel. My bike uses about 700W to cruise at top speed, yet all of my powerful lights together pull less than 20W. That means my lights consume about 2.8% of my battery. In other words, my total ebike range will be 2.8% less with all of my lights on. I’m rarely cutting it that close, but if I ever did, I have my lights on multiple switches so I can power just my front and rear running lights (less than about 1W) and not my giant headlight (about 18W) if I needed to conserve power while remaining visible. More on that below, including pictures and diagrams.

I recommend that every ebike rider use main battery powered ebike lights for the simple reason that you’ll never be caught in the scenario where your lights are dead and you’re forced to ride with cars in the darkness. For me this is simply a safety issue.

Ebike lights – three main options

There are three ways to power your ebike lights from your battery:

1. Ebike lights with a built in DC-DC converter
2. Use a separate 12V DC-DC converter and then use 12V automotive lights
3. Use 12V automotive lights directly from your battery, in series to achieve proper voltage

The first two options require some form of voltage converter, either in the lights themselves (making them more expensive and less reliable) or as a separate unit. That’s why I much prefer the third option, which allows you to simply use 12V lights without any other electronics involved. I’ll show you how to do all three options below though, and you can choose the method that’s best for you.

Option 1 – Ebike lights with a built in DC-DC converter

This option is probably the simplest, but not the cheapest or most reliable. Ebike lights with a built in DC-DC converter are designed to mount on an ebike and receive power from a range of battery voltages, usually something like 12-80V, but you should check each light to confirm your battery is within its range.

My absolute favorite ebike lights with DC-DC converters come from Grin Technology (commonly known as ebikes.ca) in Canada. They designed their Electrolights line in-house and manufacture the lights themselves to very high standards. They are 100% waterproof, super rugged (they claim that you can run it over with a car or beat it with a hammer, though I don’t plan to test that on my mine) and can accept any voltage from 15-100V DC. Grin Technologies has a front light for $70 and rear light for $60. Grin also sells their CycleLumenator which is a super bright 1,000 lumen headlight, but at $145 I haven’t tested that one yet.

Grin Technologies has the best quality ebike lights, though as you’ve seen, that high quality and top notch service comes at a cost. I believe it’s worth the cost, but if you’re on a tight budget or want a cheaper DC-DC converter light to play around with before you start upgrading in the future, there are some other options.

I’ve been using this 18W ebike light that runs on anything from 12-80V (I run it at 52V). This is a bright light and is definitely a “seeing” light, not just a “be seen” light. I originally mounted it with the angle a bit too high and was apparently blinding drivers for a few hours until someone yelled at me. Oops.

I simply mounted mine on my handlebar stem using cable ties, but you could screw it into any part of your frame using a self tapping sheet metal screw, or bolt it to the fender mount on your fork.

At just over $7, this has proven to be a great main headlight.

For a main tail light I don’t need something so bright, so I went with this “be seen” style 12-80V tail light. It pulls less than 2W but is very bright and visible from at least a few hundred meters, the farthest I could find a flat, straight path to test it.

The housing snaps together at the lens and made be a bit worried that water might eventually sneak inside, so I added a bead of silicone at the parting line and sealed it up. It’s been working great so far, though I’ve only been testing it for a couple months. But at $2.50, it’s already exceeded my expectations.

Option 2 – A standalone DC-DC converter and 12V lights

There are thousands of 12V LED lights that come in every shape and size imaginable. These are great for ebike lights because they allow you the most flexibility to customize your ebike. The problem is that you can’t run them straight off your battery because the voltage of your pack is too high. Most people use an ebike battery between 24-48V, with some people using higher voltage in the 70V and 80V range.

The solution? A standalone DC-DC converter. I’ve used this converter which has worked very well for me. It’s sealed so you shouldn’t have any water issues and accepts any voltage from 24V-80V which should fit most ebike batteries.

A DC-DC converter like this will step down your battery voltage on a separate circuit and provides an output of 12VDC. It won’t affect your regular battery voltage; it just creates a separate “tap”, so to speak, that outputs 12V for accessories like lights, horns, alarms, etc.

From that 12V you can run all sorts of 12V lights meant for cars and trucks. While this option works well, it requires an extra component, the DC-DC converter, which I don’t like. I try to keep my ebikes as simple as possible with as few parts as necessary. Every extra piece is something else that can fail and a new problem to search for. That’s why I use a combination of option 1 above (lights with built in DC-DC converter) and option 3 below, where I’ll show you what lights I use.

Option 3 – Using 12V lights in series straight from the battery

This is my favorite method because it uses the least amount of parts and is the most reliable. You don’t need any DC-DC converters, not even in the lights themselves. That means it’s also the cheapest option, since all you need are the lights (and maybe a fuse added in line for extra protection just in case.).

As you recall, those 12V lights can’t run off the higher voltage ebike battery directly because the voltage doesn’t match, but we can solve this by running a few 12V lights in series.

Here is how the process works: series connections in electrical circuits are made when components are connected end to end (positive to negative). A voltage drop occurs across each component individually. 12V automotive lights require 12V DC, and so by stringing together a few in series, we can get a total voltage drop equal to the voltage of the battery.

We can wire four 12V lights together in series and the voltage required for the string is 48V, which is perfect for a 48V battery! The same thing can be done with three 12V lights for a 36V battery, or two 12V lights for a 24V battery, etc.

In actuality, the 12V LED lights can take a decent range of voltages, usually between 10-16V will work, which is good for us because the voltage of an ebike battery decreases over time but stays within this range (per light, that is).

On my ebike, I use four 12V LED strips connected to my 52V battery, which gives something between 11-14V per light, depending on my battery’s level of charge.

The four 12V light strips I use work great as ebike running lights. They are meant for automotive purposes so they are already waterproof. The specific ones I use are fairly short pieces, about 12″ long, but you can buy strips by the roll if you wanted to go nuts and cover your bike in them.

I have two white light LED strips mounted on the front on the fork and two red light LED strips on the rear of the bike that I purchased here. The lights themselves mount with double sided tape that comes mounted to the rear of the light strip. I went ahead and added a couple cable ties over the strip just to make sure the tape stayed in place.

The white lights on the front are mostly for being seen by other cars, though they do illuminate the road a little bit too. The red strips on the rear of the bike shine upwards at about a 45 degree angle due to the angle of my frame, but are still quite visible from a distance. The effect is something like a Tron bike riding around at night, making me super visible to cars from all angles.

And that’s just my running lights – when I turn on my main head and tail light then I’m even more visible and can light up the road in front of me.

Don’t forget that I’ve got all of that light without one single standalone DC-DC converter. My running lights are those LED strips that are running in series straight from the battery, and my head and tail lights have their own built in DC-DC converter. This is a combination of options 1 and 3 from above.

In the future, I’d actually like to replace my DC-DC converter lights with simple 12V lights. I can put two 12V motorcycle headlights in the front and two 12V tail lights in the rear, which in series requires 48V, perfect for my 52V battery. Piece of cake!

Until then, this combination has worked well for me. Good luck on your own ebike lighting project, and let me know how it goes!