Black Death

[Gordon JC Pearce]

Tony Duell wrote:

> Another machine that suffeers -- baddly -- from battery corrosion is the 
> Whitechapel MG1. There are 5 AA NiCds on the power distribution PCB, if 
> they leak, they will corrode the connector between that PCB and the 
> mainboard, if not the mainboard itself.

Has anyone ever come across the copper in the negative lead from a nicad 
pack turning black and crumbly?  It seems to happen from the battery 
outwards, and progresses up the inside of the insulation.  I've seen 
this happen with radios, camera battery packs, "sun gun" battery packs 
(portable movie lights) and RC models.

On a similar note, there are two nicad batteries in the instrument 
cluster of certain older BMWs (3- and 5-series spring to mind).  After 
10-15 years, the batteries start to fail, and don't hold a charge.  This 
makes the service light start to come on all the time, although if you 
reset it with the plug under the bonnet it goes out until the next time 
you turn the ignition off.  If it's not caught in time it will drop 
corrosive (and conductive) gunk all over the circuit board with the 
warning lights, giving rise to all manner of weird warning light 
indications.  BMW will relieve you of nearly 300 quid for a new 
instrument cluster, or you can replace the nicads for next to nothing.

Gordon.