You are right on this, this is just how the peek detecting chargers work. I have been peek charging my batterys with a voltage meter for years. I don't do it all the time, just when I want to see how a battery is doing or I want cycle a Nicd

When the battery peeks out and drops about .2 volts (it can very just a little without being peeked) back down from the highest reading its peeked , I call it charged and take it off charger.

I would not fly a rx 4.8 volt battery down below 4.8 volts for a nicd , in fact I try very hard not to go below 5.25 volts .I want to stay above 5.5 volts for the 5 cell 6 volt NiMh batterys, I think the NiMh drop off a little higher than the Nicd.

remember we have to cycle our Nicd batterys once in awhile. I like to take mine down to about 1 volt a cell. A four cell would be 4 volts. If they are not cycled the drop off voltage goes up on the Nicd's.

good luck,

sticks

forgot one thing, the higher the amperage that a battery is charged the higher the peek voltage. But the static voltage level under load after chargeing it will be about the same as the lower charging rate.