12V-Only System, No Inverter

[speculant]

I am hoping to design/price out a system for my mother-in-law with only one or two 500W (if they will fit, less W if space is limited) on top of the van, so I would like to save every W possible. This means removing the inverter from the equation as it would be mostly running electronics that operate on DC, so the conversion from DC to AC and back to DC seems completely ridiculous and unnecessary as it increases heat & noise output and increases idle consumption. We already have a 12V fridge/freezer that she has used in the past when the power goes out so we can re-use that for the van. The small electronics aspect I think I can cover on my own with various 12V to 19V adapters for the TV & laptop and then 12V-12V adapters for any remaining 12V electronics like 4G/5G router, the existing 12V mini fridge (which may be able to operate at up to 14.4V but I will have to research that), and a stereo system & light strips.

I am looking for advice from people who have installed 12V inverter-less van or small RV systems that have ran appliances like an electric kettle, portable AC, coffee maker, and possibly a small cooktop. High amp draw 12V items would all be ran as physically close to the 12V battery as possible (or batteries in parallel to increase amp output) since it would require large AWG cables (which I am fine with to keep the system inverter-less and 12V for everything else). I have heard of the Ecoflow Wave portable AC but it is somewhat expensive and I wasn't sure if there were other lower-cost options. All in all, appliances as stated above are not strictly required, but I would love to know if it is possible to source/install (relatively) affordable 12V versions of the above appliances and if anyone here as experience with it.

 

[Rednecktek]

an electric kettle, portable AC, coffee maker, and possibly a small cooktop.

Grabs popcorn...

Do such beasts exist? I know there are 12v mini-splits you can get for trucks, but honkin wires are required. A cooktop or kettle would be 150a of draw off the batteries...

 

[justinm001]

DC to a good AC inverter is like 90%+ and to devices like laptop chargers are 99%+ efficient.

On top of all that you're getting protections and simplicity.

Also don't forget there's plenty of losses when running just 12v from wire size.... Unless you're planning on running 4/0 everywhere

 

[Dave in AZ]

systems that have ran appliances like an electric kettle, portable AC, coffee maker, and possibly a small cooktop.

I hate to say it, but I wouldn't wish a 12v kettle or coffee maker on my worst enemy! I did all the research, and the heat times and wattages for those devices are so slow and low. From 120v ac, an electric kettle or coffee maker are virtually 100% efficient, every watt consumed goes to heat. So only the brief ac inverter use would apply, and a 1500W inverter to run a full up kettle or coffee, can be had at 90% efficiency. From room temp to boil, you might lose 10 Watt-hrs, but gain 20 minutes! I have a whole long writeup on cooking Watt-hrs efficiency and actual measurements here on the 12v or cooking forum.

Small cooktop, I assume induction, will also need 1500W inverter for anything reasonable, the 1000w or lower induction cooktops have endless 1 star ratings and a 3" actual heating ring.

If she wants any of those 3 items, I would absolutely bite the bullet and get a 1500W inverter. Just turn it iff when not in use.

Edit, forgot what forum I was on, my cooking power writeups are on ExpeditionPortal and OverlandBound.

 

[speculant]

Grabs popcorn...

Do such beasts exist? I know there are 12v mini-splits you can get for trucks, but honkin wires are required. A cooktop or kettle would be 150a of draw off the batteries...

From my limited research, DC-powered portable AC units exit such as the Ecoflow Wave and Zero Breeze but both are over $1000. I'm not sure if cheaper options exist that are DC powered. Unfortunately a window unit or mini-split wouldn't be feasible as it would be too large for the van. So since AC would be required where I'm at, I may have to bite the bullet and include an Ecoflow Wave in the estimate as the reviews are pretty good for the latest model.

 

[speculant]

I hate to say it, but I wouldn't wish a 12v kettle or coffee maker on my worst enemy! I did all the research, and the heat times and wattages for those devices are so slow and low. From 120v ac, an electric kettle or coffee maker are virtually 100% efficient, every watt consumed goes to heat. So only the brief ac inverter use would apply, and a 1500W inverter to run a full up kettle or coffee, can be had at 90% efficiency. From room temp to boil, you might lose 10 Watt-hrs, but gain 20 minutes! I have a whole long writeup on cooking Watt-hrs efficiency and actual measurements here on the 12v or cooking forum.

Small cooktop, I assume induction, will also need 1500W inverter for anything reasonable, the 1000w or lower induction cooktops have endless 1 star ratings and a 3" actual heating ring.

If she wants any of those 3 items, I would absolutely bite the bullet and get a 1500W inverter. Just turn it iff when not in use.

Edit, forgot what forum I was on, my cooking power writeups are on ExpeditionPortal and OverlandBound.

That may be the end result, to get a 1500-2000W inverter with a remote switch that would only be turned on when the appliances are used. For resistive loads like a cooktop, coffee maker, electric kettle, I wouldn't need a pure sine wave inverter, so any inexpensive modified sine wave inverter (from a reputable company of course) would work correct? As long as I'm not trying to run inductive/sensitive loads (like AC compressors, microwaves, or other motors) off it.

 

[AntronX]

Some small TVs and laptops will run on 10 - 14V direct. 4G router/modem will run on 12V LFP battery direct as well, no need for 12/12V converter.

240V 5.5" resistive stove top element runs at 1200W. You could do it at 12.8V direct with around 90A and 5 feet of #4AWG copper cable with only 2% loss. You just need to find 1000W 12V cooktop heating element. Quick search brings up 12V induction cooktops but reviews say they top out at 400W which is not enough for cooking.

