2nd Gen Non-Engine/Transmission electrical issue

[JDinterman]

Hey guys the past week my truck has been cranking real slow but always starts( starter is new). The check gauges light comes on and the voltage is always way low. then after about thirty seconds of run time the voltage pops up to 14. where could i be loosing power I've checked all connections I replaced both batteries about a month ago. Any help would be aprreciated.