Yea flux core.
It’s a small point iron. It’s a tiny wire. It’s not beautiful but solid.
A lot of those joints look cold and ready to snap off 
Definitely not safe enough for the vibration full environment PEVs live in. A different soldering iron tip should work wonders
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Nah bro just better technique, you can do balance wires with about 2 seconds of heat on a small iron, using proper technique
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IDK, with a decent iron I think you’d have to work to get results that bad. @hummieee are you using a small 15 W non-temperature adjustable unit or something? A better iron will make all your soldering easier if you are. Either larger or more powerful and temp controlled or both. They aren’t expensive either. My current iron is https://www.amazon.com/gp/product/B09GJ2NJVX which also requires tips and a DC wall wart if you don’t have one, but can make solder joints to nickel much better than those in a couple of seconds each easily.
I forget what iron I have bit a simple single temp n single small pointy bit. May not be pretty but they’re solid. Wire this thin I find springs off the nickel and doesn’t lay. Strong enough to last till potted for sure and then has no stress on it
We should all have a balance wire soldering showdown
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insert poast nonsense here
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Oh that is a very bad sign, sounds like more a fire starter than a tool for high power electronics.
Jokes aside, there really is a strong line between efficient DIYing to cut costs, and saving a penny to lose a pound. Soldering a $10 arduino project that runs for two weeks powered by a 9V cell is very very different to a multi-kW battery pack for an EV. The tools are expensive, if you’re building a single pack and don’t already have gear it’s not cost effective to DIY it the majority of the time. I know you’ve made packs before (and provided excellent decks and motors for the rest of us to use), but using a dollar store death trap is not going to yield good, safe results. Especially if you’re not going to invest the serious time and luck into technique needed to wrangle an iron like that.
You have said yourself you don’t like to use soldering because it pushes too much heat into the pack or doesn’t give good results; this is why.
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Yeah, I wouldn’t use that for esk8 if you paid me.
You don’t need a three-digit Hakko, but that Weller is incredibly outdated and underspecced for the demands of high-power electronics.
You can get a Chinese soldering station that takes Hakko T12 tips for as little as $50 or so, that will absolutely run circles around that old thing.
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This is true, I was recently stranded with only a Weller 60 watt station available. It was extremely painful to use and I was wishing I had my old Xtronic 3020 which I also thought was junk. But so much better than the Weller. Today I’d recommend a TS100 or Pinecil.
That right there is 100% of your problem.
Use a chisel or truncated conical tip, not a pencil type. I guarantee you will have better results.
Even when doing small SMD shit or breadboarding, I basically never use the conical pencil tip. It’s always a small chisel, or a truncated conical. It just works so much better.
I have a Pinecil, and it is fantastic for a portable iron.
I still prefer my desktop soldering station for bigger stuff (12AWG and up, large thermal mass) simply because it can deliver more power.
I fin that even with a full 60 watts on tap with the pinecil, it doesn’t actually ever draw that much, even if I dip the iron in water to give the greatest possible thermal load.
I suspect that the TS100-style tips have a suboptimal thermocouple placement or other weird thermal design that is limiting the performance of the iron compared to something like the Hakko T12 system, or the Aoyue WQ system which is very similar (and what my desktop station uses).
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I use a Weller 80watt for larger stuff 10awg/12awg/ braid. Works well, loads of thermal mass. Dirt cheap. Between a Pinecil and that you have the two tools you need to solder a battery for very little cost.
Still I’d like to have a desktop station when I obtain the space.
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If and when my current Aoyue 2930 desktop station dies, I’m probably going to replace it with one of those cheap clone soldering stations that takes Hakko T12 tips. Absolute best bang for the buck.
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It depends on what you are soldering onto as well, big pieces of metal sink away the heat.
I first put a bit of solder on the nickel, then on the wire, and then mash them together.
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I have the one from HobbyKing, and its a crazy good for 15$
I have gone through 4x heaters already but the power supply still works, and the whole basically soldering iron (the part you hold in your hand) costs like 3$ to replace from aliexpress. Its crazy how cheap yet good it works for me 
I made the mistake of building a pack with i AWG series connections with a TS100, I await the well deserved oofs. It did work in the end, but it was a miserable experience and I can’t remember if I presoldered the nickel before welding or just subjected the cells to that. It’s been retired since then
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Did you install custom firmware on the TS100? Enables up to 450C vs 400C
For the life of me I can’t get this batch of P26A’s to weld, the positive side is totally fine but the negatives are refusing to hold even at 50J
Kweld with 6Ah lipo, 0.15mm nickel
Was supposed to be a quick and dirty 12s2p while I procrastinate the 15s5p but now it’s deciding to be a bitch 
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try 60J
if no bueno
70J
You get the picture.
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