The length of the power reserve on a watch can be seen at first as just another number. Yet, it has to be regarded as something a bit more important than that. While on automatic watches, the length of the power reserve might not be so important at first (as when the watch is worn, it should be fully wound most of the time), it only makes sense if you wear this watch on a daily basis. What if you have more than one watch? The need to wind regularly them will be required. And this is even truer when it comes to hand-wound timepieces because you know… hand-wound means going back to this futile (yet pleasant) morning ritual! For this reason, having a watch with over 72 hours of power reserve is a considerable benefit, for a simple reason. Imagine you have a dress watch for the week. You unstrap it on Friday evening, wear a dive watch for the weekend, and then strap it back on Monday morning. 72 hours are thus enough to ensure that your watch is still running, and to avoid readjusting the time (and the calendar indications if there are some).
Then, of course, brands have decided to do more than only 2 or 3 days of power reserve. For instance, IWC now has 7-day power reserve watches and with Panerai you can even get an 8-day power reserve. This really starts to be quite some power stored in a movement. However, the question is: is it important? No, not more than an 800bhp supercar. At a certain point, we don’t talk about utility anymore, but about achievement, about pushing the limits of what is possible… And that’s what A. Lange & Söhne did with the massively powerful Lange 31.
When it first debuted in 2007, the A. Lange & Söhne Lange 31 replica watches were the wristwatch with the longest power reserve available on the market, and the first watch to have 31 days / 744 hours of energy stored in a single movement. Although some others later achieved a massive 50 days / 1,200 hours power reserve (Hublot with their MP-05 LaFerrari) this was only because the movement was stacked with 11 mainspring barrels. In the case of the Lange 31, everything comes directly from a single barrel, although with two mainsprings – and what mainsprings we are talking about… However, such power also implies various issues. Once you’ve stored such energy, the watch must be able to use it and to deliver it to the escapement, in a linear way. This is where the situation becomes properly complex.
First: storage… How to store 744 hours (or 31 days) of energy in a single barrel, without having a movement sized for a desk clock? Miniaturization has always been one of the main fields of research in watchmaking, and even if the A. Lange & Söhne Lange 31 is a rather massive watch, it remains wearable on the wrist. All this energy is stored by two mainsprings that each measure no less than 185 centimetres uncoiled (approximately the length of an average Joe). In a standard automatic watch, with an approximate 40h power reserve, the single mainspring of the movement is around 25cm-30cm long… Here, the A. Lange & Söhne Lange 31 has a total of 370cm of spring fake watches UK. Yet, the length is not the only issue, as the strength of these springs (mainly guided by their thickness) is much superior to standard mainsprings, all of which allow the Lange 31 to deliver its energy for 31 days.