Q1

I am debating fitting a high capacity dascam battery.

They recommend that the 15amp fused lead is connected to the car battery but it would be far easier to tap of the cabin fuse box.

Is there a limit to the power we can pull from that fuse box?

 

Q2, If i did go the main battery is there a suitable grommeted hole throug the bulkhead I can use?

This should help you:

 

Thank you but that isnt what i needed to know sorry.

I am asking if there is a limit to how many extra amps i can pull from the fuse box. I need to pull another 10 to 15 amps.

In domestic installations the systems are designed with a toatal load taken into account ( apart from the weird application of diversity rule) so i wonder if the main supply cable(s) to the fuse box are at their limit or have a decent enough spare capacity.?

I'd think there will be plenty of spare capacity.