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XT60 "pops" when plugged in -- is that normal?

joshuabardwell

Senior Member
Mentor
#1
I'm building my first quad. When I plug in the battery, the XT60 connector pops/arcs. None of my planes do this. I can't figure out whether this is because the planes have only one ESC and so don't pull as much current when they're first plugged in, or whether something is wrong.

I had written it off originally, but yesterday I was soldering a connector onto an ESC and I think I overheated the ESC, because when I plugged it in, it smoked and died. When I first plugged it in, the connector arced and I quickly un-plugged it and inspected everything. Everything looked okay so I figured it was the same as when my quad did it (although this plane had never done it before). When I plugged it back in, whoosh, fizz, dead ESC. So now I'm a little worried that something is wrong with one of the ESC's on my quad--although I didn't solder any connectors on them, so I doubt I damaged them.
 

joshuabardwell

Senior Member
Mentor
#2
BTW, I put an amp meter on the quad and it doesn't show that it's pulling any current (well, less than 0.1 amp) when the battery is plugged in, so I don't think there is any short or anything like that.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
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#3
Mine typically "pops" as well, but I've always figured that's from the extra overhead of three more ESCs and a control board booting up.

As for your now-dead ESC . . . are you sure you soldered it in right? They REALLY don't like reverse voltage.
 

Craftydan

Hostage Taker of Quads
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Moderator
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#4
BTW, if you've got a large capacitor on each ESC (or a large capacitence on a 4-in-1), the pop is mostly the inrush current from charging these Caps.
 

joshuabardwell

Senior Member
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#5
As for your now-dead ESC . . . are you sure you soldered it in right? They REALLY don't like reverse voltage.
**** me, you're right.

Here's the ironic thing. I re-soldered the connector because I added a voltage sensor for telemetry to the ESC's main lead. When the ESC fried, I said, "Well, let's make lemonade out of lemons," and I desoldered the leads from the board so that at least I wouldn't have to re-solder the connector when I got the new ESC.

In other words, if you hadn't pointed this out, the next thing I would have done would be to solder the same harness onto the new ESC... and fry it.

Thank god I didn't do this on my brand new quad. I would have fried four ESC's instead of one.
 
Last edited:

RoyBro

Senior Member
Mentor
#10
I did the same thing once and fried my 9x transmitter. On the plus side, I was so despondent that my wife let me replace it with a Taranis.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
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#12
Thanks for the edit Josh.

Dropping an F-bomb has become too common these days, but emotional expression is fine.

Now for how we do it here . . . thanks for helping keep it family friendly ;)
 

Balu

Moderator
Staff member
Admin
Moderator
#14
I did the same thing once and fried my 9x transmitter. On the plus side, I was so despondent that my wife let me replace it with a Taranis.
You do realized that now everyone owning a 9x is going to fry his transmitter to have a reason to replace it with a Taranis?
 

DDSFlyer

Senior Member
#16
When I first started soldering my own connectors I have definitely done this before...on,y one I didn't catch before powering up was when I resoldered a connector for my multicolored LEDs and fried the controller...in front of many people no less...
 
#17
Im paranoid about doing the same with my battery connections too.
the last bit of soldering I did, I triple checked, and checked once more before I plugged it in the first time.
Like they say, its not if but when..
 

willsonman

Builder Extraordinare
Mentor
#20
The pop is normal. For my large electric models this is more prevalent but usually only after the model has sat for a few days and the energy in the capacitors has dissipated. I'll fly them multiple times at the field but usually only one big pop on the first connection. There are anti-spark connectors but are a little overkill for your application.

The spark can cause problems with some setups. A good example is a model with electric retracts. The in-rush of current to charge the caps will also cause a voltage dip to the BEC. This causes the retracts to fault on initialization and the retracts will not work or seem "dead". A common problem when people first started using E-tracts. They figured they were DOA but in reality, the initialization faulted out. This is why I always cycle my E-tracts as part of my pre-flight. Using an anti-spark connection fixes this issue entirely. Of course, a separate BEC on a separate battery would also solve the problem. There are pros and cons.

Another observation is that more expensive ESCs utilize low equivalent series resistance (ESR) capacitors. because of the lower resistance of the caps the inrush of current is less inhibited causing a greater spark. The upshot is that they work more efficiently for the ESC and generally have less lag to your pulses for the motor. I'm not an electrical engineer but I've played with these caps in the past and they do make a difference. Putting on low ESR caps does make a noticeable difference in performance, but not by very much.