Soldered connectors lasted 2 years but now some melt.

[Bill Brandt]

Ok heres one for ya.

8S, 850kv motor. Motor does not overheat. Esc is fine and not very warm. I’ve got 4 season championships with my setup. Each 4S is 50C 5000mah. Batts about a year old. 6.5 bullets on 10Awg wire. Some bullet connectors are starting to unsolder during race. Wires getting hot but batts ok. Resistance problem? I’m baffled.

 

[PropNut]

Batteries are suspect. Check battery IR.

 

[Paul Traufler]

Are the connections tight?

 

[BretMartin]

If the connectors are getting hot I would replace them. Also cut off a short piece of wire (if possible) and start fresh. The "gold" surface can ware off, an almost invisible corrosion can build up, and as Paul says, slightly loose.

 

[Bill Brandt]

I will be replacing all. The 10awg does seem to fill the connection

 

[Hydro Junkie]

Heating in an electrical connection is always caused by resistance. If the connection was good for two years but has recently started to heat enough to melt the solder, something that usually requires well over 200 degrees(some low temp solders will melt that low, most require over 300), that says the resistance has gone up and in a very significant amount from what was there when initially soldered. Resistance will increase due to:
1) worn conductive plating(Thank You Bret)
2) loose fittings(Thank You Paul)
3) an already failing solder joint
Every time you run the boat, connect or disconnect an SEC, motor or battery pack, you flex the wires or cause wear on the connectors. Over time, as the fittings loosen/wear or the solder starts to separate from the wires and/or connectors, the resistance increases and, even though the current and voltage remain the same, generates more heat. Regardless of the cause, as the resistance starts to increase, the solder starts to melt, causing more resistance and more heat, ending in the failure mentioned in the first post.
I doubt a battery pack issue will cause a solder joint failure as it doesn't cause the resistance to increase. Increasing the voltage or current could cause an increase in heating but only if there is already a resistance issue

 

[Don Ferrette]

Ok let's get down to the nitty gritty here............

Unless the connectors are visibly worn and/or physically loose they most likely are not the issue. The more likely culprit with connectors suddenly de-soldering (and I speak from experience) is amp draw has increased for whatever reason as the solder is usually the first to fail with high heat. FE motors regardless of size will require a certain amount of watts to get the job done and the formula is simple and etched in stone- volts x amps = watts. I always choose higher voltage to reduce amp load as higher amp draw creates more heat, known fact. The NAMBA 1/8th scale guys are limited to 8S (we go to 10S in IMPBA) so they will generally pull more amps to do the same work. With Bill's boat being at champion winning levels odds are his set up is tweaked for max performance so margins for error will be tighter. I have seen connectors de-solder from increased amp loads so the first thing to look for is what might have changed. A slightly tweaked/dinged (or changed) prop can increase the load quickly and draw higher amps. A strut that has been "bumped" and moved can increase amp draw with little difference to how the boat runs (been there) so I would start with tabling the boat to be sure NOTHING has changed in the set up (strut, turn fin, sponson AOA), then check the prop, cable drag (broken shaft windings will create crazy drag under load). Has the motor ever seen any excessive load (like picking up debris in the prop) that could have "hurt" it? And lastly an under performing battery pack will definitely increase the amp draw issue and create excessive heat (been there too) so do not rule out a premature failing lipo pack. Hope this helps you Bill.

 

[longballlumber]

Good information from Don... I would also add that FE motors don't last forever. Just because they run doesn't mean they aren't tired. Bearings degrade after while and the magnets de-magnetize.

 

[Bill Brandt]

All great answers. I won’t say I’ve not worked with some different props. Maybe on the edge there. Batteries probably are getting somewhat tired. I just soldered up a couple sets for s friend and he ran flawlessly last outing. My connectors are getting dark and a little grungy so i feel they’re suspect. I’ll keep pecking away.

 

[Don Ferrette]

All great answers. I won’t say I’ve not worked with some different props. Maybe on the edge there. Batteries probably are getting somewhat tired. I just soldered up a couple sets for s friend and he ran flawlessly last outing. My connectors are getting dark and a little grungy so i feel they’re suspect. I’ll keep pecking away.

Bill your original post says 4 seasons on the set up, how many heats and equivalent practice would you equate that to?

 

[Bill Brandt]

No practice. Just heats and finals. Replaced motor once. 4 sets batteries over the period. 5 x race x12 x4. About 250

 

[LohringMiller]

A hint I got suggested wrapping the wires with desoldering braid for a snug fit in the connectors. That way the wire may stay connected even if the solder softens. Also, there's a difference in the connected resistance of the various connectors. See the tests by Joerg below. Heating is proportional to the resistance squared. It doesn't take a lot of increased resistance to cause more heating. Try replacing the connectors with high quality ones like the Castle 6.5 mm connectors.

Lohring Miller

 

[Bill Brandt]

That is what I’m using for connectors. 10 AWG wire fills cavity. The connectors have worked for two years. I think replacement with new 6.5 connectors will solve.

 

[Don Ferrette]

A hint I got suggested wrapping the wires with desoldering braid for a snug fit in the connectors. That way the wire may stay connected even if the solder softens. Also, there's a difference in the connected resistance of the various connectors. See the tests by Joerg below. Heating is proportional to the resistance squared. It doesn't take a lot of increased resistance to cause more heating. Try replacing the connectors with high quality ones like the Castle 6.5 mm connectors.

Lohring Miller

Can't get file to open

 

[LohringMiller]

It's a standard .pdf file that opens with Adobe reader. Just be sure you unclick the McAfee offers.

Lohring Miller

 

[MarkF]

That is an old chart. The latest chart suggest these are the best connectors on the market right now.
http://www.lehner-shop.com/en/accessories/high-current-connection-400-a.html

 

[MikeWettengal]

https://caig.com/deoxit-gold-g-series/