I wouldn't charge the receiver pack any higher than 3 amps.  It very well may false peak the first time or two that you charge it.  Keep charging until you feel the battery begins to get warm, that's how you know it fully charged.  After the first charge or so, it should take a full charge on the first try without any false peaks.  The charger has a mAh screen, so you can gauge how much of a charge the battery is taking by looking at that screen.  The 2500's, you won't be able to charge them through the charge jack because of the reverse polarity protection in the charger and the transmitter.  You will have to charge them in a separate holder, which you should be able to find at Radio Shack.  I wouldn't go any higher than 2.5 amps if you're in a hurry because they are a smaller cell, but otherwise 1 amp on those should be fine.  Again, the warmth in the battery is a good indication if they're fully charged.