Battery charging issue

[EvergreenZ71]

@Evergreen71

The way my trucks behave is that if the primary is dead, using the key does not start the truck, but it can be remote started using the fob. That assumes there's enough juice left in the battery to energize the isolator. If the primary is completely dead, jumper cables are needed.

The only 175-amp fuse on my trucks is the primary megafuse. If that blew, it would sever the only electrical connection between both batteries and the truck, immobilizeing it.

The only thing I can think of is that your truck has a second 175-amp megafuse for the secondary battery. On mine it's 125-amp. If that blows, it simply isolates the secondary, and you'd never notice unless something went wrong with the primary

Interesting about the key fob start, but other than that what you described is what I was assuming except that the secondary battery was receiving a charge leading me to believe it was the primary fuse … except that the truck still started. I’ve also never heard of anyone blowing that fuse (though obviously it’s there for a reason) so I’m worried I’m not getting the real story.

 

[B-train]

So, I'm new to this type of dual battery setup. I've installed a second battery in my 2008, but have it parallel to the original. It seems as though the system you have is overly complex, but with a couple neat caveats. Good thread so far

 

[intheburbs]

So, I'm new to this type of dual battery setup. I've installed a second battery in my 2008, but have it parallel to the original. It seems as though the system you have is overly complex, but with a couple neat caveats. Good thread so far

If you simply have them in parallel, then the only benefit is capacity. The factory system has an isolator that electrically disconnects the secondary battery to ensure you always have power to start the vehicle. It's tied to the ignition, so it's completely automatic. Absolute worst case is you have to jump-start yourself, which is particularly entertaining if you do it in a public area.

 

[EvergreenZ71]

Absolute worst case is you have to jump-start yourself, which is particularly entertaining if you do it in a public area.

Outside the bridal dress shop picking up my daughter’s dress, basically in front of a BestBuy.

Next DIY is setting up a jumper cable gauge jumper line with a quick connect (to normally be left disconnected). I think I only need a positive cable because the grounds are both always grounded already.

 

[Tozan]

You next DIY should work fine as long as you have solid grounds located in the same places. You could use a knife blade battery connection when you want to jump it off.

My dual system is set up for camping. The primary battery is for normal automotive operations.

The secondary battery for powering up camping & interior lights, refrigerator, winch and other camping related needs.
The secondary battery is in isolation mode unless there is more than 13.5 volts going to the isolator via the power cable. My power cable is the same size as a jumper cable and is connected to the primary battery. If I need to jump it I can use that cable.