As far as I know of, all Duramaxes come with dual batteries. I'd assume that they are standard so they'll have increased CCA for starting?

Here is one of interesting thing about auxiliary battery. What really surprise me is how small the wire leading to auxiliary battery are. It looks like #10 or #8 to me. I thought that it should be a minimum of #2 at least, if you are using batteries for power feeds. One of thing I know about this setup is the isolator. As far as I know of, once the truck is shut off, the isolator will separate the connection between these two batteries. The auxiliary battery will feed accessory power such as trailer power feed, maybe truck lamps and radio too? This will keep the main battery from draining so you still could start your truck.

My real question is why are the auxiliary battery wires so small? Is it just that the isolator is not rated for high load current? Any reason for this?

I might be wrong here. But I think the wire on the battery you are talking about is larger than 8 gauge (if that is what you are talking about).

Your asssessment is not the case w/my '02

wxmn6,

I see from your signature that you have a 6.0L gas engine. I'm not familiar with all the details but I'm fairly certain that your 6.0L dual battery setup will be wired different than the Dmax dual battery setup. As you indicated the Dmax has two batteries to handle the load of cranking a high compression diesel engine. On the Dmax both batteries are simply wired in parallel with “large” cables – same size on each battery. Sounds like your setup is intended to feed isolated feed power to a trailer or other accessories (??).

:)

Yeah that's what I thought. Small gauge because the isolator may not be able to handle high current. So are you saying that on all Duramaxes there is no isolator at all?

No isolator! Later! Frank

Let just say that Duramax could start with one battery easily and you'd like to have 2nd battery for more CCA. Would you rather have 2nd battery on isolator or not? Just asking for opinion. Thanks.