This Thing Rules

Soldering is cancelled, now we use ‘solder seal connectors’

We're done with burning our fingers and huffing solder fumes.

If you follow me on Twitter, you know that I’m currently in the middle of creating an 18 kWh powerwall out of reclaimed electric scooter batteries. Weird flex, I know. Right now I live in an apartment, but someday this powerwall will store solar electricity for use in the off-grid home I fantasize about living in. A millennial can dream, can’t he?

Ten of the finest reclaimed scooter batteries money can buy.Evan Rodgers

But the thing about these reclaimed scooter batteries is that they’re cheap for a reason; they’re not at all ready to go. They’re the polar opposite of the Goal Zero 1500X that I’m currently in the process of reviewing. Each battery has a proprietary connector that must be stripped, and in its place a standard connector must be attached. I have to do this to 40 batteries, so this means an extremely non-trivial amount of soldering is in order.


Maybe you’ve never soldered before. That’s fine, because 1) I’m not gatekeeping soldering (lol) and 2) it actually really sucks and I would prefer not to do it. You see, to solder two wires together both sides of the wire need to be supported while you poke at them with the soldering iron. This would require three hands, and that’s why things like the age old “helping hands” gadget were invented.

The classic. If you know, you know.

I could have 3D printed an alternative, but even this really only works for longer wires, and in this context we’re talking about 1.5 inches of wire followed by a brick of a battery. So I needed something better.

Enter the "solder and seal" connector

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I discovered these heat-shrink solder joints while cruising Battery YouTube and I shit you not, these things are a game changer. For my entire life I’ve struggled and burned myself while trying to solder two wires together (especially the big ones). How do these things work? Well, in theory you just slide both ends in and point a heat gun at the connection. The tubing around the outside shrinks while the low-temperature solder in the middle melts and everything just connects without even a puff of solder (technically flux) fumes. Plus, there's adhesive on either side of the low-temperature solder, so the connection is mechanically reinforced. Brilliant.

Here you can see the solder seal connectors first shrinking, then melting, then soldering.

In practice these soldering joints aren’t quite so magical, but they are pretty darn close. I’ve run into problems with the big sizes (10-12 AWG) and the smallest sizes (24-26 AWG). With the big ones, it takes a lot of heat to get the thick wires up to the temperature necessary to melt the solder into the ends of the leads, and this can lead to burning some of the connector's plastic. The same is true of the small wires, but in that case it’s because cheap, high-gauge wire almost always uses low-quality insulation. But with some careful movement you can mitigate both, and if you plan ahead and add a little heat-shrink tubing to your joint, you’ll be golden.

Unfortunately, these solder joints can’t be used for everything. If I were using these batteries for something that required a lot more amperage and, by extension, thicker wires, I would have the de-solder the surprisingly wimpy scooter wires that come pre-soldered to the batteries and use something beefier. Soldering 10 AWG wires takes some skill, and soldering them without frying the board you’re trying to attach them to does even moreso.

In the end, there’s no substitute for a good soldering iron and just straight-up getting better at soldering, but it’s encouraging that the bread-and-butter side of it (just connecting two wires together) has been mitigated by good old human ingenuity. Well, really material scientists who decided to have mercy on us DIY plebes, but hey, let’s spread the praise around while we enjoy our unburnt fingers.