Ordered Dual Alternators, And I Have Dual Batteries Too?

[GreyGoose]

So, I was checking out my truck today, crawling under it, looking at stuff and open the hood and I have dual alternators, which I ordered fine, but I have dual batteries, and there are multipul wires coming off both the positive ends of the battery. what does each battery do? When the battery dies, which one do I replace? Are the batteries special or can I just put in a yellow top optima or is something better for these trucks. I changed out the battery 3 times on my 2002. This looks like more of an issue.

[Shatterz]

One battery is just for starting the truck and the other battery is used when electrical accessories are runningwhen the truck is off (so you don't drain the starting battery if you run things too long). There might be a little more to this setup but I believe this is basically how it works. This way you will always be able to start the truck if you run down the aux. battery. There is nothing special, each one is just a standard automotive battery (I forget what group size these ones are). I wouldn't run out and get a new battery to quick, these newer style top posts don't seem to be plagued with the many issues as the crappy acdelco side posts batteries (I know I have replaced plenty myself of side posts types found in older gm trucks).

[markw8]

It's very possible that the system has changed to what was said above. However, my 2000 silverado with dual batteries, the aux battery was only live with the key in the run position. It did nothing for starting or to power a camper. Ask me how I know.

 

Mark

[Rat4go]

Because your new truck is a diesel based on your other post, I'm 99.9% sure that on diesels, both batteries are used for starting (and glowplugs) and are NOT isolated for camper/accessory use like others have suggested. Diesels have monster current draw when starting them cold due to glow plug draw and high compression ratio and I'm also 99.95 sure that all diesels come with 2 batteries for this reason.

 

When you replace them, just make sure you replace them with NON-Vented batteries. I learned this the hard way on my '03. I repalced my OEM delco units after 6 years with aftermarket units. After a few months with the aftermarket units, I found that they didn't like heat(especially the one on the right side) and since they were vented units, they vented acid all over. Made a huge mess in my truck. OEM's never did this. I replaced the vented aftermarket batteries with Deka AGM batteries and haven't had the issue since, but it was an expensive, painful lesson.

[markw8]

The diesels are wired different. If you need to disconnect a battery to do work, you need to disconnect both.

 

Mark

[Diesail]

Yep, if it is a diesel the are wired together in parallel and both work together all the time.

[GreyGoose]

Yep, if it is a diesel the are wired together in parallel and both work together all the time.

 

Thanks guys for the input. Love the truck, just so much to learn, I mean I had no idea it came with two batteries. I took it on a 100 mile trip and it was perfect. think it got just over 19mpg, amazing to me for such a huge truck.

[jandersinc]

Wow. If you're spending that much on a truck and you don't even know what you're getting... Hey I have a bridge for sale...