I'd say it depends on how often you drive the rig. You could measure the parasitic draw and see what it is. If only a few milliamps, I would probably hook it up directly. Its nice to have it working without the key in for some loads, like charging a phone.

If you use the truck once a week, it should be fine with good batteries. If it's parked more often that that, consider a switch, or use a battery maintainer.

There are models of that USB charger socket that have an integrated switch.

 

Personally I would not direct wire due to the parasitic draw. I believe Sous had a toggle switch of some kind in the past. Lots of ways to accomplish it but I feel it is best not left “on” when the truck is just sitting.

Edit: BWST responded while I typed. I like his answer better. My truck sits a lot so wasn’t really considering a daily driver in my response.

 

I just put mine on a relay so that its key on only power to the bottom cigarette lighter.

 

The fellas have done a great job of providing you a path to success above. I will provide my personal thoughts on the matter and what I did.

At first I installed the same USB/voltmeter you have now and I too was worried about the parasitic draw. My truck stays parked for a couple/few months during the off season for camping. I do have a trickle charger on the truck now though, so my concerns about the parasitic draw are negated by the charger. Although, we are not always home and often go boondocking out in the middle of nowhere for long periods of time.

With all of that in mind, I installed a simple SPST switch so that I could toggle the USB/voltmeter on/off when I felt the need to use it, as Jason mentioned.

I have since gone to a manual GPR switch and wanted to use the USB/voltmeter switch location for the GPR switch. Still following?

So, I bought another USB/voltmeter with an integrated switch, as Jeff mentioned above.





Image source: https://www.ford-trucks.com/forums/1...l#post19749131

This is by far the best mounting and utility of the USB/voltmeter that I could come up with and it is perfect for my application. I leave it off 99% of the time and now that I have a hardwired cordless phone charger I don't use the USB ports for that. I do use the USB ports to maintain a charge on my 2 way radio in order to stay in contact with my wife in the chase car. The USB ports are there if I need them, as well as the voltmeter.

I still have the always on USB/voltmeter somewhere in the garage. I will probably give it away one day.

 

Sous, thanks for the info, as well thanks to Jeff, jgg123, and Jason.

I have now ordered the dual USB with integrated switch which was linked in your GPR thread.

I did see the single USB with switch but wanted the dual since there are 2 devices in the cab to be charged. As well not realizing until yesterday that the power port is an always on circuit I wasn’t too concerned about being able to turn it off.

Installing the relay would work for ignition source power but would not provide cranking during gpr load health of the batteries.

The currently in my hand dual USB volt meter will get installed in the travel trailer so I can see real-time voltage battery health while boondocking instead of the current 1/3, 2/3, full on the factory panel.

 

For kicks and giggles I have hooked up the USB volt meter to a sitting on the bench 12V battery.

Ohm meter shows 12.16 v where USB shows 12.6. .5 of a volt is huge when considering diagnosing a no start with a 7.3, or when to fire the generator up on the trailer.

I am going to leave it hooked up for one week and monitor the voltage drop daily.

 

Still in the process of measuring voltage drop over a one week period.

Will post up the results on Sunday.

It’s been raining here for the last 2 days but today cleared up and got hot. Noticed condensation on the windshield so went out and checked what’s up.



Drivers side

Passenger side.


I know what I’m doing on Saturday.

 

A smartphone-connected multimeter called Pokit can be left hooked up for the week to perform data-logging duties for you.

 

My first USB voltmeter had a .2 drop in voltage reading when installed. My new and currently in use USB voltmeter is spot on what the batteries read using a multimeter on the battery terminals. I checked it a few times shortly after install and it was spot in each time.

As for your .5v low reading, I agree that is not desirable. Are you using the multimeter at the battery terminals or on the spade clips/connectors of the USB/voltmeter? You probably know this, but there will likely be a small amount of loss due to the wire gauge, quality and length.

Lastly, I am sure none of these USB adapters are built to any sort of standard, so there is that.

 

Thats a pretty cool looking little device. Not much more than what I spent on my current multi-meter. If mine ever dies I will seriously consider that as an option. For now I will take the 30 second walk to the shop to check up on it.

The USB voltage gauge is registering .5v higher than measured at the battery post voltage at the beginning of the week test.

Currently .4 higher at day 4 of the monitoring and to date have only registered a .05 voltage drop on the test battery.

​​​​​​Lastly, I am sure none of these USB adapters are built to any sort of standard, so there is that.

Yes Sir… there most definitely is that. Hoping for better accuracy results from the next one currently on order.

 

I misread your post earlier, my apologies. Strange that the USB voltmeter is reading .5v higher...

 

Again. I agree with you there. Has me questioning the accuracy of my current multi-meter. Too bad I don’t have another to compare the reported numbers.

The current is scheduled for return to Amazon by the 10th of October based on the higher readings. The new is scheduled to arrive on September 24th so I will have both and will be able to compare their readings against each other. If they line up then it’s time to look sideways at my multimeter.

However based on price point alone the first is going back @ $10.00 more without the ability to manually turn it off.

This will be revisited once I have both to compare side by side.

For now the more pressing issue is the leaking rear cab vents which I will address on Saturday.

 

Me and these vents are currently in a love / hate impasse.

I have done a search and read where it is possible to pull them without jacking the cab, or alternatively sliding the box back. This I assume is provided that the front of the box has never had something slide into it under heavy braking and causing it to bow out towards the cab.






Figured that pulling the box bolts and sliding it back would be the simple way to get this done.

My truck has been treated to not one- but 2 layers of spray-in Line-X.



I was hoping to make the least invasive hole / divot as possible but it turns out the washer is attached to the box bolt.



Since the Line-X is Polyurethane based I will fill the holes in later with a STPU caulking.

One down and onto number 2.

Houston. We have a problem. Two barked up knuckles and a broken T-50 bit. Off to the parts store for a replacement while the box bolts take a soak of PB.

 

6 of the 8 out now and the second man is down.

Too bad because this was a nice looking kit.

Edit: This time it’s a tool store. Found a single T-50 was hoping for an impact grade 1/2” drive but T-60 is the smallest in 1/2”. These last 2 will get some persuasion with a MAP gas treatment.

 

Any guesses as to which bolt won’t come out???