High amperage 12VDC power outlet with terminal connectors?; Venza camping upgrades?

I need a high amperage 12VDC power outlet - at least 20 or 30 A, preferably more. And I want it on a panel that also has terminal connectors for wires. I will to pay a mechanic to install it in my car, with a pass through from the battery. (I may also have the mechanic install an isolated deep cycle marine battery - but there isn’t much room in my car to install it, and tie it down so it doesn’t go flying during a fast stop. The hood isn’t large enough to put a second battery and an AC inverter inside.)

Where can I find such a device?

BTW, if anyone has other ideas on how to customize a Toyota Venza station wagon for better car camping, I would love them.

It’s a lousy car camper. The 12VDC power outlets are sized slightly too big to make good connections to most 12V devices, and if I plug in my laptop to one, it blows the fuse.

(On top of that, it doesn’t hold as much as an SUV, let alone a van, the windows have terrible visibility, I can’t figure out where the front and sides of the car end while driving, though lowering the mirror helps a little. The fittings that I had to put a roof rack on don’t make for solid reliable connections, so I have to keep them very tight. To install a full size spare tire, I had to raise the back cargo area, and deflate the tire. I had to add front and rear tie downs. Spare parts are expensive, and hard to for a non-mechanic to change, because the user manual is not written well and is poorly illustrated. It can’t take much cargo weight, or tow a decent size trailer. Sometimes it locks itself when the key is still inside.)

(On the plus side, it fits inside low parking garages, I can reach the roof racks without a step stool, it has AWD, high road clearance, fairly good gas mileage, and Toyotas are supposed to reliable. Also, it has several 12VDC power outlets, the rear cargo area is flat and big enough to sleep on, and its long enough to fit my whitewater kayak, paddles and skis inside. It has a big center console with a USB connector inside, and a wire pass through. But overall, I wouldn’t recommend a Venza to anyone taking extended car camping trips.)


Whoa… I think we need to start at the beginning instead of somewhere in the middle.

How much power does the laptop draw, and what else are you planning on powering. It’s pretty rare for a laptop car cord to blow a fuse. What size fuse is blowing?

It’s highly unlikely for factory accessory ports to be oversized. It’s much more likely that your car cords are sub standard, and perhaps under performing.


"Practical beats popular every time." ~ Truth Matters

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I do a good bit of electronics work. The main factors limiting power at a DC Auxiliary Power Port are the AWG wire size connected to the port and the length of the wires. Also, some DC ports are better made and can handle more current. Generally they are designed to handle about 10Amps or 120watts (on 12v)

The center positive wire connection is usually the weak point. Solid soldering it can sometimes increase it’s current capacity.

The wire needs to be 12 Gauge for 25Amps and 10 Gauge for 30amps. Then the connections to the DC Port itself need to be capable of carrying the current. Connecting the wires directly to the battery is good, just be sure to add a fuse near the battery.



AFAICT, my Venza has a 15A fuse on all the DC power outlets combined, which is 180 watts at 12V. That ought to have been more than enough to run my laptop, whose AC power supply was probably rated at 70-80 W at most (I’m now using a different laptop). Unless - maybe the DC connector doesn’t limit the DC current used to charge the laptop battery. Also, it is possible the DC power isn’t input at 12V, but goes through a simple voltage divider, so it really draws more than 15A… E.g., if it uses 5V, it would only get about 15*5=75 watts at 15 amps. Plus, it might contain a voltage regulator, which might increase the mean and/or RMS current draw.

If it isn’t practical to get a 20-30 amp DC outlet to feed a laptop or AC inverter…

Do you happen to know how automotive fuses in DC are rated? E.g., 15 amp AC house breakers are rated to eventually trip at 12 amps , which is 20% less than 15 amps.

