What's the lowest your battery can get and still start the truck?

I was looking at gauges and thinking about one for the battery. When I'm out I'll listen to sports and stuff without the truck running. So if I add a gauge, what would I need to be looking for. I thought I saw one that let's you set a warning light, which would be cool. But where do I set it? I kinda use an internal timer theory now. Like "Oh shit, when is the last time we ran the truck? Please start...please start... please start..."

 

There are too many variables to give a universal answer.
Temperature, barometric pressure, overall condition of the battery, type and age of fuel, condition of the spark plugs....the list goes on and on.

I guess I don't understand why one would want to abuse a battery like this on purpose.

 

Plugs and cheap gas. I never thought about any of that.

 

Starting batteries are not designed for deep cycling. By doing so, you are prematurely killing it. Please see Section 7.1.8 in the Car and Deep Battery FAQ on www.batteryfaq.org. For a dual battery solution, please see Section 7.1.9.