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[crock]

Hi,


 I've got a couple of oldish batteries, one definately NimH the other possibily a nicad, but they both 'surge' when being discharged ie in use.  I get the normal full blast as it were and then they drop off quite dramatically then after a few minutes go back to what I assume is 'normal or almost normal power discharge levels.


  I've only got an old Robbe 50/100/500Ma charger so charging is a bit variable.  The 2 batteries are a 1.8 ah and a 2.3ah.  As an after-thought, how long can or should I charge at 50 milli-amps ?   Have I over-cooked them by asking too much power from them ?  Graupner 700BB 12V in a 36" Perkassa.


I suspect a decent peak charger is the only sensible option ??


help and thanks

[malcolmfrary]

If charging was 100% efficient, the 2300mAH would take 48 hours.  Since it isn't, 60 hours is more feasible.  In practical terms, the battery could be floated on a 50mA charger indefinitely without harm to either.
Normally, batteries charge at the 10 hour rate (1/10th AH figure) for 12-ish hours, or overnight.
If the battery shows a high "just charged" voltage, then settles for its proper discharge time at about its nominal voltage, thats OK.  It just means that whatever is plugged into it has to be able to withstand the initial voltage, but be able to fully function on the nominal voltage.  If they drop to nominal -1.2 volts quickly, it means that there is a dead cell in there, and they have become ballast.