Volt Meter Idea

[sonicj]

Originally Posted by JohnnieB

Old-School knob w/pointer.

i believe chicken head is the proper terminology

Originally Posted by yurtle

Cutting boards from WALMART are usually quite good, even at HV HF.

tj maxx, ross, tuesday morning, etc are also good sources. you can sometimes find the good acetal ones for cheap.
-sj

[simple man]

Originally Posted by yurtle

My rule of thumb for conductive plastics is to microwave them. That's good for HF AC, but overkill for chopped-DC. My experience is that black is usually bad and white is usually good.

Cutting boards from WALMART are usually quite good, even at HV HF.

Please enlighten me on this, as I always understood plastics to be insulators!

[yurtle]

Originally Posted by simple man

Please enlighten me on this, as I always understood plastics to be insulators!

Many plastics contain additives such as carbon, that are somewhat conductive. If you place an item in a microwave and it gets hot, it isn't a good choice for high frequency high voltage. Most folks think buggies are DC, but they're really chopped DC.

BTW, Mr. Brown delivered my lugs so I'll be soldering, then silver plating soon.

[yurtle]

Originally Posted by JohnnieB

FWIW: I had to replace a transformer in an X-Ray machine because the ring terminal for a monitoring circuit was stacked between the main cable and the transformer terminal, vaporized and the plasma cut nearly through the stud when a megawatt (200KV @ 5A) passed through it. Needless to say, the repairman that didn't read the manual got some remedial education from my size 16 boot.

I assume the lugs weren't bare copper, unless they were in a climate controlled environment. That's why I'm silver plating mine. Copper is really a bad choice for high current in a hostile environment like a buggy.

AllTrax tins their copper terminals. Trojan uses lead and SS. Stock and upgraded FNRs have a copper stud - as is required - but use plated steel nuts, and all solenoids use plated steel studs and nuts.

[JohnnieB]

Originally Posted by yurtle

I assume the lugs weren't bare copper, unless they were in a climate controlled environment...........

I think it was tinned copper and it was exposed to room air, so it was more or less climate controlled. I believe the major contributing factor was that it was a relatively small diameter ring terminal with a relatively large hole while the terminal lug on the main cable looked like a fender washer had a matching surface on the transformer. The contact area of the nut was far smaller than the contact area of where the lug was supposed to be touching, so the current density through the small ring terminal skyrocketed. Basically it was a design flaw, but the stacking order was clearly spelled out in the service manual, so they were off the hook.

Another thing that is overlooked, the pulsed DC isn't just between the controller and motor, it is throughout the the motor drive circuit, so we are pulse discharging the batteries. I would be interesting to put a scope on it, but I don't have a portable scope, so about the best I can do is measure average amps and duty cycle and do some number crunching.

[sonicj]

Originally Posted by yurtle

I assume the lugs weren't bare copper, unless they were in a climate controlled environment. That's why I'm silver plating mine. Copper is really a bad choice for high current in a hostile environment like a buggy.

AllTrax tins their copper terminals. Trojan uses lead and SS. Stock and upgraded FNRs have a copper stud - as is required - but use plated steel nuts, and all solenoids use plated steel studs and nuts.

im not so sure Silver is the best choice for plating... reason being that in a galvanic cell, copper will corrode to protect it's more noble silver plating. the presence of electrolyte & humidity in the battery bay create a environment ripe for the galvanic process. residual flux could also act as electrolyte. just something to think about...
-sj

[yurtle]

Originally Posted by sonicj

im not so sure Silver is the best choice for plating... reason being that in a galvanic cell, copper will corrode to protect it's more noble silver plating. the presence of electrolyte & humidity in the battery bay create a environment ripe for the galvanic process. residual flux could also act as electrolyte. just something to think about...
-sj

http://www.cool-amp.com/

I work in an industrial setting, and we use silver plated copper for most very high amperage connections and buswork, low and medium voltage, 480 V to 25 kV, in hostile environments.

Go to any industrial supplier like Grainger or ?? and you'll find plenty of silver plated bus bars, many of which will be installed in non-climate controlled environments.

I'm simply following industry standards by plating my lugs. I'm not going to tin them, so no residual flux involved.

Oxidized copper is a horrible conductor. On the other hand, silver oxide is a great conductor. Gold would be better, but...

[sonicj]

thats a interesting plating technique.

all of the lugs i have ever used have been electroplated from the manufacturer. i always assumed they were tin, but could be silver i suppose...

anywho, the phenomena i was referring to is called "red plaque" if you want to read up on it.
-sj

[yurtle]

Originally Posted by sonicj

thats a interesting plating technique.

all of the lugs i have ever used have been electroplated from the manufacturer. i always assumed they were tin, but could be silver i suppose...

anywho, the phenomena i was referring to is called "red plaque" if you want to read up on it.
-sj

I'll look it up. I do know that the stock cables I removed appeared to be plated, though not with silver. The previous owner replaced several bad cables and used copper lugs. They were all green and deeply corroded when I bought the buggy, even though they were newer, but the old stock ones are still shiny.

What we use at work are high amperage plated lugs bolted with plated bolts to copper plated bus bars. Often, this switchgear is located in condensing environments - which don't always have internal space heaters installed or wired up - and with medium voltage, corona often occurs. Corona can create nitric acid and ozone, both of which are quite hostile.

Here's one for you to look up, "corona".

I'm not saying any of this occurs in a buggy, but if silver plating can hold up to the hostile environment at work, I would hope it would be fine in a buggy.
If not, I'll simply tin them.

It all comes down to proper maintenance. Bare copper should never turn green, though brown is normal. If it does, someone hasn't done their job of properly cleaning and protecting them. Technically, we shouldn't need to heat-shrink a soldered connection, but it's a good idea. I was planning on coating mine with liquid electrical tape, to seal them, then heat-shrink for cosmetic purposes. Then I found a heat-shrink tubing that has a built in gooey substance that completely seals them from the inside - something lots of other heat-shrink tubing fails to do.

All of the above is just my philosophy of the day, and subject to change, based on new ideas, corrections by other posters, or me finding new and wondrous stuff in a box I've long forgotten about - like my Weidmullers, to get back on topic.

[yurtle]

Originally Posted by sonicj

thats a interesting plating technique.

all of the lugs i have ever used have been electroplated from the manufacturer. i always assumed they were tin, but could be silver i suppose...

anywho, the phenomena i was referring to is called "red plaque" if you want to read up on it.
-sj

Interesting. "This article does not cite any references or sources", but I'll follow up. It's surprising that all metal-clad switchgear at work uses silver plated bus bars, if this is a problem. Perhaps it all goes back to maintenance and inspection, along with thermal infrared scans.