I have several aftermarket accessories that need a direct line to the battery (subwoofer, etc).

Up until this point, I have had a Group 34/78 battery that has both sets of battery terminals, so I've just attached them to the top posts.

However, that battery died and now the replacement battery is a Group 78 that does not have the top posts. Curious how others have connected their devices.

Thanks!

EDIT: 2013 Chevy Express 2500

 

What accessories?

 

Currently, I have a subwoofer and a light bar attached with ring terminals on a ring terminal connector.

In the future, might add an ARB compressor as well.

 

I used the POS battery terminal of the underhood fuse box.
Added an 8 gauge wire to an auxiliary fuse box for my accessories, auxiliary lighting and trailer brake control.

 

Yeah as long as you're not adding more than a few hundred watts of load, you can use the auxiliary positive stud in your underhood fuse box. Make sure you connect after the factory megafuse if you have one (you did not give us any details about what vehicle you're driving) or you'll fry your wiring.

 

2013 Chevy Express 2500

 

Also - does there happen to be a lead I can tap into that is switched on and off with the ignition?

 

One of these stud posts should do the job nicely:

EDIT: Or this from Autozone: https://www.autozone.com/batteries-s...der/296092_0_0

 

Compressors can draw a lot of inrush current. You should probably give it a dedicated circuit.
You'll need a break-out fuse panel connected to battery, and run the circuit through a relay energized by a manual switch.
I would be extremely careful about hacking into existing wiring if you don't want problems down the road. GM electricals are not exactly confidence inspiring to begin with.
See the electrical manuals on gmupfitter.com