Hello Team and pardon my ignorance, but what's the idea/purpose for having a Dual-battery setup..??

I'm a first time truck owner so please bear with me.

Thanks

 

Cranking power sums it all up.

 

Welcome , What is it that you want to do , may get you what your looking for ,
the basics are a dual battery system is having a battery isolator that the charge wire from alt. goes to then each battery goes to one of two connectors on the isolator , so that the alt. can see the need for charging either batt. seperatly, so that you can use 1 batt. for starting truck and then 2nd batt. for running radio , and if you run the radio long enough to run that battery down , then you still have 1 to start truck with .
this is not including the 2nd gens. and up that come from the factory with 2 batts. , thats becouse it takes a lot to start these trucks , the 1st gens , came with 1 batt.
So if you want a dual batt. system the 2nd batt. for running other stuff should be a deep cycle [ intended to be discharge deeply ].
This is why if you said what you wanted , it could have been a shorter story.

 

Well, considering you have a diesel truck we can assume your asking why your truck has two batteries and not a gasser? If so, JD has the answer and you can ignore John's post. (No offense John)

Dual batteries in a diesel are needed because a diesel engine requires more oomph to turn over than a similar sized gasoline engine to get started. This in turn requires a stronger starter, and more cranking amps to power that starter. There's also the need to power the heating grid (or glow plugs in some other makes) before starting.

 

Ya another reason is diesel fuel dosen't ignite nearly as easy as gas, therefor it takes more pressure to fire diesel fuel.

 

and on a cold day, your starter will peak draw about 1000 amps until it settles down to ~400 amps once the engine gets turning... now that is after the grids have been on for 10-30 seconds sitting there drawing close to 100 amps.. yeah, the more batteries the better

 

Yeah- I don't know exactly but a diesel has roughly twice the compression of a gasser, thus the need for a larger amperage draw on the starter. Whenever battery goes out , best to get two new batteries at once. Mine died once at the grocery store, and I had to get a friend to get a Peterbilt Semi with GOOD jumper cables to each battery before I could get enough juice to turn 'er over !