Add new electrical accessories

[radioactiveman]

Hello

I'd like to add some small accessories to my car to make it a bit more comfortable. Basically a USB charger and a radio.

I'd like to keep things safe and not stress the existing wiring too much. My plan:

1. Run two new 17amp cables to two new fuse boxes inside the car. Both will have inline 17.5amp fuses at the battery end.
2. One cable will go directly, and one will go via a relay that's switched when the ignition is on.
3. These fuse boxes can then step down the switch/constant supply to more appropriate ratings for their task.

ATM I have a dynamo, do you think that will struggle?

[simmitc]

It depends on what accessories you are going to run. The dynamo should quite happily run a standard radio (not a massive sound system) and charge a phone. If you want to run a ceramic heater continuously then it's a different story.

Have you considered +ve earth or -ve earth? If the wiring is rated at 17 amps then I would use a 15 amp fuse rather than a 17.5 - you want the fuse to blow before the wire melts.

[radioactiveman]

Yes, good point on the 15amp fuse.

I believe the car is negative earth (negative wire attached to the body).

[simmitc]

Negative earth should be fine for all modern accessories, no need for any special isolating and earthing requirements

[geoberni]

I have a Dynamo equipped SII, when I got it there was already a radio cassette and a charger socket.
Other than ditching the radio cassette in favour of a Radio/CD, I've changed nothing and all is fine. The power for both is just picked up behind the dash, nothing special run in; neither of them takes more than a couple of amps.