On Sun, Feb 22, 2009 at 10:00:02PM +0000, Wayne Stallwood wrote:
On Sun, 2009-02-22 at 11:04 +0000, Chris G wrote:
The 'memory effect' in NiCd batteries (I don't think it occurs in NiMh batteries at all) is very specialised and very specific. The chances of it occurring in normal usage are vanishingly small.
You sound knowledgeable on this subject but I have to disagree with the above. HiMH do suffer from memory effect, it is less of a problem but it is still present. Also most NiCd cells in "normal" use will show the memory effect very quickly if the cells are repeatedly not fully discharged or only partially charged.
I was experiencing this in the early 90's when I was a bench technician at an electronics company and one of my first jobs was replacing less than year old (therefore in warranty) batteries in the first generation cordless phones. Their typical usage was possibly the worst application case for a NiCd because either the handset was picked up from the cradle and used briefly before being placed back down or it is left to discharge and then removed from the cradle before the charge is complete.
Well go and search on Google, the *first* hit I got for a "NiCd memory effect" was this one:-
http://www.repairfaq.org/ELE/F_NiCd_Memory.html
... and the next hit says exactly the same, as do lots of others. They're from reputable places too.
All the wonderful "our charger discharges your battery first" extras are completely pointless. The real guaranteed way to make your NiCd batteries useless is to leave them charging indefinitely which is what a *lot* of older/cruder chargers do, especially the ones that come with cordless tools.
Of course good cordless tools now use Li-pol batteries..For NiCd and NiMH a trickle charge at 10/C or preferably 15/C will probably be better for the batteries than a fast charge from an intelligent charger. and certainly at the latter rate you could safely leave it there for some time but as you say not indefinitely.
Long term on a trickle charger at the 'normal' rates will certainly kill the batteries in the long term.