Sunday, May 5, 2013

Project report: Installing dual 12 volt power outlets

If you save your Vespa for toodling around the neighborhood on sunny summer afternoons (which, by the way, is a perfectly good use for a Vespa), your Vespa is perfect when it rolls out of the showroom.

If, like me, you log more than 5,000 miles a year commuting to and from the office, there are some things you want to add to your Vespa before very long.

One of those things is a 12 volt power outlet.  Exactly the kind of outlet that comes with every car (and often more than one).

When I got my first Vespa I had installed a 12 volt outlet in the glove compartment before the first riding season even started.  Now that I have my GTS, adding the power outlet was also a top priority.

I learned a thing or two about making modifications to Vespas in the three years since I embarked on this most excellent adventure. One of the things I learned was that I should have installed a terminal strip in the legshield.  If this is Greek to you, it was Greek to me too when I first came across the suggestion.  The advantage of a terminal strip is that installing new circuits for accessories is much easier and keeps things tidier.

I went to a local electronics store and picked up a terminal strip.  I promptly cut it into 2 six terminal strips and then tie-wrapped them back to back.  I then bridged one set of six terminals with red wire, and the other set of six terminals with black wire.

If my description leaves you numb and not understanding what it is I have done, here is a mercifully short video that may help:
The first terminal on the red terminal strip is connected to a wire connected to the positive battery terminal, and the first terminal on the black terminal strip is connected to a wire that goes to the negative battery terminal.

With that bit of electrical plumbing out of the way, I designed the circuit for some twelve volt outlets.
Adding a relay is the way to ensure that the outlets are only live when the Vespa's ignition is on.  It's a precaution to make sure that the Vespa's battery doesn't run down if something is left plugged into the outlet.

On the LX 150 I installed a single 12 volt outlet inside the glove compartment.  That was a good choice.  It kept the outlet out of sight, and was a minimally invasive change to the Vespa's leg shield.  The GTS has two "knee pads".  Who knows why they are called knee pads.  They don't offer any padding for your knees, that's for sure.  The nice thing about the knee pads is that they are cheap to replace and they are the natural place to install outlets, accessory switches, and the like.  If you need to restore the bike to stock, all you need to do is buy a new knee pad.

It turned out that one of the challenges for this modification was finding suitable 12 volt outlets.  When I did the 12 volt outlet on the LX 150, I got everything I needed at The Source (formerly Radio Shack).  This time around, I couldn't find a suitable outlet anywhere.

Following some advice from a Modern Vespa thread, I searched for "marine 12 volt outlet" on Ebay.  I found a great deal on two outlets that cost me under $15 including shipping.

I drilled out two symmetrical holes in the left knee pad and installed the outlets.  Getting the holes to the right size involved from free-hand dremelling, but it was a simple and relatively easy thing to do.
Following my circuit plan, I used crimp connectors so that if I needed to remove the knee pad in the future, I would be able to disconnect them easily.
The rest is easy.  Plug in the positive and negative leads, and re-install the knee pad.
And there you have it.  Now I have a place to plug in my Garmin Nuvi GPS, and my iPhone.  Or my iPhone, and my GoPro camera.  Or my GoPro and my Sena SMH10 Bluetooth headset... well, you get the drift.
Another successful modification, and one step closer to having the ultimate Vespa commuting (and touring) bike.


Dar said...

Wow you have a lot of doodads on the Vespa. Cool good for you David!

David Masse said...

Thanks Dar! It's the Boy Scout in me.

SonjaM said...

Your cockpit starts to look like the bridge of Starship Enterprise ;-)

David Masse said...

Sonja, if you can believe it, last Thursday I took a conference call with Swedish lawyers and our tax department riding into work. I found out about the call that had been scheduled at 4h00 at 7h45 once I was already underway. The call ran from 8h00 to 8h35 and was winding up as I entered the underground garage at the office. Plus, Siri voice dials for me, and I can ask her to read text messages that come in. It is pretty Star Trek-ish when you think about it.

I love following your travels. Don't stop sharing. Every now and then the two of you pop up on the computer screen in the kitchen, and now that you are so far away, there is a little tinge of sadness, and happiness for you.

All the best to you and Roland.

VStar Lady said...

David - the 12 volt outlet was the first thing I had added to the Star (after the heated grips.) Don't use it for the Garmin though - he's such a necessity that he's wired direct. But I don't do it myself - got an excellent "guy" for that!
I am so impressed by those who can do it by themselves.

David Masse said...

