Efficiency in a van electrical system?

So I've been doing some watching videos of van builds and also doing some searches for information on power in a van. I've been unable to find an answer to this particular question, so this seems like possibly the best place to pose it and create a discussion and see what everybody thinks or does for their situation.

I want to preface this post by stating that I am most certainly not a professional in the area of electrics/electronics, my experiences are more towards mechanical/machining/fabricating/R&D.

I see almost every van build using a single inverter up around the 3kW size to power all the 110v appliances used in the van either simultaneously, or by intention based on their purpose and draw. I have also heard it mentioned in many of those videos that regardless of the wattage draw of the plugged in appliance, the current draw will still be enough to power anything up to the maximum of the inverter (please correct me if I am mistaken).

I will break out my question into a list to make it easier to read instead of an obnoxious text for reading comfort, as well as referencing with responses (hopefully).

1. If the build budget allows, wouldn't it make more sense to use a more modular system with multiple inverters sized (with safety factor) to specific plugs/outlets labeled specifically with the maximum wattage draw for that run?
   • For example, in my case, I would be building a van with a workstation so I could do tech work from the road. This means I would need an outlet for my laptop of 300W (my brick is 230W) specifically for this device, a second outlet for monitors with their own inverter matched to their power needs. Both outlets would be labeled with the devices they are for and also the maximum wattage available for each outlet.
   • For devices for example a toaster oven, microwave, refrigerator, heated flood pad 110v, etc. These would be higher wattage outlets wired to where they will specifically be used and labeled/designated as above.
   • As an example I am looking at using electric floor under the finish floor, the electric floor mat I am leaning towards is 110v and has a draw of 540 watts and a single point of power supply (The mat is 20" wide by 13.12' long, no need to heat where I can't put my feet) In this instance I would want a single outlet/switch GFCI outlet where the mat originates near the back of the van close to the whole power system. I would most likely want to have this single run use a 600W pure sine power inverter just for this system. During warmer season, or warmer geographic locations, this whole system could be shut down so no draw/loss would occur.
   • Ideally, I would want to use as many 12v appliances as possible and would integrate 12v outlets in many locations with integrated USB-A plugs as seen in the image below ($22).

I hope I have provided enough information to create a discussion on the pros and cons of creating a modular system of inverters compared to a single max size inverter. I would love to hear any thoughts, ideas questions, comments, or criticisms on this idea. I am going to add some of the initial pros and cons I have come up with so far to get things rolling:

Modular System:

• Con: Increases cost due to needing multiple inverters
• Pro: Being modular, if any of the inverters fail the remainder of the system is unaffected
• Pro: Smaller inverters are relatively cheap to replace versus a single 3kW full system inverter
• Pro: When a system isn't needed it can either be turned off at the breaker, or a switch near the outlet
• Con: More wire needed to fully complete the build from individual inverter runs
• Pro: More efficient use of the available power in the vehicle power bank
• Con: The multiple inverters will use a little more space because of more components along with the single high wattage inverter

These are just some of my initial thoughts, if I have made any incorrect assumptions or ideas, please let me know, so I can factor this information into my future build.

Thank you,

rg

First, welcome and thanks for joining us!

Others will also contribute, but my observations are:

Inverters draw an amount of current from the house batteries based on the load being applied, plus a small amount of overhead and standby current even with no load applied.

Plus, inverters are typically around 75% efficient. (That's an average, some are higher efficiency but usually only at certain percentages of load)

For example, and keeping it basic, suppose you have a 1000 watt inverter powering a laptop that draws 100 watts. (for this conversation, pure sine and modified sine are more or less equal in power consumption since I am only trying to explain the basics)

The laptop usage at 100 watts is around 8 amps at 12 volts, (I'm rounding and averaging) plus 25 % for losses making the current draw probably around 10 amps when the laptop is on and also charging it's battery. (of course you can buy DC laptop power supplies but I'm using this as an example)

If you unplug the laptop (or turn it OFF and assuming the laptop battery is fully charged) then the inverter current from the 12v house batteries will drop to a very low level, which will be the standby current...which might be 500 ma, or half of an amp.

Now, suppose you plug in a 900 watt hotplate. Turn it on, and watch the inverter pull about 80-90 amps or more from the house batteries! If you dont have solar or shore power, this will cause a significant drain on your house batteries.

Many people (including me) outfit the system with two inverters, one for large loads, such as microwaves, and another for smaller loads, such as laptops and cordless tool chargers.

