Head Torches and Batteries

Although the days are gradually getting longer the nights are still very cold and dark. Despite the obvious nature of the night-time the local Mountain Rescue Teams are regularly called out to people caught out without a torch and unable to continue. Without a very bright moon there are no sources of light, no street lamps, no car headlights, nothing to see where you are putting your feet, or see a hand in front of your face. The depth of the darkness cannot be over-estimated. A head torch is essential for getting off the fells.

This blog post will only really look at head torches and not hand torches, because for walkers a head torch leaves both hands free for walking poles, scrambling, keeping hold of the dog, or whatever. That isn't to say that a hand torch isn't also useful, or that the technology mentioned isn't also applicable, just that taking a head torch is really a no brainer.

So how do you go about picking the right head torch for you? The long time masters of head torches was always Petzl and particularly the Zoom which really was the only thing worth having and preferably with an exotic xenon bulb. These days we have so many manufactures of quite stunningly impressive LED torches you can get a bit overwhelmed with choice.

Before we move to the technology of your main light we'll mention one little head torch that breaks most of the suggestions we'll go on to make. Consider putting a tiny torch such as the Petzl e-Lite in your rucksack. Why? Because it really is tiny, it weighs a minuscule 28g, and at just 16 lumens light output it is not going to let you see far but it will show you where you are putting your feet. Which is enough to let you follow a path back to civilisation, or change the batteries in your other light. Powered by a couple of lithium coin cells which will stay ready to use for a number of years. Just leave it in your pack and you'll always have some light.

So to the main head torch. You'll see the word "Cree" mentioned in torch literature a lot. This is a manufacturer who seems to have figured the art of getting the maximum number of lumens (a measurement of light) from Light Emitting Diodes (LED) for the least amount power than any one else. It's a good word to look for.

The other part of the equation is batteries. Here it is really quite a nightmare of options as the onward march of battery technology has brought us a fantastic abundance of different varieties; however the choices you make with the type of battery dictate the model of torch, and vice versa.

To shed some light on batteries, think about what you want the torch for. If you are fell running you probably want something very light weight, but you'll then need to compromise on brightness, or duration. Simply put, the more light you want the more power it takes, therefore for a given battery capacity the shorter the duration the light lasts. Pick any two from light, bright, and duration.

For a hiker how much it weighs, within reason, doesn't matter and you'll likely be out for longer. So a heavier head torch, and battery, wouldn't be a burden.

Here is a table of the major battery technologies:

type	voltage	case style	pro's	con's
Alkaline	1.5v	AA, AAA, C, D	cheap, available everywhere	poor capacity in cold
Lithium (Ultra)	nominally 1.5v	AA,AAA	holds capacity better in cold than Alkaline. Stocked by some supermarkets, available online	expensive, not rechargeable
Lithium	3.3v	CR123a	small size, light, holds capacity down to -20°C	high cost, not available in all shops
NiMH (rechargeable)	1.2v	AA, AAA	readily available. New ones have much lower self-discharge and come pre-charged.	heavy. Capacity fades below about 0°C
Lithium-ion (rechargeable)	3.6 - 3.7v	14500, 18650...	light, highest power density	capacity fades below -18°C. Specialist charger required, care in handling and storage as risk of fire!

Even within the major technologies we've shown above there are subtle differences in chemistry which can have significant effects. For example, the NiMH Enerloop XX in AA format has a greater capacity of around 2450mAh but lower charge cycles of 500 compared to the plain Enerloop at typically 2000mAh but extended life of over 1000 charge cycles.

Now when it comes to lithium you have three basic types of cell. There is the primary, i.e. non-rechargeable, Lithium (Ultra) Li/Fe 'voltage compatible' chemistry which is a direct replacement for your standard 1.5 volt AA or AAA cells. Then another primary cell uses Lithium-Manganese which is the CR123a used in some older cameras and torches. Finally we have the Lithium-ion battery which can have all manner of slightly different chemicals in it to tweak its properties, and is most likely to be recognised in the form of a mobile phone or laptop battery. Head torches are increasingly using a single Li-ion in the 18650 case form because it's relatively light and contains as much energy as four much heavier NiMHs, so you can have a simple and very powerful all in one unit.

