Black wire corrosion

If the battery can leak/vent then you can get electrolyte on the copper and that is a bad thing. I would think if a LiPo leaked it would be shot/swollen.

Jim

From reading Red's website it has to do with the electrolyte leaking out of a NiCd. NiMH use the same sort of electrolyte (potassium hydroxide) and similar seals, so I would expect it there.

I don't think that LiPos are at all the same, however.

It is dependent on the electrolyte used in the system, both Ni-Cd and Ni-Mh employ KOK (caustic) which is one of the ingredients for black wire corrosion we see, LiPos on the otherhand don't.

KOH you mean. Not that it matters in the grand scheme of things.

So, why do we not see this on the + side?

KOH you mean, not that it matters in this conversation.

But why don't we see this on the +ve side? Is it due to the construction of the cells that leakage happens on the -ve side?

MJD

Here is a dissertation on the subject of black wire corrosion:

The black wire syndrome is an occurrence in battery packs (Ni-Cds) where the negative wire becomes corroded (turns from shinny copper to blue-black). This is the result of either a shorted cell in the pack, the normal wear out failure mode of Ni-Cds, or cell reversal when a pack is left under load for an extended period. The sealing mechanism of a Ni-Cd cell depends to some degree on maintaining a potential across the seal interface. Once this potential goes to zero the cell undergoes what is called creep leakage. With other cells in a pack at some potential above zero the leakage (electrolyte) is "driven" along the negative lead. It can travel for some distance making the wire impossible to solder and at the same time greatly reducing its ability to carry current and even worse, makes the wire somewhat brittle. A switch left on in a plane or transmitter for several months can cause this creepage to go all the way to the switch itself, destroying the battery lead as well as the switch harness. There is no cure. The effected lead, connector, switch harness must be replaced. This leakage creep takes time so periodic inspection of the packs, making sure that there are no shorted cells insures against the problem. The cells should also be inspected for any evidence of white powder (electrolyte mixed with carbon dioxide in the air to form potassium carbonate). In humid conditions this can revert back to mobile electrolyte free to creep along the negative lead. Some "salting" as this white powder is referred to, does not necessarily mean that the cell has leaked. There may have been some slight amount of residual electrolyte left on the cell during the manufacturing process. This can be removed with simple household vinegar and then washed with water after which it is dried by applying a little warmth from your heat gun..

My bad, Sr. fingers. You are right it is KOH, not KOK (whatever that is).

It is electrochemically driven so it is usually seen on the negative side.

Long dissertation follows: The black wire syndrome is an occurrence in battery packs (Ni-Cds) where the negative wire becomes corroded (turns from shinny copper to blue-black). This is the result of either a shorted cell in the pack, the normal wear out failure mode of Ni-Cds, or cell reversal when a pack is left under load for an extended period. The sealing mechanism of a Ni-Cd cell depends to some degree on maintaining a potential across the seal interface. Once this potential goes to zero the cell undergoes what is called creep leakage. With other cells in a pack at some potential above zero the leakage (electrolyte) is "driven" along the negative lead. It can travel for some distance making the wire impossible to solder and at the same time greatly reducing its ability to carry current and even worse, makes the wire somewhat brittle. A switch left on in a plane or transmitter for several months can cause this creepage to go all the way to the switch itself, destroying the battery lead as well as the switch harness. There is no cure. The effected lead, connector, switch harness must be replaced. This leakage creep takes time so periodic inspection of the packs, making sure that there are no shorted cells insures against the problem. The cells should also be inspected for any evidence of white powder (electrolyte mixed with carbon dioxide in the air to form potassium carbonate). In humid conditions this can revert back to mobile electrolyte free to creep along the negative lead. Some "salting" as this white powder is referred to, does not necessarily mean that the cell has leaked. There may have been some slight amount of residual electrolyte left on the cell during the manufacturing process. This can be removed with simple household vinegar and then washed with water after which it is dried by applying a little warmth from your heat gun..

Red S. Red's R/C Battery Clinic

"mjd" wrote in message news:wQvvh.37$ snipped-for-privacy@news.sisna.com...

I knew you knew what you meant.. ;-) I can only assume KOK is some ancient god of male fertility.

Thanks for the write up on the corrosion issue!

MJD

(electrolyte)

Don't mean to shatter your universe here.. but you can get black wire corrosion on any negative wire on a DC circuit that's had the exposed part of the wire exposed to moisture.

Motorcycles get it in their rear light and indicator earth wiring, the wires that are about the furthest away from the battery on the bike.. and it's a lead acid battery on the bike not ni-cads... well some are sealed gell cells,

but i'm just trying to say black wire corrosion is not exclusive amoungst modelers who use ni-cad batteries,

i've had it on vehicle trailer sockets, sensor wires on engines, the wiring from a cheap solar panel,

it's always the negative wire that's affected, and in all cases the wires connections had been exposed to moisture, on motorcycles it's the rear light assembly, and on cars the trailer socket assembly as they are behind the rear wheels and thus get all the road spray,

the solar panel wasnt sealed underneath, so moisture got to it easily.

just curious is this also a ploy by car manufactures to rot cars away quicker by changing to - earth

I would agree 100%. In the 40+ years I have been fooling with electronics, I see it in a number of applications, not just NiCd and NiMH driven. Marine, vehicle, some aircraft, and even techs in the telephone industry have told me about it.

The common (ish) denonimators seen to be batteries (of any chemistry) moisture, time and PVC-covered wire. Although not exclusively.

There is an obscure MIL-STD (or may have been HDBK) that I can no longer find on aerospace wiring that either banned, or severly restricted PVC covered wire. The main reason was that PVC burns giving off toxic gases, but a secondary reason was that under some conditions, chlorine and the plasticiser can leach out of the insulation, combining with moisture to generate corrosive compounds. I think that is the most likely reason. I'd presume electrochemistry explains why we only see it on the negative lead.

Until somebody comes up with a foolproof way of stopping it, the easy detection method is to use transparent insulation on the negative lead.

Barry Lennox

That IS interesting..heat and or light breaking down PVC to give chlorine->Hcl->CuCl.

Under electrochemical action..

I think that may be the correct answer.

Except that copper chloride goes green usually..when wet..when dry it can be brownish apparently..