In 1975 or so, when all of my electric drills had cords, not battery packs, I purchased a battery powered soldering pencil. In a nut shell, it was awful:
Took too long to get hot,
The tip was hard to keep tinned,
My finger did not like staying on the power button,
If I used the switch latch to keep the iron on all the time, it got too hot,
And, battery technology in 1975 was not quite where it is in 32 years later.
I bought one of those double “A” pen soldering gizmos a year or so ago and I ended up giving it away. Tried to use it to solder my feeder wires to the track, just never seemed to get a good enough soldering joint, [banghead] what a pain. The soldering iron is one tool that I have no problem keeping wired.
About 20 years ago we had a battery-powered Wahl iron that worked quite well. You’d think in a machine shop floor there’d be plenty of power - well there was, but most of it was high voltage multiple phase. We used it to make repairs on the CNC and EDM machines, and it worked very well. Even witht he lttle light to illuminate the workspace, like on a big soldering gun, it ran for a reasonable amount of time on a charge. Since the state of the art was NiCad batteries back then, once it was dead it took a long time to recharge, and it did not have a swapable battery pack like my cordless drill does. We had a butane powered iron as a backup, just in case.
When it comes to tools - cheap anything can be worse than no tool at all. For a once in a rare while use, you can probably get away with cheap no-names, but if you want to tool to use on a regular basis AND last more than a month, the higher cost of a known brand is a worthwhile expense.
I just purchased a Weller BP645, 6Watts, 4.5 volts, runs on 3 double a’s. I don’t care for it at all. Having to hold the button in and it seems to take for ever to heat up. I like that its cordless, but other than that its a loser.
My boss got me a cold heat soldering iron for a Chrismas gift. I’ve tried it out on wire joints and it does work. I haven’t tried it to solder wires to rail but feel that it would not be to good at that since you need alot of heat fast to do it right. I’ll use it for the little wire jobs and save the heavy stuff for the heavyer jobs.
That said, the Wahl soldering irons are very good. They hold a charge and are quick to heat up. Usually you don’t need to hold them on for a long time just to solder a lead wire on, or even to solder the rails together in a rail joiner.
Micro Mark sells these and they do last a long time.