But in any case, the inverters will NOT pull the full rated current all the time when a small load is applied. They will pull the amount of current that the load needs plus a small amount of 'overhead' that runs the inverter itself.

The rule of thumb you can use is: Move the decimal one place to the left to get an idea of current draw thru the inverter under a known load.

100 watt load = 10 amps
300 watt load = 30 amps
1500 watt load = 150 amps

One other observation: Trying to use electrical floor heat (or any electrical space heating) with batteries and inverters is a short trip to having dead batteries, unless you have nearly unlimited solar input and hundreds of pounds of batteries.

Yes it CAN be done, but it will be VERY involved and very expensive to maintain, depending on where you will be spending the colder months.

It is 'doable', but not practical for most of us.

Again, welcome and please keep us posted on your progress.

3,000 watts is a lot of power. Probably a generator will be required to meet your needs. I’m sure there are systems out there with new battery technologies that rhetorically make it possible but it will be extremely expensive and difficult to keep batteries charged.

Yes, good point, it usually makes much better sense to power large intermittent loads such as a microwave or an electric skillet with a generator, or, shore power.

This……
I’m a minimalist but if one wants to go maximalist it’s Generator time or a really huge power station system or both.

(maybe consider living in a house?) ducks
jonny boi

CNC rg said:

For example, in my case, I would be building a van with a workstation so I could do tech work from the road. This means I would need an outlet for my laptop of 300W (my brick is 230W) specifically for this device, a second outlet for monitors with their own inverter matched to their power needs. Both outlets would be labeled with the devices they are for and also the maximum wattage available for each outlet.

Click to expand...

Laptops are usually ~DC 19V at the input. You absolutely do not need an inverter. I go from 12V to 19V using a DC boost converter that is far more efficient. I think it was ~$30 on Amazon, for ~400W.

Same with your monitors. Some will run on 12V which is ideal and this voltage doesn't need to be exact. Make sure to size your wires for minimal loss.

Your laptop brick is converting 110v to DC. That's it's entire function in life. Most likely you can find a DC laptop adapter for your model. It might be aftermarket, but they work well.

Monitors are the same depending on what you're powering. Give us an idea of what you're planning on using.

The floor heating is cool, but power hungry and inefficient. Consider a small diesel heater.

You can absolutely have more than one inverter as @tx2sturgis mentioned.

Once you determine what AC needs you'll have that are high draw, you'll know what you need for your large inverter. Cooking appliances seen to be the majority of larger inverter needs.

If you make a list of AC items you think you'll have, we can give you better info.

Happy Camper said:

Your laptop brick is converting 110v to DC. That's it's entire function in life. Most likely you can find a DC laptop adapter for your model. It might be aftermarket, but they work well.

Click to expand...

Like mine, it sounds like the OP has a gaming laptop, and it's hard to find a DC laptop adapter that will handle the watts.

Here is a boost converter for 12 to 19V that will handle 380W:



https://www.amazon.com/uxcell-Conve...prefix=boost+converter+12v+19v,aps,214&sr=8-6

rruff said:

Like mine, it sounds like the OP has a gaming laptop, and it's hard to find a DC laptop adapter that will handle the watts.

Click to expand...

That booster would do the trick. And there are some DC adapters that should handle the load.

Hey OP, if you give us a model number for your laptop we can look into it.

Relax, cut the cord physically and mentally. Just because you do CNC work that does not mean you need a bunch of electrical, circuit board controlled smart devices to cook your meals. A small butane burner will handle cooking needs. That will give you more available power for your computer.


The only CNC equipment I am traveling with is a professional vinyl cutter. It is not very power hungry, I run it on an small
150 watt inverter. If I want more equipment options and electrical power for a project I can travel and stay near Maker Spaces. There is one in Flagstaff AZ, dues are $50 per month and nomads are welcome, 24/7 access. The parking lot is too small for a big RV or travel trailer but there is street parking. The city does have a no camping (sleeping in vehicles) ordinance within city limits which includes private property unless it is a licensed camping facility.

If Linux suits you, I've found the Raspberry Pi to be a nice little low-power vehicle computer that is "good enough" for most of my work. Portable monitors, some with built in batteries, on Amazon in various sizes. For those few Windows applications that I have to use occasionally (looking at you, wincupl), Wine is "good enough" (although slower than usual, since the Pi has to emulate the whole x86 architecture instead of using x86 virtualization).

