OK, quick question. I charged my RX battery on Wednesday night for 12 hours. I want to go flying saturday, will they still be ok? Or do they need another night cause of the delay?

Just a few hours wouldn't hurt. With a stock walwart charger another overnight charge won't hurt it either.
NiCads, as I understand, can lose as much as 2% charge per day just sitting.

Put them on the wall wart again overnight.

Ditto

Ken

Yep - yep

15 to 17 hrs the night before a flight day is normal. if you didn't fly I'd do 15 more the night before..
get an expanded scale volt meter it puts a load on the battery much like the receiver and servos would. this will give you a pretty good idea of the status of the charge

It depends how old they are. I have 2- 6 cell NiCd's That (I swear) loose about 30% In one night. But they are 8 years old. I have another pair 1 year old and I can't notice a difference in charge even If I overnighted them a year ago.

Hope that helps!
Electorlight

while batteries dont get better with age . there is no garrantee new ones will hold charges for very long either. you can get weak or bad cells in new packs.3 days is too long to take a chance.ESV is the only way to check & be sure . make sure you attach it for at least 30 sec to stabilize for surface charges.I hope you cycle your packs once every so often . otherwise you have no way to know if they are wearing out or not .

Do the math.

A wall wart charger output with (say.. for example) 50 ma output, and a 1000 mah battery.. divide the 50 into the 1000 and you will get.. 20 hours. Add 20% overhead (heat and other overhead) and that is the amount of time to fully charge the battery from completely drained.

The wall wart battery charger is also a trickle charger and will top off the battery in a few hours (as said above by several others). If you have any doubt or questions, put it on the charger, overnight if necessary. You won't hurt it.

CGr.