I was once told by an electrician that most AC fuses and breakers are “mean responding” (sensitive to mean amperage), but a few are “RMS responding” (sensitive to RMS amperage). (However, the mean responding fuses and breakers are rated according to what RMS amperage would be, which is theoretically roughly proportional to the mean power (not taking power factors into account), would be if the draw were sinusoidal. Further, the relationship between those 2 depends on the shape of the draw - e.g., sinusoidal, sinusoidal with square wave cutoffs ([approximately what switching power supplies draw). But what about automotive DC fuses? Are they mean responding or RMS responding?

I wonder if it actually makes more sense to add an AC inverter, with a switch, which I would only turn it on while the motor is running, to avoid running down the battery. Then I could use ordinary house current devices, which are cheaper.

Maybe I should remove the passenger seat or rear seat bench to get more space inside, for things like a deep cycle marine battery, with a battery isolator circuit, AC inverter, and DC power outlets, and lots of camping gear. Perhaps other things.too, like a portable toilet or dressing/sponge bath area, and a way to put a privacy curtain around it.

Except: many house current devices, like small electric burners, are now designed to draw high power (e.g., 750W), though they cycle on and off to use lower average powers. Even if the inverter was 100% efficient, 750W = 62 amps at 12V- I wonder if my alternator can produce that + run the car, whatever inefficiency exists, while the car is in idle. Whereas 12VDC devices are probably designed to draw more reasonable currents. So maybe I should have an AC inverter TOO - inside the engine compartment - though I’m not sure they can take the heat of an engine compartment, or the humidity when the car sits in the rain.

Maybe I should also pay the mechanic (or an auto electric specialist) to add an AC cord feed through for external A/C power for when I’m in a campground with AC power. I don’t want to have to open a window to mosquitos.

Maybe I should remove the passenger seat or rear seat bench to get more space inside, for things like a deep cycle marine battery, with a battery isolator circuit, AC inverter, and DC power outlets, and lots of camping gear. Perhaps other things.too, like a portable toilet or dressing/sponge bath area, and a way to put a privacy curtain around it.

Trying to turn a station wagon, even a crossover SUV like the Venza, into a good weekend car camping vehicle for paddling, hiking and ski trips, is probably crazy… But it has some advantages over conversion vans and RVs. For one, I already own it, and can’t afford another vehicle, nor do I have a place to park it. For another, when I’m not sleeping in it, it would draw no special attention. It might be easier to drive than a much bigger vehicle, and can go in low parking garages. it can be legally parked on the street in almost any neighborhood

Though it is a bit long, and is therefore a bit hard to park. Maybe I can figure out a way to add extra mirrors for better side and front visibility

I’m not very smart about all this, and am probably omitting important things.

I found a few higher amperage DC outlets myself, by searching google








Electronics can be a royal pain because they are often not well documented. Batteries pull the power they want to charge themselves, but the house power cord might be limiting what the battery can draw, while the car cord isn’t and the battery is trying to pull more watts/amps than the original wall charger would allow.

A separate house battery charged via an isolator is almost always a good idea.

If I had enough room to lay flat in the back, I wouldn’t remove the front seat. I guess the back seat is a matter of weighing the pro’s against the con’s.

An indoor toilet might be difficult do to space requirements, but a bedpan might work for emergencies.

For showers, I would get a shower tent, back into a parking space at a park where you’ll have grass directly behind you. Pop up the tent & take your shower. I have done this many times when I’ve had a low top caan and wanted a stand up shower. Nobody ever gave me a second glance.

I don’t normally use an inverter, all of my typical uses are powered by 12v, USB, or fuel.


"Be the reason someone smiles today!" ~ Van_Dweller

Your laptop doesn’t use anywhere near that much power (except maybe while charging a discharged battery) and even then the charge rate is controlled by a BMS on the battery pack internally.
It should do just fine even on 2A or down to .5A depending on the laptop while running normally and not charging the battery. Expect 1 to 2 Amps draw while charging the battery unless stated otherwise in the manual.

