Why do climbers not use electrically heated suits to climb peaks like Mt. Everest? Or am I just mistaken and they already do it?
Edit: It turns out battery-powered heating in clothing actually is used on Mt. Everest: Hotronic makes battery-powered heated insoles that are used by Everest climbers, for example. Battery powered jackets and other types of clothing are also common, but the models I checked only provide warmth for a few hours (e.g. this jacket, which runs 3-10 hours on a single 6000mAh power bank that's about 200 grams). Mt. Everest can take days or weeks to climb, depending on how acclimatized you are, so that's a lot of batteries to have to carry, even if you're not running every article of powered clothing nonstop.
Besides, better technology is already available. For example, Aerogel jackets are a thing - in fact, they've been tested on Everest, and they're so effective that the climbers actually overheated in early designs.
In 2010, apparel maker Champion put aerogel inside a jacket lining and sent mountaineer Jamie Clarke up Everest; he overheated
Aerogels are among the lightest artificial materials and most efficient artificial insulators, and they're also surprisingly strong structurally. A jacket made of that material is therefore going to be lighter and more reliable than a complex battery-powered electrical system.
Aerogel is 90 percent air and 10 percent silica. The silica is extremely porous, but because the holes are 1/10,000th the diameter of a human hair, they block nearly all airflow, making it supremely effective as an insulator. It’s also shockingly light: the hockey-puck-size samples shown here—enough to outfit a pair of mountaineering boots—weigh just nine-tenths of an ounce each
Aerogel is an extreme example, but even with more common insulators (e.g. down, wool, synthetic) the point remains the same: the human body produces a lot of heat on its own, so you only need a decent type and amount of insulation to retain enough of that heat to keep the body within a healthy temperature range in any environment. Since insulation requires no energy and little maintenance, functions at very low temperatures, is generally lightweight, and is resilient to damage and wear, there's been no need to replace it - climbers have relied on it successfully throughout history.
- Firstly there's the weight issue - as Paparazzi commented, batteries are heavy!
- Then there's temperature - battery performance drops considerably in the cold
- And finally reliability - if your electrical circuit goes, you will freeze unless you have properly insulated clothing...
so why bother having the batteries at all?