Carwyn Edwards

a yes from me, a maybe from Vic (as she’s working late that Thursday)

Hi Andrew

Wouldn’t class myself as an expert in electronics and batteries, but I would be wary of anyone selling a AA-sized rechargeable battery with a capacity rated >2850 mAH… as far as I’m aware that’s pretty much the maximum capacity you can currently get in an AA-sized NiCd or NiMH rechargeable battery due to limitations with the chemistry and the size.

You can get lithium-based disposable batteries (not the same as rechargeable lithium ion batteries) which have a rated capacity of 3500mAH for AAs, but these are expensive compared to normal disposable alkaline batteries, but they apparently keep their charge in the cold and they don’t self-discharge in the same way as other batteries so maybe good for a spare torch in the bottom of a pack?

Some manufacturers recommend against using certain types of batteries in their lights too, I have a Petzl Actik CORE, which Petzl say can use alkaline, lithium or Ni-MH batteries (or a petzl-specific rechargeable battery pack), whereas Alpkit apparently recommend against using Lithium disposables in their torches (according to this thread on UKC anyway: https://www.ukclimbing.com/forums/gear/rechargeable_batteries_and_headtorches-486163)

There are a lot of sellers on eBay/Amazon and other online marketplaces that will advertise impossibly high mAh ratings for all sorts of rechargeable batteries, so i’d probably stick to a name brand (e.g duracell) to try and ensure you’re getting the actual named capacity. Panasonic make some batteries under the ‘Enerloop’ brand name which get a lot of good reviews, apparently they work better in the cold than other equivalent rechargables and don’t lose their charge as quickly in storage (apparently), they are pretty extortionate tho (£18 for 4 AA on amazon at the moment).

Modern LED torches will likely all have some internal electronics to maximise efficiency and make the light level consistent throughout the battery life of the light (as well as providing different light levels, flashing modes etc). Battery voltage tends to drop as they get used up and LEDs tend to like having a consistent voltage to work correctly.

In your example of a torch powered by 1 AA battery, there’ll be some electronics there to ‘boost’ the voltage up from the battery-supplied ~1.5V (which in practice for a alkaline battery, could be from ~1.6V to ~1.0V, depending how much juice is left) to what the LED needs, which from memory is around 3.6Vish for a white LED. This boosting process isn’t that efficient, which means some of the battery capacity is going to be ‘wasted’ in the process, which makes a direct comparison hard. I’d reckon the burn time on a single AA head torch is likely to be less than 1/3 of a comparable 3-AA light tho, for the same light output due to those losses.