The GPIO header is also dandy for interfacing to various vehicle and ham radio things, if you are (like me) a nerd. ;D

FWIW, I suspect that most of these newer LED monitors probably use a <= 12v power supply internally (some of the older TFT ones need a 36+v backlight, so that's a no-go), and could be relatively easily converted to DC power with one of those little DC-DC converter boards of Amazon. The "portable" monitors are fairly expensive for what you get, so if you are handy with a soldering iron this might be a good way to save a few bucks.

Lee_ said:

FWIW, I suspect that most of these newer LED monitors probably use a <= 12v power supply internally (some of the older TFT ones need a 36+v backlight, so that's a no-go), and could be relatively easily converted to DC power with one of those little DC-DC converter boards of Amazon. The "portable" monitors are fairly expensive for what you get, so if you are handy with a soldering iron this might be a good way to save a few bucks.

Click to expand...

There are some excellent smaller monitors available for very low cost. They sip battery, but have limited size. Usually based on laptop screens so think 15.6 inches with speakers and inputs. If your phone is capable, you can connect via cable and use the monitor for desktop purposes. There are some that have an internal battery. Nerds unite!

ForHelp 15.6inch Portable Monitor,1080P USB-C HDMI Second External Monitor for Laptop,PC,Mac phone,PS,Xbox,Swich,IPS Ultra-Thin Zero Frame Gaming Monitor/Premium Smart Cover https://a.co/d/33FDEmK

CNC rg said:

So I've been doing some watching videos of van builds and also doing some searches for information on power in a van. I've been unable to find an answer to this particular question, so this seems like possibly the best place to pose it and create a discussion and see what everybody thinks or does for their situation.

I want to preface this post by stating that I am most certainly not a professional in the area of electrics/electronics, my experiences are more towards mechanical/machining/fabricating/R&D.

I see almost every van build using a single inverter up around the 3kW size to power all the 110v appliances used in the van either simultaneously, or by intention based on their purpose and draw. I have also heard it mentioned in many of those videos that regardless of the wattage draw of the plugged in appliance, the current draw will still be enough to power anything up to the maximum of the inverter (please correct me if I am mistaken).

I will break out my question into a list to make it easier to read instead of an obnoxious text for reading comfort, as well as referencing with responses (hopefully).

1. If the build budget allows, wouldn't it make more sense to use a more modular system with multiple inverters sized (with safety factor) to specific plugs/outlets labeled specifically with the maximum wattage draw for that run?
   • For example, in my case, I would be building a van with a workstation so I could do tech work from the road. This means I would need an outlet for my laptop of 300W (my brick is 230W) specifically for this device, a second outlet for monitors with their own inverter matched to their power needs. Both outlets would be labeled with the devices they are for and also the maximum wattage available for each outlet.
   • For devices for example a toaster oven, microwave, refrigerator, heated flood pad 110v, etc. These would be higher wattage outlets wired to where they will specifically be used and labeled/designated as above.
   • As an example I am looking at using electric floor under the finish floor, the electric floor mat I am leaning towards is 110v and has a draw of 540 watts and a single point of power supply (The mat is 20" wide by 13.12' long, no need to heat where I can't put my feet) In this instance I would want a single outlet/switch GFCI outlet where the mat originates near the back of the van close to the whole power system. I would most likely want to have this single run use a 600W pure sine power inverter just for this system. During warmer season, or warmer geographic locations, this whole system could be shut down so no draw/loss would occur.
   • Ideally, I would want to use as many 12v appliances as possible and would integrate 12v outlets in many locations with integrated USB-A plugs as seen in the image below ($22).

I hope I have provided enough information to create a discussion on the pros and cons of creating a modular system of inverters compared to a single max size inverter. I would love to hear any thoughts, ideas questions, comments, or criticisms on this idea. I am going to add some of the initial pros and cons I have come up with so far to get things rolling:

Modular System:

• Con: Increases cost due to needing multiple inverters
• Pro: Being modular, if any of the inverters fail the remainder of the system is unaffected
• Pro: Smaller inverters are relatively cheap to replace versus a single 3kW full system inverter
• Pro: When a system isn't needed it can either be turned off at the breaker, or a switch near the outlet
• Con: More wire needed to fully complete the build from individual inverter runs
• Pro: More efficient use of the available power in the vehicle power bank
• Con: The multiple inverters will use a little more space because of more components along with the single high wattage inverter

These are just some of my initial thoughts, if I have made any incorrect assumptions or ideas, please let me know, so I can factor this information into my future build.

Thank you,

rg
View attachment 36146

Click to expand...

