Battery charger burns out - Is it preventable?

[rjenkinsgb]

as pretty all NiCd's used for that purpose failed within a relatively short time,

Interesting!

I wonder if it relates to the power-on vs power-off time?
All the old+good ones I've seen have been in industrial gear which is very rarely unpowered, or regularly off for only a low percentage of the time such as over a weekend, so the battery never has chance to fully discharge.

I have seen plenty of failed ones in equipment that has been taken out of service or on spare boards pulled from equipment.
They are obviously no longer on trickle charge, which is why I included the "permanent" clause.

I suspect the difference could be that with consumer gear such as TVs and computers etc., they are can be left to go flat at times and that causes the degradation?

Edit - Or, designers not bothering to check the spec for the cell type and using "1/10C" for button cells, which are the commonest backup type?
Those cannot tolerate that for long periods, if I remember right; they need a rather lower current with a permanent supply.

 

[Nigel Goodwin]

Interesting!

I wonder if it relates to the power-on vs power-off time?
All the old+good ones I've seen have been in industrial gear which is very rarely unpowered, or regularly off for only a low percentage of the time such as over a weekend, so the battery never has chance to fully discharge.

I have seen plenty of failed ones in equipment that has been taken out of service or on spare boards pulled from equipment.
They are obviously no longer on trickle charge, which is why I included the "permanent" clause.

I suspect the difference could be that with consumer gear such as TVs and computers etc., they are can be left to go flat at times and that causes the degradation?

Edit - Or, designers not bothering to check the spec for the cell type and using "1/10C" for button cells, which are the commonest backup type?
Those cannot tolerate that for long periods, if I remember right; they need a rather lower current with a permanent supply.

VCR's were never unplugged, and the batteries died in those just the same, likewise TV's are VERY frequently used and certainly never left long enough for the batteries to go flat - most were Philips sets. Nice little earner replacing batteries and setting everything back up again

VCR's tended to use button cells, and Philips TV's used sort of 'AA' type sized ones (there were a couple of different sorts).

 

[rjenkinsgb]

Strange, different field and totally different experiences..

In personal oddments, I had a surplus button pack as backup battery in a DIY digital alarm clock for over 20 years, permanently on without problems, and two large surplus button cells in an old geiger counter, which was only rarely charged and rarely used.
They were fitted around 40 years ago and I've just replaced them in the last few weeks (with a couple of AAA NiMH), as they had lost a good part of their capacity and only worked for an hour or so - but again, no leakage.

I can only guess it's to do with either cell quality or charge characteristics, that some have a short life?

 

[Kart31]

I know the preferred charge rate for NiCd is 0.1C. What would be a trickle charge rate?

 

[Nigel Goodwin]

I know the preferred charge rate for NiCd is 0.1C. What would be a trickle charge rate?

0.1C (or lower) is the trickle charge rate - 0.05C would probably be a good choice.

 

[Kart31]

What is the recommended fast charge rate for NiCd? (sorry never gave it much thought until now)

 

[Mickster]

What is the recommended fast charge rate for NiCd? (sorry never gave it much thought until now)

This may help:
**broken link removed**

 

[gary350]

Every component has smoke built in, once you let the smoke out, it's dead.

 

[Kart31]

Every component has smoke built in, once you let the smoke out, it's dead.

I am well aware that electronics work by way of magic smoke and hamsters.

 

[schmitt trigger]

Indeed!
Smoke doped silicon.

I believe that place silicon wafers in barbecue pits, then wrap them in aluminum foil, before encapsulation.