Soldering irons are great when mains power is nearby. For those times when you need to crawl under a car dash, the Hakko battery-powered version suits the need better.
Access to power for soldering irons has been a chief concern when we've been out on remote jobs. In the future, this little unit will come with us, and no more worries about AC power.
Designed for use with 4 AA cells, you'll easily get up to soldering temperatures. The data graph included shows easily an hour of useful soldering time on a fresh set of batteries, with temperatures between 400 and 600 degrees C (750 to 1100 degrees F), which is well capable of melting electronics solder.
It's a decent, inexpensive insurance policy to have in your toolkit.