Burnt a QS8 connector today and am confused.

[kratonwatch]

I had a total of 3 successful runs with my K8S until my esc wire decided to burn itself while connected to a pack. I had no power forward or reverse and when I went full throttle I got the magic smoke and now have the smell in my nose forever. The first two times I ran the truck i noticed the connector getting more burnt each time and figured that was normal for the QS8 set up, but I’m sure I was wrong. Does anyone know why it kept getting more burnt on one side, the positive side/lead (8s, so 2 4s packs were used) and not the other? This is from one 4s SMC 10600 120c pack, so I know there was enough power for the max 5 combo im running. Or was running. It’s 800kv on 37/39 gearing with punch at 4 if that helps.

Not sure what my options are. If I cut the now fried QS8 connector and solder a new one on, my overall length will be quite short to connect my packs. I’m also now worried about a fire with either the SMC packs or the connection itself. Might bite the bullet take this one to a hobby shop I know and trust for help.

TIA

 

[Dales396lt4]

What does the bullet look like?

 

[kratonwatch]

What does the bullet look like?

Tough to get a good shot.

 

[kaladeth]

Burnt connectors is never normal .

You will want to replace that connector by desoldering / having someone desolder for you, esp if cable length is an issue.

Was that connector easy to pull off more than the others? I ask because the build up is likely due to sparks from improper contact esp that single face on the bullet. Did you make adjustments to make it smaller?

If stock, you may want to claim for warranty.

 

[kratonwatch]

Burnt connectors is never normal .

You will want to replace that connector by desoldering / having someone desolder for you, esp if cable length is an issue.

Was that connector easy to pull off more than the others? I ask because the build up is likely due to sparks from improper contact esp that single face on the bullet. Did you make adjustments to make it smaller?

If stock, you may want to claim for warranty.

It was so tight at one point I could barely get the connection off. I made it a bit smaller to be able to make a connection, but maybe I went too small? I didn’t realize there is a sweet spot for these connectors re: bullet size

Is the battery still okay to use once I put a new connector on the esc wire? It’s a brand new SMC and it would break my heart to toss it.

 

[kaladeth]

Yup too small will do it. Hard to tell when adjusting esp needs to be equal. Good reminder for me I just installed new ESC and adjusted down - need to check every run or so for the signs.

Battery should be fine see if you can clean the battery connector thoroughly . Worst case replace the connector on the battery too. Those packs are gold .

 

[kratonwatch]

Thanks for all the help everyone. I’ll solder a new connector on and make sure it’s snug.

 

[RCbuzz]

That looks like the anti-spark resistor has died.

The top part of the barrel connector (above the red line) is actually connected through a resistor to avoid the spark and slowly charge the caps, the area that is burnt is the direct connection. Since arcing occurred in that area of the connector the chances of poor connection go way up...

 

[kratonwatch]

That looks like the anti-spark resistor has died.

The top part of the barrel connector (above the red line) is actually connected through a resistor to avoid the spark and slowly charge the caps, the area that is burnt is the direct connection. Since arcing occurred in that area of the connector the chances of poor connection go way up...

View attachment 359713

I’ll be replacing this as well. Thank you so much for the help. Was pretty bummed earlier

 

[RCbuzz]

I’ll be replacing this as well. Thank you so much for the help. Was pretty bummed earlier

I can relate, when you start getting into large scale higher voltage RC's everything gets a little more complex. Those connectors take on more wear and tear the higher the voltage it deals with since the resistor is a fixed value. Also, in order to size everything accordingly I bet the connector would be way too big.. There are others on the forum that had the same issue with the resistors going out.

Some say plugging it in slower will help with the spark but also be more likely to overheat and blow the resistor in the connector, plug it in faster and you may still have some arc.

A link with some more info: https://endless-sphere.com/sphere/t...ti-spark-mechanism-to-fail.96129/post-1408357

 

[Surchaufeur]

I doubt its a burn. Can you clean it and see if it goes away?

 

[Dan B.]

Burnt connectors is never normal .

No, that’s not true at all. Even with resistors in QS8’s there is usually a spark resulting in tiny burn spots like you’re seeing here.

That looks like the anti-spark resistor has died.

The top part of the barrel connector (above the red line) is actually connected through a resistor to avoid the spark and slowly charge the caps, the area that is burnt is the direct connection. Since arcing occurred in that area of the connector the chances of poor connection go way up...

View attachment 359713

I’m not sure that the chances of a poor connection rise at this point, you’re just going to experience a bigger pop when you connect them. Running 8s, this will happen.

 

[RCbuzz]

No, that’s not true at all. Even with resistors in QS8’s there is usually a spark resulting in tiny burn spots like you’re seeing here.

I’m not sure that the chances of a poor connection rise at this point, you’re just going to experience a bigger pop when you connect them. Running 8s, this will happen.

I had a couple connections where the arced surfaces were uneven and had material buildup that prevented the rest of the bullet from making proper contact. Just used a little sand paper on the bullet and knocked the edges back down.

 

[kratonwatch]

I had a couple connections where the arced surfaces were uneven and had material buildup that prevented the rest of the bullet from making proper contact. Just used a little sand paper on the bullet and knocked the edges back down.

I’ve got some plastic at the base of the bullet. As much as I don't want to solder a new qs8 on there I feel like it’s the only way I’ll sleep at night. Feels like a major F up and learning experience today, so soldering is me paying the price for it. The battery I was going to try and clean up, but doubt I’ll be able to clean up much considering the small diameter and the size of my finger. There’s also that rubber gasket thingy in there that I have to get past to remove some of the damage for lack of a better word

 

[RCbuzz]

I’ve got some plastic at the base of the bullet. As much as I don't want to solder a new qs8 on there I feel like it’s the only way I’ll sleep at night. Feels like a major F up and learning experience today, so soldering is me paying the price for it. The battery I was going to try and clean up, but doubt I’ll be able to clean up much considering the small diameter and the size of my finger. There’s also that rubber gasket thingy in there that I have to get past to remove some of the damage for lack of a better word

I wouldn't beat yourself up about it, I don't think it was anything you did? Just happens.

 

[kaladeth]

Thanks Dan - so maybe kratonwatch is ok then? The buildup looked pretty heavy esp on the bullet side.

 

[kratonwatch]

Tried to get some better photos of bullet

There is also a considerable amount of resistance when I try to put the battery on and off. Just more food for thought.

 

[Dan B.]

Thanks Dan - so maybe kratonwatch is ok then? The buildup looked pretty heavy esp on the bullet side.

He got some of it off, it appears.

Tried to get some better photos of bullet

There is also a considerable amount of resistance when I try to put the battery on and off. Just more food for thought.

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I’d hate to be the one giving poor advice, but after seeing those pics of the ESC male connector bullets, I would certainly continue to run it. The female with the anti-spark resistor might be another story. And I’m with you, I do not enjoy soldering batteries at all.

 

[I_Am_Doug]

@kratonwatch - I responded to my thread.... Sorry for the delay. TL;DR - Just swap the connectors out for new ones and make sure everything is snugly plugged in:

https://www.arrmaforum.com/threads/help-one-side-of-my-qs8-connector-looks-burnt-after-fairly-easy-run….69316/#post-1073682