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Maintaining a nicad pack

Many modelers believe that they should 'deep discharge' their nicad packs so that a nicad 'memory' doesn't develop. But most nicads today are fairly resistant to the 'memory' effect. Furthermore, one is more likely to severely damage the pack through cell-reversal by doing this. That is, if the pack isn't completely balanced, one cell will be 'lower' in charge than the others and will reverse polarity by the time the others reach zero charge. Reversal of polarity is very damaging to the cell and will dramatically reduce it's reliability and capacity. Remember: one bad cell can ruin your whole day.

For most purposes, one should discharge the pack gently to 1.1 volts/cell and then charge at an overnight rate to balance the pack. However, I have found that a periodic individual cell deep discharge is beneficial to really balancing a pack and diagnosing the cells' condition. To do this, discharge to 1.1 volts/cell as before and then wire up a tiny motor or flashlight light bulb to each cell individually. Discharge each cell completely. You may find some dispersion in the charge state of some of the cells. This discrepancy will probably be ``fixed'' by the deep discharge (but if it isn't, you should probably toss out the bad cell). When you are done, resume charging as before. I usually individually deep-discharge my flight pack cells once every 4-8 weeks and my radio packs every 4-6 months. This is a simple but very cheap way to ``cycle'' a pack reliably.



Craig Kulesa
Fri Dec 4 18:46:39 MST 1998