NB: this is all rather out of date - we were funded with a Harlington grant app in 2007 to replace all of these with Vertex mounted Petzl Duo 14 LEDs
Sometime in 2005/2006 we replaced all the Halogen bulbs in the FX3s with Low Wattage (1W?) Luxeon LED lights. We bought these with our own money (SGI) as the Union in their infinite wisdom wouldn't fund headlights as essential safety equipment for a caving club.
These have been brilliant - and give a supposed endurance of around 35hrs on a full FX3 (NiCd) battery.
However, as of April 2007, all our FX3 batteries are showing loss of capacitance, and the FX3 connector blocks all have bad contacts. Most of these could probably be fixed with careful flexing of the 4-leaf pins, and cleaning of the plug sockets.
However - FX3s are unpleasent to use underground, and it makes sense to jump on to some kind of LED-FX3/Helmet Mounted battery system before a wholesale upgrade of the club lights.
Dave Wilson suggests the following: (April 2007)
"If the existing 'bulbs' are two-thirds of a Watt (circa 250mA),
3xAAs would give reasonable life, but would be a
pain to handle loose. If you were going to solder
cells together to make up packs with race-pack
connectors, you might as well use 4/3A, 7/5AF,
18670s, to give a better capacity than AAs
(4-4.5Ah - likely last a weekend of anything but the hardest caving)
A multiway smart (~0.5C / 2hr) charger wouldn't
be too hard to make. If you weren't bothered
about the display side (just a 'charged' LED per
connector), and people weren't going to mess
about with it too much (swapping batteries while
it's running), something basically like the one I
made for myself, but programmed to charge a set
of batteries in turn wouldn't take a huge amount
of extra electronics or programming. A 5-gang one
might even be squeezable into the 18-pin PIC chip
design I use for my existing charger with slight
mods for sequentially charging the various packs."
