There's more to Jeep maintenance than just changing the battery if the rig don't start. You should have checked alternator output when you started the rig (should be around 14 volts). You check the battery leads and clean them, than test your negative lead to ensure you have a good ground. Simple to do,put one lead of the multimeter on the battery and the other where the cable attaches to the engine or frame, no voltage drop is allowed. Any voltage drop here changes the voltage going to the rig to start it or run the engine/lights etc. You can also have a bleed back of voltage to the rig all the time even if the key is off if the alternator has a problem. It usually also shows up while running though, as a decrease in alternator output.