Powering a PI (and accessories) from a 12v 15A rail.

There are some adaptors that have dual 2.1A or a 2.1 and 1A output.

Most portable USB drives come with a double USB lead for powering the drive from two USB outlets.

This could be an option.

The alternative is to find a proper 12v to 5v step down regulator.

Personally I would use the cigarette outlet and change the fuse to something like 5A.

It's probably time to rip apart the 2.5 A supply to see if it's a switch mode version.

If the design is what I'm thinking then it could run with 12v input.

Mark

There are some adaptors that have dual 2.1A or a 2.1 and 1A output.

Most portable USB drives come with a double USB lead for powering the drive from two USB outlets.

This could be an option.

The alternative is to find a proper 12v to 5v step down regulator.

Personally I would use the cigarette outlet and change the fuse to something like 5A.

It's probably time to rip apart the 2.5 A supply to see if it's a switch mode version.

If the design is what I'm thinking then it could run with 12v input.

Mark

Hi Mark,

Are there reasons other than personal preferences for your choice of the cigarette outlet?

John

John, I think that's because he thinks that the 1A fuse in the radio power lead will limit him.

Joshua, all power-requirements are usually "maximum required". It should be safe to calculate with those. But on the other hand, it pays to quickly look at what you are REALLY going to use. So for example the pi3 power requirements include drawing 500mA on each of the four USB ports. Similarly your USB hub specifies a similar powerbudget that includes lots of maximally loaded ports. My guess is that if you look a bit more carefully at what you are going to use, then you can quickly decimate your power requirements. First you're not going to use ALL of the USB ports. And secondly you're not going to use them all at 500mA.

Officially USB devices should report their power requirements in 2mA increments. That USB camera can be examined easily. Just connect it and use lsusb -v to list its requirements.

Cheap LM2596 based DCDC converters are fine to power a pi or a hub. If you really want to go for the "full 5A" you can split the work between two of them. One for the pi, one for the hub. And, as has been said: just put in a 2A or 3A fuse, that should be plenty.

Several reasons ...

The wiring size is usually less.

It may also be that the connection further back shares a connection that feeds something else, so while you can draw more, the connection point at the fusebox may become overloaded.

Generally radio outlets are fed from the accessories, so everytime you go to start the vehicle, it will drop power while it is cranking.

Mark

In theory, the size of the wires dictates the fuse or the other way around. So if you see a 1A fuse, they could've used a wire that is so thin that it would carry ONLY "well over 1A" when shorted at the end. In practise it is much cheaper to just use the same wire as everywhere else.
Also, in general it is not common to have a cascade of fuses and then say a 15A fuse at the start and then subdivided into exactly 15 smaller groups of 1A. Even if that were the case you can safely get away with upgrading one to 2A or 3A.

But.... That third argument is quite valid. Just for that one, I'd say: Yes, do that!.

(On the other hand, if it is on the accessory line, you can have the pi up and running in the acessory position of the key. That would allow you to listen to the radio while waiting somewhere without the motor running.  Does the cigarette lighter work in that position? When off? I've seen both. A cigarette lighter that would go off with the car and one that would stay on even when the car was off..... ).

Does the cigarette lighter work in that position? When off? I've seen both

Without more info it is a guess what version the OP has.

The more modern cars switch it off with the key to stop children setting fire to cars by playing while left 'unattended'.

Fusing and the currents are an interesting science.

Domestic House wiring fuses/breakers are there to protect the wires, not the load.

in this case the fuse/breaker will run at it's rated current for 4 hrs before rupturing, but the curve for above that varies between manufacturers.

My advise to halkun is load up his Pi and then measure the current.

This will give him some ideas about his options.

Mark

When you say "decimate your power requirements" do you mean?

verb (used with object)

, decimated,

decimating.      

I assume you are not out to destroy people even every tenth one (#1 & #2), so do you want 1/10 of the power requirements as in #3?

Clem