If your vehicle dies, once stated up and running, and after you remove teh battery cables, then the alternator is bad.
All a battery does is start teh car. once started, the alternator actually provides all the vehicles electrical power AND re-charges the battery.
Now, once the alternator dies, the vehicles battery will provide power, since the alternator is no longer doing so. HOWEVER< the battery has a finite amount of power and will draw down to zero, rather quickly, and once that happens, your vehicle will die too.
jumping a car with another car or battery.
the thickness of the cables use to jump from one battery to another are most important. THich Copper cables are expensive well over a $100 for just 3ft of cable. that is why most thick cables are aluminum, not copper. Copper provides more electricity flow and preferable to Aluminum. COpper is also much heavier that aluminum.
Rather than spend on high quality copper wires, its much better to spend money on replacing a tired, old, worn battery.
If you do buy cables, spend a $200 and get a set that will last you a lifetime.
BE WARNED< they will disappear.
Firends, Kids, Brothers, everyone will borrow them and someone will forget to return them
ask me how I know!
I just buy bulk copper and fit my own ends on them.
Helpful I grew up surrounded by Electricians and can get it wholesale.
SO, re start your truck. pull the cables of the battery and see if it dies. if so, replace the alternator.
if not, the truck rund without being connected to teh battery, replace the battery.
get batteries from O'Reillys, they have DECCA batteries, which are highly rated.
right now, Sams CLub Duracell brand is also a Decca made battery.