Checking batteries with a battery checker is less than worthless- it fools the unknowing into believing it is a helpful test.
Our first Spektrum radios (first ones on the market) all worked perfectly and so do the present ones .
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I find that using my battery load checker provides me with significant information. I do NOT fly with LiPOs for the radio system. I use Nicads, Nimah, and Li. ION. Have not lost a machine with battery problems since about 16 years ago. Nicads are rated as 1.2 volts therefore the normal pack is 4.8. However it will charge to 5.7-5.8. Now that we can get 2500 and more MAH packs, one can fly much longer and/or with more servos than 25 years ago when 600 mah was a big pack.
As far as your comment concerning the early first-on-the- market Spectrum 2.4 radios, I dare say that a number of folks using them at the year's Joe Nall Event just might well disagree with you about that item.