The APR18650M1A LiFePO4 batteries are high powered and low cost. They have a rated capacity of 1100 mAh, a rated voltage of 3.3V, and a rated current of 30A. 10 pieces cost $36 on eBay. I measured their internal resistance with the SKYRC B6AC V2 Charger.
I bought them because they’re lighter than the 1.3Ah 12V SLA battery used for the car horns on my bicycle, quite safe, and long life.
Possible applications of the batteries include battery pack rebuilding, power tools, flashlights, battery backups, and e-bikes. Note that they’re 3.3V which is lower than the 3.7V cells commonly used in electronics. They also need a charge voltage of 3.6V instead of 4.2V.
To test them, I installed them into a custom built 4 cell 18650 battery pack and connected it to the charger.
Compared to other LiFePO4 batteries bought from DealeXtreme, the APR18650M1A batteries have a low internal resistance. Those from DX have an internal resistance of about 0.18 ohm, or up to three times higher. If your applications are high current such as electric vehicles and power tools, you’ll need a lower internal resistance.
I have tested the batteries with a pair of car horns. With two horns, they should draw 10 amps which means the battery pack voltage drops to 10 to 11V. Unlike other 18650 batteries I used before, the horns didn’t click.
If you’re interested in a battery that’s lightweight, high powered, safe, and long lasting, I would recommend the APR18650M1A batteries or something similar.
The instructions are for the car horns set up for bicycles.
The battery used in the setup is SLA which should be kept at full charge for maximum life. If they are stored with low charge, the battery will be permanently damaged as sulphur crystals form.
The following instructions are for smart chargers which makes sure that it properly charges the battery. Since it probably has an internal thermometer, make sure that your battery and charger are at the same temperature. If you’ve cycled in the cold and the charger was in a warm location, wait for your bike to warm up before charging. If you’re using other battery chemistries, the charging instructions will be different.
How to charge:
Charge at least once every month
Charge more often if stored at higher temperatures or if the horn is used more often
Wait for your battery’s temperature to match that of the charger before charging
Do not fully drain the battery
Installation requires custom mounts. You can try mounting your setup on your frame, handlebar, basket, or pannier rack. You can use cable ties and velcro straps installation.
For safety, make sure that it doesn’t cause mechanical problems for areas such as steering, braking, pedalling, wires falling into the spokes of wheels, and the sagging of basket. You should:
Use cable ties to keep the wires in place
Install the button where you won’t have to remove your hands from the grip if you have to honk. You should be able to brake or steer
Use rubber or duct tape to keep the button from slipping
Make sure that wires won’t disconnect from vibrations. Use cable ties or duct tape near the horn and battery connectors. To reduce vibrations, you can put form under the battery.
For waterproofing, you can wrap the button and enclosure with a plastic bag.
I have installed car horns onto my bicycle in addition to custom bike lights.
Car horns can alert drivers of your presence. For example, when they’re about to turn and you’re going straight.
They seem effective. When you honk, drivers often brake their cars even though it’s coming from a bike.
My setup can be found at Instructables. In my setup, the horns and batteries were in the basket and the button was on the handlebar. I used the FIAMM El Grande Horns.
The cost of the materials were:
El Grande Twin red electric horns:29.99
12V 4Ah SLA battery: $16.95
12V 500mA 12BC0500D lead acid battery charger: $29.50
My bicycle used to have the Airzound horn but I switched to car horns almost a year ago. Its advantage over the Airzound are:
Easier to reach buttons
Possibly better safety for hearing
Longer honk duration for a single charge
Familiar sounds may shorten reaction times of drivers
Suitability for cold weather
The button should be easy to access because the sooner the driver reacts by braking, the shorter the stopping distance. In my setup, my thumb can be close to the button most of the time when I’m riding. If I see obstructions ahead, I won’t need to spend too much time finding them.
I believe that car horns are safer for your hearing than the Airzound because it doesn’t cause ringing in my ears in the open. Maybe that’s because they’re quieter and deeper. The car horns were tested to be 112 dB and the Airzound 115 dB at one metre.
Car horns last longer. On a full charge, the battery should last a few minutes depending on the battery capacity. With the Airzound, it lasts 8 seconds at full volume.
SLA battery was used because the horns needed plenty of power, and they were affordable and easy to find locally. You need a 12V battery than can handle 12 amps. You can find the information from their datasheets.
If the battery can’t supply the current required, the horn clicks or sound distorted which was what happened when I used Li-ion batteries from Deal Extreme. You need your horns to be reliable.
Lee’s Electronics carry the 12BC0500D smart charger. Smart chargers stop charging when your battery is full to prevent overcharging. To prevent damage to the battery, make sure that the charge is always topped up. How often you should charge depends on the storage temperature and how heavily the battery is used. Batteries lose charge faster at higher temperatures.
The horn button was installed close to the gear shifter. A custom mount was required. You can experiment with pipe clamp, cable ties, duct tape, and foam.
The horns were installed in my basket. For my second setup, there was clearance beneath and I installed them underneath. This saves space in the basket. The wires wereattached to the basket with cable ties to keep them from flexing too much or coming off the basket.
Since the battery is heavy, I used the bar that attaches to its base and the quick release of the wheel. That way, the basket won’t sag.
