Multiple USB charge ports

Hi guys

I'm interested in installing usb charge ports in a 14 seater passenger vehicle, Please understand I'm not a auto electrician but I'm keen on learning... my queries are :

(1) How many ports can I safely install?
(2) Is there enough power from the vehicle, it uses a 12V battery
(3) What components would be necessary to accomplish this task?

You can buy USB charging outlets to mount in vehicles, eg.
**broken link removed**

They have the electronics built in, they just need a 12V supply.
(Search ebay for "vehicle USB outlet).

To be safe, allow two amps current (at 12V) per outlet, wire in groups of five and fuse each group at 10A, using wire rated at a minimum of 10A

That would allow up to 15 units in all in three groups, so feed the three fuses fuses with wire rated at a minimum of 35A and a 35A fuse from the battery.

That could be via a suitably rated switch (or switch and relay) to control the power feed to the outlet devices, so you can turn them off when the engine is not running so you do not flatten the battery.

If you use a relay, the feed to the relay contact could come from the battery (via the 35A fuse) and the switch that controls the relay from the ignition accessory circuit, so everything is off when the ignition switch is off.

(Wires at every point must be rated at least as high as the fuses that feed them & preferably rather higher, to avoid any risk of fire in case of an electrical fault).

I really appreciate ur input , but I'm wondering if wire length (gauge) will be a factor or not??..and, the amps..which kind should I get??..Thanx in advance

You need to use USB charger sockets that run from 12 V. They convert the 12 V to 5 V at the socket. As a result, the voltage drop isn't too important and they will give out 5 V even if the input voltage is a bit less than 12 V.

I don't know what the maximum current rating of the sockets will be, but they will consume about half the current that they give out.

(It's not magic, the power they give out is less than the power consumed. E.g. if the socket is giving out 2 A at 5 V, that is 10 W. If it is taking in 1 A at 12 V, that is 12 W, so it is losing 2 W in heat and it is 83% efficient)

There are various online voltage drop calculators that you can use. If you are connecting the -ve of the socket to ground near the socket, the length of the ground wire will be less. A lot of the calculators expect the ground and power wires to be the same length, so they show the combined voltage drop for both wires. For ease of calculation, assume that all the current is taken by the socket furthest from the supply.

rjenkinsgb advice is good. Having them in groups will keep the wire size needed down, and reduce the problems if there is a fault.

Also, those sockets all use some power keeping the 5 V converter working when there is nothing plugged in. You don't want them all taking current when the engine is off. Also, if one of the 5 V converters goes wrong, it could overheat, so you want to reduce the risk of that in an unattended vehicle.

It doesn't really matter whether you fit 1 or 100 sockets. 1 socket could flatten the battery if the vehicle is left for a week or two, and if the engine is running the vehicle's alternator will have no trouble keeping up with all the loads that 14 passengers are likely to bring along. So the answer to the question in your first post is that you can install as many as you like, as long as they are disconnected when the engine stops.