However, there are downsides to lithium batteries: they don't like being damaged, over-charged, or excessively discharged. When charging they don't like being cold - 0°C or too hot - 40°C when being charged, the charger has to be compatible with the particular battery you are using. You cannot put Lithium batteries in an old charger meant for NiCad/NiMHs. The result of misuse is fire and in some circumstances an explosion. Not good. Look after them. Buy batteries that say they are "protected", and only from a reputable source that doesn't exaggerate their capacity. The maximum an 18650 should be is currently around 3400mAh, anything more is probably fairy stories. "IMR" batteries are really aimed at very high discharge currents that are far beyond what a head torch can use so avoid them as they have reduced capacity.

I have to admit I don't like lithium batteries. I was never keen as I knew of the volatility of lithium, but after seeing two mobile phone batteries puff up like a balloon without provocation I have to admit I'm very cautious about them. But I rather like the high power density and the ability to carry a spare battery (18650 size) that weighs only around 47grams instead of 120grams for 4xAA NiMHs they look pretty attractive.

Looking around you'll notice some head torches are "regulated" and some aren't. This simply means it has electronics in it so that the light output is as constant as possible regardless of the charge state of the battery. i.e. it doesn't start gradually getting dimmer within a few short minutes of turning it on. Generally having a regulated torch is a good thing. The length of time a torch will run for is usually timed until either the battery is classed as exhausted, or the light level drops to 1 lumen which is long past the stage of being useful.

If you are going to be out in the winter a handy thing is to take large, e.g. 4xAA cells, battery pack off the head band, clip an extension into the wire that goes to the light unit and put it in an inside pocket to keep warm. Then you can use any battery type and still get its best capacity.

As we've already mention the type of battery you would like to use impacts which model of head torch you can use with it. Each battery type has a different output voltage which the torch electronics would have to cope with. As well as accommodating the widely different form factors, it is simply not practical.

So now you've probably made a choice over your battery technology and understand how this changes which torches will be available to you. How do you choose between them, as there is still a pretty big range.

The thing I look for is something that throws a good beam for middle distance vision, but still sends some light off around the surroundings so that you can see where you are about to put your feet. Some people like a wide beam and don't worry about the path monsters just outside the flood of light. This is very much down to personal preference so I don't have any recommendations here. Most torches are fixed these days, but there are a few that can adjust the beam like the old Zoom but I have no experience of them.

At some point or another you will undoubtedly find yourself out in the dark and rain. This is where having a waterproof head torch is handy. Electrics and water aren't great mates, so see if it has an IP rating. These are a numeric rating of dust and water proofing but many torch manufactures refer only to the water rating, so you may come across: IP54, or IPX8, for example. The bigger the individual digit the better protection. IP54 means it'll resist dust getting in, and is splash proof. IPX8 means it can be submerged to to a minimum of 2m or more which may be detailed further in the literature. If you really do like being out in the rain a splash proof rating really isn't going to do the job.

Another thing that's going to be personal preference is things like "reactive lighting" where the torch can dim the light so you don't blind yourself when you look down at a map. It strikes me that it might be a good thing, but it might also annoy me like hell if it gets it wrong. It's also pretty expensive. I think I prefer to have a good, large button that I can still use with my gloves on to dim the light in a predictable manner. A caution with torches with different coloured LEDs as well as the main beam is that under red light, contours and other features on a map may disappear.

So (deep breath) that's all very well but can I just go and buy the latest Petzl like we always used to and get out there. Well yes, you can. But remember what I said about the batteries. That all comes of significance when push comes to shove and you find yourself in the pitch dark, freezing cold, and your batteries are cold too and have curled up under a rock to sleep till the summer.

Whilst I was doing research for this blog post I came across some very nice updates of my old torches and a nifty looking IPX8 rated Fenix HL55 head torch that uses a lithium 18650 battery. So I'm off to see how much money is left in the piggy-bank....

Tagged: equipment, safety

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