I use inverters and have about 5 or 6 of them ranging from 300watts to 3000watts. They have a small parasitic load of about 500 milliamps to about 1 amp for the biggest one. I only use PSW inverters since MSW inverters are less efficient and some devices just like clean power better. Especially fridges and delicate electronics. MSW inverters produce more heat in motors. More heat is bad.

Don’t over think this. It’s not that complex. The standard 10A (or 15A) DC Aux Power Outlet should be more than enough for your laptop. Unless you are designing electronics, I wouldn’t worry about all the mathematics of RMS etc. Just assume a 15A fuse is good for 15A and you’ll do fine.

You are limited by your batteries. I use LiFePO4 batteries due to their energy density. I do also have large LA batteries but they are so heavy and take up too much space compared to the LiFePO4 batteries. I always have 2000 watt hours of LiFePO4 on board. That is USABLE watt hours. To get that from LA batteries would require about 200lbs of batteries minimum.

I am lucky in that I have a Dodge Caravan (2 actually) and they make great economical travel / camping vans. I did add a backup camera :slight_smile:


It “should” have been enough, but it did blow the fuse. It was charging the battery while running. If the wires in the Venza are too small, there would have been a significant voltage drop too. The Venza hides interior fuses in a place that is hard to see and access. I had to work blind, and wasted hours changing it. So, while fuses are cheap, I’m not going to experiment with my current laptop.

Based on my previous trips, I want my batteries to work (charge and discharge) well from roughly -10 to 110 deg F (-23.3 to 43.3 deg C). While a few LiFePO4 batteries are rated to discharge over that range, many websites say they shouldn’t be charged below about 32 deg F (0 deg C). One website suggested discharging them somewhat first in cold weather, just to warm them up. I could also use the vehicle heater to warm them up too, though that would take a long while. And I guess I’d need a manual switch so they don’t charge while cold.

What brand and type battery do you use, and over what approximate temperature range? Is there a better battery chemistry for the range I want?

I should have bought something more like your Caravans, or the Ford or Chevy equivalent. They were cheaper than the Venza. As far as switching vehicles, it is hard to sell uncommon vehicles like the Venza, and I’ve already wasted a lot of time and money adding tie downs, as well as first class roof racks and tires.

But maybe I should rethink this, and wait till I can afford to switch vehicles, and choose one better suited, instead of fighting the design category.

In the mean time I could use battery clamps instead of power outlets. I’ve also got an old (lead acid) portable power station that just needs a new battery. Maybe a cheaper approach in the end would be to get a new minimal laptop designed to draw very little power. (I’ve tried cell phones and tablets, but they can’t do as much or as well, and are much clumsier to use than a PC.)

Do you mind if I ask what exact laptop you have?
Do you have a special graphics card in it or something else in it or connected that draws more power than normal?

My LiFePO4’s stay inside my vehicle at all times. That said, it never gets below freezing in my vehicle regardless of where I am because I’m either in it and keeping it warm or it’s parked in the Sun keeping the inside warm. I’m not in a cold latitude either so that helps…

The Venza isn’t the “worst” vehicle for camping. Better than a Prius or some of the smaller cars I hear people camping in. The advantage to the Caravan is headroom and cubic feet. I find it about as small a vehicle I would want to camp in yet comfortable and roomy enough to get by.

Fully loaded on my last over the road excursion I got 26mpg on the highway. Not too bad considering I was carrying 600lbs of gear. I can actually stretch that to 30mpg if I do not use cruise control and peddle the hills gingerly, letting the vehicle slow a bit going up then regaining the momentum on the down side of the hill… AC drags mpg down to 22mpg so I try not to use it much.

I have a 45quart DC fridge, diesel heater, 2000watt generator, 2 buddy heaters, propane stove, water, food, color TV, Laptop, bed, 10 days of clothes, tools and a wide array of electronics and equipment I carry with me in case I have work to do. I also carry a fire extinguisher.

