question regarding fuse/power upgrade

[20ducks]

I have an aftermarket device that will surpass, on occasion, the 30A power slot it is currently connected to. My question is: Do I connect this new device to a slot (right side footwell fuse box) that is labeled in the Owners Manual "Not Used (spare)"? Fuse Number 4 is rated 20A is an example. Before connecting, I would change the fuse from the 20A to 40A to accommodate the increased power draw.

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[mc68386]

I have an aftermarket device that will surpass, on occasion, the 30A power slot it is currently connected to. My question is: Do I connect this new device to a slot (right side footwell fuse box) that is labeled in the Owners Manual "Not Used (spare)"? Fuse Number 4 is rated 20A is an example. Before connecting, I would change the fuse from the 20A to 40A to accommodate the increased power draw.

I don't have any definite answers, but a couple of thoughts.
It's possible since it's labeled "spare" it's not even wired for power on all cars.
If it is wired for power, and has a 20 amp fuse, pushing it up to 40 amps could exceed what the wires/harnesses connecting it can take. And frying that circuit might cause collateral damage on other nearby circuits.
If it was my car I'd probably install a new (fused) fat wire directly to the battery and thread it through the firewall to wherever I need to go. Put the fuse as close to the battery connection as possible.

 

[20ducks]

If I hook it directly to the battery won't it draw off the battery even if the car is off?

 

[mc68386]

If I hook it directly to the battery won't it draw off the battery even if the car is off?

Yes it would - most devices that use high current have a separate power switch line that you connect to a (low power) accessory power circuit that turns it on when the car is running.
If your device takes high power *and* needs to be powered on only when the car is running *and* doesn't have a separate power switch line, then all of your options have downsides.

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