Not familiar with your jeep, but in general battery voltage with engine running should be 13.5-14.5V. With engine off, a fully charged battery should show around 12.9V (half an hour after engine shutdown)
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.