You may be able to modify existing 230V European glass top infrared resistive cook top by removing 230V heating wire and replacing with your own nichrome wire strands in parallel for 12V 90A load. Use DC contactor to turn it on/off with signal from existing thermostat.

Drip coffee maker is a problem unless you can make external 12V water heater for it at least 600W power capable. There are 12/24V automotive air conditioners using inverter drive compressors available from China.

 

[justinm001]

From my limited research, DC-powered portable AC units exit such as the Ecoflow Wave and Zero Breeze but both are over $1000. I'm not sure if cheaper options exist that are DC powered. Unfortunately a window unit or mini-split wouldn't be feasible as it would be too large for the van. So since AC would be required where I'm at, I may have to bite the bullet and include an Ecoflow Wave in the estimate as the reviews are pretty good for the latest model.

If costs are a factor then definitely stick with 120v and an inverter. 12v wire is 10x as much as 120v.

A simple inverter type portable AC with a window vent is a few hundred bucks.

 

[time2roll]

Grabs popcorn...

Do such beasts exist? I know there are 12v mini-splits you can get for trucks, but honkin wires are required. A cooktop or kettle would be 150a of draw off the batteries...

How do you make 12 volt popcorn??? I am thinking propane for these items.

Skip the A/C as there will never be enough solar so might as well just fire up the generator from the get go. May as well use the generator for the rest too.

For the OP: inverter takes little power in comparison to the appliances plugged into it.

 

[AntronX]

Skip the A/C as there will never be enough solar

I have Midea U 12K BTU ac that pulls 107 Watts on slowest speed and blows 57F air. Maximum input power at full blast is 1200 W.

 

[justinm001]

I have Midea U 12K BTU ac that pulls 107 Watts on slowest speed and blows 57F air. Maximum input power at full blast is 1200 W.

Sure but how many btu is it cooling at 107watts? I'm assuming under 1000btus. A person produces around 350btu/hr. On top of that it's not even how many btus but also how often the air is circulated.

 

[AntronX]

At 107W and COP of 3.5 at least 375W or 1280 BTU. But likely more since at slow speed and cool outside temps COP goes up. Good for overnight cooling and humidity removal.

 

[speculant]

I have Midea U 12K BTU ac that pulls 107 Watts on slowest speed and blows 57F air. Maximum input power at full blast is 1200 W.

I have the 5500 BTU model and I love it for my living room. It’s the perfect size to supplement my home HVAC with my solar panels. I’ve been looking to see if I can find a dual hose portable AC that uses the same inverter technology but I can’t seem to find one I’m going to keep looking.

 

[0truck0]

Dreaming....

They are right, this is a fools errand. Stick with the inverter, they are efficient enough for what you are doing, and I would not get the mindset that every single last watts counts hat much. Use a smaller inverter, the smallest that your items run on, or get two, a small one for small things, and a big one for your stupid things - ru the one needed only at that time.

I would love to go electric cooktop, but that means a big, stupid big, inverter, so I stick with propane. Instead look into diesel cooktops. These burn diesel, readily available everywhere, and the exhaust gases go outside, not inside like a propane stove.
Look at the diesel heaters for that matter. I have the smallest diesel heater made and I run it on LOW and it still cooks me out on sub-freezing nights.

Yes, a 12v device can run on 14 volts! Your vehicle actually puts out 13.6-14.x volts when running, so all DC devices for "cigarette lighter plug" will handle 14 no problem. Most Dc devices have a range like this11-15. I had a defective charger that put out 18 volts and I ran everything off 18 volts when plugged in, nothing ever blew, but maybe their life was being shortened, but nothing ever died either.

5500btu AC should be big enough for a van, depends how well insulated it is, are there exposed metal body panels showing on the doors or walls? The glass is the big heat loss source.

FInd the smallest mini-split you can, these are more efficient that the typical window unit, but do the math, if a 5000btu window unit uses less than the smallese mini-split (9000btu??) then that is what counts. AC is a hard thing, so easy to use a small generator. A Coleman Easy Start $179 will greatly help an AC start up on a 2200 watt inverter generator too.

You just will not have the roof space for the amount of solar you need here, and further handicap by your in-law likely being illiterate on RV things and may not can ever learn sufficiently.

 

[HarryN]

On most vans, you are better off using solar panels in the 150 - 200 watt range and mounting them cross wise. This will be much more tolerant of the real life conditions on top of a van driving down the road with cross winds.

Set it up to be a 24 volt system. Nearly everything works better on 24 volt and all of the wiring and fuses that you would use will still work just fine on 24 volt - it is like buying one candy bar and getting one for free. For the couple of odd lots, you can use a 24 - 12 volt converter as required.

Power can be pulled from the alternator fairly easily on a Transit. On the other models it is slightly more difficult but not bad.

Propane is a great fuel for van related heating appliances.

Reality though is that a microwave and coffee maker can do a lot of stuff. It is a "van / RV", for recreation.

If she wants bacon for breakfast, either use pre-cooked or go into Ihop.

 

[Aussieguy]

makes absolutely no sense to use smaller panels for crosswind protection
especially since I don't drive when crosswinds are real crappy
at 65mph constant driving panels should be mounted real good no matter which orientation

8 foot wide trailer ... no obstructions on the rood after the air conditioner
put 2 x 370w panels up there with enough room between to shuffle walk.

 

[efficientPV]

I have a 12V house and have an inverter for the fridge that only turns on when needed. Same with the dishwasher which draws less than 100W. Older TVs are 12 or 19V. I see no need for upgrading to 120V and just wasting power.