USB charger wiring

[Daveyd]

Hi all, I purchased a marine boat usb style charger and put it in my glove box. It is the kind that always reads voltage. I thought it would be best to hook up to ground and the existing cigarette lighter hot wire. The only problem is even when the key is out. The one in the glove box is lit and reads 11.8. I'm guessing this will drain the battery sing the original uses the lighter or whatever to connect the circuit. Is there a better way to wire this so it only turns on when the key is on? Thanks!

 

[wsager]

Radio power?

 

[DirtDonk]

Yes that's exactly what's going on. And yes, eventually it would probably drain the battery. But that would likely take a very long time.

But a better place to tap in for its power would be either one of the switched fuses in the stock fuse box, an unused wire under the dash, or easiest of all most likely is the center stud on the back of the ignition switch.
This stud can have one or multiple wires on it already, but most early model Broncos have a single black with green stripe wire. You simply remove the nut, attach your new USB wire, put the nut back on and you're done.

 

[sprdv1]

Hi all, I purchased a marine boat usb style charger and put it in my glove box. It is the kind that always reads voltage. I thought it would be best to hook up to ground and the existing cigarette lighter hot wire. The only problem is even when the key is out. The one in the glove box is lit and reads 11.8. I'm guessing this will drain the battery sing the original uses the lighter or whatever to connect the circuit. Is there a better way to wire this so it only turns on when the key is on? Thanks!

I got to get me a darn usb set up in mine too

 

[McLeod]

I installed two 10A cigarette lighter sockets in the passenger side interior quarter panel.
I used direct power from my "always powered" amp feed in the rear passenger corner and used the old existing radio lead (or any other switched lead) to activate a relay (low draw this way) that turns the new cigarette lighter sockets on and off with the key.

Having it wired to a large direct battery feed (like your existing cigarette lighter feed) ensures that you will have sufficient power if you end up with a high draw. A small existing switched wire *may* starve your power needs or overheat the existing wires if pulling lots of amps thru it.

Of course, all this is highly dependent of what you are doing with it.

 

[Tulsa76bronco]

Following

 

[Yeller]

A USB port does not draw that many amps, pick a key on or accessory key on spot from the ignition switch or fuse panel and wire it up, of course a 5-7.5 amp fuse is still needed.

 

[EPB72]

A USB port does not draw that many amps, pick a key on or accessory key on spot from the ignition switch or fuse panel and wire it up, of course a 5-7.5 amp fuse is still needed.

As Yeller stated not much draw and really no draw untill something is plugged into it ... remember USB is a 5v output source. 1.0 and 2.0 USB ports deliver upto about 500ma and a 3.0 900ma.. however 3.0 USB ports with a dedicated charging line can go upto 1500ma,, which would equate to about 7.5watts..

Most of the usb to cigarette lighter adaptors I've seen with blown fuses had a 2 amp fuse in them..

to the OP to test current draw on the port you have with the volt display you could hook up a amp meter inline and you will no for sure ,,

 

[McLeod]

A USB port does not draw that many amps, pick a key on or accessory key on spot from the ignition switch or fuse panel and wire it up, of course a 5-7.5 amp fuse is still needed.

This would be better than tapping into a circuit that is already being used by something else.
The fuses should be sized to protect the WIRE feeding the device.

As Yeller stated not much draw and really no draw untill something is plugged into it ... remember USB is a 5v output source. 1.0 and 2.0 USB ports deliver upto about 500ma and a 3.0 900ma.. however 3.0 USB ports with a dedicated charging line can go upto 1500ma,, which would equate to about 7.5watts..

Most of the usb to cigarette lighter adaptors I've seen with blown fuses had a 2 amp fuse in them..

to the OP to test current draw on the port you have with the volt display you could hook up a amp meter inline and you will no for sure ,,

Some of the devices I've seen supply up to 4 or 5 amps each.
I know OP was talking one device but hey, let's add a second one "because we don't have enough".
Also, you need to consider if the circuit you are tapping into and the current that it handles already. You should never be more than 80% of max current on a continuous basis and even less if your wiring is 50 year old subpar condition.

Will it work like you describe, yes, most likely.
All this is highly dependent of what you are doing with it.
End user with eyeballs on the truck needs to assess for himself.

 

[Broncobowsher]

The USB plug draws power even when no USB is plugged in. Happens all the time on the motorcycle forums. They have a tiny battery and after sitting a few weeks is dead. The circuit to power up the USB is always drawing a little power so the USB is "ready" to be plugged in. The volt meter is the same as well. Takes a little power to keep the LEDs on and the little processor doing its thing to read the voltage. They can be made to draw extremely little power, but that costs money. So they do the cheap way out and it just draws very little power instead. When running, makes zero difference. Even overnight it won't really do much. Leave it parked a few weeks, at least it will tell you how dead the battery is.

Yes, move the power to a switched power source. Radio is perfect.

 

[Yeller]

Remember we're talking about 5 amps at 5 volts that equals 2.5 Amps at 13 volts and that is if you get a high amp quick charge model. The ones I've been installing are dual port with a maximum output of 5amps at 5 volts over both ports

 

[Broncobowsher]

Remember we're talking about 5 amps at 5 volts that equals 2.5 Amps at 13 volts and that is if you get a high amp quick charge model. The ones I've been installing are dual port with a maximum output of 5amps at 5 volts over both ports

It is the time factor that is the killer. When you are talking hundreds of hours between uses (48 hours = 2 days, 96 hours = 4 days, yes hundreds of hours is a realistic number) even a very small draw is murder to a battery. Not even talking amps at this point, milliamps add up over time.

 

[McLeod]

Remember we're talking about 5 amps at 5 volts that equals 2.5 Amps at 13 volts and that is if you get a high amp quick charge model. The ones I've been installing are dual port with a maximum output of 5amps at 5 volts over both ports

Your point is taken.
5a at 5v is the device output.
The device is actually a 12v device. I wouldn't be surprised to find out that the efficiency of the conversion is less than 75%.

Granted it is a low overall amp draw, being selective on the power source chosen would still be prudent vs just grabbing the closest switched wire with no regards to what that circuit is actually currently supporting.

And also, one of the biggest complaints of many Bronco owners is grounding issues, especially behind the dash.
Is it a good idea to potentially add to the problem or to start off on the right foot by going to a more direct source and not daisy chaining a new project?

 

[67sport]

I installed an independent circuit for my usb and power port, through a switch on the dash. The circuit is fed from an unswitched aux fuse panel behind the dash. I also installed a cheap digital Volt meter in parallel with the circuit.

I can continue to charge stuff when the truck isn't running, and the cheap voltmeter lets me monitor the battery whenever it's on. Because the voltmeter is not fed from the ignition, I can also monitor voltage when cranking etc. There is a risk of leaving the switch on and killing the battery, but that's user error.

Works for me.

 

[jckkys]

Here's a good thread by electronic nerds that quantifies the effect on a car battery;https://www.bigmessowires.com/2016/01/28/standby-current-of-a-usb-car-charger/.

 

[Steve83]

I'm guessing this will drain the battery...

The battery will drain regardless. The amount of time it takes to drain varies by (among other factors): temperature, construction, parasitic draws, state of charge, age (sulfanation)... The draw from that tiny LED display is not significant - it won't affect the time your battery takes to die enough to notice or measure. If the battery is OK, it'll run that display for a few weeks between drives. If you're gonna park the truck longer than a week, you should put a good trickle charger on it - I recommend BatteryTender Jr.