Low battery alarm for your camping vehicle?

[Spencer]

Those of you that have a car or truck that you use to power your camping amenities like a camp fridge for example. Is there a way to rig up an alarm that will sound when the battery gets to a certain level so you don't accidently kill your battery beyond what will start your car or truck?

 

[smritte]

I'm sure one exists. If I had one, I wouldn't have killed my batteries or at least known they were low. Most of the fridges will shut down on low battery so not to prevent the car from starting. Now you have dead batteries and ruined food.
BTW...solar is a great way to prevent this. Too bad when it happened to me, I was parked in the shade.