LVD

Good afternoon everyone
I have this issue that keep happening
Driving down the road and then the truck would act like there is no more charge in the battery so it will disconnect the supply to the cigarette lighter and all the lights inside and fridge however still have the 14v on the gauge so I replaced the LVD with a new one and unfortunately the new one did the same thing except the new one freaking beebs so it’s driving me crazy please if anyone has an idea I need some help it’s a Freightliner Coronado thx.