The original LEDtechno (CustomDUO) packs used 7/5 AF 3600 mAh NiMh cells (3s), a simILr approx. size to 18650 li-ion cells. These ni-mh cells were rather tricky to get hold of in 1995, but are now widely available in capacities around 4500 mAh. Although superceded in many applications superceded by higher capacity, lighter weight li-ion cells, they do however have the advantage of being more robust and toleratant to a good soaking. If you wish to use higher capacity, lighter weight li-ion 18650 cells then a more waterproof battery box is essential (such as a Rude Nora Box). 10 years ago such boxes may have accomodated as many as 4 cells (possibly series wired for high voltage). However, things move on, and such boxes are an increasingly hard sell. With significant improvements in both LED and battery technology it is far more likely that these boxes will now accommode 2 cells, typically parallel wired cells at 3.7v with suitable protection circuitry.
In the UK, ex mining lamps (Oldham and CEAG) have been readily available, and hence widely used by cavers for many years, and provided the first platform for the use of LEDs for caving.
The appearence of high capacity NiMh cells in the mid 90s (not long before the arrival of white LEDs) initiated a transition from large waist mounted batteries to helmet mounted packs. The favoured method of attaching these interchangeable battery packs was the 'old style' Mk1 Petzl battery box.
Consequently, the original LEDtechno (now CustomDUO) 3 cell 3.6 volt NiMh battery (3 series) for Petzl boxes, double heatshrunk with Tamiya II plugs (or other similar connectors), became very much the standard configuration for helmet mounted mining lamp conversions. These battery packs were significant in the development of the first LED based caving lamps, incorporating LED bulb conversions. How time flies. And we're still blinking well at it.
Simple by modern standards, these bulb based conversions used the first white 5mm Nichia LEDs, and were also manufactured by LEDtechno (CustomDUO) from 1997. These were our first commercial LED based products and were sold widely by caving shops in UK and internationally, representing the first significant use of high brightness white LEDs by cavers.
Though by no means anywhere near as widely used by cavers today, mining lamp conversions retain a following, as they are robust, maintainable and cost effective. A lamp constructed from a surplus Oldham headset, CustomPITLAMP Module, Mk1 Petzl Zoom battery box and 3.6v Nimh cell pack certainly wouldn't be a bad solution. It is worth noting that the Mk1 Zoom box has been discontinued by Petzl, and a new one is difficult to get hold of, the best approach being to buy an orginal Petzl Zoom second hand via ebay. However, these can be snapped up quickly by cavers still faithful to this approach, often by those who go into a blind panic at the price tag of high end caving lamps, and equally have no time for cheap made in China headtorches.
Within a couple of years, largely due to demand, we had our Nimh battery packs for Petzl Zoom boxes professionally manufactured by Strikalite. The original Ledtechno (Customduo) design is still manufactured by Strikalite Batteries, in 4.0ah and 4.5ah format, (Product ID 871 and 872). Strikalite also offer suitable battery chargers.
Alternatively AA batteries can be used. You can get AA holders, but the battery contacts are often affected from being bashed around, and it would be fair to say that these are not the most reliable things ever. Heatshrunk battery packs using 3 or 4 good quality AA cells, such as Eneloops can also be effective, but probably not the optimum solution. We have in the past had packs of this configuration built by the 'Component Shop' . If you are UK based, these guys are worth a try.
If considering a mining lamp conversion, we manufacture a range of CustomPITLAMP modules to meet your needs. You no longer need to use our original LED bulb inserts featuring 1 to 7 LEDs, 3 LEDs having been the most popular version (see photos left, now discontinued lol). It just doesn't seem so long ago that these were the first LED solutions used by cavers, commercially available in 1997. Prior to this our efforts involved mixing red, green and blue LEDs to create white light, but the results were not great, certainly nothing that offered the commercial sucess of the Nichia LED bulbs and Nimh battery packs. The same could be said for our attempts at the first PITLAMP modules (circ 1997, at the same time as we were building the LED bulbs). In various forms, the 7 LED module pictured left was 'just slightly dangerous !!' as it incorporated a photo slave circuit and flash. What were we thinking. Indeed, the LED module conversions for mining lamps did not really float as a concept until around 2005 when these first offered a viable alternative to the LED bulbs (when Luxeon released first high power 1 Watt plus white LEDs). The first modules incorporating these high power LEDs were introduced by Bisun and Mine Explorer, which pretty much marked the end for our LED bulb conversions ..... and the beginnings of the CustomPITLAMP Modules !!
Within the time window between the LED bulb based conversions, and the first high power LED modules, it is worth noting that Speleo Technics introduced the Headlite (around 1999 at a guess). This used a CEAG like reflector with 7 or 14 LEDs 5mm nichia LEDs built around the edge. Interestingly, the Headlite went on to be, we believe, the first commercial caving light to use a li-ion battery (manufactured by Saft).
But moving on, the thing that we have always found a pain with mining lamps is the very large diameter cable, which is a troublesome to solder (at risk of a massive under statement). We had always assumed that the cables were impregnated (at manufacture) with some horrible shite, but in actual fact it can be attributed to the cable cores being of aluminium, and the associated oxide layer. When working on ex mining lamps we therefore tend to exchange the old cable for a rather more appropriate 5.7mm cable. This more flexible cable allows for preferable routing inside of the helmet. We bought a big reel some time ago, so in case you need a couple of meters we have made it available in the Bargain Bazaar. We typically use some heavy duty adhesive lined heat shrink (get from ebay) to bump up the diameter at the point the cable enters the headset (and to form a shoulder to stop cable pulling out), and then we set in place with some epoxy. The heat shrink can also be used to form a shoulder to retain the cable in an original style Petzl Zoom box, if using one of these. There are a number of other ways to tackle the Oldham and CEAG cable issue, this just being how we have historically done it. We also generally seal up the through headset charging port for obvious reason.
See Customduo Shop for current stock of Oldham lamp / Petzl battery box based caving lights, which is at best rather sporadic and dependant on available parts.