USB continuous draw?

[VanTalk00]

This may have been asked before, but it's too hard to search for.

I thought I heard somewhere that USB ports draw power even when nothing is plugged in.  Is that true?  Is it noticeable or worth putting on a separate circuit?  Is there any other DC device that draws power when it's not being used?

Thanks,

Jim

 

[mpruet]

Are you talking about the port or something plugged into the port? 

A lot of USB ports will have a small LED light which will shine showing that the port has power.  I guess that would be a small (rather small) draw.

 

[John61CT]

Any DCDC converter has a self-discharge, same with inverters left on while not in use, lots of meters, combiners, electronics in general.

A switch is needed upstream of the device, IMO a central panel combining CP is ideal.

And a master switch to isolate at each battery bank when not using the vehicle. Optionally a bypass for the ECM, radio presets, etc.

 

[B and C]

I leave a lot of stuff plugged in on standby. This is the stuff I call my base load and it is 1.2 Amps. My propane detector and CO detector are each 0.1 Amps. I have other loads on too, a old cell phone that never gets unplugged (my night stand clock velcroed to the wall) connected to my mifi jetpack, a tv, etc. The 4 permanently mounted Blue Seas 4.8 Amp USB outlets only draw 1 Milliamp each as a parasitic draw (0.001 Amps). Not enough to worry about.

 

[VanTalk00]

Thanks.  I'm thinking it's not worth having a "USB" master switch to turn these off when not in use.  I hadn't thought about the gas sensors etc.  Good points.

 

[maki2]

If you are creating a charging station that has several USB ports in it you can put in a single switch to control that cluster. It could be a DIY thing or you could use some of the pre cut panels from companies such as Blue Sea to create a custom setup from their components. You can build up from components something along the lines of this unit that has a master circuit breaker switch to cut the power off to the components in that panel. You can see the wiring diagrams in the link as well as what such a panel looks like. https://shop.pkys.com/Blue-Sea-Syst...EoCiz7DkHUe_gDVHMcr5IQNWq73Q-avYaAhTTEALw_wcB

I am fortunate to have several good marine supply stores close to where I am doing my build where I can purchase sockets, circuit breakers, switches, fuses and even panel fronts. But it can also be done from some of the auto parts store and car audio store components.

 

[DLTooley]

A circuit breaker used as an on off switch is good design. I’m not sure about the quality/price point of the lower amp models.

 

[blars]

A circuit breaker used as an on off switch is good design. I’m not sure about the quality/price point of the lower amp models.

Circuit breakers are usually not designed for switching on and off frequently, they may only be rated for a lifetime of 100 such. So it lasts less than 3 months of daily switching. Switches are usually rated at 10's or hundreds of thousands of activations. Poorly designed ones of either may fail much sooner, as will using AC-only rated switches on DC.

 

[John61CT]

Yes if you want a switch get a switch.

Or put in a ciggie port and just pull out the 12V USB charger when you don't want the parasitic draw.

 

[VanTalk00]

I like that idea.  Not being a longtime user of 12 v systems,  how many ciggie type sockets would you include in a build?  Would most of the stuff I buy for 12 v need a ciggie socket?  I have noticed these little USB fans.  Is there much else that uses USB other than phone/tablet charging?  

This is probably a different thread, but what do people do with their laptop charging if they don't want to plug into an inverter?  I see that my laptop adapter outputs 19 v DC.

Thanks,

Jim

 

[Almost There]

  how many ciggie type sockets would you include in a build?  

I included a total of 8 12 V outlets in my build. Not that I would ever be using 8 at a time but so that they were in convenient spots.

I put 2 beside the side door so I could run cords outside for sitting outdoors. It's also handy when I'm sitting in the passenger seat which swivels. I put one on the wall beside the kitchen counter, 1 under the counter for the freezer unit, 2 under the edge of the bed, one which was meant for the fridge, one for general use and 2 up on the wall above the foot of the bed intended for 12V TV and DVD use.

The two that were meant for the fridge and freezer were removed so I could hard wire the fridge and freezer. The 12V plugs that came with the units were inferior and were causing me problems.

But then I also wired in 2 duplex outlets for 120V use and another 2 duplex units that are connected to the inverter.

Yes, some might consider it overkill but I never have to run cords very far or move me so that I'm within reach of power...

 

[DLTooley]

Do you have a cite for that circuit breaker durability figure? I like keeping my wiring simple, as each device is a point of failure.

 

[John61CT]

Varies by model of course.

Any decent CB will have the rating listed on its spec sheet.

A distribution box will have both CP and switching centralized.

Note CP must be on the source end of the wire, a switch should be placed where convenient for the user.