Anyone any suggestions for getting longer life out of NiCd drill batteries. Mine always seem to expire after a couple of years or is this normal life? I only use the drill every couple of weeks for perhaps 10 minutes work and only recharge when its completely flat. When I've opened up a battery pack, I usually find one or 2 of the 10 cells is really low on voltage, the others being on about 1.2volts.
Geoff.
Sounds like typical cheap Ni-Cads. And probably a nasty charger. But don't run the batteries totally flat - the 'memory' thing is a con. Recharge after there is a drop off in performance. Quality Ni-Cads with a sensible charger should have a life of about 5 years with this sort of use.
If a cell reads zero volts, it has probably dendrited - whiskers of metal form and short the cell. These can often be recovered by passing a very brief, heavy current (10-30 amps for a C-size cell for a second or 2 max) through it.
Which will cause some cells to reverse charge and damage them.
They will be the cells you have damaged.
They need to be recharged at the first hint of falling voltage. They also need to be charged correctly, rather than just left on an endless trickle charge. An automatic cut-off charger is the best way.
Mike Harrison explained :
The safest way is to charge up a high value capacitor (from a car battery or similar), then discharge it across the cell to blow them away. If you feel braver (and perhaps more foolhardy), splashing the contacts across a car battery also works if you are quick. Make sure it is positive to positive.
Geoff Norfolk brought next idea :
Some suggest that the memory effect is a myth, however....
Reverse charging is what happens when you have several cells in series and you discharge them to the point that the weakest ones voltage first falls to zero, then starts to become charged with the wrong polarity as the stronger cells continue to discharge through that cell.
The charging process pushes the current through one way, during the discharge the current flow is the opposite way. You can never get perfectly balanced and equal capacity cells, therefore the one with least capacity will become reversed charged if the discharge process were to continue after the weak one had fully discharged itself.
So for best life, you should always put the battery pack on charge at the first hint of the drill slowing down.
What on earth are you referring to? As you posted upside down and failed to trim, your response make little sense.
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