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Comment by Zak | Hacker News Reader

What I'd really like somebody to do is just stick a field-replaceable 18650 or 21700 battery in the handle. If you want to get fancy, add a dial for temperature control.

Webserial and such makes for a cool tech demo, but I just want portable soldering with standard field-replaceable batteries.

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I like the idea but you can't ensure the battery supports the load and it's a matter of time before someone puts the shittiest of 18650s inside it and it explodes

Something I've seen in flashlights is voltage sag detection: if voltage drops faster than expected, power is reduced. A temperature sensor built into the handle would also help; the risk of thermal runaway starting while the battery is below 80C is very low, and for user comfort, thermal limits should be set lower than that.

Is the discharge rate for an 18650 be enough for a decent soldering iron?

I normally power mine off either a power bank with PD, or a LiPo battery that I also use for drones.

Yes. The Sony VTC6, for example is rated to deliver up to 30A with temperature monitoring to ensure it doesn't exceed 80C. At 3.0V (partially discharged and with voltage sag from the load), that's 90W.

I don't actually need 90W in the application I have in mind. I'd be more than happy with 60, and there are quite a few 18650 cells that can do 20A comfortably. Runtime at full power would be short of course, but I don't find I'm continuously heating work for very long in the field.

Here's a test of the VTC6. It does look like it's struggling a bit at 30A, but it's happy at 20. https://lygte-info.dk/review/batteries2012/Sony%20US18650VTC...

> Max. discharge current vs. time: 30A-40A > 44s

I figure that might be workable for a few power cycles and a few big solder joints, but it would probably be a frustrating experience for anything more than quick fixes in the field.

If you're using full power for longer than 40 seconds, you're almost certainly doing something wrong (or, need to switch to a chunkier soldering iron). At a certain point, the limiting factor becomes how quickly you can transfer heat from the iron into the solder, and you won't pull 100W anymore.

I have a JBC iron capable of 130W. It never pulls 130W, even on extremely chunky power planes, besides when initially heating up (on startup). When trying to heat some super thick, I can watch the power meter max out at ~70W (and it pulses 70W, not continously). And this is on a thick tip, far chunkier than what I see from iFixit.

Yeah, I didn't mean to suggest that someone would do that whole 40s all in one go... maybe a handful of seconds of full-power here and there... but heat accumulates and people probably want to put the iron down well before the battery in the handle hits its thermal limits. It just seems to me like it would be a good candidate to get hot quickly and suffer in both performance and comfort due to it. I'm sure it would probably be perfectly fine for light field use.

I’d think for the vast majority of uses it’d be just fine. The duty cycle of a soldering iron is extremely low. Most of the time it’s sitting there topping up the heat on the iron, barely sipping power. If you’re truly cranking heat into some ground plane, a wireless iron is unlikely to be the correct tool for the job. Also, you could set the threshold for backing off the iron to be lower than “too hot to hold” if that’s a concern.

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