In fact, the package of our
headlight and SLA battery pack makes for a really great bike headlight
system - plenty of light, excellent durability, very cheap running costs and an
up-front price that's well under many premium bike lighting systems.
Or if you wish, you can place the SLA battery in a shoulder or
belt pack and use it as a very powerful and light hand-held
So what makes this design so effective?
Firstly, the light beam is tightly focused by a convex glass
lens. But isn't this expensive?
Well, no - not when you use a magnifying glass! The lens used
in our bike headlight is a 70mm diameter magnifying glass. And it is
actually glass, rather than being made from plastic. Using such a large
lens works very well in focusing the beam which is produced by an incandescent
bulb and its dedicated reflector.
Secondly, the design uses a good quality multi-faceted
reflector. It's from an Eveready torch - model E250K (and it appears that the
Eveready E220, E250 and E251 torches are very similar).
This is a two 'D' cell torch with a reflector that's 45mm in
diameter. It costs about four dollars so it's certainly not expensive. We'd
expect that any torch with a decent quality reflector would be able to be used
in this application.
Finally, the bulb is matched very carefully to the battery so
as to give a very good output while having appropriate durability.