Double batteries for pickup?

I’ve got a great '95 Silverado 3/4 ton pickup that carries a camper out into the wilds of Oregon. It is rigged for two batteries and I recently replaced one of them. How much will I gain by replacing the second battery–is it worth the cost? I do value reliablility due to the places I take the truck.

Have the second battery “load tested.” If it passes, keep it. If it fails, get a new one. The load test is the best test of a battery’s ability to start your vehicle.

What is the battery setup?  Are they both being used in parallel with no switching between them?  Are they separated electrically where one functions for the engine and the other for the camper?

they are rigged in parallel

In parallel operation the batteries need to match each other by age. The older battery may not get a full charge. A couple year old battery has probably already lost 50% of its capacity. A deep discharge below 80% is hard on an auto battery if you run a lot of things in the camper. I have a camp that runs off my vehicle battery. Just plug the house into the car.

But they are rigged in parallel with an isolator, correct? If it is a factory setup, there is assuredly an isolator (think big diode) in the circuit to keep one battery from discharging in to another.

thanks, but did you reallly mean plug the house into the car?