UKH

Any clear evidence and references for whether a rechargeable (petzl) lithium battery is any worse at altitude/extreme cold compared with individual lithium batteries?

Many thanks.

Have you tried asking Petzl?

Personally I'd probably ask Petzl for the results of their extreme cold tests.

And then ask someone else you want to compare (duracel? panasonic? whatever?) for the same info.

I wouldn't bother with the altitude angle, you're basically talking about pressure there and the nature of a lithium battery means I'd be surprised if there was much difference in performance with the kind of tiny pressure differences you would experience at any height you can walk to (i.e. 0 to 9km).

I've found all my Petzl rechargeable torches (2 tika rxp, 1x swift) to be dangerously bad in extreme cold. They last about 30 seconds glacier skiing in my experience, you can guess the rest.

I emailed Petzl as it was so bad I couldn't believe it wasn't a fault. My email actually went through to Lyon distribution, who kindly wrote back a long reply that ultimately wasn't much use (I'm an electronics engineer so it's possible my email had some difficult questions in, I can't remember, but could look it out and pm it to you if you like).

I've moved onto 18650 torches now which seem a little better - the batteries are cheap and plentiful too.

Tl;Dr - I'd not touch Petzl torches with a barge pole for extreme cold.

Thanks guys. 

How extreme are you thinking? I've used my Petzl (whichever model preceded the current 'Actik' one) with a Core battery at -15 or so without any obvious issues. Though that was mostly for tent cooking, night pissing etc, not prolonged night navigation - or glacier skiing.

As an aside from this, nitecore sell an 18650 which is supposed to be good down to -40C. I've not tried it because it's very expensive relative to normal 18650s. They also sell a battery pack which was s supposed to go down to the same sort of temperature, and I believe that that works by having a heating circuit on board.

-15 degC is not extreme by standard, in a mountaineering forum (but it would certainly tick to box in a Brazilian surfing forum).

to really talk about extreme in any mountaineering context, it should be in -30 to -40 range (some would still comment that any temp higher than -40 would not be extreme, though).

and yeah modern electronics and proper extreme temps don’t match too well. Most will How ever work just fine up to -20 or so. But remember that windchill has a nasty way of making things colder than the airtemp. Skiing downhill at -20 at any reasonable speed will soon have and effective temp well into the extreme range. So fast moving snd cold air often means batteries stored inside your clothing.

This is common sense - it should be taught at school!  It's been standard practice in very cold conditions since people first started carrying portable electonics into the Arctic and Antarctic - the equipment has been designed for 60 or 70 years to take a cable so you can keep the battery close to the body.

Not so comfortable if it was a large combined HT/LT/Grid Bias battery or a 24v 4AH nicad!

I’ve spent quite a few days in the arctic winter doing unsupported, multi-day fat bike riding, so lights are essential gear when it’s only daylight for 6-8 hours with temperatures at -20C and below .  Essentially, LiPo rechargeable batteries lose about half their normal capacity at low temperatures, so run your batteries inside your clothing where you can. The most effective batteries in these conditions are are Energizer Lithium (non-rechargeable) where they last 3-4x what you’d get out of a LiPo rechargeable. 

Excellent that was my understanding too. 

Likewise, on a number of Antarctic trips (so obv not using headtorches, but other things) we came to the conclusion just taking enough of these batteries was best. We had a solar charging set up for some things, but not everything, and it couldn't be taken on a route. Sony rechargeable AA batteries just never lasted.

But I'm assuming the OP and anyone else is keeping the device warm, the batteries warm, then taking it out and using it in the cold, preferably, in the case of a headtorch, still keeping the batteries warm in a separate pack within their clothes. Most items, with any battery, if it's all allowed to just sit there and get to -40C will lose power very quickly, as in a few seconds sometimes.

I tried keeping the batteries and torches warm (in deep chest pockets all day) but as soon as they're in use with a bit of airflow they cool down very quickly so in practice it made little difference. 

Goodness me, don't people improvise any more?

Use whichever head torch you like most and suits you best.

*  If it's not cold use standard rechargeable, the Panasonic Enloop pro are a bit more pricey but good quality and should be good for more charging cycles than standard rechargeable 

*  If it's a bit cold, like freezing or a bit below, the petzl core batteries are noticeably better than standard rechargeable.

*  If you need to go somewhere genuinely cold. Improvise, make yourself a wooden "battery" from a bit of dowel and drill a hole through (longitudinally) and another in the middle from outside (laterally) halfway - to join with the longitudinal hole. Solder some metal end caps to wire and thread it so the wire comes out of the middle.

Attached is a pic of a shockingly bad example that's a hasty bodge, with a bit of time you should be able to make a much better job than my pic, also it's AA size and you probably want AAA for most head torches and you want a much longer wire than this picture. Genuine Petzl part, honest! 🤣

Make one or more additional wooden"batteries" that just connect the two end caps together (if you need to fill up other battery positions in series)

Now you can run your torch from an external battery holder that you keep inside your jacket. This will cost you some wire, a couple of blobs of solder, small bit of wood (or two/three). Problem solved.