Are Cobwebs conductive?

[ClockmanFrance]

After 24 hours of rest and resetting AC Coupling, I switched the 300amp breaker on for my OzInverter and my battery cupboards lit up inside. Just for a brief milli second, remined me of a quick/fast fuse blowing.

On further checking, I thought that I had blown my cables, I was puzzled to see all the cobwebs had gone on the Negative side of my batteries.

My charging sources were still all connected and the battery bank working normally, but some how that huge inrush to the OzInverter had sizzled the cobwebs that were connected to earth/ground outside, and yes everything is properly earthed TT copper stakes.

Very strange.....

[frwainscott]

What are you feeding your spiders??? Think it could be acting like a relay will without a diode?

[MadScientist267]

Just thinking out loud...

Cobwebs themselves (silk), non-conductive.

Condensation/Dew etc on cobwebs, might get a mix going that's conductive enough at a high enough voltage...

But what it really sounds like to me was maybe you got lucky, had a flaky connection, and it possibly set off a small amount of hydrogen... which... is rather exothermic... and cobwebs respond to that kind of heat by melting away and collecting into bundles...

Just some thoughts that came to mind... if it was the latter (hopefully it wasn't), I'd be checking and cleaning all my battery connections if it were me... Got one myself that I'm going to have to replace soon before it causes me more trouble (or worse)

Odd indeed, but there's a reason for everything... Carry on then

Steve

[bj]

Good thinking Steve---this one caught my eye as well, so yesterday tried some in the shop,
(no shortage, lousy housekeeper), and couldn't find evidence of conductivity.
Didn't think about the hydrogen end of it,  but it sure makes sense.
Clockman--what do you think?  Possible?

[ClockmanFrance]

Thank you for your kind replies.

FRW, This time of year, mid-winter, there's not much for the spiders to eat.
The relay thing sounds possible especially as its blowing to ground.

I have 12 strings of 4off 12v batteries, giving me 48v at 1300ah. They are all gel types. I am used to connecting stuff in and out with cobwebs about, but it seems that the OzInverter, on a re-start, does something bizarre on the negative side to ground.

Cobwebs do collect a little dust, but so strange to se them light up like that.

Thanks MS, that's what I thought initially, so I checked and checked, but couldn't find anything obvious, and as I said the system is and was running normally.
Hydrogen, possible as the nearest battery to the cobwebs, even though Gel, could still gass.

Just odd to watch a continuse light from one end to the other, and not just a blow in the middle.

bj,  Try a OzInverter on a battery bank, oztules reckons at start up "there is serious splat material".

My cobwebs do collect dust, can hydrogen form/or stay on cobwebs, how much dust ?

[solarnewbee]

Hydrogen gas is lighter than air but if they were still charging up and obtaining close to full charge gas production can be pretty high I'm just not sure where a spark came from. Moisture, dust, humidity and St. Elmo?

[oztules]

interesting, we have 60000uf@50v to charge, I think .5*(e^2 x C) or about 75 joules
If we look at that as a joule is a watt second, thats 75w for 1 second... imagine that as a one hundredth of a second.... suddenly we are generating 7500 watts... at one thousandth it is getting out of hand at 75000 watts or 75 kilowatts.... in the hundredths scenario we are in the 7500/50 or 150 amps..... I know from tests it is very very much higher than this.. around the 400 amps and more. ( talking the 15kw boards)

We can see that this takes the end off your screw fittings easily.. so start up current is massive if you don't introduce some resistance into the start up procedure.... I use a 50R resistor to charge the caps then just connect the battery wire without any fireworks....without it,  it throws the 180 amp o/load... takes 2 goes to charge the caps. For instant shut down, it must be in the 400 amp range.. maybe more for that to happen.

So terminal and H2 perhaps... but usually the H2 is more spectacular than this, unless the web was fine and thick enough to hold some H2.

The fact that the web was vaporized is enough to stir up the imagination though.


.................oztules

[rossw]

so start up current is massive if you don't introduce some resistance into the start up procedure....

My SP-481 inverter has three "monitoring" leads, quite light (basically just hookup wire), one to battery bank negative, one to positive, and one to the midpoint. (Yes, it monitors midpoint to detect bank imbalance).

You cannot turn the inverter on until it has done a "pre-charge". Takes 5-10 seconds to slowly charge up the main caps via the "monitoring" cables. Only when it's charged, do the lights come on and you are even able to press the "On" button. No bangs or sparks with this beauty

(It also uses these to monitor the battery terminal volts, and to calculate power loss in the battery cables during operation)

[ClockmanFrance]

Thanks 'oztules', your comments duly added to the OzInverter Book.

I am at about 14,000 words 52 pages, 67 colour photos and drawings, done the material lists, toroid, and just finished the Boards. Now on Chapter 6, The enclosure and Cooling design.

I have added your observation, comments, discussions as appropriate as the story unfolds....

About another 26 pages to go, and allowed 10 pages for the 'Oz Really Technical Chapter'

rossw, Yes, I might fit a momentary switch and 50r resistor on a thinish wire for a start up switch on my No2 the 'BigOzInverter' and another on the No3.

Note to self, must hoover the 2 ton battery cupboards at least once a year......

[MadScientist267]

Note to self, must hoover the 2 ton battery cupboards at least once a year......

Woah there, boss... Hopefully that's metaphoric and not literal...

I have yet to see a vacuum cleaner that doesn't have an amp-chewing, high-flying, carbon-to-copper bonafide spark throwing machine built right into it's very core, that the sucked up air doesn't pass right thru for taking away the copious heat the thing generates during operation.

Some might argue that the chances are slim to none, and the air rushing in to replace that which is snatched up by the hose might place the resulting mix below LEL for hydrogen... but isn't one mystery enough for now?

(Short version: Hydrogen. Spark. Boom.)

Jus' sayin'... if it twer me......

[rossw]

I have yet to see a vacuum cleaner that doesn't have an amp-chewing, high-flying, carbon-to-copper bonafide spark throwing machine built right into it's very core, that the sucked up air doesn't pass right thru for taking away the copious heat the thing generates during operation.

Some might argue that the chances are slim to none, and the air rushing in to replace that which is snatched up by the hose might place the resulting mix below LEL for hydrogen... but isn't one mystery enough for now?

(Short version: Hydrogen. Spark. Boom.)

Our vacuum uses an ECM. No brushes, no arcs 'n sparks, no ignition source.
The alternative, for those who DO want to vacuum "safely", would be to use compressed air and a venturi.

[dang]

compressed air and a venturi & hearing protection.

[MadScientist267]

Good news on the ECM... wondered if the good ol' series wound would ever see retirement. I'd still have concerns that not every machine would have an ECM within, even if they've come into the vacuum market.

Personally, a half reasonable foxtail brush works fair enough on cobwebs... but I don't see any real issue with the venturi method either. Just as long as ol' sparky isn't a part of the fun.

[ClockmanFrance]

Thanks MS, your comments duly noted.