I used a 1.3Ah battery instead of a 4Ah battery for my second setup. It’s lighter and smaller but still works because it can supply at least 12 amps. The only problem I noticed was that it’s quieter only when the button was tapped. If you can find Li-ion or NiMH batteries that work, you can charge them less frequently, or use them for other accessories because they don’t need to be kept at full charge.
The horns were attached to the basket with cable ties. I drilled their mounting brackets for the cable ties. The horn still worked even though the instructions said not to modify the brackets.
So far, my horns haven’t been stolen or vandalized. They don’t have a quick release mount.
I started using car horns in October 2015. I haven’t noticed road rage yet. Only twice did drivers honk back. Sometimes, bystanders look surprised. There was a situation in which the face of a passenger was contorted when the driver was turning right and I honked.
My recommendation is to use it for safety. For example, I would honk to alert the driver of my presence if he’s cutting me off rather than honk after being cut off. There’s a risk of over-correction when used improperly.
What are your thoughts about bicycles with car horns?
The computer measures your speed, trip distance, total distance, how fast you are relative to your average speed, and whether you’re accelerating or decelerating.
The computer is wired which means you need only one battery. I’ve used a wireless one before. I stopped using it because its receiver’s battery runs out even though I used it lightly.
I bought it because it’s reliable based on reviews and displays your speed in km/h. Based on its reviews, it’s more reliable than some of the similarly priced models. It’s easier to pace yourself with a speedometer than by feel which is beneficial when you want recovery days.
You can use the speedometer to test if your speed is affected by different tires, inner tubes, inflation pressures, road conditions, and postures and see if they affect your speeds. I use the 700x38c Schwalbe Marathon Greenguard tires which are considered fast rolling.
I still use Strava on my tablet to record the other details such as time, elevation, maximum speed, and average speed.
Have you ever felt invisible on your bike or find cyclists hard to see? I’ve felt that way before which is why I built a custom 7.5W tail light.
I felt that my previous bike light setup wasn’t enough because of a recent near-miss. The driver of a van behind me didn’t slow down and even started accelerating. I decided to move into an empty parking spot in case he wouldn’t slow down. Fortunately, I was safe.
It actually happened on the Off-Broadway bike route in Vancouver near Granville St. Close calls should never happen on bike routes. I try to find the safest bike routes. Now I feel that it’s not a bad idea to use a custom tail light on traffic calmed bike routes.
Whenever I experience a near-miss or drivers making mistakes, I feel that if the driver had enough time to decide, they can be prevented or be made less scary. You can give them more time to react by using brighter bike lights because they can see you further away. More time to make decisions shortens stopping distances, and reduces the likeliness and severity of a crash.
If a bike light is effective, you should feel that people drive more safely around you. You should see them giving you more space when passing, changing lanes sooner, and leaving more space in front of them, all of which makes cycling feel safer.
The bike light was built to improve visibility by:
Using two 45° amber side marker LEDs pointed 45° from the rear
Using two 45° amber side marker LEDs pointed 90° from the rear
Using 45° amber rear-facing side marker LEDs
Using 15° red rear-facing LEDs
Spacing the LEDs
Attaching the side marker LEDs close the the sides of the bike
Mounting it unobstructed by panniers and racks
Front view of the tail light.
Centre LEDs pointed at 45°.
Circuitry and battery pack.
Tail light mounted on the pannier rack of my bike.
Right view of the tail light.
Left view of the tail light.
Patterns of the 45° and 90° facing LEDs.
Patterns of the rear-facing LEDs.
The light has a custom made circuit. It has a micro-controller programmed with strobe patterns for daytime, nighttime, and power saving. Using strobe increases its battery life and visibility. The micro-controller also remembers your last setting and monitors the battery voltage. If the battery is low, the LEDs will dim to let you have enough time for visibility before recharging its batteries. It has a circuitry for stepping up the battery’s 13.2V to power a string of LEDs which require at least 20V.
It might seem like a lot of work to build the bike light when you could just go to the bike shop to get bike lights. The advantage of the custom made bike light over store bought bike lights is that:
Only one battery pack is needed for all 10 LEDs
One button controls all 10 LEDs which is useful for frequent stops
There’s no need to dismount the light every time you park it, saving you time
You can customize its strobe patterns and other features
It’s brighter than store bought tail lights
There’s side visility which may be important for road curves, junctions, and traffic outside your lane
The bike light may be more effective when there’s plenty of space for passing. If a four-lane road is quiet, you might see many drivers behind you using the inside lane and few using your lane within one block. It should reduce the chance of passing too closely when there’s an available lane next to your’s. If the lane is too narrow to share safely, you may still have to ride in a position that controls the lane. There’s no guarantee that it will work all the time.
The bike light was installed a week ago. My goal is not just to avoid crashes but also avoid close calls. Sometimes I get comments about the light from other cyclists. They often liked the design. Some people thought it was over done. To me, commuting safely and stress free is worth the investment.
I would still recommend using a backup light, a front light, and a helmet light.
In the future, I plan to convert the bike light into a turn signal light and possibly a brake light. Cree LEDs are recommended for higher efficiency and power ratings.
I plan on including this bike light in one of my future Instructables. Feel free to subscribe.