Battery Voltage drop
 

My 2002 3500 seems to loose voltage quickly. It can be charged to 12.7 or .8 volts. It has new batteries, replaced under warranty. Within 3-5 dyas(parked), it is down to 12.2, whcih, as I understand, Is 75% depleted. Is this normal, or shoud I have the ******* check it out under warranty?
I use it to primairly pull our 5vr, every 2weeks-1 month.

I wouldn't be concerned unless it goes below 12 volts.

I would pull the positive terminal off and then do an amperage check to see if anything is drawing power with supposedly nothing on.
Of course you could remove the positive terminal when you park it for a few days and check the battery voltage again just before you reinstall the terminal. That reading will give you an idea if something is drawing power when it is not supposed to be drawing power.

The IOD (ignition off draw) on these trucks is rather high. Read your owners manual, if I'm not mistaken it will say the truck must be started at least every 21 days.

you should be able to charge it to about 13.2 volts (2.2 volts per cell) 12 volts is approximately 50% discharged.