Ok. I hard wired a dashcam in ages ago using a piggyback fuse to a fuse in the footwell fusebox. I think it's a 5A rated fuse location. I later needed another USB socket so I swapped the usb charger for a 2 socket one.

However I now ideally need 3 USB feeds.

I'm not 100% on how the amp ratings for each fuse location works so don't know what I'm best doing. Should I find a second fuse location that is ignition switched and run a separate USB socket or should I be ok to have one of those 3 socket chargers?

Just worried Im gonna blow something! FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Which location in the fuse box are you using? Fuse number?

The USB devices that you connect should draw more then 0.9 amps. (that is for USB 3.0 which is the worst case)

For three devices that's 2.7 amps on a 5.0 amp fuse.

It should work fine.

As long as the other device on the circuit isn't drawing much power.

Back to my original question.

Which fuse?


Good Luck

Paul

I think your saying you piggie backed into the fuse box a 12v to 5v step down converter with a single 5v USB outlet. The piggie back has a 5a fuse, at 12v, so 60watt. You want to power 3x 2.1a usb outlets at 5v so about 31.5 watt plus the heat losses in the converter ( this will vary by technology type).

Strikes me that the fuse will be more than man enough, but what the wiring is like and the actual rating of the proposed 3x usb devices I don't know, so I can't be 100% sure.

Thanks for all the replies. Will check tomorrow what fuse number I'm using.

The actual wiring is a 12v cig lighter socket wired into the piggy back fuse, with a normal car USB charger plugged into that.

But I think I've been misreading ratings and getting my Watts and amps mixed up! FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Chuck,

You can buy one of these and measure the current draw by the circuit


https://www.amazon.com/302M-Fuse-Buddy-Min...fuse+buddy





If you measure the current draw then measure worst case with battery on your phone depleted for example if you are charging the phone)





Results from the current measurement test

1.0 AMPS Stop thinking about this problem and go have a pint
2.0 AMPS Feel good about what you accomplished, pat yourself on the back
3.0 AMPS Tell all off your friends that you are gifted when it come to electronics
4.0 AMPS Its time to look at using a circuit rated for more current
5.0 AMPS Stop using the setup and find a 10 AMP circuit to tap into (or two 5 AMP)


Good Luck

Paul

Thanks Paul - very useful. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Or one of these. I hadn't finalized my wiring for under seat batteries. So just plugged them into the cigarette lighter socket. 20 amp fuse, maximum draw I had charging up the batteries was 11 amps.

Click image to enlarge