Extra 12V outlet rating?

[dbailey]

This evening I tried plugging my laptop into a Canadian Tire 200W inverter running off a 12V outlet in my 19'. The laptop power supply says its 65W, so I wasn't expecting any trouble, but it didn't work.

The inverter has a display on it that shows the input voltage. Before I plugged the laptop in, it read 12.1V. The solar controller shows 12.5V, so they're in the same ballpark. When I plugged the laptop in, the overhead light started to flicker a bit, and the voltage started to drop. Once it dropped down to 10V, the inverter cut out.

This surprised me...

I had plugged the inverter into the extra outlet I had installed. I decided to try it in the stock outlet in the dinette bench. Here it worked fine.

This suggests to me that the wiring used to install the additional outlet isn't of sufficient gauge for a 65W draw. (OK, a bit more than 65W, actual amount depending on how efficient the inverter is). 65W isn't that much power...

Have other people run into this?

[Devil Dog]

Sounds like they taped into your over head light power supply ( flickering light ). Follow the wires back and see where they go.I think they should go to the fuse box with a heavy gauge wire so it doesn't heat up and cause trouble.

[GaryH]

Sounds as if the inverter you used was a modified sine wave, which doesn't work so well with electronics. They work good with resistive loads though. You need a pure sine wave inverter.
Inverters | GPElectric

[dbailey]

Gary,

I'm not sure I agree. Yeah, the Canadian Tire inverters are fairly inexpensive, so they might not work well in general. But a laptop power supply is designed to handle all sorts of dirty power with wildly varying voltage. Plus it works fine off one outlet in the trailer, but not the other. That tells me there's definitely something different between the outlets.

So, yeah, maybe a better inverter will work better, but there definitely seems to be something amiss with the one outlet in my trailer.

[dave1]

Need to talk with escape. I would expect that all factory installed 12 v plugs would work the same where ever they are installed. Please keep us posted.

[Jim Bennett]

Not sure what my laptop draws, but a 300W inverter just barely keeps it going. It is a Crappy Tire model too.

[dbailey]

I haven't heard back from Reace yet, but I've done a bit more crawling around myself.

With a good tester hooked up, I monitored the voltage with a 50W light bulb used as a load. With the light bulb turned on, voltage dropped 1.2V at the additional 12V outlet. At the original outlet there was still a voltage drop but only 0.6V.

Looking at the wires themselves, they seem to be about 16 gauge. They might be 14 gauge, but I'm not certain just by looking at them. Using a voltage-drop calculator on the web (Voltage Drop Calculator), the numbers I'm seeing are consistent with 16 gauge wire -- the calculator gives a 0.5V drop at 10 feet, and a 1.2V drop at 25 feet (assuming 6 amps).

I presume these outlets are protected by a fuse, and I assumed it would probably be a 15A fuse. I need to verify that, though. It strikes me that wiring a 15A circuit with 16 gauge wire is not a great idea.

[Brian B-P]

Excellent troubleshooting, Doug.

Originally Posted by dbailey

It strikes me that wiring a 15A circuit with 16 gauge wire is not a great idea.

Not good for voltage drop, but perhaps (I'm not an electrician) fine for safe wire capacity. For comparison, a 15A household circuit uses 14 gauge wire... only one size larger. You might be surprised how small most wires in a car are.

I would want larger gauge, and a dedicated circuit... but my Boler doesn't have that, and I don't know if any RV manufacturer does.

[cpaharley2008]

Doug,
Can you please tell us where these outlets are in relation to the converter and if they are wired directly to the converter or if they are off an existing 12v circuit? This may help with the wire sizing issue.

[dbailey]

The converter is in the driver-side dinette bench. The standard outlet is installed in the passenger-side dinette bench. About 4' away, but probably about 8-10' of wire between them.

The outlet that I had added and that is giving me problems is in the front of the kitchen cabinet, just below the sink and stove. I traced the wires as far as I could, and they are routed towards the back of the trailer to the storage area just under the bed, then down through the floor. Since I have the spray insulation, that's where I lose them. I would guess that the total length is about 20-25'.

When I was playing with the voltage drop calculator last night, I used 10' and 25' as the respective lengths. The results I measure are fairly close to what the voltage drop calculator predicts for 16 gauge wire.

I don't see any indication that the wire is shared with anything else -- no splices that I can see -- though it might share a fuse. I haven't yet looked at the converter outputs or fuse labelling to see if anything is shared.

As for using 16 gauge wire with a 15A circuit, I'm worried more about heat generation in the wire than voltage drop. I don't have any notion of who much heat might be generated. If the wires are embedded in the spray insulation, there's also the issue that the heat can't dissipate. I'm also not sure it's 16 gauge -- that's just a guess looking at the wire. It might be 18 gauge, and it might even be 14 gauge. But the voltage drop is consistent with 16 gauge so that's my guess.

Still no response from Reace. He did respond promptly to some other questions I had before this one, so I'll give him another couple of days before I nudge him.

[cpaharley2008]

There are no 12v wires in the spray insulation. All of your wires are inside the trailer shell either behind the refer or over the door on their way to the converter. Unless you have tank heaters, the only wires in the foam are your tank sensors. All of the kitchen 12v go down under your bed and across to the street side to the front.

[RickM]

I believe Reace is super busy getting the new 21 ready for the Escape Rally, which starts this Friday.

[barry]

Originally Posted by dbailey

Still no response from Reace. He did respond promptly to some other questions I had before this one, so I'll give him another couple of days before I nudge him.

I popped into the factory today and it was hard to find a parking place with trailers all over the place ...... real busy right now.

With regards to using an inverter on a 12v receptacle; I wouldn't use anything larger than a 150 watt one as the receptacle isn't really designed to use anything larger ....... even though they are sold. If you want larger then think about hard wiring one in.

Barry

[Devil Dog]

Doug, you are dead on with the heat and voltage drop (resistance ) observation. They are related. If you can, use the one with the less voltage drop until you have the issue sorted out. We have the one up at the front dinette, works fine with a 400w converter.

[dbailey]

You know, in all the excitement with my new trailer, I had forgotten Escape was busy on the new 21'... I guess I'll give him a few extra days before I ask again...

Good to know about the wire run locations. If they're not embedded in the insulation, there's a lot less danger of heat generation.

But, it doesn't change my run-length estimates.

I don't have any trips planned where I'll need the laptop until August (hmmm... "need"? Probably not the right word...) so I'm not going to sweat this one. I'll pick away at a solution in the mean time, and just avoid any higher wattage loads on that outlet for now.

[Devil Dog]

Ya, I was there on Monday to pick up a spare tire and they are busy..busy. Everyone wants there trailer and up grades asap. Talk about pressure...and only 4 days till the Rally...Phew.!

[kstock11]

I've been following this post and have a question. Why don't you use a 12volt car adapter for running your laptop? It seems like you are taking 12volts, running it through a converter, then plugging in your laptop to convert back to 12 volts for the laptop.

[cpaharley2008]

Exactly and with each conversion you lose efficiency, almost all televisions and computers operate off DC and the little black box included is a little converter, converting ac to dc. Perhaps finding a proper DC plug would be a better solution?

[dbailey]

bird-in-hand... I have the inverter and the wall plug for the laptop. I don't have a car adapter. That would be a better solution in the long run.

[Jrn56]

Originally Posted by cpaharley2008

Exactly and with each conversion you lose efficiency, almost all televisions and computers operate of DC and the little black box included is a little converter, converting ac to dc. Perhaps finding a proper DC plug would be a better solution?

I think the only downside to that is the need to buy another proprietary dc plug for the laptop. And of course having more cables to bring with you.