Does anyone make a dynamo light buffer battery that will keep it going at full power?

Question

I have a nice SP dynamo hub and an old Supernova E3 Triple dyanamo light. However, the dynamo light isn't very bright when I'm starting my ride, as my ride has a long hill at the very start, so I don't go very fast. Then it's a lot of stop and go riding for the rest of my commute with a few more small hills. The standlight kind of sucks until I've been riding on a straight stretch for a while. Looking forward, I would consider buying new gear to help, but I'm not sure what I need (other than just only using battery powered lighting).

Basically, I want my bike to always have lights on while I'm riding through the winter months where I'm commuting both to and from work in the dark, and not loose lighting when I'm stopped or going slow on a climb (where I'm very venerable). Currently, I have to supplement having dynamo lighting with battery powered lights since the dynamo lights cut in and out due to my hilly commute with lots of stop and go urban riding.

Does anyone make an inline power buffer for dynamo based lights to provide (a) Immediate on when you want to start riding and (b) Constant power while stopped? Or are there lights or other equipment that provide this feature (without forcing me to build my own circuit boards and such)

Answer 1

There are standlights, which are essentially supercapacitors combined with LED headlights. They're designed to be charged from the dynamo while riding and give you a few minutes of extra lighting when stopped at a stoplight. However, all the ones I know will self-dissipate after a while, so they're useless for your purposes of starting off the day with full beam strength (unless you want to bike around on the flats for a few minutes charging them).

For full strength lighting at any time, you really need a battery.

I don't know of any commercial battery-charged dynolights. I built my own circuit that takes the AC from the dynamo, rectifies it, uses the DC to charge an 18650 that then powers my LED headlights and taillights (and charges my cellphone). The circuitry is trivial by itself, but you'd have to know enough about soldering small circuitboards and I can't do any customer support, so I haven't shared it.

The reason I built the rig was that I wanted more powerful LED night lighting (10+ watts) than my dynamo could reasonably deliver at one time. So I charge my 18650 by riding during the day; and then at night, I have instant full power.

My assumption is that if you know enough about electronics to solder it, you should know enough to design it. All parts are available from sparkfun in terms of rectification and smoothing, lithium batter charger, battery, switch, LED current limiter, breadboard, and so forth.

Answer 2

I have recently installed the Cyo-T head light by the German manufacturer Busch & Müller. It has a daylight riding feature that is buffered to have up to 4 minutes of light when standing without energy supply from the dynamo which powers the daylight riding light LEDs. The buffer is good enough that if I switch off the light right after stopping, it does still make the daylight riding LEDs light up after having the bike parked in the shed for the whole weekend.

By that, you have at least the daylight riding light immediately after you start cycling. And since the circuitry seems to be developed in a way that the daylight riding LEDs get enough power to go to full brightness before the main light is powered, you will at least have full brightness in them – definitely enough to be seen on the road.

So to answer your question: yes, there are such lights, but I don't know whether you will be able to grab some of those or find something equivalent where you live.

Answer 3

So you already have a capacitor based standlight, but want it charged from the beginning of your ride. You can manually charge it before starting your ride:

1. Turn off the lights if the standlight charges while the lights are turned off.
2. Go find the leads where your dynamo connects to the lighting system
3. Apply 5V DC to it for a few seconds, for example from a USB-Charger or USB battery. You can sacrifice a USB cable for this, cut off the Mini-/Micro USB connector, split the wires and just manually touch them to the appropriate contacts on the bike (at least on mine, those are already exposed). The capacitor should then be charged. Usually those dynamos produce 6V AC, so 5V DC shouldn't damage the system no matter the polarity. "A few seconds" depends on the power source, but a normal phone charger can provide like three times the power of a hub dynamo and capacitors charge pretty much instantly. There might be a bottleneck in the circuitry surrounding the capacitor, but no matter what it shouldn't take long.

Before you try: Do it on your own risk. The lighting system wasn't designed for this any may thus break - but I don't think it's likely for the reasons explained above.

That being said; I used to commute like that, LED lights, hub dynamo and a climb at the start. I never had problems, the lights intensity was reduced during the climb, but seemed bright enough even at very low speeds. So either you want more light than me, or you have some components in your lighting system which are of lower quality/efficiency. You also mention stop and go, so I assume this is in an urban area, where there are likely street lamps. So I would say that it's pretty likely that your lights are good enough already.