If you’re blowing a 15A fuse then I suspect there is a wiring fault or problem with the DC power port unless the circuit is shared with something else. How many watts does your laptop pull at home?

I recently added a 7" 1080P backup camera. I use it a LOT. Now I’m usually looking at the camera when backing more than the mirrors.

I’m planning to pull out all the stops with my other Caravan because it’s a Grand Caravan and is about 17 inches longer and bigger inside. That one’s gonna get a full build top to bottom for camping and Van Dwelling…but first I want to rebuild the motor and transmission.

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It was an older laptop. I’m not using it anymore, and am not sure of the exact specs.

I think it had an 80-90 watt AC adapter. If an inverter was 100% efficient, that would be 7.5 amps at 12V, well under 15A. But as I said, there may have been a voltage drop, and maybe the DC power supply went through a voltage divider, so it might have drawn substantially more - and maybe the DC power supply wasn’t current limited the same way as the AC power supply. It was the only device plugged in, and the fuse blew as soon as I plugged it in. I have no idea what the peak draw is - it wouldn’t be surprising if a transformer and switching power briefly draws a higher peak load because it has an inductive core, and it probably has to initially charge the capacitor(s). I also don’t have a clear idea how efficient typical inverters are.

My current laptop is an HP 210 G1 PC, baseboard 2257, 1.7 Ghz Intel Core i3-4010U CPU, 8 GB of memory, running Windows 10 - about the minimum needed for video streaming, but newer hardware might use less power. I added an oversized battery, and larger disk drive. I don’t have a DC adapter for yet yet. The AC adapter is rated for 45 W. I just measured actual max power draw, with a mostly discharged battery, when streaming or reading the disk drive, according to a Kill-A-Watt meter (claimed accurate within 1%): 45.4 watts max when on, 40.4 when off but charging. So a 100% efficient inverter might draw 45.4*1.01/12=3.82 amps at 12V.

Maybe I should just try it again with the newer laptop, with a DC adapter or inverter, and accept that I might waste a few more hours changing that difficult to access fuse again.

That said, there are other things I might want to simultaneously use electricity for. I could use battery clamps, with large gauge DC wires so there would be little voltage drop.

The Venza has a built in back-up camera. The lines on the screen don’t exactly correspond to the edges of the vehicle at ground level. I should calibrate that, by placing objects on the ground around it, of various heights. I should stretch a tape measure across the dash, so I can calibrate how close I am to the curb, by seeing where it intersects the closest point I can see of it in front of the vehicle - but, with the long wheelbase, that would only apply to the front.

I previously had a Chevette hatchback, 3 VW buses, including a VW/Westphailia Camper van, a Ford Ranger (with a cap), and a Honda CRV. From a camping perspective I like the Venza least. But it has some nice features, and the AWD works surprisingly well and smoothly on ice and snow, considering that it has an automatic transmission. I was able to add a tow hitch to create a rear tie down, and under-the-hood-bolted-to-frame front tie downs. Adding roof racks with bars cut to vehicle width and a long enough baseline for fragile sea kayaks was a pain, but its done. Heater and A/C work well. Seats are quite comfortable. It gets 20-24 mpg, depending on terrain, speed and traffic, not bad for a 2013 station wagon, and has a big fuel tank. Engine is pretty quiet. True to Toyota’s reputation, it’s been completely reliable, since bought it in 2020. It’s not a bad car - just not ideal for picky me.

In this situation, if it were me…
I would go ahead and add direct (fused) wiring to the battery for powering the laptop.
I would then use a small PSW Inverter of 300-500watts with low parasitic drain and call it done.
14 AWG (or 12 AWG depending on distance) wire should do

It would only cost 250-500mA to do it this way to power the inverter and you’d no longer have to worry about the cars wiring issues.

I’ve had very good luck with inverters and use them a lot.
That said…I do DC - DC direct when possible. I have 3000watt hours of 48v LiFePo4 that I use a 48v to 12v Buck converter and it is 95% efficient.