Ok, I'm a little blown away with the responses and wonderfully surprised at helpfulness of this community. I am still digesting all of the responses and want to properly respond (not from my phone) so I am hoping to have time tomorrow to begin responses, and also to provide some more specific information that would shed some light on what I was initially thinking. Thank you all for the responses so far, I have some notes jotted down, this has been very useful. And thank you for the community that is here, it is a breath of fresh air...(Don't venture to the Arduino forum with a question unless you are a masochist... Lol)

Great insights for options. Thanks for bringing up different strategies to approach the need.

Only thing I can offer to this is adaptability.
Maybe try on the cheap to live in limited parameters and develop from there.

When putting time and money into a solution, it's good to provide yourself with some wiggle room to adapt to what does and doesn't work ( for you).
Power sources, like plumbing may require adjustments which usually aren't easy or fast unless it's subtraction.

Gaming computer perhaps. But if into CNC then just as likely the fast processing is needed for high end 3D CAD software. Gaming computers are fairly decent for that type of work. It is also very useful to have dual monitors. …Speaking from experience. CNC and 3D CAD Design are an essential pairing of technology

Welcome to the forum

CNC rg said:

...my experiences are more towards mechanical/machining/fabricating/R&D.

Click to expand...

There are several people here with similar backgrounds, maybe more will chime in...

Adding to what rruff and Lee mentioned about running things directly from DC, one of the best electrical engineers I worked with lives in an off-grid house in rural AZ that runs almost entirely on 120V DC, with the inverter only needed to run his washer and a few other appliances. The lights, computer, whole house vacuum, electric hot-plate, etc. all connect directly to 120VDC.

It works because a lot of switching power supplies like laptop chargers already rectify the input internally. And vacuums/hair dryers do the same because they use high-RPM DC brush motors rather than AC induction motors.

But you have to be careful because some appliances like washers, dryers, non-RV fridges and older air conditioners require AC power, and you'll blow the fuse/breaker or burn up the motor if you plug them into DC.

Full-time live-aboard here, with over two decades in our constantly-evolving 1996 ExpeditionVehicle.
.
a)
Budget?
Where will you camp?
How often will you move?
Full-time live-aboard?, a few weekends annually?.
Carpentry skills for your custom cabinets and desks?
.
I think your employment equipment requires an enormous photovoltaic system and bank.
To meet your requirements, I think you need a crew of experienced professional engineers and installers.
.
I think you owe that to your future customers.
.
For example, our ExpeditionVehicle has six 305-Watt panels, a total of 1,830-Watts.
.
Our bank is 24v LiFePo4, custom built to our specifications by MAC'S BATTERIES AND SOLAR in Eugene Oregon.
They installed our bank in a custom cabinet we designed and they built.
Our bank is the equivalent of sixteen BattleBorn 106ah batteries.
.
Our photovoltaic is split into two identical -- redundant -- stand-alone sub-systems, as is our bank and associated gadgetry.
.
[edited to add]
But our needs are miniscule compared to your concept.

And another point:
.
b)
A -- Irregardless of the amount of thinking you think you need prior to getting going, I think you would probably benefit from starting small, then seeing how it goes.
.
B -- Somebody mentioned modular modules (maybe it was me (I am 'getting on' these days, and have my spells...).).
.
I wonder about building resilience into your Mobile Work Station.
I think you owe that to your customers.
.
If I was me, I might have a stand-alone system for each computer, its own private photovoltaic and battery bank.
I would probably have another stand-alone system for some of my monitors, and another for the others.
.
Second class citizens, the printer and flat-bed scanner can suffer-along by occasionally piggy-backing on one of the other systems during an idle time.

from the I Wonder About That department:
.
c)
Some 'health' faddists are 'researching' a bunch of nutso claims of 'detrimental' 'effects' from alleged electronic 'emissions'.
.
Apparently, some of the less wacky of them are under the delusion 'invisible rays' are shooting out from computers, plus something they call 'Blue Rays' are shooting out from the LEDs in monitors and telephones.
On those rare occasions they crawl out from under their tin-foil hats, they claim it will 'cook your innerds'!
.
Bad as a bunch of dang vegantarianists, tell you what.
.
If I was me, I might schedule an hour outside playing in the sunshine for every ten minutes sitting at work.
Or two hours for each five minutes.
.
[edited to add]
But I suspect -- without a shred of evidence -- anything over about three hours or so for a single minute of work, well, I think that might be edging into the territory of 'retirement'...

INTJohn said:

(maybe consider living in a house?) ducks

Click to expand...

Or at least something bigger than a van. I big box truck maybe. And park in the sun.