Q-13: I have a rather expensive seven-cell Ni-Cd high-capacity battery pack that seems to have lost a lot of capacity after one year of use. How would you feel if I bought a sampling of these same cells and subjected them to all types of charging and charging techniques? I would be happy to report on my findings.
A-13: Thank you for your offer but consider a few facts. Despite our hobby use of both Ni-Cd and NiMH batteries, we are a small customer in a big market. Our model-aircraft battery needs can be filled in a period of a few hours rather than days or weeks. If you select two-, three-, eight- or ten-battery packs as your test subjects, you aren’t close to a representative sample of a total production run. Because of this, nothing will really be gained by your testing. I’ve had one surplus Ni-Cd battery pack that lasted for 10 years. I’ve also had a new, expensive battery pack drop out of service with only a few months of use. These things happen regardless of the charging techniques employed. It doesn’t matter if you C/10 before going to flying field, if you never C/10 and just fast charge at the field, or you store your batteries discharged or charged. None of these charging techniques will shorten the service life.
It is possible that a particular brand of battery cell might produce longer life than another. If you experienced a relatively short life with one brand of cells, try another. Keep records of battery capacity from the start. Often I have claimed that a battery dropped out too fast, then I checked my records and realized it was in service for more than two years.
I would not spend my time sample-testing new batteries. You won’t be able to predict service life with any degree of certainty.