ive always used spektrum 4.8v 1100 mahr nicd 4 cell rx pack batteries i saw a good deal on ebay for jr sport 1500mah 4.8v nickel metal hydride batteries so i got 2 of them but after i got them they seem a little smaller will they do the same as my spektrum batteries or is there a difference?

If they are rated at 1500 Mah then yes, you will have a larger capacity. Sometimes the physical size of the cell can vary slightly. Go off of the ratings for the pack.

Ken

The stock Spektrum pack is made up of four A cells. You probably bought a pack made up of four AA cells. A cells typically have a much higher current drain capacity than AA cells. I've used AA cell packs in my planes that have standard servos, but I get four or five A cell packs for my planes with high torque servos, and for any planes with a Spektrum receiver in them, so I don't have to worry about a brown-out reboot of the receiver.

i highly reccomend going with 5 cell packs(6v) I wont fly with a 4.8 pack anymore. Goodluck though ...... I use this pack in all my 40-120 size birds http://www3.towerhobbies.com/cgi-bin...&I=LXNHS4&P=ML

Not too long ago during a preflight check my 5cell pack read 6.7 or so volts , then after the flight it read about 5.6 (cant remember exactly) ....turns out i lost a cell, i didnt bother to examine each cell to verify, but everyone at the field agreed and said i was fortunate i use 6 volt packs

Joco,
The big thing is that the packs you are used to are Nicd's, and you bought a Nimh pack which has a power density of about 2-3 times a typical Nicd pack, so although you bought one with higher current capacity, it is also smaller.
Have fun with it and if you are used to cycling your Nicd's every month, only do it every three with the Nimh.
Curtis