You’ve surely seen the TS-100 soldering iron. It has an OLED display, an ARM processor, and will run with an external battery pack. They are not too pricey, but at $80 or so they aren’t exactly an impulse buy, either. [Drone Camps RC] used one in the field and decided to try a Hakko FX-901 instead. He did a video review that you can see below.
The FX-901 is about half the price of a TS-100. Granted, it doesn’t have a fancy display and you can’t hack it to play Tetris. However, it does take batteries (including rechargeable) without an external pack. The manufacturer claims up to two hours of use and that it will melt solder in 40 seconds. From the video, the iron actually melted solder in under 30 seconds. The two hours, by the way, is with rechargeables. Alkaline AA batteries should give about 70 minutes of operation.