andysnook said:
The specs are very impressive indeed, but i have to be honest - as soon as you make things complicated, they have a habit of letting you down. And this thing looks VERY complicated.
They are not as complicated as they seem.
Lithium cells require the drain on them and the charge applied to them to be carefully regulated, otherwise they have the potential to explode.
With the increased popularity in lithium cells being used in mobile devices there are loads of semiconductors (micro chips) available on the market that regulate said loads and charges.
The LED that are used are already commonplace in things such as mobile phones, sign lighting, hand torches and even kitchen lighting, again regulation circuits are readily available to control the loads supplied for the LED.
With the correct circuit which could consist of as little as 6 components, including the Lithium cell(s), LED and switch, you could have a perfectly feasible caving light that would run on any voltage input from 1.2v up to 36v providing light for in excess of 25 hours. Making the enclosure is the hard part.
If you have ever taken and Oldham headset apart its simplicity at its best. It is however reliant on moving parts, susceptible to internal corrosion and not designed to be submersible without modification. The FX headsets of traditional style look and feel like kids toys and perform as well.
Comparing the two types, if something goes wrong with the newer LED lights, fixing it could be a major problem, the older mechanical lights can nearly always be fixed underground unless it’s a problem with the cells or bulb and spares are not being carried. But you should always have another form of light on you.
From my experience, LED lighting in all the guises made for caving use (apart form the old FX units) are tried and tested, and are almost bullet proof.
I have included some pics of my homemade hybrid unit using LEDs in the much loved Oldham headset.