Slow-mo filming of the magic smoke coming out !

[Crowz]

This was wild

This is what happens when the magic smoke gets out of your inverters !

 

[OffGridForGood]

The importance of PRE-CHARGE explained in 12 minutes!

 

[timselectric]

Pre charge wouldn't help.
To much voltage is too much voltage.
Pre charge is to restrict current flow. (For the BMS)

 

[Hedges]

The importance of connecting your PV panels with correct polarity. Or the inverter having reverse-polarity clamping diodes.
And paying attention to Voc.

But lithium battery with no BMS or fuse, and no pre-charge, could potentially do something like this.
Shorting a capacitor to discharge can also.

 

[sunsurfer]

The importance of PRE-CHARGE explained in 12 minutes!

Thats what my mind images when I forget to charge up the caps.

 

[timselectric]

The importance of connecting your PV panels with correct polarity. Or the inverter having reverse-polarity clamping diodes.
And paying attention to Voc.

Absolutely

Shorting a capacitor to discharge can also.

Agree

But lithium battery with no BMS or fuse, and no pre-charge, could potentially do something like this.

I don't see how, if the voltage doesn't exceed the capacitors rating.

 

[Nobodybusiness]

This was wild

This is what happens when the magic smoke gets out of your inverters !

We used to put caps like that on guys work benches in the sockets.
They would come in the morning and flip on their bench and POP!

Harmless fun.

 

[Hedges]

Agree

I don't see how, if the voltage doesn't exceed the capacitors rating.

Nor does zero volts.

Shorting a 60V charged capacitor to zero, or shorting a 0V discharged capacitor to 60V (with very low series resistance), what's the difference?

I'm not sure, but I think the discharge scenario causes joule heating of some part of the capacitor, shorting it. Stored energy then dumps into the material. If anything, the charging case could be worse because you have a whole battery bank behind it. Remember the guy who splattered a busbar on his golf cart pack (without blowing fuse, must have been current-limited by bad contact and plasma impedance.)

 

[timselectric]

Actually, now that I think about it. Shorting a fully charged capacitor shouldn't be a problem either. This is standard practice for making them safe to handle.
I think that over voltage is the only thing that can damage them. Other than end of life failure. Or physical damage.

 

[littleharbor2]

How do they pack that much smoke into that little cap?

 

[Hedges]

Actually, now that I think about it. Shorting a fully charged capacitor shouldn't be a problem either. This is standard practice for making them safe to handle.

That is what I thought, and told a colleague he could just short out a charged capacitor to discharge it. He reported the cap blew up.
It seems discharge through a resistor is advisable. Then a short can be left connected, to bleed off any recharge that occurs and electrons migrate out of the dielectric.

Shorting a high voltage electrolytic - damaging?

I have a high voltage (400V) electrolytic capacitor, and I sometimes discharge it by shorting the terminals with a screwdriver. I get a fat spark and a bang. However, apart from minor damage to the

electronics.stackexchange.com

"If excess a rush current due to drastic charge/dis-charge was applied to conductive polymer aluminum solid electrolytic capacitors, and conductive polymer hybrid aluminum electrolytic capacitors, it may cause a short circuit or an increase in leakage current. Therefore, Please do not apply a rush current that is larger than 10A.

So if you're using the conductive polymer type, that's a clear danger. Tantalums also have a well-known propensity to self-immolate if subjected to excessive transient current."


In a similar vein, some resistors are pulse rated, some are not. I forget the exact topology, but we had some tiny SMT resistors that carried current pulse when power was first applied to a circuit, like up to 80A for 10 microseconds. Repeated switching, I was able to catch varying height pulses with scope. The resistors were failing open. Substituted "pulse rated" resistors and those survived.

 

[timselectric]

Good information.

 

[fpgt72]

Roughly 40 years ago I blew up a 30,000 uf cap.

I think my ears are still ringing from that.

 

[teal95]

High voltage caps use (or used to use) wax as the insulating layer. They wax molecules would slowly reorient themselves to the electrical field. After you drained the cap the wax would slowly return, effectively recharging the cap.

 

[KITROBASKIN]

From 7 minute mark to 8 minutes is one of the amazing sequences on that video.

 

[OffGridForGood]

30,000 uf cap.

Just a question: why do we call it a 30,000 micro-farad capacitor
why not a "30 farad" capacitor?

{I guess we do the same thing in machining "30-thou" not "3 one-hundredths"}
Convention?

 

[timselectric]

And the answer is, just because. lol

 

[Hedges]

Because we should call it an 0.030 F capacitor. Or a 30 mF capacitor.

 

[OffGridForGood]

Because we should call it an 0.030 F capacitor. Or a 30 mF capacitor.

So, someone made the "Farad" unit too damn big, like trying to measure fractions of an inch using the mile?

 

[SparkyJJO]

So, someone made the "Farad" unit too damn big, like trying to measure fractions of an inch using the mile?

Blame Mr. Farad.