Hey guys, what types of solder do you use for motor connections and bullet connectors? What ratio do you use and what brand?

Thanks!

I prefer 63/37 solder with rosin core. Usually I get mine from MG Chemicals. Frys carries it if you have one near you. 60/40 is good too, it's just not as consistent as the 63/37

Silver solder is technically cleaner but it requires more heat (not ideal for sensitive electronics) which means you may need to hold the iron on the solder tab longer than usual. So I've stopped using it and went back to lead solder

As far as bullets, I use TQ 5mm and 4mm bullets for my batteries and I really like Castle's 4mm bullets for motor wires if you want the option of disconnecting the motor without desoldering. And the added resistance hasn't hampered my motor's performance.

I'm using Kester 24-6337-0027, I like it much better than TrakPower silver solder.

This will probably start an argument with all the experts but I've tried just about everything there is and the easiest to use and best results for me has always come from just good old Radio Shack 60/40 rosin core. The only other solder I ever liked was in a limited structural (not electrical) application where a special high temp acid core silver solder was almost as strong as brazing but man it was a pain to use in comparison.

I only use MG solder because Frys carries it to be honest lol. I'd use whatever they had so long as it was 63/37 or 60/40

Agreed, I also use Kester 63/37 solder, been using it professionally for over a decade, & liked it so much I started buying it for my personal use, very happy with it. Those who are interested in silver solder should keep in mind that 1., yes, it does take more heat to make a good joint with it, & 2., the point in soldering is joining two materials, & the solder, as long as it joins them properly, will not have any large effect on the electrical resistance of the materials, there's just no point is paying the price & going through the extra trouble to use silver solder. Additionally, some may want to try lead-free solder, but that's also mostly a hassle, as lead-free is not very easy to use(higher chance of bad solder joints), & if you exercise care, you can work with regular lead solder(63/37 or 60/40) with little to no risk....

60/40 or 63/37 are the standard solder alloys for electronics for a number of reasons - mainly, they are reasonably easy to use, and they form a joint with good electrical and mechanical properties. I'd really hesitate to recommend anything else without a very good reason, and especially not for someone who is not an expert.

have you guys encountered wire before where no amount of heat or flux will make solder stick to it? I cut the leads on a older (but still good) lipo a while back and literally nothing would stick to it.

At worst I've had wires that took a few seconds more before the solder would wick into it. Maybe try to break up the threads and then twist it gently to open things up a bit. Are you using lead solder or silver solder? And which iron?

lead solder rosin core (standard stuff). 60w iron on full. basically the same combo i usually use on 10awg wires, but wouldn't work in that particular circumstance on a thin wire for a 250mah lipo. didn't try to break up the threads...maybe do that next time.

There could be some residue on the wire. Sometimes the resin core flux is insufficient, it's good to have extra flux on standby.

My first thought is that maybe the wire has an enamel insulation coating. While I haven't come across that in battery leads, it's common in low-voltage audio cables (such as for headphones and microphones), and of course we see it all the time in motors.

My second thought is that the wire isn't copper.

I'd start by separating the wire into separate strands, and then gently scrape or sand the surface to remove any insulation or oxidization. If it has an insulation coating, you can also use heat to remove it (a solder pot is preferable, but I've used a small butane torch as a field-expedient methods); just be careful not to overheat the battery cell itself!

I was under the impression that the only solder you can get is lead free. Am I wrong? Gotta love RoHS

You can get the good leaded stuff from china.
RoHS has good intentions, but that's all I'll say about them.

No, i can assure you that I used a lot of flux on it (not from the solder).