Save even more money by not buying one at all, properly used the wall wart charger that came with your radio will do the job just fine.

Modern Nicads as generally used to power radios in sport/trainer airplanes will last for well over 500 charge/discharge cycles (104 saturdays a year, or, at least 5 years in normal sportflyer use).

On a plane like your trainer charge overnight before you fly and you should get 90-120 minutes before your batteries are tired.

A cycler just burns another charge/discharge cycle unnecessarily.