Karen, the electrical work is not finished yet.

I want to add another line direct to the battery terminating in a two-prong SAE plug.

I'll be able to use that plug plug in my portable compressor, plug in jumper cables that I can use to help someone out, or plug in a line with two power outlets that I could use when touring to re-charge whatever couldn't be plugged in during the ride (Sena headset, GoPro, etc.). That plug will also be used for the battery tender for winter storage.

Unknown said...


I think we need a Labeling machine so we don't get our GoPros, Senas and other electronic stuff mixed up as we are taking turns charging all of our stuff on your bike

Riding the Wet Coast

Prof. Lee said...

Hi David
What would the wiring diagram look like to have a 12v outlet and a new stebel nautilus horn?

David Masse said...

Hi Lee, welcome to the ScootCommute! I think you'll find the answer in my post on installing the Stebel: click here.

Prof. Lee said...

Thanks! I have two questions: 1) does the terminal strip simply supply 12v to all things connected? 2) I'm new to this, how and where do I find the ignition to only allow the outlet to work when the ignition is on?

David Masse said...

To answer your questions...

1) Yes, the only use for the terminal strip is to provide a more convenient place to get electrical power direct from the battery into the space behind the left kneepad.

2) To make sure your outlet is only live when the ignition is on I added a simple automotive relay which you can get at Canadian Tire.

The reason I use the relay is that I know I'm getting pure power from the battery for whatever accessory I'm adding, instead of relying on the capacity present in the white wire on the alarm connector. Some people just wire the positive outlet terminal to the white wire on the alarm connector and negative terminal to any ground.

If you decide to go with power straight from the battery (necessary it you add a powerful horn like the Stebel Nautilus) you get the positive current for the relay (terminal 86) by tapping into the white wire on the alarm connector. The alarm connector is the unused female multiwire accessory plug you'll find just sitting there in behind the left kneepad.

The 85 terminal of the relay goes to the ground. When the ignition is turned on, the current running between terminals 86 and 85 activates the relay and closes the circuit between terminals 30 and 87. Terminal 30 should go direct to the battery (or the red connection on the terminal strip in my case). Terminal 87 (be sure to add a fuse, I added a 15 amp fuse) should be wired to the positive terminal of the 12V outlet. The negative terminal of the 12V outlet is wired to ground (in my case to the black lead on the terminal strip).

Prof., you're in Montreal I believe, I'd be happy to give you a hand if you'd like.

Prof. Lee said...

Thanks! Gotta try this on my own. Appreciate the help!

Prof. Lee said...

Does this mean I need 2 relays? 1 for the horn and 1 for the control of the power by the ignition?

David Masse said...

Yes it does.

The 85 and 86 terminals of the relay for the horn receive the wires that were plugged into the original Vespa horn. Those wires come straight from the horn button. The current they provide is sufficient for the stock horn, and sufficient to drive the relay, but insufficient for powerful aftermarket horns like the Stebel Nautilus.

One of the terminals on the new horn is connected to the 87 terminal of the horn relay, and the other terminal on the horn is connected to ground.

The 30 terminal on the horn relay is connected to the positive battery line (in my case a line that comes from the positive side of the terminal strip) and that line must be fused at 25A, because when the horn operates it draws around 20A.

David Masse said...

Oh, one other thing, avoid a mistake I made, the positive and negative wires should always be of identical gauge. I used 12 gauge automotive wire everywhere.

Prof. Lee said...

Thanks David! Got the horn in today and works like a charm! Next time will be the addition of the 12v. Appreciate the help

David Masse said...

Glad to hear it. You'll be very pleased with it when you need to get someone's attention.

Unknown said...

Fast forward to a 2018 GTS Super Touring. I only needed one 12V outlet so ordered up one off of Amazon. Then I removed the left knee pad. Whoa! What's this, no access to the guts behind the leg shield? Well, there is but it requires cutting out some of the plastic behind the knee pad! There are two 'pre-perfed' areas, one about 1.25" by 1.25" and one about 3"x5". I cut out the small one but held off for now on the other piece. By careful alignment, I can get one 12V outlet in the knee pad lined up with the cut out in the interior piece. I'm going to fish my wires through the area behind the leg shield and connect the 12V outlet hot to the battery. At least that is the plan.

David Masse said...

Sounds like you’re on the right path. I’d love to know why Piaggio decided to add those panels that need to be cut out. They add no benefit or value. The just make more work and head-scratching for owners.

The copyright in all text and photographs, except as noted, belongs to David Masse.