Bright Lights All Night?
(3 approaches to brighter lighting)
 High-Wattage bulbs and the LVR2
  Twin Headlights with a generator
   Three Micros with Lithium power

Bikecurrent Archive



High-Wattage bulbs and the LVR2
by Francis Cooke

The tiny sealed halogen bulbs using the 2-pin MR-11 or MR-16 mounting systems give an exceptionally fine, smooth, unpatterned wide beam. Some riders feel that power is being wasted by the extremes of the beam shining upwards or to the sides, but I have found that the sheer quality of light is quite addictive, unlike anything available from any other cycle lights, and its very difficult to go back to any other system after having experienced these.
My own experience is of the tiny Vistalite VL500 lights, but similar lights are available from Nightrider and Nightsun. My preference is for the 5W bulb, for decent runtime with a lightweight system, and this gives good light for normal riding speeds. The 10W bulb just gives more of the same, with a wider central spot, and is good enough for long sweeping downhills taken at speed, with the added entertainment value of picking out all sorts of startled animal life in the hedgerows.

Lights like these work best off rechargeables - a lightweight system would be 5x 4Ah NiMH cells, giving 6V 4Ah, running a 5W bulb for nearly 5 hours and weighing just 300g. But these are expensive to buy and need a bit of care to keep them in A1 condition.

Alkaline cells, of whatever size, will not be able to handle this sort of current drain. The light will start bright, very rapidly become ordinary, and soon after that descend through yellow and brown to infra-red.
On a 400km night ride I set out to match the performance of Sheila’s superb 5W system (using NiMH rechargeables) by using Alkalines, thus proving a viable system using easily obtainable batteries for PBP.
I used a pack of 8xC cells in series - giving about 13 Volts initially - run through a Willie Hunt Lighting Voltage Regulator (or LVR2). This was set to drop the voltage to precisely 6V, which gave a good steady bright light using the 6v 5W HOT bulb. I got a run time of just over 6 hours at full brightness plus 2 more hours of usable, if less bright, light. The pack weighs 630g, over twice as much as the NiMH pack, but the run time is just right for a night ride, and of course there is an advantage in that the battery can be jettisoned at dawn.

Note that without the LVR2 this is simply a non-starter. Run-time would be half and the quality of light would be dismal.
So here are some notes about this remarkable device.

How - or why - does the LVR2 work? (techie bit on a separate page)

The LVR2 is a public domain circuit. However, you would be mad to attempt to build your own, as Willie Hunt can supply it ready built precisely to your requirements. Willie's circuit board is a masterpiece of miniaturisation and if requested he can also weatherproof it for you.

The maximum input voltage is 15V - so it would be possible to use 9 Alkaline cells in series for maximum runtime. I prefer to use 8 because it is physically much easier to make an 8-pack, using two 4-cell battery holders bolted back-to-back. A C-cell pack built like this is smaller than a can of Coke - although it weighs nearly twice as much! Adding the 9th cell would increase the runtime at full brightness, from just over 6 hours to just under 7, with a 5W bulb.

Output voltage can be set to any value above 3V. I set it to precisely 6V, but of course it could be set anywhere in the range 5V to 6.5V, for a trade-off between brightness and runtime. At 5V the 8-cell pack would give over 7 hours. Its best to discuss this with Willie when ordering the unit, in fact simply describe to him your precise lighting setup.

The LVR2 features a 'low battery warning' which consists of a slight flickering of the light when the input voltage drops below a certain level. This is an essential feature for use with rechargable packs, but is mildly irritating when sucking a pack of Alkalines dry. This feature can be disabled by changing the value of one of the resistors on the circuit board - it is possible, but fiddly, to do this yourself, but again its much better to ask Willie to do this at time of building.

The LVR2 also features a sexy 'slow start' which magically works even when you switch on using the normal switch on the lamp head - the light fades up over about half a second. This valuable feature reduces thermal shock and extends the life of the bulb.

The LVR2 weighs about 15g, and can be mummified in plastic tape making a package about 6cm by 2cm. This simply sits inline between the battery and the lamp head.

For more information see Willie Hunt's WWW pages
Lighting Voltage Regulator

With any system using separate packs and cables, one thing you should carry is a spare cable - they are all too easily damaged, and not always easy to repair.
Spare bulbs are a bit more problematic. The sealed units as used in the VL500 or Nightsun SunSport are bulky and quite fragile at the pins end, not to mention expensive. They do however have 10x the life expectancy of a ‘normal’ halogen bulb, and even more when used with a LVR2, which is very kind to bulbs. So I would pack just one of these. Protect the pins with a plug of expanded polystyrene and press into an old plastic 35mm film canister.

Back to Bicycle Headlights Page
Back to Bicycle Lighting Resource Page