Your transmitter shows voltage over 9.6V, right? And your receivers show voltage over 4.8V, right?

Is this the 50% difference?

That is normal. Your TX has an 8 cell pack that is twice as many cells as in the RXs. If you hook up the JR set, the TX and RX, and charge them overnight with the JR charger, they should show over 9.6 for the TX and over 4.8 for the RX. The charger that comes with a radio set would fill up the capacity of both batteries at about the same rate.

What amount of charge does your quick charger say it's putting into the packs when you use it?