Extra 12v Power Plugs in Sprinter Dash

RVwithDogs · 11-14-2019, 07:33 AM

Good Morning,
I wanted extra 12v power plugs up front for easier access, the one under the ashtray is hard to deal with. I built the one in the photo out of some scrap aluminum plate and some plugs with the wiring fished down the left side then into the Sprinter floor battery and a inline fuse holder at the battery connection. So I have 2 questions, the wire from the battery up to the rocker switch is 12 gauge and the wires from the switch to the plugs is 18. At most I suspect I would have 2 phones and a secondary camera display and volt meter at the same time. Any thoughts on the fuse size needed ? Right now I am using a 10amp for testing the plugs. And, I may consider changing the wiring to go back to the house batteries. Has anyone found a easy way to fish a wire set from under the dash back to the house battery under the steps ?

Winterbagoal · 11-14-2019, 07:41 AM

Aren't most 12VDC cigar lighter "bullet" plugs fused at 5A, usually built into the plug?

Why not add a 12VDC cigar lighter bullet to your "panel" as the input power source and plug it into the outlet below the ashtray? Just run the wire down the left side past the ignition key hole and under the ashtray into the outlet. Accomplishes the same thing, and the fuse is built into most 12VDC cigarette lighter plugs. When not in use you can unplug it to limit chassis battery drain.
Or, if you want to run it off the outlet in the ashtray, it will shut off power when the ignition is off.

**ThomB** · 11-14-2019, 08:03 AM

Do you absolutely need to go back to the batteries?
I added a couple extra circuits directly into the chassis fuse panel which should be fairly close.
These things are great for that: https://www.amazon.com/10-Pack-Add-c...s%2C231&sr=8-4
you'd just need to pick up a ground someplace and you can wire these into either a switched or unswitched existing fuse.

I have a 12v plug wired into a switched fuse for our dash cam. It comes on with the ignition. As I have an amp-l-start my chassis battery is maintained while we are plugged in.
I'm not really concerned that I will kill the chassis battery with the additional USB ports that I have installed that are always live as they are attached to an unswitched fuse.

RVwithDogs · 11-14-2019, 08:10 AM

That would accomplish the same thing but I wanted to keep the lower outlet and the ashtray outlet free. I wired it to both places in testing out the layout and decided against that.

RVwithDogs · 11-14-2019, 08:17 AM

Good point ThomB, had not thought about using those. At the time the easiest option was going straight down beside the radio and into the battery box.

Morich · 11-14-2019, 01:46 PM

Most 12v outlets are not used much of the time, so I go for picking the supply up by tying into what is already there, unless there is some special heavy use involved. I rarely add more fuse holders, as what is already supplied is often way more than the newer electronics use so that piggy backing works fine. First step is finding and deciding which battery, house or chassis is best to tie the new stuff on and then finding that circuit near where I want it.

thataway4 · 11-20-2019, 07:59 PM

I use a 3 way splitter for the built in cig lighter plug, and run two GPS 7" displays and a tire pressure monitor from this. I charge from the USB plugs built into the 2013 dash under the top cowl. This works fine, without extra wiring

Winterbagoal · 11-20-2019, 09:11 PM

Quote:

Originally Posted by RVwithDogs

That would accomplish the same thing but I wanted to keep the lower outlet and the ashtray outlet free. I wired it to both places in testing out the layout and decided against that.

Why do you want to keep the 2 most conveniently located 12V DC power outlets "free"?

One is ignition activated, and the other is always live off the chassis battery.
Your call, it's your van/motorhome.

bkg · 11-20-2019, 09:20 PM

Quote:

Originally Posted by RVwithDogs

So I have 2 questions, the wire from the battery up to the rocker switch is 12 gauge and the wires from the switch to the plugs is 18. At most I suspect I would have 2 phones and a secondary camera display and volt meter at the same time. Any thoughts on the fuse size needed ? Right now I am using a 10amp for testing the plugs.

18 AWG for 12 volt is rated at 16 amps for intermittent loads and just under 3 amps for power (transmission) loads. However, the length of the run has to be factored in but I hardly think you are more than 36 inches - not much loss in that short of a run.
In my opinion I think you are kinda small on the 18 gauge even though you are only powering USB phones and a camera.
Find the load of the devices (cameras and phone) add 15% and size the supply wire gauge accordingly. Keep in mind the USB is a power adapter (12 volt to 5 volt) too so it will use a small amount of current as well.
In regards to the size of the fuse, if you stay with the 18 gauge wire I would go with a 5 amp fuse. If you run 12 gauge all the way, no larger than 10 amp since USB port is rated for 5 amps (per port).

Quote:

Originally Posted by RVwithDogs

I may consider changing the wiring to go back to the house batteries. Has anyone found a easy way to fish a wire set from under the dash back to the house battery under the steps ?

Yes, you can easily hook to the house battery under the passenger seat. Under that seat is where the jump start solenoid is and it is also the loacation of a load center that is served by both the chassis and house battery.

It is very easy to get to, however, you have to pull all the front mat out. Once the mat is removed you will see the Mercedes harness channel that runs from the center dash down to between the seats.
Winnebago used this as well when they built the coach. It has sufficinet room to run more wire, however I would run any wire in loom or run it in loom that is already there. I would also suggest if pulling power from this area grab it from a fused source and not directly at the solenoid post or terminal block.

Nice work on the dash panel.
If you really want a custom job with lettering and images check out Front Panel Express: Front Panel Design Software and CAD Conversion Service: Home

RVwithDogs · 11-21-2019, 05:13 AM

I started out using the 2 stock plugs but did not like the wires hanging down the dash and the one in the ashtray can be a bit cumbersom. (I am still a smoker and use the real cigarette lighter) Using the top panel just seems to keep it all a bit more organized.

RJ2 · 11-21-2019, 01:55 PM

In the past I have pulled power to put footwell LED light strips in by tying into the back of the Lighter socket.
Since then I have discovered the easiest place to tie in for power is dropping the glovebox and tie into the glove box light socket.
In the process of putting in another set of footwell , and also step lights for door opening/entry....which is a WINNEBAGO overlooked problem area .
Opening doors and entering when dark , is certainly not up to what you would think would be a Mercedes standard .
On the step Well or under step bar , I am tying into the overhead dome light circuit .
There are wireless steplighta
Available , just opting to go wired .
As far as placement of add on usb sockets ,